- Agreement
The degree to which more than one individual undertaking an assessment or scoring of an instrument agrees with the outcome (diagnosis)
- Attention deficit hyperactivity disorder (ADHD)
A developmental disorder with onset in childhood and with impairments in the ability to maintain attention to task combined with impulsive and hyperactive behaviour. Criteria for diagnosis defined in ICD-10 and DSM- IV-TR.
- Autism
A neurodevelopmental disorder with onset in childhood characterised by impairments in reciprocal social interaction and social communication, combined with restricted interests and rigid and repetitive behaviours in children, young people and adults. Autism is the term used in this guideline for all autism spectrum disorders (and pervasive developmental disorders) in line with recent Department of Health publications.
- Autism spectrum disorders (ASD)
A term used synonymously with pervasive developmental disorder.
- Best available evidence
The strongest research evidence available to support a particular guideline recommendation.
- Bias
Influences on a study that can lead to invalid conclusions about a treatment or intervention. Bias in research can make a treatment look better or worse than it really is. Bias can even make it look as if the treatment works when it does not. Bias can occur by chance or as a result of systematic errors in the design and execution of a study. Bias can occur at different stages in the research process, for example in the collection, analysis, interpretation, publication or review of research data. For examples see Selection bias, Performance bias, Information bias, Confounding, Publication bias.
- Biomedical test
A test carried out on the body or on a sample of body fluids defined by expected norms.
- Blinding or masking
The practice of keeping the investigators or subjects of a study ignorant of the group to which a subject has been assigned. For example, a clinical trial in which the participating patients or their doctors are unaware of whether they (the patients) are taking the experimental drug or a placebo (dummy treatment). The purpose of ‘blinding’ or ‘masking’ is to protect against bias. See also Double blind study, Single blind study, Triple blind study.
- Case–control design
The comparison of cases with and without a particular disorder. See Case – control study.
- Case–control study
A study that starts with the identification of a group of individuals sharing the same characteristics (for example people with a particular disease) and a suitable comparison (control) group (for example people without the disease). All subjects are then assessed with respect to things that happened to them in the past, such as things that might be related to the subjects getting the disease that is under investigation. Such studies are also called retrospective as they look back in time from the outcome to the possible causes.
- Case report (or case study)
Detailed report on one patient (or case), usually covering the course of that person’s disease and their response to treatment.
- Case series
Description of several cases of a given disease, usually covering the course of the disease and the response to treatment. There is no comparison (control) group of patients.
- CG array
Comparative genomic hybridisation technique: a method of analysing samples for gene duplications and deletions.
- Checklist
See Study checklist.
- Child and adolescent mental health service
The service specialising in mental health for children and adolescents.
- Child development centre
A location housing the facilities for assessment of (usually young) children with developmental problems, sometimes attached to a hospital or separately in the community, and part of the child health services.
- Chronological age
The exact age in years and months of a child measured from birth.
- Clinical effectiveness
The extent to which a specific treatment or intervention, when used under usual or everyday conditions, has a beneficial effect on the course or outcome of disease compared to no treatment or other routine care. (Clinical trials that assess effectiveness are sometimes called management trials.) Clinical ‘effectiveness’ is not the same as efficacy which establishes whether a treatment ‘works’ or not under ideal conditions.
- Clinical impact
The effect that a guideline recommendation is likely to have on the treatment, or treatment outcomes, of the target population.
- Clinical importance
The importance of a particular guideline recommendation to the clinical management of the target population.
- Clinical question
This term is sometimes used in guideline development work to refer to the questions about treatment and care that are formulated in order to guide the search for research evidence. When a clinical question is formulated in a precise way, it is called a focused question.
- Clinical trial
A research study conducted with patients which tests out a drug or other intervention to assess its effectiveness and safety. Each trial is designed to answer scientific questions and to find better ways to treat individuals with a specific disease. This general term encompasses controlled clinical trials and randomised controlled trials.
- Clinician
A healthcare professional providing patient care, such as a doctor, nurse or physiotherapist.
- Cochrane Collaboration
An international organisation in which people find, appraise and review specific types of studies called randomised controlled trials. The Cochrane Database of Systematic Reviews contains regularly updated reviews on a variety of health issues and is available electronically as part of the Cochrane Library.
- Cochrane Library
The Cochrane Library consists of a regularly updated collection of evidence-based medicine databases including the Cochrane Database of Systematic Reviews (reviews of randomised controlled trials prepared by the Cochrane Collaboration). The Cochrane Library is available on CD- ROM and the Internet.
- Coexisting condition
A disorder which exists in association or together with the index disorder
- Cognitive assessment
Assessment of IQ and learning using an intelligence test
- Cognitive impairment
A deficit in some aspect of intellectual ability and/or learning
- Cohort study
An observational study that takes a group (cohort) of patients and follows their progress over time in order to measure outcomes, such as disease or mortality rates, and make comparisons according to the treatments or interventions that patients received. Thus within the study group, subgroups of patients are identified (from information collected about patients) and these groups are compared with respect to outcome, for example comparing mortality between one group that received a specific treatment and one group which did not (or between two groups that received different levels of treatment). Cohorts can be assembled in the present and followed into the future (a ‘concurrent’ or ‘prospective’ cohort study) or identified from past records and followed forward from that time up to the present (a ‘historical’ or ‘retrospective’ cohort study). Because patients are not randomly allocated to subgroups, these subgroups may be quite different in their characteristics and some adjustment must be made when analysing the results to ensure that the comparison between groups is as fair as possible.
- Cohort
A group of people sharing some common characteristic (for example patients with the same disease), followed up in a research study for a specified period of time.
- Common Assessment Framework
A systematic questionnaire to record in a standardised way the additional needs that a child may have with the aim of determining how they should be met. It is intended to enable agencies to work together.
- Co-morbidity
Co-existence of a disease or diseases in the people being studied in addition to the health problem that is the subject of the study.
- Confidence interval
A way of expressing certainty about the findings from a study or group of studies, using statistical techniques. A confidence interval describes a range of possible effects (of a treatment or intervention) that are consistent with the results of a study or group of studies. A wide confidence interval indicates a lack of certainty or precision about the true size of the clinical effect and is seen in studies with too few patients. Where confidence intervals are narrow they indicate more precise estimates of effects and a larger sample of patients studied. It is usual to interpret a ‘95%’ confidence interval as the range of effects within which we are 95% confident that the true effect lies.
We have presented this range as two numbers separated by a comma and space e.g. (95% CI 1, 10).
- Confounder or confounding factor
Something that influences a study and can contribute to misleading findings if it is not understood or appropriately dealt with. For example, if a group of people exercising regularly and a group of people who do not exercise have an important age difference then any difference found in outcomes about heart disease could be due to one group being older than the other rather than due to the exercising. Age is the confounding factor here and the effect of exercising on heart disease cannot be assessed without adjusting for age differences in some way.
- Consensus methodology
The process of agreeing a particular course of action based on the collective views of a body of experts.
- Consensus statement
A statement of the advised course of action in relation to a particular clinical topic, based on the collective views of a body of experts.
- Control group
A group of patients recruited into a study that receives no treatment, a treatment of known effect or a placebo (dummy treatment) in order to provide a comparison for a group receiving an experimental treatment, such as a new drug.
- Controlled observational study
A study to evaluate an intervention or test involving two (or more) groups of participants. One (the experimental group) receives the treatment, test or investigation that is being tested, and the other (the comparison or control group) receives an alternative or no intervention/test. The two groups are followed up to compare differences in outcomes.
- Cost–benefit analysis
A type of economic evaluation where both costs and benefits of healthcare treatment are measured in the same monetary units. If benefits exceed costs, the evaluation would recommend providing the treatment.
- Cost-effectiveness analysis
A type of economic evaluation comparing the costs and the effects on health of different treatments. Health effects are measured in ‘health-related units’, for example the cost of preventing one additional heart attack.
- Cost effectiveness
Value for money. A specific healthcare treatment is said to be ‘cost effective’ if it gives a greater health gain than could be achieved by using the resources in other ways.
- Cost-minimisation analysis
A form of cost-effectiveness analysis where the treatment alternatives are considered to be equally effective. Where treatments are equally effective the least costly is the most cost effective
- Cross-sectional study
The observation of a defined set of people at a single point in time or time period – a snapshot. (This type of study contrasts with a longitudinal study which follows a set of people over a period of time.)
- Data set
A list of required information relating to a specific disease.
- Decision analysis
The study of how people make decisions or how they should make decisions. There are several methods that decision analysts use to help people to make better decisions, including decision trees.
- Declaration of interest
A process by which members of a working group or committee ‘declare’ any personal or professional involvement with a company (or related to a technology) that might affect their objectivity. For example if their position or department is funded by a pharmaceutical company.
- Developmental age
An estimate of the functioning age equivalent of a child.
- Diagnosis
The identification of the nature and cause of symptoms in any individual.
- Diagnostic study
A study to assess the effectiveness of a test or measurement in terms of its ability to accurately detect or exclude a specific disease.
- Differential diagnosis
The conditions that may have similar features to each other and need to be considered in identifying a diagnosis
- Disability Living Allowance
A benefit (non-means tested) intended to provide financial support to persons caring for anyone with a disability.
- Double blind study
A study in which neither the subject (patient) nor the observer (investigator/clinician) is aware of which treatment or intervention the subject is receiving. The purpose of blinding is to protect against bias.
- Echolalia
Frequent repetition of set words and phrases
- Economic evaluation
A comparison of alternative courses of action in terms of both their costs and consequences. In health economic evaluations the consequences should include health outcomes.
- Economic model
A health economics model is a way of synthesising costs, outcomes, probabilities and decisions for part of a clinical pathway or a whole clinical pathway. They can be useful where decisions about the cost effectiveness of care depend on the effectiveness of multiple combinations of healthcare options (tests, treatment, long term follow-up). Economic models are simplifications of reality representing a complex process. Mathematical and statistical techniques are used to provide decision-makers with information about the likelihood that a decision is cost effective and the impact of changes in one part of the treatment pathway to the overall cost effectiveness of treatment for a specific condition.
- Educational psychology service
The educational psychology service provides consultation and advice in relation to the education and development of children and young people. It is a statutory service. Educational psychologists have gained a psychology degree and undertaken postgraduate professional training in educational psychology.
- Effectiveness
See Clinical effectiveness.
- Efficacy
The extent to which a specific treatment or intervention, under ideally controlled conditions (for example in a laboratory), has a beneficial effect on the course or outcome of disease compared to no treatment or other routine care.
- Empirical
Based directly on experience (observation or experiment) rather than on reasoning alone.
- Epidemiology
Study of diseases within a population, covering the causes and means of prevention.
- Evidence-based clinical practice
Evidence-based clinical practice involves making decisions about the care of individual patients based on the best research evidence available rather than basing decisions on personal opinions or common practice (which may not always be evidence based). Evidence-based clinical practice therefore involves integrating individual clinical expertise and patient preferences with the best available evidence from research
- Evidence based
The process of systematically finding, appraising and using research findings as the basis for clinical decisions.
- Evidence table
A table summarising the results of a collection of studies which, taken together, represent the evidence supporting a particular recommendation or series of recommendations in a guideline.
- Exclusion criteria
See Selection criteria.
- Experimental study
A research study designed to test if a treatment or intervention has an effect on the course or outcome of a condition or disease; where the conditions of testing are to some extent under the control of the investigator. Controlled clinical trials and randomised controlled trials are examples of experimental studies.
- Experimental treatment
A treatment or intervention (for example a new drug) being studied to see if it has an effect on the course or outcome of a condition or disease.
- Fragile X
A condition in which there is a genetic abnormality in the X chromosome associated with intellectual disability, mainly, but not exclusively, in boys.
- Generalisability
The extent to which the results of a study hold true for a population of patients beyond those who participated in the research. See also External validity.
- Genetic test
A test for genetic disorders which involves examination of an individual’s DNA. In the context of autism, it is often used to identify carriers of genes which code for specific coexisting conditions, or genetics sequences believed to be causative of autism.
- Global developmental delay
A term used to describe a delay in all aspects of development usually in young children before they are able to complete a standardised test of intellectual ability.
- Gold standard
A method, procedure or measurement that is widely accepted as being the best available.
- Grading of Recommendations Assessment, Development and Evaluation (GRADE)
A system for grading the quality of evidence and the strength of recommendations that can be applied across a wide range of interventions and contexts.
- Grey literature
Reports that are unpublished or have limited distribution, and are not included in bibliographic retrieval systems.
- Guideline recommendation
Course of action advised by the guideline development group on the basis of its assessment of the supporting evidence.
- Guideline
A systematically developed tool which describes aspects of a patient’s condition and the care to be given. A good guideline makes recommendations about treatment and care based on the best research available, rather than on opinion. It is used to assist clinician and patient decision-making about appropriate health care for specific clinical conditions.
- Health economics
A branch of economics which studies decisions about the use and distribution of healthcare resources.
- Heterogeneity
Lack of homogeneity. The term is used in meta-analyses and systematic reviews when the results or estimates of effects of treatment from separate studies seem to be very different – in terms of the size of treatment effects or even to the extent that some indicate beneficial and others suggest adverse treatment effects. Such results may occur as a result of differences between studies in terms of the patient populations, outcome measures, definition of variables or duration of follow-up.
- Hierarchy of evidence
An established hierarchy of study types, based on the degree of certainty that can be attributed to the conclusions that can be drawn from a well- conducted study. Well-conducted randomised controlled trials (RCTs) are at the top of this hierarchy. (Several large statistically significant RCTs which are in agreement represent stronger evidence than one small RCT, for example.) Well-conducted studies of patients’ views and experiences would appear at a lower level in the hierarchy of evidence.
- Homogeneity
Where the results of studies included in a systematic review or meta analysis are similar and there is no evidence of heterogeneity. Results are usually regarded as homogeneous when differences between studies could reasonably be expected to occur by chance. See also Consistency.
- I2
Statistical indication of the amount of heterogeneity between studies included in a meta-analysis.
- In-depth interview
A qualitative research technique. It is a face-to-face conversation between a researcher and a respondent with the purpose of exploring issues or topics in detail. Does not use preset questions, but is shaped by a defined set of topics or issues.
- Inconsistency
The unexplained heterogeneity that is not adequately explained by the study investigators arises from inconsistency of results or unexplained heterogeneity
- Indirectness
A type of bias that can occur when a comparison of intervention A versus B is not available, but A was compared with C and B was compared with C. Such studies allow indirect comparisons of the magnitude of effect of A versus B.
- Information bias
Pertinent to all types of study and can be caused by inadequate questionnaires (for example difficult or biased questions), observer or interviewer errors (for example lack of blinding), response errors (such as lack of blinding if patients are aware of the treatment they receive) and measurement error (for example a faulty machine).
- Intellectual disability
A broad concept of mental disability that encompasses mental retardation characterised by significantly impaired cognitive functioning and deficits in adaptive behaviours.
- IQ (Intelligence quotient)
An intelligence quotient is a score derived from one of many different standardised tests designed to assess intelligence.
- Isolated speech and language delay
A delay in speech or language or both without intellectual impairment or other developmental disorder
- Landau–Kleffner syndrome (LKS)
A rare form of epilepsy that only affects children. It is characterised by the sudden or gradual development of aphasia (the inability to understand or express language) and an abnormal brain wave recording (electro- encephalogram [EEG]) affecting the parts of the brain that control comprehension and speech. The disorder usually occurs in children between 5 and 7 years. The main epileptic activity happens during sleep. While many of the affected individuals have seizures, some do not, thus the epileptic activity may not be obvious to others but can be seen in a sleep EEG. The disorder is difficult to diagnose and may be misdiagnosed as autism, hearing impairment, learning disability, attention deficit disorder, learning difficulties or emotional/behavioural problems.
- Literature review
A process of collecting, reading and assessing the quality of published (and unpublished) articles on a given topic.
- Longitudinal study
A study of the same group of people at more than one point in time. This type of study contrasts with a cross-sectional study which observes a defined set of people at a single point in time.
- Looked after children
Children in the care of the local authority.
- MECP2 (methyl CpG binding protein 2)
A gene located on the long arm of the X chromosome that provides information for making a protein important in brain development. Mutations in this gene are responsible for most cases of classic Rett syndrome.
- Mental retardation
See Intellectual disability.
- Methodological quality
The extent to which a study has conformed to recognised good practice in the design and execution of its research methods.
- Methodology
The overall approach of a research project; for example the study will be a randomised controlled trial of 200 people over 1 year.
- Morbidity
Disease or disability or poor health due to any cause
- Mortality
Death.
- Multicentre study
A study where subjects were selected from different locations or populations, such as a cooperative study between different hospitals or an international collaboration involving patients from more than one country.
- Non-therapeutic support
General support without a therapeutic or healing aim.
- Objective measure
A measurement that follows a standardised procedure which is less open to subjective interpretation by potentially biased observers and study participants.
- Obsessive compulsive disorder (OCD)
Recurrent obsessional thoughts (ideas, urges or images that are unwanted and often distressing) or compulsive acts (behaviours/actions that have to be carried out repeatedly even if they make no sense).
- Observation
A research technique used to help understand complex situations. It involves watching, listening to and recording behaviours, actions, activities and interactions. The settings are usually natural, but they can be laboratory settings, as in psychological research.
- Observational study
In research about diseases or treatments, this refers to a study in which nature is allowed to take its course. Changes or differences in one characteristic (such as whether or not people received a specific treatment or intervention) are studied in relation to changes or differences in other(s) (such as whether or not they died), without the intervention of the investigator. There is a greater risk of selection bias than experimental studies.
- Odds ratio
Odds are a way of representing probability (such as in betting). In recent years, odds ratios have become widely used in reports of clinical studies. They provide an estimate (usually with a confidence interval) for the effect of a treatment. Odds are used to convey the idea of ‘risk’ and an odds ratio of 1 between two treatment groups would imply that the risks of an adverse outcome were the same in each group. For rare events the odds ratio and the relative risk (which uses actual risks and not odds) will be very similar. See also Relative risk, Risk ratio.
- Oppositional defiant disorder (ODD)
A persistent pattern of markedly defiant, disobedient, provocative behaviour to those in authority, clearly outside the normal range of behaviour for a child of the same age. The individual may blame others for their own mistakes, lose their temper easily and act in an angry, resentful or touchy manner.
- Outcome
The end result of care and treatment and/or rehabilitation. In other words, the change in health, functional ability, symptoms or situation of a person, which can be used to measure the effectiveness of care or treatment or rehabilitation. Researchers should decide what outcomes to measure before a study begins; outcomes are then assessed at the end of the study.
- P value
If a study is done to compare two treatments then the P value is the probability of obtaining the results of that study, or something more extreme, if there really was no difference between treatments. (The assumption that there really is no difference between treatments is called the ‘null hypothesis’.) Suppose the P-value was 0.03 (P = 0.03). What this means is that if there really was no difference between treatments then there would only be a 3% chance of getting the kind of results obtained. Since this chance seems quite low we should question the validity of the assumption that there really is no difference between treatments. We would conclude that there probably is a difference between treatments. By convention, where the value of P is below 0.05 (that is, less than 5%) the result is seen as statistically significant. Where the value of P is 0.001 or less, the result is seen as highly significant. P values tell us whether an effect can be regarded as statistically significant or not. The P value does not relate to how big the effect might be: for this we need the confidence interval.
- Pathological demand avoidance
Proposed by Professor Elizabeth Newson, Consultant Psychologist at the University of Nottingham, this is not a diagnosis in ICD-10 or DSM-IV-TR. It is considered to be part of the autism spectrum disorders but individuals with PDA are said to possess superficial social skills and to have a theory of mind, to mimic others and to be much more demand avoidant than those with ASD. They often engage in manipulative, domineering behaviour.
- Peer review
Review of a study, service or recommendations by those with similar interests and expertise to the people who produced the study findings or recommendations. Peer reviewers can include professional and/or patient/carer representatives.
- Pervasive development disorder
A term used in the ICD-10 and DSM-IV-TR classifications to describe the group of disorders characterised by qualitative abnormalities in reciprocal social interactions and patterns of communication and by restricted stereotyped repetitive repertoire of interests and activities pervasive of the individuals functioning in all situations. ASD is the equivalent term used in this guideline in the evidence statements and tables.
- Power
See Statistical power.
- Prevalence
Prevalence is a statistical concept referring to the number of cases of a disease that are present in a particular population at a given time.
- Primary care trust
A primary care trust is an NHS organisation responsible for improving the health of local people, developing services provided by local GPs and their teams and making sure that other appropriate health services are in place to meet local people’s needs.
- Primary care
Health care delivered to patients outside hospitals. Primary care covers a range of services provided by GPs, nurses and other healthcare professionals, dentists, pharmacists and opticians.
- Prognostic factor
Patient or disease characteristics, such as age or coexisting condition, which influence the course of the disease under study. In a randomised trial to compare two treatments, chance imbalances in variables (prognostic factors) that influence patient outcome are possible, especially if the size of the study is fairly small. In terms of analysis these prognostic factors become confounding factors. See also Prognostic marker.
- Prognostic marker
A prognostic factor used to assign patients to categories for a specified purpose – for example for treatment or as part of a clinical trial, according to the likely progression of the disease. For example, the purpose of randomisation in a clinical trial is to produce similar treatment groups with respect to important prognostic factors. This can often be achieved more efficiently if randomisation takes place within subgroups defined by the most important prognostic factors. Thus if age was strongly related to patient outcome then separate randomisation schemes would be used for different age groups. This process is known as stratified random allocation.
- Prospective study
A study in which people are entered into the research and then followed up over a period of time with future events recorded as they happen. This contrasts with studies that are retrospective.
- Protocol
A plan or set of steps which defines appropriate action. A research protocol sets out, in advance of carrying out the study, what question is to be answered and how information will be collected and analysed. Guideline implementation protocols set out how guideline recommendations will be used in practice by the NHS, both at national and local levels.
- Publication bias
Studies with statistically significant results are more likely to get published than those with non-significant results. Meta-analyses that are exclusively based on published literature may therefore produce biased results. This type of bias can be assessed by a funnel plot.
- Qualitative research
Qualitative research is used to explore and understand people’s beliefs, experiences, attitudes, behaviour and interactions. It generates non- numerical data, such as a patient’s description of their pain rather than a measure of pain. In health care, qualitative techniques have been commonly used in research documenting the experience of chronic illness and in studies about the functioning of organisations. Qualitative research techniques, such as focus groups and in-depth interviews, have been used in one-off projects commissioned by guideline development groups to find out more about the views and experiences of patients and carers.
- Quality adjusted life years (QALYs)
A measure of health outcome which looks at both length of life and quality of life. QALYS are calculated by estimating the years of life remaining for a patient following a particular care pathway and weighting each year with a quality of life score (on a 0 to 1 scale). One QALY is equal to 1 year of life in perfect health, or 2 years at 50% health, and so on.
- Quantitative research
Research that generates numerical data or data that can be converted into numbers, for example clinical trials or the national Census which counts people and households.
- Quasi experimental study
A study designed to test if a treatment or intervention has an effect on the course or outcome of disease. It differs from a controlled clinical trial and a randomised controlled trial in that: a) the assignment of patients to treatment and comparison groups is not done randomly, or patients are not given equal probabilities of selection, or b) the investigator does not have full control over the allocation and/or timing of the intervention, but nonetheless conducts the study as if it were an experiment, allocating subjects to treatment and comparison groups.
- Random allocation, randomisation
A method that uses the play of chance to assign participants to comparison groups in a research study, for example by using a random numbers table or a computer-generated random sequence. Random allocation implies that each individual (or each unit in the case of cluster randomisation) being entered into a study has the same chance of receiving each of the possible interventions.
- Randomised controlled trial
A study to test a specific drug or other treatment in which people are randomly assigned to two (or more) groups: one (the experimental group) receives the treatment that is being tested, and the other (the comparison or control group) receives an alternative treatment, a placebo (dummy treatment) or no treatment. The two groups are followed up to compare differences in outcomes to see how effective the experimental treatment was. (Through randomisation, the groups should be similar in all aspects apart from the treatment they receive during the study.)
- Referral
The process of passing from one service or stage in the health service to another.
- Retrospective study
A study that deals with the present/past and does not involve studying future events. This contrasts with studies that are prospective.
- Review
Summary of the main points and trends in the research literature on a specified topic. A review is considered non-systematic unless an extensive literature search has been carried out to ensure that all aspects of the topic are covered and an objective appraisal made of the quality of the studies.
- Risk assessment
The process of quantifying the probability of a harmful effect.
- Risk ratio
Ratio of the risk of an undesirable event or outcome occurring in a group of patients receiving experimental treatment compared with a comparison (control) group. The term relative risk is sometimes used as a synonym of risk ratio.
- Safety netting
The provision of support for patients in whom the clinician has some uncertainty as to whether the patient has a self-limiting illness and is concerned that their condition may deteriorate. Safety netting may take a number of forms, such as dialogue with the patient or carer about symptoms and signs to watch for, advice about when to seek further medical attention, review after a set period, and liaising with other healthcare services.
- Sample
A part of the study’s target population from which the subjects of the study will be recruited. If subjects are drawn in an unbiased way from a particular population, the results can be generalised from the sample to the population as a whole.
- Sampling frame
A list or register of names which is used to recruit participants to a study.
- Sampling
Refers to the way in which participants are selected for inclusion in a study.
- School transitions
The process of moving from one school year to another and particularly from primary to secondary or secondary to further education.
- Secondary care
Care provided in hospitals.
- Selection bias
Selection bias has occurred if the characteristics of the sample differ from those of the wider population from which the sample has been drawn or there are systematic differences between comparison groups of patients in a study in terms of prognosis or responsiveness to treatment.
- Selection criteria
Explicit standards used by guideline development groups to decide which studies should be included and excluded from consideration as potential sources of evidence.
- Semi-structured interview
Structured interviews involve asking people pre-set questions. A semi-structured interview allows more flexibility than a structured interview. The interviewer asks a number of open-ended questions, following up areas of interest in response to the information given by the respondent.
- Sensitivity
In diagnostic testing, it refers to the chance of having a positive test result given that you have the disease. 100% sensitivity means that all those with the disease will test positive, but this is not the same the other way around. A patient could have a positive test result but not have the disease – this is called a ‘false positive’. The sensitivity of a test is also related to its ‘negative predictive value’ (true negatives) – a test with a sensitivity of 100% means that all those who get a negative test result do not have the disease. To fully judge the accuracy of a test, its specificity must also be considered.
- Single blind study
A study in which either the subject (patient/participant) or the observer (clinician/investigator) is not aware of which treatment or intervention the subject is receiving.
- Social communication disorder
A descriptive term for a problem in social interaction and social communication but not currently a diagnosis. This may change in DSM-V.
- Specificity
In diagnostic testing, it refers to the chance of having a negative test result given that you do not have the disease. 100% specificity means that all those without the disease will test negative, but this is not the same the other way around. A patient could have a negative test result yet still have the disease – this is called a ‘false negative’. The specificity of a test is also related to its ‘positive predictive value’ (true positives) – a test with a specificity of 100% means that all those who get a positive test result definitely have the disease. To fully judge the accuracy of a test, its sensitivity must also be considered.
- Standard deviation
A measure of the spread, scatter or variability of a set of measurements. Usually used with the mean (average) to describe numerical data.
- Statistical power
The ability of a study to demonstrate an association or causal relationship between two variables, given that an association exists. For example, 80% power in a clinical trial means that the study has a 80% chance of ending up with a P value of less than 5% in a statistical test (that is, a statistically significant treatment effect) if there really was an important difference between treatments (for example 10% versus 5% mortality). If the statistical power of a study is low, the study results will be questionable (the study might have been too small to detect any differences). By convention, 80% is an acceptable level of power. See also P value.
- Stereotypes
Repetitive, stereotyped, purposeless movements, actions, body patterns, speech patterns. They include hand flapping, clapping, slapping, fluttering, rocking or facial movements.
- Structured interview
A research technique where the interviewer controls the interview by adhering strictly to a questionnaire or interview schedule with preset questions.
- Study checklist
A list of questions addressing the key aspects of the research methodology that must be in place if a study is to be accepted as valid. A different checklist is required for each study type. These checklists are used to ensure a degree of consistency in the way that studies are evaluated.
- Study population
People who have been identified as the subjects of a study.
- Study quality
See Methodological quality.
- Study type
The kind of design used for a study. Randomised controlled trial, case – control study and cohort study are all examples of study types.
- Subject
A person who takes part in an experiment or research study.
- Survey
A study in which information is systematically collected from people (usually from a sample within a defined population).
- Syndrome
The frequent co-occurrence of the same signs and/or symptoms constitutes a syndrome.
- Systematic error
Refers to the various errors or biases inherent in a study. See also Bias.
- Systematic review
A review in which evidence from scientific studies has been identified, appraised and synthesised in a methodical way according to predetermined criteria. May or may not include a meta-analysis.
- Systematic
Methodical, according to plan; not random.
- Systemic
Involving the whole body.
- Target population
The people to whom guideline recommendations are intended to apply. Recommendations may be less valid if applied to a population with different characteristics from the participants in the research study, for example in terms of age, disease state, social background.
- Tertiary centre
A major healthcare/medical centre providing complex treatments which receives referrals from both primary and secondary care. Sometimes called a tertiary referral centre. See also Primary care and Secondary care. Mental health services use the terms ‘tiers 1–4, with tier 4 being the equivalent of a tertiary service.)
- Triple blind study
A study in which the statistical analysis is carried out without knowing which treatment patients received, in addition to the patients and investigators/clinicians being unaware which treatment patients were getting.
- Uncontrolled observational study
A type of study where there is no control group.
- Univariate analysis
Analysis of data on a single variable at a time.
- Validity
Assessment of how well a tool or instrument measures what it is intended to measure. See also External validity, Internal validity.
- Variable
A measurement that can vary within a study, for example the age of participants. Variability is present when differences can be seen between different people or within the same person over time, with respect to any characteristic or feature which can be assessed or measured.
- Yield
The outcome of a biomedical test that can suggest clinically relevant
findings.
