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National Clinical Guideline Centre (UK). Infection: Prevention and Control of Healthcare-Associated Infections in Primary and Community Care: Partial Update of NICE Clinical Guideline 2. London: Royal College of Physicians (UK); 2012 Mar. (NICE Clinical Guidelines, No. 139.)

Appendix KSystematic review of health related quality of life for symptomatic UTI

K.1. Introduction

In cost-utility analyses, measures of health benefit are valued in terms of quality adjusted life years (QALYs). The QALY is a measure of a person’s length of life weighted by a valuation of their health related quality of life (HRQoL) over that period. The quality of life weighting comprises two elements: the description of changes in HRQoL and an overall valuation of that description.

In order to ensure comparability and consistency across appraisals and reduce bias in the selection of values, the NICE reference case 315 requires that:

  • Measurement of changes in HRQoL should be reported directly from patients
  • Valuation of changes in patients’ HRQoL should be based on public preferences elicited using a choice-based method…such as the time-trade-off or standard gamble, but not rating scale…in a representative sample of the UK population
  • Use of utility estimates from published literature must be supported by evidence that demonstrates that they have been identified and selected systematically.

To date, the majority of existing economic evaluations which include urinary tract infection as a health state 131,153,474,500 refer to an analysis by Barry et al (1997) 33 in which the Index of Well Being (IWB) was used to estimate the quality of life experienced by young women with UTI.

The IWB was first introduced in the 1970s as one of the first attempts to develop a generic measurement of health utility. Using medical textbook case descriptions and items from community-wide health surveys, a series of 29 function levels (defined across three dimensions: mobility, physical activity, and social activity) and 42 symptom complexes were described 351. By randomly combining different functional levels and symptoms complexes across five different age groups, a matrix of 400 case descriptions was developed to represent a wide range of health states that may exist within a population. In order to derive weights or social preferences, a group of 62 American nurses and non-medical graduate students were then asked to rank each case description according to its desirability by placing it on a 16 point scale.

The IWB was the first instrument specifically designed to measure quality of life for the estimation of QALYs. For a long time, it was also one of only a few available measures. However, because it has not been used to elicit health status from patients with UTI and preference-weightings are neither representative of the general population nor elicited according to time-trade-off or standard gamble techniques, it was deemed an unsuitable source for the purposes of our economic evaluation.

The aim of this review was to systematically search the literature for generic preference-based measures of health derived from patients experiencing UTI, severe UTI and UTI-associated bacteraemia in order to identify appropriate utility values for our cost-utility analysis of intermittent self catheterisation.

K.2. Search strategy

We conducted a systematic search of the literature using the electronic databases Medline (Ovid MEDLINE(R) In-Process & Other Non-Indexed Citations and Ovid MEDLINE(R) 1948 to Present) and Embase (Ovid 1980 to 2010 week 47). A list of the search terms used in Medline is provided in Appendix F.2.4. This search strategy was adapted for use in Embase. In addition to these biomedical databases, the NHS Economic Evaluations Database (NHS EED) and Health Technology Assessment (HTA) databases (via the Centre for Reviews and Dissemination (CRD) interface) and the Health Economics Evaluations database (HEED) were searched for relevant literature. The terms used to search HEED are shown in Appendix F.2.4. These terms were adapted for the CRD interface to search the NHS EED and HTA databases. Both databases were searched from their date of inception to 3rd December 2010.

In February 2011, the Cost-Effectiveness Analysis Registry was searched for utility weights using the keywords ‘urinary tract infection’, ‘bladder infection’, ‘cystitis’, ‘pylonephritis’, ‘kidney infection’ and ‘bacteraemia/bacteraemia’ in the basic search field. The reference search section of the EuroQol website was searched using the same terms.

Studies presenting utility values derived from a generic HRQoL measurement tool or expert opinion were retrieved for full review based on title and abstract sifting. In addition to generic preference-based utility measures such as the EQ-5D, studies using the SF-12 and SF-36 instruments were also included. Although these instruments are not preference-based, there are several established mapping functions which allow the estimation of preference-based utility scores using these descriptive systems.

Studies using disease-specific instruments were excluded. Although mapping techniques could theoretically be extended to disease specific instruments, the use of mapping functions beyond the Short Form questionnaires is currently limited. Also excluded were studies published in a language other than English.

When the method of elicitation or included health states could not be determined from the abstract, full papers were retrieved for further examination. The reference lists of all retrieved studies were also searched for relevant sources.

There is a wide range of clinical manifestations and anatomic levels used to categorise UTI. For the purposes of this review, health states described in the literature were categorised according to the following criteria: ‘UTI’ was used to refer to an infection confined to the lower urinary tract or bladder; ‘severe UTI’ to describe an upper urinary tract infection, acute pyelonephritis, or any UTI requiring intravenous treatment or hospitalisation; ‘UTI-associated bacteraemia’ was used to refer to a blood stream infection with urinary tract origin.

K.3. Results

A total of 529 papers were identified by the MEDLINE and EMBASE search. Excluding duplicates, a further 98 were identified from HEED. The Cost-Effectiveness Analysis Registry returned six results (three of which were identified in the MEDLINE & EMBASE search) and the EuroQol website identified seven studies (none of which were identified in the MEDLINE EMBASE search). One additional relevant publication was uncovered by supplementary citation searching.

Eleven studies (reported in fifteen separate papers) met our inclusion criteria. With the exception of two papers 159,445 which were identified through the Cost-Effectiveness Analysis Registry and citation searching, all were retrieved through MEDLINE and EMBASE. Six studies reported utility values elicited using a method a method other than time-trade-off or standard gamble, or by expert opinion. Five elicited utility values using a validated generic measure of HRQoL; just two of these studies measured quality of life using a generic preference-based measure.

Given the heterogeneity between studies in terms of patient characteristics and elicitation methods, there was no attempt to pool results. Instead, the population, methods and results of each study are reported below. More detailed reports of studies using preference-based measures and non-preference based measures with mapped estimates are presented in Table 39 and Table 40.

Table 39. Sample characteristics and data collection methods of studies using validated generic health state utility measures.

Table 39

Sample characteristics and data collection methods of studies using validated generic health state utility measures.

Table 40. Generic preference-based health utility values for patients experiencing UTI and severe UTI.

Table 40

Generic preference-based health utility values for patients experiencing UTI and severe UTI.

The search did not identify any primary studies of quality of life in patients with UTI-associated bacteraemia. Several studies contained utility values for sepsis; however, the infections were not of urinary tract origin and were thought to describe a more severe health state than the one under review.

K.3.1. Health state values derived by a generic measure of health weighted with a method other than time-trade-off or standard gamble, or elicited by time-trade-off or standard gamble alone

As previously discussed, Barry and colleagues (1997) 33 estimated a monthly disutility of 0.2894 for persistent dysuria and a disutility of 0.3732 for patients with pylonephritis using the IWB.

Ackerman et al. (2000) 5 elicited utility values from 13 men with moderate to severe benign prostatic hyperplasia (BPH). A series of BPH-specific health states were described according to three treatments, five short-term clinical events, and 17 possible long-term outcomes. In order to assign preference weights to each health state, the standard gamble was administered to patients by a trained interviewer. Results were reported according to patients’ risk attitudes. Risk-averse individuals (n = 6) reported an average utility value of 97.2 (SE 1.1; range 94–99) for severe UTI, while non-risk-averse patients (n = 7) reported an average value of 89.3 (SE 4.6; range 77–99).

In 1998, Gold et al 159 published a catalogue of 130 health state values developed using the Health and Activity Limitation Index (HALex). The HALex score was derived from the answers to two questions asked in the US National Health Interview Survey about activity limitations and self-rated health. Between 1987 and 1992, 84 443 people were included in the survey; at the time of each survey, a total of 384 people reported having a bladder infection and 387 reported having a kidney infection. Based weights developed from a correspondence analysis and multi-attribute utility model, bladder infections were assigned a mean HRQoL value of 0.73 (median 0.84; IQR 0.4) and kidney infection a value of 0.66 (median 0.63; IQR 0.36).

K.3.2. Health state values based on expert opinion

Unable to find relevant utility data for patients with acute pylonephritis, Yen and colleagues (2003) 525 asked a panel of six emergency physicians and internists to develop utility weights using the standard reference gamble technique. Based on the results from the expert panel, pylonephritis was assigned a QALY of 0.90, 0.87 for pylonephritis with mild side effects, and 0.81 for pylonephritis with serious side effects.

Sonnenberg et al (2004) 445 elicited the utility associated with UTI from ‘a convenience sample of female members of the research team and advisor pannel’ using the time-trade-off technique. They report a short-term disutility of 0.0192 associated with UTI. Similarly, Lawler and colleagues (1991) 254 used their own judgement to arrive at an estimated utility value of 0.99 for patients suffering from UTI.

K.3.3. Health state values elicited using a generic preference-based measure of health or generic measure of health with validated mapping algorithm

Two studies measured the impact of UTI on quality of life among otherwise healthy adult women. In 2000, Ellis and Verma 120 conducted a case-control study to evaluate the effect of UTI on quality of life in women using the SF-36. Although the authors mentioned that quality of life was lower in patients with severe UTI, these results were not reported. The authors of this study were contacted for further information; a reply was received but additional data was not available. The algorithm published by Ara and Brazier (2008) 21 was used to map the mean reported SF-36 dimension scores to EQ-5D health state values (Table 40).

More recently, Ernst et al (2005) 123 conducted a study to evaluate quality of life among 157 women with acute cystitis and the impact of treatment on quality of life. Patients were randomised to receive either trimethoprim/ sulfamethoxazole for 3 days or nitrofuratonin for 7 days. The Quality of Well Being (QWB) questionnaire was administered at baseline and 3, 7, 14, and 28 days after the initial visit. The QWB value at baseline (i.e. suffering from UTI) was 0.68 (SD 0.03) and 0.81 (SD 0.11) at 28 day follow-up (i.e. cured from UTI). Patients who experienced clinical cure had significantly better quality of life scores at days 3 (0.77 vs. 0.72), 7 (0.82 vs. 0.71) and 14 (0.83 vs. 0.76) compared to those who failed treatment; this difference was not due to treatment assignment. To our knowledge, this is the only study to examine the effect of treatment failure on quality of life in patients with UTI.

Maxwell et al (2009) 286 measured quality of life in older adults living in care homes using the Health Utilities Index Mark 2 (HUI2). Results were reported according to the presence or absence of several different clinical conditions, including urinary tract infection. The HUI2 was scored according to the published Canadian preference weights.

Two different research groups have used the Short Form questionnaires to evaluate the effect of UTI on individuals with spinal cord injury. Haran and colleagues have published a series of articles reporting the use of the SF-36 in individuals with spinal cord injury 174,257,258. The 2005 paper specifies that individuals suffering UTI have worse general health, vitality, and mental health domain scores than those who do not have UTI, but does not report specific domain values for these groups. This paper cites a website containing SF-36 data stratified by age, sex, and impairment group, but at the time of press this link was not functional. The authors were contacted but were unable to provide additional information. In 2008, the group published mapped SF-6D values derived from both the full SF-36 and the recalculated SF-12 scores 257.

A long-term cohort study of individuals with spinal cord injury (SCI) by Vogel and co-workers (2002)483 was identified in the literature search. This study reported a statistically significant difference in SF-12 scores for subjects suffering from UTI and severe UTI compared to patients who did not experience UTI. However, SF-12 values for these groups were not reported. Upon request, the research group provided us with anonymised patient-level SF-12 responses from their most recent follow-up 482,529. Five of the 415 cases contained missing data; they were assumed to be missing completely at random and were omitted from the analysis. Using an algorithm developed by Gray et al (2006) 164 and the accompanying spreadsheet available on the Health Economics Research Centre website 180, EQ-5D values were estimated based on raw SF-12 data. Because the Gray algorithm contains random number generators, it was necessary to run a simulation (10 000 times) in order to obtain mean EQ-5D estimates for each health state. All calculations were performed using Microsoft Excel 2007. The results of the mapping, as well as the physical and mental component summary scores are presented in Table 40.

K.4. Discussion

Health state utility values are key parameters in economic decision models. Values for equivalent health states can vary substantially depending on the measure used and method of valuation 46. This has a direct impact on the results of economic analyses.

This review identified utility values elicited from adult women, older adults and adults with spinal cord injuries using generic preference-based measured compatible with the NICE reference case. Currently, similar health related quality of life values do not appear to to have been elicited from chidren experiencing UTI. By performing this review we were able to systematically identify and select the most appropriate utility values with which to populate the economic model and identify important gaps in the literature.

K.4.1. Acknowledgements

We are very grateful to Drs Kathy Zebracki, Lawrence Vogel, Caroline Anderson, and Ms. Kathleen Chlan for providing us with access to SF-12 data collected from their research cohort and for their comments on the manuscript.

Copyright © 2012, National Clinical Guideline Centre.

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The use of registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant laws and regulations and therefore for general use.

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Cover of Infection: Prevention and Control of Healthcare-Associated Infections in Primary and Community Care
Infection: Prevention and Control of Healthcare-Associated Infections in Primary and Community Care: Partial Update of NICE Clinical Guideline 2.
NICE Clinical Guidelines, No. 139.
National Clinical Guideline Centre (UK).

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