Table 1Terminology for reporting on harms

Active surveillance of harmsParticipants are asked in structured questionnaires or interviews about the occurrence of specific adverse events, or predefined laboratory or other diagnostic tests are performed at prespecified time intervals.
Adverse effectA harmful or undesirable outcome that occurs during or after the use of a drug or intervention for which there is at least a reasonable possibility of a causal relation.
Adverse eventA harmful or undesirable outcome that occurs during or after the use of a drug or intervention but is not necessarily caused by it. When causality is uncertain or the purpose of the Comparative Effectiveness Review is to establish causality, “adverse event” should generally be the default term over “adverse effect” or “adverse reaction/adverse drug reaction.”
Adverse reaction/adverse drug reactionAn adverse effect specifically associated with a drug.
ComplicationsA term often used to describe adverse events following surgery or other invasive interventions.
HarmsThe totality of all possible adverse consequences of an intervention.
Passive surveillance of harmsParticipants are not specifically asked about or tested for the occurrence of adverse events. Rather, adverse events are identified based on patient reports made on their own initiative.
Risk-benefit ratioA common expression for the comparison of overall harms and benefits. However, because benefits and harms of an intervention are usually very different in character and are measured on different scales, a true “risk-benefit ratio” is rarely calculable. In addition, there may be several distinct benefits and harms. A preferred term is “balance of benefits and harms.”
SafetySubstantive evidence of an absence of harm. Do not use this term (or the term “safe”) when evidence on harms is simply absent or insufficient.
Serious adverse eventAny adverse event with serious medical consequences, including death, hospital admission, prolonged hospitalization, and persistent or significant disability or incapacity.
Severe adverse eventAn adverse event whose intensity is considered severe (including “nonserious” adverse events). For example, a rash could be “severe” but not “serious” (i.e., not resulting in death, hospital admission, prolonged hospitalization, or persistent or significant disability).
Side effectsUnintended drug effects (beneficial or harmful) given at doses normally used for therapeutic effects. Use of this term may tend to understate the important of harms because the word “side” may be perceived to suggest secondary importance.
TolerabilityThis term is often used imprecisely but should be used to refer to a patient’s or subject’s ability or willingness to tolerate or accept unpleasant drug-related adverse events without serious or permanent sequelae.
ToxicityThe term “toxicity” is used in pharmacology and microbiology to refer to the quality of being poisonous, especially the degree of virulence of a toxic microbe or of a poison. It is often measured in terms of the specific target affected (e.g., cytotoxicity or hepatotoxicity). In the context of systematic reviews, the term is often used to refer to laboratory-determined abnormalities, such as elevated liver function tests. However, the terms “abnormal laboratory measurements” and “laboratory abnormalities” are more specific and appropriate.

From: Assessing Harms When Comparing Medical Interventions

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