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Bias in case-control studies. A review.

Open access
Kopec, J A, Esdaile, J M·1990·Journal of Epidemiology and Community Health
DOI 10.1136/jech.44.3.179PMC PMC1060638
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Abstract

It has been widely accepted that one reason for inconsistent or contradictory results of epidemiologic studies is bias.Therefore, an appreciation of potential sources of bias has become a critical issue in epidemiology.A large number of different sources and possible mechanisms of bias have been described but a consistent terminology has not evolved.Different authors have used different terms when referring to essentially the same type of bias.For example, Kleinbaum et al' and Rothinan2 classify biases into selection bias, information bias and confounding.Sackett offered a more detailed classification, with five major types of sampling bias (eg, admission rate bias, membership bias) and four types of measurement bias (eg, diagnostic suspicion bias, recall bias).3Feinstein distinguishes, inter alia, among susceptibility bias, performance bias, transfer bias and detection bias.4Last's Dictionary of epidemiology5 gives definitions of 26 biases but fails to mention many of the terms proposed by other authors.It is not our objective to provide a comprehensive list of biases, or to propose a new, improved taxonomy.Our purpose is to review the most common threats to validity in the design of case-control studies-commonly regarded as being particularly susceptible to bias-and to discuss some useful strategies in dealing with these problems.Certain issues will not be addressed, notably methods of controlling confounding, and the statistical analysis of case- control studies.Greenland and Morgenstern, case-control studies are distinguished from cohort studies by their use of "outcome-selective sampling".1oMiettinen rejects the case-control versus cohort duality entirely.In his view, the "case-referent strategy" consists in: (1) identifying and classifying all ofthe cases in the "study base"a, defined as the "population experience captured in a study", and (2) drawing a sample of the base to obtain information on the exposure.12 A good illustration of this concept is a "nested", or "within cohort" case-control study, which can be regarded as an efficient form of the cohort design, rather than an entirely different type of study.'3It may be noted that the two aspects (or "axes") of the design, ie, order of measurement and method of sampling, are interdependent.The reason for determining exposure status for all subjects in most cohort studies is to obtain as valid information as possible for the relatively few cases-to-be.Therefore, in cohort studies all potential cases are classified as exposed or unexposed.The logic behind the case-control method is to make the design more efficient by classifying only the actual cases, since information about the source population can be obtained by sampling.This, however, implies a particular order of measurement (directionality), namely ascertaining the outcome first.Measuring exposure for all members of the study population after the cases have been ascertained is unnecessary and impractical, if the disease is rare.

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  • The study minimised the potential for misclassification by using hospital based fractures as the outcome and by considering cumulative levothyroxine dosage over the previous year rather than a single prescription to estimate drug use.

    “We minimised the potential for misclassification by using hospital based fractures as our outcome and by considering cumulative levothyroxine dosage over the previous year rather than a single prescription to estimate drug use.66”

    From Levothyroxine dose and risk of fractures in older adults: nested case-control study (2011) · cites this paper as [66]

    The review’s “Secondary Base” section says that verifying diagnoses with auxiliary sources, including hospital records, can reduce outcome misclassification. Its “Measurement of Exposure” section favors improved measurement quality, but does not address fractures, levothyroxine, or whether cumulative dosage over a year is more accurate than a single prescription. Page numbers were not supplied for these passages. (LLM, conf=0.82)

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Research works printed but not linked: 1

  1. Poole C. Exceptions to the rule about nondifferential misclassification (Abstract). AmJEpidemiol 1985; 122: 508.

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Authors
Kopec, J. A., & Esdaile, J. M.
Affiliations
  • McGill University (CA)
  • Montreal General Hospital (CA)
ORCID
Venue
Journal of Epidemiology and Community Health
Publisher
BMJ
Published
1990-09
Volume
44
Issue
3
Pages
179-186
ISSN
  • 0141-7681 (ISSN-L)
  • 0143-005X
  • 1470-2738
DOI
10.1136/jech.44.3.179
PMC
PMC1060638
OpenAlex
W2073495439
Cited by
190
References
71
Citations by year
2026: 3 · 2025: 9 · 2024: 6 · 2023: 10 · 2022: 8 · 2021: 14 · 2020: 16 · 2019: 18 · 2018: 15 · 2017: 18 · 2016: 4 · 2015: 11 · 2014: 9 · 2013: 5 · 2012: 12
FWCI
2.34
Type
journal article
Language
en
Open access
Locations
  • Journal of Epidemiology & Community Health (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Epidemiology
  • Social Sciences › Decision Sciences › Statistics, Probability and Uncertainty › Meta-analysis and systematic reviews
  • Health Sciences › Medicine › Oncology › Global Cancer Incidence and Screening
Keywords
case-control study, bias, selection bias, information bias, confounding, recall bias, measurement bias, sampling bias, nested case-control study, research validity, exposure assessment, exposure misclassification
MeSH terms
Humans, Population Surveillance, Bias, Case-Control Studies, Randomized Controlled Trials as Topic

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