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Related Experiment Videos

Biases in prevalent cohorts.

R Brookmeyer1, M H Gail

  • 1Department of Biostatistics, Johns Hopkins University School of Hygiene and Public Health, Baltimore, Maryland 21205.

Biometrics
|December 1, 1987
PubMed
Summary

This study investigates biases in Acquired Immunodeficiency Syndrome (AIDS) research when using follow-up time instead of time since infection. Understanding these biases is crucial for accurate interpretation of AIDS natural history studies.

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Area of Science:

  • Epidemiology
  • Biostatistics
  • Infectious Diseases

Background:

  • Natural history studies of Acquired Immunodeficiency Syndrome (AIDS) often rely on individuals infected before study enrollment.
  • The preclinical course of AIDS is best studied using time since initial infection, but this is often unknown in prevalent cohort studies.

Purpose of the Study:

  • To investigate biases introduced by using follow-up time instead of time since infection in AIDS natural history studies.
  • To evaluate the impact of these biases on estimating cumulative distribution functions and hazard ratios in proportional hazards models.

Main Methods:

  • Analysis of biases in statistical estimations for AIDS natural history.
  • Investigation of proportional hazards models with fixed and time-dependent covariates.
  • Establishment of bounds on biases, considering the epidemic curve's shape.

Main Results:

  • Follow-up time introduces biases in estimating AIDS progression metrics compared to time since infection.
  • The magnitude of bias is influenced by the epidemic curve's characteristics.
  • Bounds for these biases were established, providing quantitative insights.

Conclusions:

  • Results aid in interpreting prevalent cohort studies of AIDS.
  • Comparing prevalent and incident cohort studies using these findings can assess consistency.
  • Accurate interpretation of AIDS progression requires accounting for time-since-infection biases.

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