A study was conducted to assess the relationship between race and end-stage renal disease. Two groups of pathologists independently studied specimens from 1,000 kidney biopsies. The first group of pathologists was aware of the race of the patient from whom the biopsy came, while the second group was blinded from the patient's race. The first group reported "hypertensive nephropathy" much more frequently for Black patients than the second group. This study best demonstrates which of the following types of bias?

Question

A study was conducted to assess the relationship between race and end-stage renal disease.  Two groups of pathologists independently studied specimens from 1,000 kidney biopsies.  The first group of pathologists was aware of the race of the patient from whom the biopsy came, while the second group was blinded from the patient's race.  The first group reported "hypertensive nephropathy" much more frequently for Black patients than the second group.  This study best demonstrates which of the following types of bias?

Quizplus · Accepted Answer

Observer bias occurs when the investigator's decision is adversely affected by knowledge of the exposure status. In this case, some pathologists' decisions were influenced by the fact that hypertensive nephropathy is a common cause of endstage renal disease in the Black population. The pathologists who were blinded to the subjects' race were not under this influence, so their interpretation was more unbiased. (Choice A) Confounding is present when at least part of the exposure-disease relationship can be explained by another variable (confounder). No information on possible confounders is given in this scenario. (Choice B) Respondent bias is present when the outcome is obtained by the patient's response, and not by objective diagnostic methods (e.g., migraine headache). In this case, the diagnosis was ascertained via kidney biopsy. (Choice C) Recall bias results from inaccurate recall of past exposure by patients. It is not applicable to this case. (Choice D) Selection bias results from the manner in which the subjects are selected for the study, or from the selective losses from the follow-up. Educational objective: Observer bias occurs when the investigator's decision is adversely affected by knowledge of the exposure status.

A Study Was Conducted to Assess the Relationship Between Race