A research group is studying a new biomarker for prostate cancer screening in a random sample of asymptomatic men 50 years of age. As the majority of prostate cancers are slowly progressive, the investigators are concerned that the benefits of the new screening tool will be overestimated due to detection of a disproportionate number of slowly progressive, benign cases. The research group is most likely concerned about the presence of which of the following types of bias?

Question

A research group is studying a new biomarker for prostate cancer screening in a random sample of asymptomatic men >50 years of age.  As the majority of prostate cancers are slowly progressive, the investigators are concerned that the benefits of the new screening tool will be overestimated due to detection of a disproportionate number of slowly progressive, benign cases.  The research group is most likely concerned about the presence of which of the following types of bias?

Quizplus · Accepted Answer

Explanation: 11ec2b69_c182_fbda_8f63_716d6434af79_MD0005_00 The researchers in this scenario are concerned about length-time bias. In the case of prostate cancer (as with many other chronic diseases), some patients have a rapidly progressive disease course with a high mortality while others have a slowly progressive, more indolent course. Those with slowly progressive disease tend to be asymptomatic for a longer time period, increasing the likelihood that they will be diagnosed based on screening rather than clinical symptoms. These slowly progressive cases also have lower mortality, which may give the impression that screening improves disease survival (but in actuality, it only identifies more benign cases). (Choice A) The Hawthorne effect occurs when participants modify their behavior due to their awareness of the fact that they are being studied. However, this study is not assessing subject behavior. (Choice B) Lead-time bias is another common bias seen with screening tests. It occurs when a test diagnoses a disease earlier and as a result, the time from diagnosis until death appears prolonged even though there actually is no improvement in survival. This is different from length-time bias, which identifies more benign cases. Lead-time bias (Choice D) Observer bias can occur when researchers subconsciously or consciously manipulate aspects of a study often due to their own preconceived expectations. However, there is no evidence that the researchers in this example are skewing results in favor of the screening test. (Choice E) Sampling bias occurs when study subjects are collected in a non-random process that is more likely to exclude some members of the target population than others. Sampling bias is unlikely to be a concern in this study, as the subjects were randomly collected. Educational objective: Length-time bias occurs when the survival benefits of a screening test are overstated due to the detection of a disproportionate number of slowly progressive, benign cases.

A Research Group Is Studying a New Biomarker for Prostate