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Lead time bias occurs if testing increases the perceived survival time without affecting the course of the disease. Lead time bias happens when survival time appears longer because diagnosis was done earlier (for instance, by screening), irrespective of whether the patient lived longer.
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Lead time bias implies that by screening individuals are diagnosed with a disease earlier than without screening, but that early detection does not postpone the time of death. This figure shows the survival times for a) patients diagnosed clinically and b) patients diagnosed by screening.
Nov 8, 2021 · Two other important forms of selection bias are lead-time bias and length time bias. Lead-time bias occurs in the context of disease diagnosis. In general, it occurs when new diagnostic testing allows detection of a disease in an early stage, causing a false appearance of longer lifespan or improved outcomes. [14]
- Aleksandar Popovic, Martin R. Huecker
- 2023/06/20
- Rutgers NJMS, University of Louisville
Lead time bias occurs when cases who were detected by screening seem to have survived longer than diagnosed cases just because the disease was detected earlier, not because death was delayed. For example: Consider the following 2 scenarios of a patient who suffers from dementia since the age of 65:
Lead-time and length-time bias are critical in analysing clinical trials involving time-to-event analysis. This article aims to simplify the concepts of lead-time and length-time bias and some solutions for controlling them.
Aug 31, 2010 · Lead-time bias is related to a study assessing the impact of a screening test on survival. Even if people die at the same time with or without early diagnosis, the length of time between early detection of the disease attributable to the screening test can appear as a gain in survival.
Mar 27, 2020 · Lead‐time bias causes problems when the survival of patients with a particular disease is being compared between regions with and without screening programmes. In nephrology, it has become widely known as a problem of cohort studies comparing policies of early and late start of dialysis.
