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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:
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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.
Lead-time bias occurs when the detection of a disease earlier does not alter the predetermined time of death (ie, discovering an incurable disease earlier and applying an ineffective therapy may seem to offer a survival benefit compared with therapies that are started later in the disease process).
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
- Background
- Example
- Impact
- Preventive Steps
The premise of screening is that it allows earlier detection and treatment of a disease or health condition, leading to a greater chance of cure or at least longer survival. A disease or condition is clinically diagnosed after an individual display’s certain signs and symptoms. Individuals with disease detected through population screening receive ...
Badgwell and colleagues compared survival in women with breast cancer, aged 80 years or older that had accessed mammography screening regularly, irregularly or not at all in the five years prior to their diagnosis. Using a Medicare linked database, they reported that statistically significant improvements in overall and breast cancer-specific survi...
The benefits of early detection are often communicated to doctors and patients in the form of extended survival times. Extended survival may occur because early detection is effective but some of the observed benefit will be due to lead time bias. Therefore, without correcting for lead time, longer survival is not necessarily proof of the benefit o...
In randomised control trials evaluating screening, lead time bias can be countered by taking the time origin as the point of randomisation, not the point of diagnosis, or by comparing the number of deaths occurring in a given period of time instead or as well as the number of people surviving. In observation settings, an alternative time origin to ...
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.
Sep 28, 2023 · Abstract. Lead time bias refers to the apparent increase in survival when a disease is diagnosed earlier and survival is measured from the time of diagnosis to the time of death. In screening studies it is avoided by measuring survival from the time of screening, not the time of diagnosis. Download chapter PDF. Keywords. Lead time. Screening. Bias.
