Length time bias
🧠 Psych - 63 / 100
Hey, there.
Today, We will be talking about the Length time bias.
What is it?
It is observed that patients with slowly progressing diseases are more likely to be detected through screening.
Example -
Where does it occur?
A lot of patients with said diseases are not immediately identified.
This is due to slow cases are detected more often simply because they are slowly progressing.
Why do I need to know?
For example, A man with metastatic lung cancer dies at age 70. His cancer was discovered 1 year ago, when he was 69. Therefore, it appears as if he lived for 1 year with the cancer.
However, imagine that instead his cancer was discovered on a screening CT scan when he was 65 years old. If he still dies at the age of 70, it now looks like he survived for 5 years with the diagnosis of cancer (the 5 year survival rate is much better), but in fact there was no real change in his survival.
Takeaways:-
The "effectiveness" of the screening is of questionable clinical value since the form of the disease detected earlier is less dangerous disease.
References & Studies:-
https://radiopaedia.org/articles/length-time-bias
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