Pull Test and Telogen Effluvium

Why is a pull test positive in cases of telogen effluvium but not in mpb. If a pull test was positive is this a definate indication of telogen effluvium

The pull test can reflect many conditions, including a variety of autoimmune alopecias, telogen effluvium, possibly even androgenetic alopecia when it is very active. The test constitutes grasping about 60 hairs between two fingers near the scalp, then pulling gently (but firmly) on the hair. A positive test will yield 6 or more hairs and it is often done on 4 different parts of the scalp.

Do not wash your hair for 2 days prior to doing the test. If you decide to do the test on yourself, do not keep repeating it as you can pull out more hair than you really want.

This would not be a reliable test for male pattern balding diagnosis, because the hair loss from this condition varies. I suspect that when the process is not active (like when a patient is using finasteride / Propecia), the hair loss has stabilized so that the pull test would or should be negative. There are much better ways to make the diagnosis of MPB than by using the pull test.