Investigations
1st investigations to order
clinical diagnosis
Test
Usually no tests are necessary.
Result
features of alopecia areata on history and physical examination
positive hair pull test
Test
A pinch of closely grouped hairs (or about 50 hairs) is grasped between the thumb and the index and middle fingers, and gentle traction is applied as the fingers are pulled firmly and slowly away from the scalp. Normally, 2 to 5 hairs will be obtained in this manner.[Figure caption and citation for the preceding image starts]: Hair pull testProvided by Paradi Mirmirani, MD [Citation ends].
Result
more than 5 hairs is considered to be a positive pull test
Investigations to consider
skin biopsy
Test
In most cases diagnosis of AA can be made clinically.
If the diagnosis is uncertain or needs to be confirmed, biopsy may be useful. It is best to take two 4-mm biopsies (1 for vertical sectioning and 1 for horizontal sectioning).
Result
peribulbar, follicular lymphocyte-predominant inflammatory infiltrate; increase in telogen hairs; increased uniform miniaturisation of follicles; hyalinisation fibrous tracts in the subcutis
trichoscopy
Test
Non-invasive imaging using a dermatoscope to observe the hair signs, vascular patterns, pigment patterns and interfollicular patterns. In a healthy scalp, follicular units contain 2 to 4 terminal hairs and 1 or 2 vellus hairs.
Result
presence of yellow dots, black dots, broken hairs, or more classic exclamation mark hairs
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