Laboratory Testing for Alopecia Areata
Investigations are unnecessary in most cases of alopecia areata, as the diagnosis is primarily clinical. 1
When to Order Laboratory Tests
Laboratory testing should be reserved for specific clinical scenarios rather than performed routinely:
Tests Only When Diagnosis is Uncertain
Order these tests only when the clinical diagnosis is in doubt: 1
- Fungal culture - to exclude tinea capitis when scalp inflammation is present 1
- Skin biopsy - when differentiating from trichotillomania, early scarring alopecia, or diffuse presentations 1
- Serology for lupus erythematosus - if systemic lupus erythematosus is in the differential 1
- Serology for syphilis - to exclude secondary syphilis when clinically suspected 1
Tests NOT Recommended Routinely
Do not routinely screen for autoimmune diseases or nutritional deficiencies: 1
Autoimmune screening - Despite the increased frequency of autoimmune diseases in alopecia areata patients, this association is insufficient to justify routine screening 1
Iron studies/ferritin - Routine testing for iron status is not recommended, as initial case series suggesting higher iron deficiency rates in women with alopecia areata were not confirmed in subsequent studies, and no published studies demonstrate treatment response to iron replacement 1
Thyroid function, vitamin D, vitamin B12 - While one general hair loss review suggests ordering these for all hair loss patients 2, the British Association of Dermatologists guidelines specifically for alopecia areata do not recommend routine screening 1
Clinical Pearls
The diagnosis of alopecia areata is usually straightforward based on clinical examination alone. 1 Key diagnostic features include:
- Exclamation mark hairs (dystrophic hairs with fractured tips) 1
- Yellow dots on dermoscopy indicating active disease progression 1
- Cadaverized hairs (hairs fractured before scalp emergence) 1
Common pitfall: Ordering extensive laboratory panels reflexively without clinical indication wastes resources and does not improve patient outcomes, as alopecia areata has no direct impact on general health that requires laboratory monitoring. 1