Laboratory Tests for Alopecia
Investigations are unnecessary in most cases of alopecia areata, as the diagnosis is usually made clinically. 1
When to Consider Laboratory Testing
Laboratory tests should be considered in the following situations:
- When the diagnosis is uncertain or atypical presentation 1
- When other conditions in the differential diagnosis need to be ruled out 1
- When there are clinical features suggesting an underlying systemic condition 2
Recommended Laboratory Tests
For Diagnostic Uncertainty
- Fungal culture: When tinea capitis is suspected (look for subtle inflammation and scaling) 1
- Skin biopsy: For difficult cases, early scarring alopecia, or diffuse alopecia areata that is challenging to diagnose 1
- Serology for lupus erythematosus: When systemic lupus is in the differential diagnosis 1
- Serology for syphilis: When secondary syphilis is suspected 1
- Dermoscopy: Not a laboratory test but a valuable diagnostic tool that can reveal yellow dots, exclamation mark hairs, and cadaverized hairs characteristic of alopecia areata 1, 2
For Nutritional Deficiencies
Recent evidence suggests testing for nutritional deficiencies may be beneficial:
- Serum ferritin: Particularly in women, as iron deficiency is associated with hair loss 2, 3
- Vitamin D levels: Lower serum vitamin D levels have been associated with hair loss in women 2
- Zinc levels: Serum zinc tends to be lower in patients with alopecia areata 2
- Folate levels: Deficiency may contribute to hair loss 2
Important Clinical Considerations
- The increased frequency of autoimmune diseases in patients with alopecia areata is probably insufficient to justify routine screening for all autoimmune conditions 1
- One study found that 70.3% of female alopecia cases were associated with iron deficiency, suggesting serum ferritin ≥60 ng/mL may be an appropriate target for hair health 3
- Early initiation of treatment (within 6 months) for iron deficiency-related alopecia shows better prognosis 3
Differential Diagnosis to Consider
When evaluating laboratory tests, keep these differential diagnoses in mind:
- Trichotillomania (compulsive hair pulling) 1
- Tinea capitis (fungal infection) 1
- Early scarring alopecia 1
- Telogen effluvium (stress-induced shedding) 1
- Anagen effluvium (drug-induced) 1
- Systemic lupus erythematosus 1
- Secondary syphilis 1
Common Pitfalls to Avoid
- Ordering excessive laboratory tests when the diagnosis is clinically evident 1
- Missing nutritional deficiencies, particularly iron deficiency which may require higher ferritin levels (≥60 ng/mL) for optimal hair growth than those required to prevent anemia 3
- Failing to consider psychological impact, which may warrant assessment for anxiety and depression 1
- Overlooking dermoscopy as a non-invasive diagnostic tool that can provide valuable information 1, 2
Remember that alopecia areata has no direct impact on general health that justifies hazardous treatments, but its psychological effects can be significant and should be addressed 1.