Evaluation of Hair Loss
Most cases of hair loss can be diagnosed clinically without laboratory testing; investigations should be reserved for diagnostically uncertain cases or when specific differential diagnoses require confirmation 1.
History Taking
Key Historical Elements to Elicit:
- Pattern and distribution: Focal patches versus diffuse thinning versus increased shedding
- Timeline: Acute onset (suggests telogen effluvium or diffuse alopecia areata) versus gradual progression (suggests androgenetic alopecia)
- Family history: 20% of alopecia areata patients have positive family history 1
- Medications and supplements: Recent changes (anagen effluvium)
- Triggers: Recent illness, surgery, childbirth, emotional stress, dietary changes
- Hair care practices: Traction from styling, chemical treatments
- Systemic symptoms: Fever, weight changes, fatigue (thyroid, autoimmune conditions)
- Psychological impact: Assess quality of life, anxiety, depression, social withdrawal 1
Physical Examination
Scalp Assessment:
Distinguish between scarring versus non-scarring alopecia first - this fundamentally changes your diagnostic approach and urgency 2, 3.
- Scarring alopecia: Loss of follicular ostia, skin appears smooth/shiny, requires dermatology referral and biopsy 3
- Non-scarring alopecia: Follicular openings preserved
Pattern Recognition:
- Alopecia areata: Smooth, round patches with "exclamation mark hairs" (short broken hairs with tapered bases) at margins; may see yellow dots on dermoscopy 1
- Androgenetic alopecia: Male pattern (frontal/vertex) or female pattern (central widening of part)
- Trichotillomania: Incomplete hair loss with irregular borders; broken hairs firmly anchored (still in anagen phase) 1
- Tinea capitis: Scalp inflammation (may be subtle), scaling, erythema 1
Diagnostic Maneuvers:
- Hair pull test: Grasp 40-60 hairs, pull gently - more than 6 hairs suggests active shedding 2
- Hair tug test: Assess hair shaft integrity
- Dermoscopy: Yellow dots indicate active alopecia areata; can differentiate from trichotillomania and scarring conditions 1
Laboratory Testing
Investigations are unnecessary in most cases of alopecia areata and should not be performed routinely 1. The British Association of Dermatologists explicitly states that routine screening for autoimmune diseases or iron deficiency is not recommended in alopecia areata 1.
When Diagnosis is Uncertain, Consider:
- Fungal culture: If tinea capitis suspected 1
- Scalp biopsy: Essential for all scarring alopecias; helpful when diagnosis unclear 1, 2, 3
- Syphilis serology: If secondary syphilis in differential 1
- Lupus serology: If systemic lupus erythematosus suspected 1
Selective Laboratory Testing (Not Routine):
One research study suggests checking CBC, ferritin, TSH, and vitamin D in all hair loss patients 2, but this contradicts guideline-level evidence. The BAD guidelines specifically state that routine iron testing is not recommended because studies failed to confirm increased iron deficiency in alopecia areata patients, and no studies demonstrate treatment response to iron replacement 1.
Use targeted labs only when clinical suspicion exists for:
- Thyroid dysfunction (TSH)
- Iron deficiency in chronic telogen effluvium with risk factors
- Systemic disease based on history/exam
Common Diagnostic Pitfalls
- Mistaking trichotillomania for alopecia areata: Look for incomplete hair loss and firmly anchored broken hairs in trichotillomania versus exclamation mark hairs in alopecia areata 1
- Missing subtle tinea capitis: Always consider fungal infection, especially in children
- Overlooking scarring alopecia: Failure to recognize scarring patterns delays critical diagnosis and treatment
- Over-investigating alopecia areata: Resist ordering extensive autoimmune panels without clinical indication 1