Diagnostic Approaches for Hair Loss
The most effective diagnostic approach for hair loss includes a thorough clinical examination, dermoscopy, and targeted laboratory testing based on suspected etiology, with scalp biopsy reserved for uncertain cases or suspected scarring alopecia. 1, 2
Initial Clinical Assessment
History Taking
- Onset and duration of hair loss
- Pattern and progression (patchy, diffuse, or localized)
- Associated symptoms (itching, burning, pain)
- Family history of hair loss
- Medication use
- Diet and lifestyle factors
- Psychological impact
Physical Examination
- Assess hair distribution pattern
- Evaluate for scalp inflammation, scaling, or scarring
- Perform pull test (gently tugging on a cluster of hairs to assess fragility)
- Examine hair shafts for breakage or structural abnormalities
- Look for specific features:
- Exclamation mark hairs (in alopecia areata)
- Hair shaft breakage (in trichotillomania)
- Miniaturized hairs (in androgenetic alopecia)
Diagnostic Tools and Techniques
Dermoscopy
Dermoscopy is a critical non-invasive diagnostic tool that can reveal:
- Yellow dots in alopecia areata
- Exclamation mark hairs and cadaverized hairs
- Hair shaft abnormalities
- Signs of inflammation or scarring 2
Trichoscopy
Using a specialized magnifying device (trichoscope/folliscope) to examine:
- Hair follicle morphology
- Hair shaft diameter
- Presence of vellus hairs
- Scalp surface abnormalities 2
Photography
- Standardized global photography for baseline documentation
- Sequential photos to monitor treatment response
- Digital image analysis for quantitative assessment 2
Hair Counts and Measurements
- Hair density measurements (hairs per cm²)
- Hair diameter measurements
- Terminal-to-vellus hair ratio assessment 2
Laboratory Testing
Laboratory testing should be targeted based on clinical suspicion:
- Complete blood count
- Ferritin levels
- Thyroid stimulating hormone
- Vitamin D 25OH 3
For suspected specific conditions:
- Androgen levels (for suspected hyperandrogenism)
- Antinuclear antibody (for suspected lupus)
- Fungal culture (for suspected tinea capitis) 2, 1
Advanced Diagnostic Methods
Scalp Biopsy
Indicated for:
- Uncertain diagnosis after initial evaluation
- Suspected scarring alopecia (essential in these cases)
- Unusual presentations of hair loss
- Treatment-resistant cases 2, 3
Trichogram
- Analysis of plucked hairs to determine growth phase
- Assessment of anagen-to-telogen ratio
- Evaluation of hair root morphology 2
Differential Diagnosis Algorithm
Determine if alopecia is scarring or non-scarring:
- Scarring: loss of follicular openings, skin texture changes
- Non-scarring: follicular openings preserved
For non-scarring alopecia, assess pattern:
- Patchy: consider alopecia areata, tinea capitis, trichotillomania
- Diffuse: consider telogen effluvium, anagen effluvium, androgenetic alopecia
- Patterned: consider androgenetic alopecia
For scarring alopecia:
- Biopsy is essential for diagnosis
- Consider discoid lupus erythematosus, lichen planopilaris, central centrifugal scarring alopecia 4
Common Diagnostic Pitfalls
- Misdiagnosing trichotillomania as alopecia areata (look for broken hairs firmly anchored in scalp in trichotillomania)
- Overlooking subtle tinea capitis (may have minimal inflammation)
- Failing to recognize early scarring alopecia
- Not considering systemic causes of hair loss (thyroid disorders, iron deficiency, medications) 2, 5
By following this systematic diagnostic approach, clinicians can accurately identify the cause of hair loss and develop appropriate treatment strategies, leading to better outcomes and improved patient satisfaction.