What are the initial steps for testing and treating a patient presenting with alopecia?

Testing for Alopecia: Initial Diagnostic Approach

In most cases of alopecia areata, the diagnosis is made clinically without laboratory testing, but when the diagnosis is uncertain or the presentation is atypical, targeted testing should include dermoscopy, fungal culture (if tinea capitis is suspected), and scalp biopsy for difficult cases. 1, 2

Clinical Diagnosis First

The diagnosis of alopecia areata is typically straightforward and does not require laboratory workup in most cases. 1, 2 The key is recognizing the characteristic clinical features:

• Look for exclamation mark hairs (short broken hairs around expanding patches) - these are pathognomonic for alopecia areata 1, 2, 3
• Examine for yellow dots on dermoscopy - regular round yellow dots indicate active disease progression and are highly specific for alopecia areata 1, 2
• Check the scalp appearance - affected skin may be slightly reddened but otherwise appears normal, without significant inflammation or scaling 1
• Assess nail involvement - approximately 10% of patients have nail changes including pitting, ridging, or dystrophy 1, 3

Dermoscopy as the Primary Diagnostic Tool

Dermoscopy is the single most useful non-invasive tool to differentiate alopecia areata from other causes of hair loss. 2

• Yellow dots, exclamation mark hairs, cadaverized hairs, and black dots are characteristic of alopecia areata 2
• A positive pull test at the margins of expanding areas signals active disease 2
• The absence of these features is characteristic of telogen effluvium and androgenetic alopecia 2

When to Order Laboratory Tests

Laboratory testing should be reserved for specific clinical scenarios: 1, 2

Order tests only when:

• The diagnosis is uncertain or presentation is atypical 1, 2
• Diffuse alopecia areata is suspected (which may require histopathologic confirmation) 2
• Other conditions in the differential diagnosis need to be ruled out 2

Specific Tests for Differential Diagnosis:

• Fungal culture - mandatory when tinea capitis is suspected, as scalp inflammation may be subtle 1, 2
• Skin biopsy - indicated for difficult cases, early scarring alopecia, or diagnostically challenging diffuse alopecia areata 1, 2
• Lupus serology - when systemic lupus erythematosus is in the differential 1, 2
• Syphilis serology - when secondary syphilis is suspected 1, 2

Nutritional and Hormonal Testing (When Clinically Indicated):

• Serum ferritin - iron deficiency is the most common nutritional deficiency worldwide and associated with chronic diffuse telogen hair loss; optimal levels ≥60 ng/mL are needed for hair growth 2, 4
• Vitamin D (25OH) - 70% of alopecia areata patients have levels <20 ng/mL versus 25% of controls, with lower levels correlating inversely with disease severity 2, 4, 5
• Serum zinc - levels tend to be lower in alopecia areata patients, particularly those with resistant disease >6 months duration 2
• TSH and free T4 - to rule out thyroid disease, which commonly causes hair loss and is associated with alopecia areata 2, 4, 5
• TPO antibodies - if biochemical hypothyroidism is confirmed 2

For Women with Signs of Androgen Excess:

• Total testosterone or bioavailable/free testosterone and SHBG levels 2
• Prolactin level if hyperprolactinemia is suspected 2
• Two-hour oral glucose tolerance test if diabetes or insulin resistance is suspected 2
• Fasting lipid and lipoprotein levels 2

Critical Differential Diagnoses to Consider

The following conditions can mimic alopecia areata and require different diagnostic approaches: 1, 2

• Trichotillomania - distinguished by incomplete hair loss with firmly anchored broken hairs that remain in anagen phase; may coexist with alopecia areata 1, 2, 4
• Tinea capitis - presents with scalp inflammation and scaling (though signs may be subtle); requires fungal culture for diagnosis 1, 2, 4
• Telogen effluvium - stress-induced shedding triggered by illness, surgery, childbirth, severe emotional stress, rapid weight loss, or nutritional deficiencies 2
• Anagen effluvium - drug-induced (particularly chemotherapy) hair loss that is typically more rapid and severe 1, 2
• Early scarring alopecia - requires biopsy for diagnosis 1, 2
• Systemic lupus erythematosus - can cause both scarring and non-scarring alopecia 1, 2
• Secondary syphilis - presents with patchy "moth-eaten" hair loss 1, 2

Practical Clinical Algorithm

Step 1: Perform dermoscopy looking specifically for yellow dots and exclamation mark hairs 2

Step 2: If characteristic dermoscopic features are present, diagnose alopecia areata clinically without biopsy 2

Step 3: If dermoscopy is inconclusive, obtain targeted laboratory tests to exclude telogen effluvium triggers and tinea capitis 2

Step 4: If diagnosis remains uncertain after targeted testing, perform scalp biopsy for definitive histopathologic diagnosis 2

Common Pitfalls to Avoid

• Do not order excessive laboratory tests when the diagnosis is clinically evident - alopecia areata is typically diagnosed clinically 1, 2, 4
• Do not overlook dermoscopy - it is a non-invasive diagnostic tool that provides valuable information 2
• Do not fail to consider trichotillomania - it requires completely different management (psychological counseling rather than immunologic treatment) 4
• Do not ignore the psychological impact - alopecia areata may cause considerable psychological and social disability warranting assessment for anxiety and depression 2, 3, 4
• Do not forget that many cases are self-limited - 34-50% of patients recover within one year without treatment, making watchful waiting a legitimate first option 2, 4

Key Historical Elements to Obtain

• Pattern and time course - patchy versus diffuse, acute versus gradual onset 3
• Family history - approximately 20% of alopecia areata patients have affected family members 1, 3, 4
• Autoimmune disease screening - thyroid disease, vitiligo, lupus 3, 4
• Medication review - chemotherapy, anticoagulants, beta-blockers can cause hair loss 2, 3
• Recent stressors - illness, surgery, childbirth, emotional stress 2
• Hair pulling behaviors - screen for trichotillomania 3, 4
• Age of onset - childhood onset carries worse prognosis than adult onset 3