From the Guidelines
Laboratory evaluations for patients with dermatitis should be tailored to the clinical presentation and suspected etiology, with patch testing being a crucial diagnostic tool for identifying specific allergens in contact dermatitis, as recommended by the British Association of Dermatologists' guidelines for the management of contact dermatitis 2017 1. When evaluating patients with dermatitis, it is essential to consider the underlying cause and tailor laboratory tests accordingly. The following tests may be useful:
- Complete blood count (CBC) to assess for eosinophilia, which can indicate allergic or atopic dermatitis
- Comprehensive metabolic panel to evaluate liver and kidney function
- Specific IgE testing or skin prick tests to identify allergens in suspected allergic contact dermatitis
- Serum IgE levels may be elevated in suspected atopic dermatitis
- Autoantibody testing, such as ANA, anti-dsDNA, or specific antibodies like anti-BP180 for bullous pemphigoid, may be appropriate in cases of suspected autoimmune dermatitis
- Patch testing is valuable for identifying specific allergens in contact dermatitis, with a sensitivity and specificity of between 70% and 80% 1
- Skin scrapings for KOH preparation or fungal culture can rule out fungal infections that mimic dermatitis
- Skin biopsies may be necessary in unclear cases or to confirm specific diagnoses like psoriasis or lichen planus
- Bacterial cultures should be obtained if secondary infection is suspected It is crucial to note that many cases of dermatitis can be diagnosed clinically without extensive laboratory testing, and the diagnosis of atopic dermatitis is made clinically, based on historical features, morphology and distribution of skin lesions, and associated clinical signs, as outlined in the guidelines of care for the management of atopic dermatitis: section 1. diagnosis and assessment of atopic dermatitis 1.
From the Research
Laboratory Evaluations for Dermatitis
The following laboratory evaluations are recommended for patients presenting with dermatitis:
- Patch testing: considered the gold standard for diagnosing allergic contact dermatitis 2, 3, 4
- Skin prick test (in vivo) or serum IgE (in vitro) test methods: used to evaluate type I hypersensitivity reactions 5
- Clinical history and physical examination: essential for diagnosing and managing dermatitis, including atopic dermatitis, irritant and allergic contact dermatitis, and hand dermatitis 3, 6
Diagnostic Options
Diagnostic options for dermatitis include:
- Patch testing: used to identify allergens responsible for allergic contact dermatitis 2, 3, 4
- Clinical history and physical examination: used to diagnose and manage dermatitis, including atopic dermatitis and contact dermatitis 3, 6
- Severity scoring: used to monitor therapy and assess the severity of atopic dermatitis 6
Allergen Testing
Allergen testing is not necessary for the diagnosis and treatment of atopic dermatitis, but may be useful in individual cases to confirm clinical suspicion or to identify atopic comorbidity 6, 5