Laboratory Tests and Ancillaries
Diagnostic
tests may be necessary for complicated or atypical diseases. There are no
serologic markers or pathognomonic laboratory tests for psoriasis. Skin biopsy,
serologic studies for syphilis, bacterial culture, human leukocyte antigen
(HLA) typing, and microscopic (potassium hydroxide) examinations may be used to
differentiate psoriasis from other conditions.
Baseline studies should
include a complete blood count (CBC) with platelet, creatinine, electrolytes, liver
function tests, hepatitis panel screening, latent tuberculosis (TB) screening (eg includes chest X-ray and purified protein
derivative test [PPD] test), and HIV screening. Other lab tests that may be
done if clinically indicated include erythrocyte sedimentation rate
(ESR)/C-reactive protein (CRP), urinalysis, lipid profile, fasting blood sugar,
interferon gamma release assay, hepatitis B surface antigen (HBsAg), hepatitis
B core antibody, hepatitis C virus antibody, and antinuclear antibodies (ANA).
It should be advised prior to starting, resuming,
or increasing therapy with systemic and immunosuppressive agents.