What is the initial workup for a patient presenting with pruritis (itching)?

Initial Workup for Pruritus

For patients presenting with generalized pruritus without an obvious dermatologic cause, obtain a focused laboratory panel including complete blood count with ferritin, liver function tests, urea and electrolytes, and perform a comprehensive medication review. 1, 2

History and Physical Examination

Key Historical Elements to Obtain

• Onset, duration, and distribution of itching (generalized vs. localized, palms/soles involvement suggests cholestasis) 1
• Presence or absence of rash (primary skin lesions indicate dermatologic disease; excoriations alone suggest systemic cause) 1
• Timing patterns (worse at night suggests cholestasis or scabies) 1
• Complete medication list including over-the-counter drugs, opioids, and recent additions (drug-induced pruritus is common and reversible) 1, 2
• Travel history, sexual history, IV drug use (assess HIV, hepatitis, parasitic infection risk) 1
• Associated symptoms: weight loss, fatigue, jaundice, dark urine, fever, changes in bowel habits 1, 3
• Personal or family history of atopy (eczema, asthma, allergic rhinitis) 1

Physical Examination Focus

• Complete skin examination including scalp, finger webs, anogenital region, and nails 4, 5
• Distinguish primary vs. secondary lesions (primary lesions = diseased skin; secondary lesions = scratching effects) 4
• Assess for jaundice, lymphadenopathy, hepatosplenomegaly 1, 3
• Evaluate for excoriations, prurigo nodularis (suggest chronic scratching without underlying rash) 1

Initial Laboratory Workup

Essential First-Line Tests

Order these tests for all patients with chronic generalized pruritus without obvious dermatologic cause: 1, 2

• Complete blood count with differential and ferritin (screens for iron deficiency, polycythemia vera, eosinophilia, hematologic malignancies) 1, 2
• Liver function tests (evaluate hepatic causes; consider adding bile acids and antimitochondrial antibodies if liver disease suspected) 1, 2
• Urea and electrolytes/renal function (assess for uremic pruritus) 1, 2
• Fasting glucose or HbA1c (screen for diabetes) 4, 5

Additional Testing Based on Clinical Suspicion

• HIV and hepatitis B/C serology if risk factors present (IV drug use, sexual history, travel) 1, 2
• Thyroid-stimulating hormone only if clinical features suggest thyroid disease (do NOT order routinely) 1, 2
• Lactate dehydrogenase, blood film, ESR if hematologic malignancy suspected 1
• JAK2 V617F mutation if polycythemia vera suspected (elevated hemoglobin/hematocrit) 1
• Chest X-ray if lymphoma or other malignancy suspected based on symptoms 1, 3

What NOT to Do (Common Pitfalls)

• Do not order routine thyroid function tests without clinical features suggesting endocrinopathy 1, 2
• Do not pursue extensive malignancy screening in the absence of specific systemic symptoms (thorough history and physical examination sufficient initially) 1, 2
• Do not overlook medication review as a reversible cause 1, 2
• Do not use sedating antihistamines in elderly patients (except palliative care) due to dementia risk 1, 2

Special Population: Elderly Patients

Before pursuing extensive workup in elderly patients, initiate a 2-week trial of emollients with high lipid content and topical steroids to exclude asteatotic eczema (dry skin). 1, 2 This common condition can mimic systemic pruritus and responds to simple measures. 1, 2

Initial Management While Awaiting Results

• Emollients (liberal use, high lipid content preferred in elderly) 1, 2
• Non-sedating antihistamines (short trial as second-line) 2
• Topical doxepin or clobetasone butyrate/menthol preparations 2
• Trial cessation of potentially causative medications when risk-benefit acceptable 1, 2

When to Refer

• Hematology referral: suspected polycythemia vera or lymphoma 1, 2
• Hepatology referral: any suggestion of significant hepatic impairment 1, 2
• Dermatology referral: diagnostic doubt, persistent symptoms despite primary care management, consideration of skin biopsy for cutaneous lymphoma 1, 2

Heightened Malignancy Concern

Maintain heightened suspicion for underlying malignancy in patients over 60 years with diffuse pruritus of less than 12 months duration, especially with history of liver disease. 5 However, do not pursue full malignancy workup routinely without specific systemic symptoms. 1, 2