What is the appropriate evaluation for severe pruritus?

Evaluation of Severe Itching

For severe pruritus without obvious skin disease, obtain a complete blood count with ferritin, comprehensive metabolic panel (including liver and kidney function), and consider additional targeted testing based on clinical suspicion rather than routine extensive workup. 1

Initial Laboratory Workup

Essential Tests for All Patients

The British Association of Dermatologists guidelines provide clear direction for chronic generalized pruritus without rash (GPWOR):

• Complete blood count and ferritin - Check in all patients (Strength C) 1
• Liver function tests - Part of standard investigation (Strength D) 1
• Urea and electrolytes - Essential for detecting renal causes (Strength D) 1

These three tests form the foundation because they screen for the most common systemic causes: iron deficiency, liver disease, and uremia.

Conditional Testing Based on Clinical Features

Do NOT routinely order:

• Thyroid function tests (unless clinical features suggest endocrinopathy) 1
• Extensive malignancy screening (unless systemic symptoms present) 1

Consider adding when clinically indicated:

• Hematologic suspicion (night sweats, weight loss, aquagenic pruritus):

  • Blood film, lactate dehydrogenase, ESR 1
  • JAK2 V617F mutation if elevated hemoglobin/hematocrit suggests polycythemia vera 1

• Liver disease suspicion (jaundice, right upper quadrant pain):

  • Bile acids and antimitochondrial antibodies 1

• Infectious concerns (travel history, risk factors):

  • HIV and hepatitis A, B, C serology 1
  • Consider malaria, strongyloidiasis, schistosomiasis screening with appropriate exposure 1

Key Clinical Pitfalls

Avoid the "shotgun" approach. The guidelines explicitly state that full investigation to rule out malignancy is NOT routinely recommended (Strength C) 1. Only pursue cancer workup when systemic symptoms accompany the pruritus.

Don't skip the medication review. Drug-induced pruritus is common - consider a trial cessation of suspect medications when the risk-benefit analysis is acceptable 1.

Iron deficiency matters even with normal hemoglobin. Check ferritin in all chronic cases, as iron deficiency can cause pruritus without anemia 1.

When to Refer

• Hematology referral: Suspected polycythemia vera or lymphoma 1
• Hepatology referral: Significant hepatic impairment 1
• Dermatology referral: Persistent unexplained pruritus may warrant skin biopsy to exclude cutaneous lymphoma 1

Practical Algorithm

1. History focus: Duration, triggers (water contact suggests PV), systemic symptoms (weight loss, fever, night sweats), medications, travel
2. Examination: Look for primary skin lesions (if present, this is dermatologic, not systemic pruritus)
3. First-tier labs: CBC with ferritin, CMP (liver and kidney function)
4. Second-tier labs: Only if clinical suspicion warrants (hematologic markers, infectious serologies)
5. Specialist referral: Based on abnormal findings or persistent unexplained pruritus

This targeted approach balances thoroughness with avoiding unnecessary testing, as supported by the 2018 BAD guidelines which represent the most comprehensive and recent guidance on this topic 1.