Initial Bloodwork for Generalized Pruritus
The essential initial bloodwork panel for generalized pruritus should include: complete blood count (CBC) with ferritin, liver function tests (LFTs), and renal function tests (urea and electrolytes). 1, 2
Core Laboratory Panel (Order for All Patients)
The British Association of Dermatologists provides clear guidance on the foundational workup:
CBC and ferritin levels are mandatory in all patients with chronic generalized pruritus without rash, as iron deficiency is one of the most common treatable causes (accounting for 25% of systemic disease-related pruritus). 1, 2
Liver function tests must be included to screen for cholestatic liver disease and hepatic causes of pruritus. 1, 2
Urea and electrolytes (renal function) are essential to evaluate for uremic pruritus from chronic kidney disease. 1, 2
This three-part panel (CBC/ferritin, LFTs, renal function) forms the backbone of your initial investigation and should be ordered universally. 2, 3
Additional Tests Based on Clinical Suspicion
Do not order these routinely—only when specific clinical features are present:
Hematologic Concerns
Blood film, lactate dehydrogenase (LDH), and erythrocyte sedimentation rate (ESR) if you suspect lymphoma (night sweats, weight loss, lymphadenopathy) or polycythemia vera (aquagenic pruritus). 1, 2
JAK2 V617F mutation if polycythemia vera is suspected based on elevated hemoglobin/hematocrit, especially with microcytosis or aquagenic pruritus. 1, 2
Infectious Etiologies
- HIV and hepatitis A, B, C serology should be considered with relevant risk factors or unexplained pruritus, particularly with travel history. 1, 2
What NOT to Order Routinely
Avoid these common pitfalls:
Do not order thyroid function tests unless the patient has specific clinical features suggesting thyroid disease, diabetes, or other endocrinopathy—routine endocrine screening is not recommended. 1, 2
Do not pursue extensive malignancy workups without specific systemic symptoms; thorough history and physical examination should guide targeted investigations rather than shotgun testing. 1, 2
Do not forget to check ferritin even if CBC is normal—this is explicitly recommended for all chronic cases. 1, 2
Special Considerations
When Ferritin Appears "Normal"
If iron deficiency is clinically suspected but ferritin is in the normal range, remember that ferritin is an acute-phase reactant and can be falsely elevated during inflammation. In this scenario, check serum iron and total iron binding capacity. 1, 2
Persistent Unexplained Pruritus
For patients with persistent, unexplained generalized pruritus despite negative initial workup, consider skin biopsy to exclude cutaneous lymphoma, as patients rarely present with pruritus and normal-appearing skin that proves to be lymphoma on biopsy. 1, 2
Medication Review
Always perform a thorough medication review, as drug-induced pruritus requires cessation trials rather than laboratory testing. 1
Clinical Algorithm Summary
- Order universally: CBC with ferritin + LFTs + renal function 1, 2
- Add selectively: Blood film/LDH/ESR (if hematologic concern), JAK2 mutation (if polycythemia suspected), infectious serologies (if risk factors present) 1, 2
- Avoid routinely: Thyroid tests, extensive cancer screening without clinical indicators 1, 2
- Consider biopsy: If pruritus persists despite negative workup 1, 2
This streamlined approach balances comprehensive evaluation with cost-effectiveness, focusing resources where evidence demonstrates the highest diagnostic yield. 2, 3