Initial Laboratory Workup for Generalized Pruritus Without Urticaria
For a patient with generalized pruritus (itching) from head to toe without urticaria, the recommended initial laboratory workup should include full blood count, ferritin levels, liver function tests, and urea and electrolytes. 1
Core Initial Laboratory Tests
- Full blood count and ferritin levels should be checked in all patients with chronic generalized pruritus without rash (GPWOR) to evaluate for iron deficiency, which is a common cause of generalized pruritus 1
- Liver function tests (LFTs) should be performed to investigate for potential liver disease, especially cholestasis, which can cause generalized pruritus 1
- Urea and electrolytes should be checked to evaluate for renal disease, as uremic pruritus is a significant cause of generalized pruritus 1
Additional Tests Based on Clinical Suspicion
- Blood film, lactate dehydrogenase, and erythrocyte sedimentation rate should be ordered if there is suspicion of hematological involvement 1
- JAK2 V617F mutation analysis should be considered if polycythemia vera is suspected (raised hemoglobin or hematocrit) 1
- HIV and hepatitis A, B, and C serology should be considered, particularly with relevant risk factors or travel history 1
- Thyroid function tests should NOT be routinely performed unless there are additional clinical features suggesting thyroid disease or other endocrinopathy 1
Special Considerations
- If malignancy is suspected (especially in patients over 60 years with recent onset of diffuse itching), a more targeted investigation approach should be used based on specific symptoms rather than routine screening 1, 2
- For persistent unexplained pruritus, consider skin biopsy to rule out cutaneous lymphoma 1
- In patients with suspected iron deficiency and "normal" ferritin, consider checking serum iron and total iron binding capacity 1
Common Pitfalls to Avoid
- Ordering unnecessary thyroid function tests without clinical features suggesting thyroid disease 1
- Failing to check ferritin levels, which is recommended in all cases of chronic generalized pruritus without rash 1
- Ordering extensive malignancy workups without specific clinical indicators 1
- Not considering medication-induced pruritus, which requires a thorough medication review rather than specific laboratory tests 1
The most recent comprehensive evidence from the British Association of Dermatologists (2018) emphasizes a targeted approach to laboratory investigation based on clinical presentation rather than extensive testing for all patients with generalized pruritus 1, 3.