What investigations are needed for a case of pruritus (itching) of the skin?

From the Guidelines

To investigate a case of skin pruritus, a full blood count and ferritin levels should be checked in all patients with chronic generalized pruritus, as recommended by the British Association of Dermatologists' guidelines 1. When evaluating a patient with skin pruritus, it is crucial to consider various potential underlying causes, including iron deficiency, iron overload, blood disorders, malignancy, endocrinopathy, uraemia, liver disease, neuropathy, infections, and infestations. Key investigations to consider include:

• Full blood count and ferritin levels to identify iron deficiency or overload 1
• Liver function tests (LFTs) to rule out liver disease 1
• Urea and electrolytes to investigate uraemia 1
• A thorough history and physical examination to identify potential malignancy or endocrinopathy 1
• Consideration of skin biopsy if cutaneous lymphoma is suspected or to confirm neuropathic pruritus 1
• Screening for infections such as HIV, hepatitis, and parasitic infestations based on patient history and risk factors 1
• Trial of cessation of medications if drug-induced pruritus is suspected 1 These investigations should be guided by the patient's clinical presentation, history, and physical examination findings, with the aim of identifying and treating the underlying cause of pruritus, rather than just managing the symptom.

From the Research

Investigations for Skin Pruritis

To diagnose the cause of skin pruritis, several investigations can be considered:

• A thorough skin examination, including visualization of the finger webs, anogenital region, nails, and scalp, is essential 2
• An exposure history may reveal symptom triggers 2
• Laboratory tests, such as:
  • Complete blood count with differential 2, 3
  • Creatinine and blood urea nitrogen levels 2
  • Liver function tests 2, 3
  • Iron studies 2, 4
  • Fasting glucose or A1C level 2
  • Thyroid-stimulating hormone test 2, 3
• Additional testing, including:
  • Erythrocyte sedimentation rate 2
  • HIV screening 5, 2
  • Hepatitis serologies 2
  • Chest radiography 2
• Consider evaluation for malignancy in older patients with chronic generalized pruritus 5, 2
• Referral to a dermatologist may be indicated for further evaluation and treatment 5

Classification of Pruritus

Pruritus can be classified into different categories, including:

• Localized vs. generalized pruritus 5
• Inflammatory, neuropathic, or mixed etiology 3
• Chronic pruritus of undetermined origin (CPUO) 4
• Psychogenic itch 5, 6

Diagnostic Approach

A thorough history and physical examination are the most important diagnostic tools for pruritus 5 The diagnostic approach should consider the patient's symptoms, medical history, and laboratory test results to narrow down the differential diagnosis 6