Laboratory and functional tests in leprosy diagnosis: a practical guide for clinical decision-making

Area of Science:

• Dermatology
• Infectious Diseases
• Neurology

Background:

• Early leprosy diagnosis is primarily clinical, focusing on skin lesions and nerve involvement.
• Complementary diagnostic tests are vital for confirming uncertain cases and managing leprosy.

Purpose of the Study:

• To review the practical application of diagnostic methods for leprosy.
• To highlight the role of various tests in diagnosis, classification, and monitoring.

Main Methods:

• Review of slit-skin smear microscopy, histopathology, PCR, serology (Anti-PGL-1), Semmes-Weinstein monofilament testing, histamine testing, electrodiagnostic studies, and nerve ultrasonography.
• Integration of bacteriological, histopathological, molecular, and serological data for post-treatment assessment.

Main Results:

• Slit-skin smears have high specificity but low sensitivity in paucibacillary leprosy.
• PCR enhances paucibacillary diagnosis but cannot differentiate viable from non-viable bacilli.
• Anti-PGL-1 serology aids contact surveillance but has low sensitivity in early disease.
• Nerve tests (monofilament, histamine, electrodiagnostics, ultrasonography) detect neural involvement and autonomic dysfunction.
• Ultrasonography shows high sensitivity for nerve thickening and inflammation.
• An integrated approach is crucial for differentiating relapse from reaction post-treatment.

Conclusions:

• No single laboratory test confirms leprosy; clinical expertise is paramount.
• Complementary diagnostic tests, interpreted in context, optimize diagnostic accuracy.
• An integrated diagnostic strategy improves leprosy management and post-treatment evaluation.