RESUMO
BACKGROUND: The nasal mucosa plays the main role as the entry and the exit of leprosy bacilli and the nasal involvement may precede the skin lesions by several years. Nasal biopsy has been used in research but its clinical application has not been described. We evaluated the contribution of the nasal biopsy for the diagnosis of leprosy and its correlation to skin biopsy and skin smear in untreated patients. METHODS: We evaluated changes in nasal biopsy in 227 leprosy patients. Patients were clinically classified and skin and nasal biopsies and skin smear were performed. RESULTS: Nasal biopsy showed positivity in 100% of the lepromatous spectrum decreasing toward the tuberculoid (TT) pole. Patients with TT or indeterminate forms did not present any nasal alterations, showing that they are the true paucibacillary forms. Also, the nasal biopsies of two patients were the only exam to show positivity. The bacillary index of the nasal biopsy was strongly correlated to skin biopsy and slit-skin smear. Additionally, the agreement among the exams was good, revealing the reliability of the nasal biopsy in leprosy diagnosis. CONCLUSION: The present study showed a rate of 48% of positivity in nasal biopsy of untreated patients, correlating well with skin biopsy and skin smear. Thus, the method in leprosy diagnosis and clinical form classification has shown great reliability.