Identification of leprosy reactions using Fourier transform infrared (FTIR) spectroscopy supervised by clinical evaluation.

Leprosy is a chronic granulomatous, infectious and disabling disease, whose etiological agents are Mycobacterium leprae and M. lepromatosis. Leprosy reactions are the main causes of peripheral nerve damage and sequelae of the disease. There is no laboratory test that alone allows the identification of these episodes, causing delays in their diagnosis and treatment. The objective of this study was to propose a methodology based on Fourier transform infrared (FTIR) spectroscopy to detect leprosy reactions in the saliva of leprosy patients, supervised by the clinical diagnosis of these episodes. A total of 131 saliva samples were included and analyzed by attenuated total reflection (ATR)-FTIR; a supervised analysis with partial least squares discriminant analysis (PLS-DA), after orthogonal signal correction (OSC), was used to classify the samples into two groups: with and without leprosy reactions. The PLS-DA model with one latent variable and one OSC component showed 100 % sensitivity and specificity both in the calibration and prediction sets. Thus, all samples were correctly classified, allowing the diagnosis of leprosy reactions in saliva with high accuracy. Therefore, the FTIR-based chemometric model proved promising for the rapid and early identification of these episodes, contributing to clinical management of patients with leprosy.