Accuracy of the Polymerase Chain Reaction of Ulnar Perineural Subcutaneous Aspirate Guided by Ultrasound for the Diagnosis and Monitoring of Leprosy Cure

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\*\*Brief Summary\*\* Leprosy is a chronic granulomatous infectious disease caused by \*Mycobacterium leprae\* or \*Mycobacterium lepromatosis\*, characterized by peripheral nerve involvement that may lead to progressive neurological damage, disability, and deformities if not diagnosed and treated early. The diagnosis of leprosy is primarily clinical and epidemiological, supported by laboratory methods such as bacilloscopy and biopsy; however, these tests have limited sensitivity, particularly due to the bacillus' tropism for peripheral nerve structures. Ultrasonography has emerged as a non-invasive imaging method capable of detecting morphological changes in peripheral nerves, including nerve enlargement, fascicular abnormalities, and inflammatory hypervascularization. Despite its diagnostic value, ultrasonography alone cannot detect the presence of the bacillus. This prospective cohort study aims to evaluate the diagnostic and prognostic accuracy of combining clinical evaluation, peripheral nerve ultrasonography, and molecular detection techniques using subcutaneous perineural aspirate. Patients with suspected leprosy attending the Leprosy Outpatient Clinic at the University Hospital of Brasília will undergo clinical evaluation, ultrasound examination of the ulnar nerves, and ultrasound-guided subcutaneous perineural aspirate for molecular detection of \*Mycobacterium leprae\* DNA and RNA using real-time PCR and RT-PCR. Participants will be followed for one year, with assessments performed at diagnosis and after one year of treatment. The study will compare clinical, imaging, and molecular findings to determine whether perineural subcutaneous aspirate combined with ultrasonography improves early detection and diagnostic accuracy compared with conventional methods such as bacilloscopy and biopsy. The study aims to contribute to improved diagnostic strategies for leprosy, enabling earlier detection of neural involvement and potentially reducing disease transmission and long-term disability.

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