Diagnostic performance of peripheral nerve palpation compared with ultrasonography in leprosy neuropathy: A prospective real-world clinical evaluation

BACKGROUND: Leprosy frequently causes peripheral neuropathy, and nerve palpation remains a cornerstone of diagnosis in many endemic settings despite its subjectivity and limited reproducibility. High-resolution ultrasonography has emerged as a sensitive, low-cost imaging tool to detect peripheral nerve involvement. We aimed to compare the diagnostic performance and interobserver agreement of peripheral nerve palpation versus ultrasonography for detecting leprosy neuropathy, with particular focus on pure neural forms. METHODOLOGY/PRINCIPAL FINDINGS: In this cross-sectional study, 29 newly diagnosed, treatment-naïve patients with clinical neuropathy underwent standardized palpation of the radial, ulnar, fibular, and posterior tibial nerves by three experienced examiners (dermatologist, orthopedist, physiotherapist). Ultrasonographic cross-sectional area was used as a comparative reference method. Overall, 232 nerves were evaluated, and ultrasonography identified nerve thickening in 26%. Interobserver agreement for nerve thickening on palpation was 60% (95% CI: 54-65%). Using ultrasonography as reference, palpation sensitivity ranged from 26% to 34%, specificity from 68% to 81%, and accuracy from 56% to 67%. Among individual nerves, the posterior tibial nerve showed the highest palpation sensitivity (44%), whereas thickening of the radial nerve was rarely detected (3%). Bilateral asymmetry (>2.5 mm²) was observed in 13% of nerves that were considered clinically normal on examination, and median nerve enlargement (at ultrasonography) was present in 45% of the participants. In patients with pure neural leprosy (62% of the sample), palpation sensitivity was 43%, resulting in frequent misclassification of operational forms. CONCLUSIONS/SIGNIFICANCE: Peripheral nerve palpation showed low sensitivity and only moderate specificity when compared with ultrasonography, with poor interobserver agreement even among experienced clinicians. These findings support the consideration of high-resolution ultrasonography as a complementary tool in diagnostic algorithms, particularly in pure neural cases, where reliance on palpation alone may lead to underdiagnosis and misclassification.