The accuracy of the Montenegro skin test for leishmaniasis in PCR-negative patients

• Published in: Revista da Sociedade Brasileira de Medicina Tropical Vol. 53; p. e20190433
• Main Authors: Pinheiro, Ana Bárbara Sapienza, Kurizky, Patricia Shu, Ferreira, Marina de Freitas, Mota, Marco Antonio de Souza, Ribeiro, Jaqueline Santos, Oliveira Filho, Edson Zuza de, Souza, Carlos Augusto, Barroso, Daniel Holanda, Sampaio, Raimunda Nonata Ribeiro, Gomes, Ciro Martins
• Format: Journal Article
• Language: English
• Published: Brazil Sociedade Brasileira de Medicina Tropical - SBMT 01-01-2020; Sociedade Brasileira de Medicina Tropical (SBMT)
• Subjects: Adult; Aged; Chronic Disease; Cross-Sectional Studies; Cutaneous; Diagnosis; DNA, Protozoan - genetics; Female; Fluorescent Antibody Technique, Indirect; Humans; Intradermal Tests - methods; Leishmania braziliensis - genetics; Leishmania braziliensis - immunology; Leishmaniasis; Leishmaniasis, Cutaneous - diagnosis; Major; Male; Middle Aged; Mucocutaneous; Polymerase Chain Reaction; Polymorphism, Restriction Fragment Length; Sensitivity and Specificity; TROPICAL MEDICINE; Mucocutaneous; Leishmaniasis; Diagnosis; Cutaneous
• ISSN: 0037-8682; 1678-9849; 1678-9849
• DOI: 10.1590/0037-8682-0433-2019

As highly specific molecular biology-based techniques may not be sensitive enough for the diagnosis of American tegumentary leishmaniasis (ATL), clinicians frequently rely on immunological tests before treatment initiation. Hence, the correct combination of diagnostic tests is imperative for ATL diagnosis. We aimed to evaluate the accuracy of the Montenegro (Leishmanin) skin test (MST) in polymerase chain reaction (PCR)-negative patients to accurately detect ATL.
Patients with a clinical picture compatible with ATL were divided into ATL (confirmed by lesion smear, culture indirect immunofluorescence, and/or histopathology) and no-ATL (diseases that can mimic leishmaniasis) groups. Conventional PCR for the minicircle kDNA of Leishmania was performed, and the MST was carried out for PCR-negative patients.
Ninety-nine patients were included in this study, including 79 diagnosed with ATL (6 with mucocutaneous leishmaniasis) and 20 without ATL (no-ATL group). The MST showed a high sensitivity of 90.0% (95% confidence interval [CI] = 69.90-97.21) in PCR-negative patients that was 10% higher than the sensitivity reported in PCR-positive population (79.66%; 95% CI = 67.73-87.96).
One of the most important reasons for PCR negativity among patients with active ATL is the presence of a strong cellular immunological response, especially in chronic and mucocutaneous leishmaniasis. This reinforces the considerable utility of the tests that detect cellular responses against Leishmania antigens such as the MST in PCR-negative patients when the performance in screening situations is questionable.