Strongyloidiasis in humans: diagnostic efficacy of four conventional methods and real-time polymerase chain reaction

• Published in: Revista da Sociedade Brasileira de Medicina Tropical
• Main Authors: Laura Francisca Campo-Polanco, José Mauricio Hernández Sarmiento, Miguel Antonio Mesa, Carlos Jaime Velásquez Franco, Lucelly López, Luz Elena Botero, Lina Andrea Gutiérrez Builes
• Format: Article in Journal/Newspaper
• Language: English
• Published: Sociedade Brasileira de Medicina Tropical (SBMT)
• Subjects: Strongyloides stercoralis; Intestinal diseases; Helminthology; Molecular diagnostic techniques; Arctic medicine. Tropical medicine; RC955-962; Arctic; Ritchie
• Online Access: https://doi.org/10.1590/0037-8682-0055-2018; https://doaj.org/article/fb01a4fa05bf4246b1c2e8f08575ab42

Abstract INTRODUCTION: Strongyloides stercoralis is an intestinal parasitic nematode that causes hyperinfection and/or a dissemination syndrome in hosts, which is often difficult to diagnose. This study aims to compare the diagnostic efficacy of four conventional methods used to diagnose strongyloidiasis with real-time polymerase chain reaction (qPCR) to detect S. stercoralis in fecal samples. METHODS: We analyzed 143 fecal samples collected from Colombian regions with varying degrees of risk for intestinal infections caused by S. stercoralis to assess the validity, performance, overall efficiency, and concordance of the qPCR using a direct stool test, modified Ritchie concentration technique, agar plate culture, and Harada-Mori technique as reference tests. RESULTS While four fecal samples were positive for S. stercoralis using conventional methods, 32 were positive via qPCR. The diagnostic sensitivity of the qPCR was 75% [95% confidence interval (CI): 20.07-100%], whereas its specificity, negative predictive value, negative likelihood ratio, and Youden’s J index were 78.42% (95% CI: 71.22-85.62%), 99.09% (95% CI: 96.86-100%), 0.32 (95% CI: 0.06-1.74), and 0.53, respectively. In addition, the estimated kappa index between the qPCR and the conventional methods was 0.12 (95% CI: -0.020-0.26). CONCLUSIONS: The diagnostic sensitivity of qPCR to detect strongyloidiasis is analogous to that of conventional parasitology methods, with an additional advantage of being capable of identifying the parasite DNA at low sample concentrations.