Comparison of parasitological methods for the identification of soil-transmitted helminths, including Strongyloides stercoralis, in a regional reference laboratory in northwestern Argentina: An observational study

Abstract

Soil-transmitted helminths (STH) are a significant public health problem in impoverished communitiesof tropical and subtropical areas. Improved diagnostic methods are crucial for NeglectedTropical Diseases programs, particularly for S. stercoralis, as traditional methods are inadequate.Thus, it is important to identify the most accurate and efficient methods for the diagnosis of STH.We performed a retrospective study analyzing laboratory data at the Instituto de Investigacionesde Enfermedades Tropicales from 2010 to 2019. The study included data from outpatientsreferred for stool analysis and public health interventions from urban and rural communities innorthern Salta province, Argentina. Samples were included in this analysis if processed throughsedimentation/concentration, Baermann, Harada-Mori and McMaster´s, with a subgroup that alsoincluded Agar plate culture method (APC). Sensitivity was calculated against a compositereference standard. Of the 5625 samples collected, 944 qualified for this analysis, with a prevalenceof 11.14% for A. lumbricoides, 8.16% for hookworm, 1.38% for T. trichiura, and 6.36% forS. stercoralis. The sedimentation/concentration method was the most sensitive for A. lumbricoides(96%), compared to the McMaster method, with a sensitivity of 62%. Similarly, for hookworms,sedimentation/concentration was more sensitive than McMaster´s, Harada-Mori, and Baermannwith sensitivities of 87%, 70%, 43%, and 13%, respectively. Most of these infections were of light intensity. For S. stercoralis, Baermann and sedimentation/concentration methods were the mostsensitive, with 70% and 62% respectively, while Harada-Mori was the least sensitive. In a subsetof 389 samples also analyzed by the APC, Baermann was more sensitive than APC for detectingS. stercoralis, and both methods were superior to Harada-Mori. Parasitological methods, mostlywhen used combined, offer adequate opportunities for the diagnosis of STH in clinical and publichealth laboratories. The incorporation of S. stercoralis into the control strategies of the WorldHealth Organization requires rethinking the current diagnostic approach used for surveys. Withsedimentation/concentration and Baermann appearing as the most sensitive methods for thisspecies. Further studies, including implementation assessments, should help in identifying themost adequate and feasible all-STH diagnostic approach.