Accuracy, acceptability, and feasibility of diagnostic tests for the screening of Strongyloides stercoralis in the field (ESTRELLA): a cross-sectional study in Ecuador.

BACKGROUND

WHO recommends the implementation of control programmes for strongyloidiasis, a neglected tropical disease caused by Strongyloides stercoralis. Specific recommendations on the diagnostic test or tests to be used for such programmes have yet to be defined. The primary objective of this study was to estimate the accuracy of five tests for strongyloidiasis. Secondary objectives were to evaluate acceptability and feasibility of use in an endemic area.

METHODS

The ESTRELLA study was a cross-sectional study for which we enrolled school-age children living in remote villages of Ecuador. Recruitment took place in two periods (Sept 9-19, 2021, and April 18-June 11, 2022). Children supplied one fresh stool sample and underwent blood collection via finger prick. Faecal tests were a modified Baermann method and an in-house real-time PCR test. Antibody assays were a recombinant antigen rapid diagnostic test; a crude antigen-based ELISA (Bordier ELISA); and an ELISA based on two recombinant antigens (Strongy Detect ELISA). A Bayesian latent class model was used to analyse the data.

FINDINGS: 778 children were enrolled in the study and provided the required samples. Strongy Detect ELISA had the highest sensitivity at 83·5% (95% credible interval 73·8-91·8), while Bordier ELISA had the highest specificity (100%, 99·8-100). Bordier ELISA plus either PCR or Baermann had the best performance in terms of positive and negative predictive values. The procedures were well accepted by the target population. However, study staff found the Baermann method cumbersome and time-consuming and were concerned about the amount of plastic waste produced.

INTERPRETATION: The combination of Bordier ELISA with either faecal test performed best in this study. Practical aspects (including costs, logistics, and local expertise) should, however, also be taken into consideration when selecting tests in different contexts. Acceptability might differ in other settings.

FUNDING: Italian Ministry of Health.

TRANSLATION: For the Spanish translation of the abstract see Supplementary Materials section.