Evaluation of five diagnostic methods for Strongyloides stercoralis infection in Amhara National Regional State, northwest Ethiopia

Abstract

Background Strongyloides stercoralis is an intestinal parasite that can cause chronic infection, hyperinfection and/or a dissemination syndrome in humans. The use of techniques targeting ova fails to detect S. stercoralis, as only larvae of the parasite are excreted in faeces. Due to the absence of “Gold” standard diagnostic method for S. stercoralis, there is a paucity of reported data worldwide. Objective This study aimed to evaluate the performance of diagnostic methods of S. stercoralis infection by taking the composite reference as a “Gold” standard. Methods A cross-sectional study was conducted among 844 schoolchildren in Amhara Region, Ethiopia, from April to December 2019. Stool samples were collected and processed with formol-ether concentration technique (FECT), spontaneous tube sedimentation technique (STST), Baermann concentration technique (BCT), agar plate culture (APC) and real-time polymerase chain reaction (RT-PCR). Sensitivity, specificity, positive predictive value, and negative predictive value of each diagnostic method were computed against the composite reference. The agreements of diagnostic methods were evaluated by Kappa value at 95% CI. Results The composite detection rate of S. stercoralis by the five diagnostic methods was 39.0% (329/844). The detection rate of the parasite from stool samples by FECT, STST, BCT, APC and RT-PCR was 2.0% (17/844), 4.0% (34/844), 10.2% (86/844), 10.9% (92/844) and 28.8% (243/844), respectively. The highest detection rate (37.8%; 319/844) of S. stercoralis was recorded by a combination of BCT, APC, and RT-PCR followed by a combination of STST, BCT, APC and RT-PCR (37.3%; 315/844). The sensitivity of FECT, STST, BCT, APC and RT-PCR against the composite reference was 5.2%, 10.3%, 26.4%, 28.0% and 73.9%, respectively. The diagnostic agreements of RT-PCR, APC, BCT, STST and FECT with the composite reference in detection of S. stercoralis were substantial (0.775), fair (0.321), fair (0.305), slight (0.123), and slight (0.062), respectively. Conclusion RT-PCR detected the highest number of S. stercoralis infections. A combination of RT-PCR with APC and/or BCT better detected S. stercoralis from stool samples compared to other combinations or single diagnostic methods. Therefore, RT-PCR and combination of RT-PCR with APC and/or BCT diagnostic methods should be advocated for detection of S. stercoralis infection.

Seroprevalence and microscopy detection rates of strongyloidiasis in Croatian patients with eosinophilia

“…The latter is important as the MIFC concentration procedure is still predominantly utilized as a standard diagnostic tool in most microbiology laboratories in Croatia and other neighbouring countries; however, it is actually insufficiently sensitive, taking into account the importance and increasing recognition of this disease. Studies have shown how the Baermann concentration technique and agar plate culture have a much better diagnostic yield, but the number of stool samples, faecal amount and/or faecal dilution also affect sensitivity and detection power (Hailu et al, 2022). Importantly, a meta-analysis by Campo Polanco et al (2014) that evaluated conventional parasitological methods for the diagnosis of S. stercoralis found the highest sensitivity for the agar plate method (89%), followed by the Baermann technique (72%), formalin-ether concentration technique (which is akin to the MIFC method) (48%) and direct wet smear (21%).…”

Cost-effectiveness of mass drug administration with ivermectin against strongyloidiasis: a modelling study

“…This assumption was based on the prevalence of symptoms among cases with diagnosed infection 26 and the fact that the sensitivity of Baermann or stool culture is in the order of 50%. 11,27,28 Therefore, we are ignoring potential YLDs in undiagnosed cases of infection, meaning that our estimates of cost-effectiveness are conservative. However, as this equally affects our estimates for school-based and community-based PC, we do not expect that this uncertainty about the proportion of infected cases with symptoms affects our conclusions about community-based PC being the most cost-effective strategy.…”

Helminth infections and associated risk factors among adults in the Lao People’s Democratic Republic

“…infection. The parasitological tests such as Baermann and Agar plate culture for S. stercoralis [54] and a coproantigen ELISA for Taenia spp. infection [55,56] would provide a considerably higher sensitivity than FECT analysis.…”