Sensitivity of Diagnostic Methods for Detecting S. stercoralis Infection and Comparison of the Total Global Number of Strongyloidiasis Cases with Other Recognized NTDs: A Systematic Review

Author(s): Heron Gezahegn

Background: Since 2005, global health policy makers have recognized and designated widespread poverty-related neglected diseases as NTDs (neglected tropical diseases). However, Strongyloides stercoralis infection is not included in the list of these recognized NTDs. A systematic review was conducted to estimate the total number of S. stercoralis infections in humans worldwide and compare the result with the prevalence data of other recognized NTDs. In addition, the sensitivity of diagnostic methods that were used for detecting Strongyloides stercoralis infection was evaluated. Methods: An electronic search of the PubMed, WHOLIS, and ISI Web of Science databases was performed for articles published between January 1990 and May 2017. Articles with quantitative data on prevalence, incidence, duration of infection, remission/cure, and mortality in humans were included. After obtaining the raw data from the systematic review, adjustments were made for diagnostic accuracy, selection of the reference population, and adjustments for age and reference year 2017 as a prerequisite for estimating the total number of strongyloidiasis cases in humans worldwide. The estimated number was then compared with other recognized neglected tropical diseases. The sensitivity of diagnostic methods for detecting Strongyloides stercoralis infection was also systematically investigated.

Findings: The electronic search included 166 articles to estimate the total number of strongyloidiasis infections. Data analysis yielded 159,542,655 and 260,710,055 strongyloidiasis infections in the best- and worst-case scenarios, respectively. Based on this estimate, the lowest estimated number of infections resulting from this review is between the fourth highest number of Schistosoma and the fifth highest number of foodborne trematodes, while the highest estimate is between the third highest number of hookworms and the fourth highest number of Schistosoma neglected tropical diseases recorded by GBD in terms of global prevalence cases. On the other hand, 47% of the diagnostic techniques identified in this review fall in the low sensitivity range, 45.2% in the medium sensitivity range, and 7.8% in the high sensitivity range.

Conclusions: The global number of human strongyloidiasis infections estimated in this report was higher than estimates for 13 of the 17 recognized Neglected Tropical Diseases (NTDs). In fact, the number of strongyloidiasis infections would have been higher if highly sensitive diagnostic tools had been used. In this context, it is important to note that only less than 10% of the diagnostic instruments used to diagnose the disease were classified as highly sensitive. Therefore, the current information emphasizes that S. stercoralis should not be neglected. Accordingly, the results of this study reflect a friendly appeal to the responsible agency to recognize human strongyloidiasis infection and add it to the list of other neglected tropical diseases.

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