Accuracy of different diagnostic techniques for Schistosoma haematobium to estimate treatment needs in Zimbabwe: Application of a hierarchical Bayesian egg count model.

• Main Authors: Nicholas Midzi (Author), Oliver Bärenbold (Author), Portia Manangazira (Author), Isaac Phiri (Author), Masceline J Mutsaka-Makuvaza (Author), Gibson Mhlanga (Author), Jürg Utzinger (Author), Penelope Vounatsou (Author)
• Format: Book
• Published: Public Library of Science (PLoS), 2020-08-01T00:00:00Z.
• Subjects: article
• Online Access: Connect to this object online.
• Notes: 1935-2727; 1935-2735; 10.1371/journal.pntd.0008451
• Keywords: Arctic medicine. Tropical medicine; RC955-962; Public aspects of medicine; RA1-1270
• Source: PLoS Neglected Tropical Diseases, Vol 14, Iss 8, p e0008451 (2020)

<h4>Background</h4>Treatment needs for Schistosoma haematobium are commonly evaluated using urine filtration with detection of parasite eggs under a microscope. A common symptom of S. haematobium is hematuria, the passing of blood in urine. Hence, the use of hematuria-based diagnostic techniques as a proxy for the assessment of treatment needs has been considered. This study evaluates data from a national survey in Zimbabwe, where three hematuria-based diagnostic techniques, that is microhematuria, macrohematuria, and an anamnestic questionnaire pertaining to self-reported blood in urine, have been included in addition to urine filtration in 280 schools across 70 districts.<h4>Methodology</h4>We developed an egg count model, which evaluates the infection intensity-dependent sensitivity and the specificity of each diagnostic technique without relying on a 'gold' standard. Subsequently, we determined prevalence thresholds for each diagnostic technique, equivalent to a 10% urine filtration-based prevalence and compared classification of districts according to treatment strategy based on the different diagnostic methods.<h4>Principal findings</h4>A 10% urine filtration prevalence threshold corresponded to a 17.9% and 13.3% prevalence based on questionnaire and microhematuria, respectively. Both the questionnaire and the microhematuria showed a sensitivity and specificity of more than 85% for estimating treatment needs at the above thresholds. For diagnosis at individual level, the questionnaire showed the highest sensitivity (70.0%) followed by urine filtration (53.8%) and microhematuria (52.2%).<h4>Conclusions/significance</h4>The high sensitivity and specificity of a simple questionnaire to estimate treatment needs of S. haematobium suggests that it can be used as a rapid, low-cost method to estimate district prevalence. Our modeling approach can be expanded to include setting-dependent specificity of the technique and should be assessed in relation to other diagnostic methods due to potential cross-reaction with other diseases.