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

Midzi, Nicholas; Bärenbold, Oliver; Manangazira, Portia; Phiri, Isaac; Mutsaka-Makuvaza, Masceline J.; Mhlanga, Gibson; Utzinger, Jürg; Vounatsou, Penelope

Background: 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. Methodology: 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. Principal findings: 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 at (70.0%) followed by urine filtration (53.8%) and microhematuria (52.2%). Conclusions/Significance: 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. Author summary: The strategy of the World Health Organization (WHO) to combat schistosomiasis is based on administering praziquantel as preventive chemotherapy to school-age children only, or including adults. For Schistosoma haematobium the treatment decision is based on observed prevalence by urine filtration which involves counting eggs under a light microscope. Urine filtration is time intensive and requires trained technicians to operate the microscope. Blood in urine is a common symptom of urogenital schistosomiasis and therefore, the use of screening tools based on the detection of hematuria has been suggested. We analyze three such screening tools, namely reagent strip to detect microhematuria, a questionnaire regarding recent history of blood in urine, and visible inspection of urine and determine their diagnostic accuracy to evaluate treatment need at district level in comparison to urine filtration in a national survey in Zimbabwe. We find that both the questionnaire and reagent strip classify districts with sensitivity and specificity above 85% at the 10% urine filtration thresholds. Wrongly classified districts generally show urine filtration prevalence in the vicinity of the 10% prevalence thresholds. We conclude that there is evidence that a questionnaire can be used as a low cost alternative rapid screening tool for S. haematobium.

ZIMBABWE; SCHISTOSOMA haematobium; WORLD Health Organization; MICROSCOPES; RAPID tooling; OPPORTUNITY costs; EGGS

PLoS Neglected Tropical Diseases, 2020, Vol 15, Issue 8, p1

1935-2727

Academic Journal

10.1371/journal.pntd.0008451