Factors influencing performance of screening methods for urinary schistosomiasis among school children in Uwandani Pemba, Zanzibar - Tanzania, 2017

Abstract

Background: Correct diagnosis for urinary schistosomiasis is essential for patient management, drug efficacy evaluations, and monitoring of large-scale control programs. However diagnostic performance of screening (indirect) methods varies in different endemic zones, age groups and sex especially when there is low prevalence after large scale praziquantel mass drug administration (MDA) in a school based schistosomiasis control programme. Main Objective: To assess the factors influencing the performance of screening methods (self-reported, macro and micro haematuria and microscopy) in the diagnosis of urinary schistosomiasis after wide scale up MDA with praziquantel in a school-based schistosomiasis control programme. Materials and methods: A cross-sectional study was conducted in Uwandani Village Chakechake District from May to June, 2017. Probability sampling applied to obtain the schools and participants of the study. Uwandani School was selected and a total of 334 participants from standard I – VI were randomly selected. A structured questionnaire was used to collect information on demographic characteristics; self reported haematuria, and status of praziquantel administration. Each participant was provided with 50mls clean, dry wide mouthed and well caped labeled plastic containers for collecting about 20ml of clean-catch, midstream urine sample between 10:00hrs and 14:00hr. The SPSS software version 16.0 was used to make data analysis. The diagnostic performance of dipstick screening test was compared with microscopic examination of urine for S. haematobium egg (filtration method, as the gold standard). Results: The prevalence of urinary schistosomiasis increased and decreased with age. The highest prevalence occur among students aged between 13 – 15 years (4.66%) and 6 – 9 years (4.33%) but lower in age between 10 – 12 years (2.0%) for both sexes, but the difference was not significant (P > 0.05). The prevalence by reported haematuria was 19.3% of which the prevalence was 15% males and 4.33% females. The prevalence by reported haematuria with age group was (6%) at the age of 13-15 years and 10-12 years (5.66%) for males while the prevalence was 0% among students aged 13-15 years and 2.0% in the age of 10-12 years in females. For pupils aged at 6-9 the prevalence was 3.33% in males and 2.33% in females. The overall prevalence by visual haematuria was 3.7% in which (1.33%) students were males and (0.33%) were females aged 13-15 years while the prevalence in students aged 6-9 years was 0.33% in males and 1.6% in females. Those students aged at 10-12 years had 0% prevalence. Urine dipstick results revealed that 70 participants had haematuria of which 38 were girls (24.2%) and 32 were boys (22.4%). The overall intensity of infection was 33 (11%) participants were confirmed to have urinary Schistosomiasis, in which 17 had light infection (5.67%), where males were 9 (3%) and 8 females (2.67%). Additionally, 5 participants (1.66%) had mild infection in which males were 2 (0.67%) and 3 females (1%) and finally 11 (3.67%) had heavy infection where 5 of them were males (1.67%) and 6 female (2%). The sensitivity and specificity of self reported haematuria was 21.2% and 81% respectively. The negative predictive value (NPV) was 89.3% while positive predictive (PPV) value was 12.1%. The sensitivity and specificity of visual examination was 33.3% and 100% respectively. The negative predictive value (NPV) was 92.4% while positive predictive (PPV) value was 100%. The sensitivity and specificity of chemical reagent strips for haematuria was 39.4%and 75.3% respectively. The negative predictive value (NPV) was 91% while positive predictive (PPV) value was 16.5%. The logistic regression analysis showed that, sex and intensity had significant correlation with false positive results and influence the performance of self reported haematuria (p < 0.05 and p < 0.001) respectively. The intensity of infection also influenced the performance of visual haematuria and microhaematuria as (p < 0.001) and associated with false positive results. Conclusion: Among the three diagnostic tests used in this study the urine dipstick for microhaematuria has been shown to be highly performing test for rapid screening of urinary schistosomiasis influenced by the intensity of infection. The visual haematuria still remain as useful test for rapid screening of urinary schistosomiasis but the test should be confirmed by microscopy (filtration method).