Helminth species-specific fecal egg counts (FECs) as recorded by the microscopists were transformed into numbers of eggs http://www.selleckchem.com/products/Rapamycin.html per gram of stool (EPG), multiplying the FEC of each Kato-Katz reading by a factor 24. To assess the infection intensity of each individual, we calculated the arithmetic mean EPG value of quadruplicate Kato-Katz thick smear readings and categorized them according to thresholds given by WHO [1]. The three infection intensity classes for S. mansoni are (i) light (1�C99 EPG); (ii) moderate (100�C399 EPG); and (iii) heavy (��400 EPG). Means were compared by Wilcoxon signed rank test and proportions by Pearson’s ��2 test. Based on POC-CCA test scores, the infection intensity of S. mansoni was categorized into light (trace or 1+), moderate (2+) and heavy (3+).
To investigate the infection intensity of all infected individuals, we calculated the group arithmetic mean of the individual arithmetic mean EPG values. When using the combined results of the POC-CCA tests from days 1 and 2, discordant scores were redefined to provide a single infection intensity measure, as shown in Table 1. Table 1 Scoring scheme to obtain final urine POC-CCA cassette test results. For determining the POC-CCA test accuracy, ��trace�� results were considered as negative in our ��gold�� standard, due to the fact that ��trace�� can indicate false positivity. Thus, the accuracy of the Kato-Katz and POC-CCA tests (considering trace results as negative (t?)) for the diagnosis of S. mansoni was determined.
As diagnostic ��gold�� standard before and after treatment we considered the combined results of quadruplicate Kato-Katz thick smears and duplicate CCA(t?), resulting in a positive case as both or either of the tests was positive (see also Midzi et al. [33]). This assumes an (almost) 100% specificity for the CCA(t?) test. Based on this ��gold�� standard, sensitivity, specificity, and negative predictive value (NPV) were calculated. The strength of agreement between quadruplicate Kato-Katz thick smears and the POC-CCA test before treatment was assessed by kappa statistics (��), as follows: ��=0 indicating no agreement; ��=0�C0.2 indicating poor agreement; ��=0.21�C0.4 indicating fair agreement; ��=0.41�C0.6 indicating moderate agreement; ��=0.61�C0.8 indicating substantial agreement; and ��=0.81�C1.0 indicating almost perfect agreement [34], [35]. Differences of p<0.
05 were considered as statistically significant. A univariable logistic regression was performed to assess the association between POC-CCA cassette test results, expressed as binary outcome variable (negative/positive), and a schistosome Brefeldin_A infection, with separate models for S. mansoni and S. haematobium. Hence, egg counts from each schistosome species were utilized as explanatory variable (eggs per gram of stool (EPG) for S. mansoni and eggs per 10 ml of urine for S. haematobium).