Assessing stool quantities generated by three specific Kato-Katz thick smear templates employed in different settings

Background:The Kato-Katz technique is recommended for the diagnosis of helminth infections in epidemiological surveys,drug efficacy studies and monitoring of control interventions.We assessed the comparability of the average amount of faeces generated by three Kato-Katz templates included in test kits from two different providers.Methods:Nine hundred Kato-Katz thick smear preparations were done;300 per kit.Empty slides,slides plus Kato-Katz template filled with stool and slides plus stool after careful removal of the template were weighed to the nearest 0.1 mg.The average amount of stool that was generated on the slide was calculated for each template,stratified by standard categories of stool consistency(i.e.mushy,soft,sausage-shaped,hard and clumpy).Results:The average amount of stool generated on slides was 40.7 mg(95%confidence interval(CI):40.0–41.4 mg),40.3 mg(95%CI:39.7–40.9 mg)and 42.8 mg(95%CI:42.2–43.3 mg)for the standard Vestergaard Frandsen template,and two different templates from the Chinese Center for Disease Control and Prevention(China CDC),respectively.Mushy stool resulted in considerably lower average weights when the Vestergaard Frandsen(37.0 mg;95%CI:34.9–39.0 mg)or new China CDC templates(37.4 mg;95%CI:35.9–38.9 mg)were used,compared to the old China CDC template(42.2 mg;95%CI:40.7–43.7 mg)and compared to other stool consistency categories.Conclusion:The average amount of stool generated by three specific Kato-Katz templates was similar(40.3–42.8 mg).Since the multiplication factor is somewhat arbitrary and small changes only have little effect on infection intensity categories,it is suggested that the standard multiplication factor of 24 should be kept for the calculation of eggs per gram of faeces for all investigated templates.

Distinct clinical characteristics and helminth co-infections in adult tuberculosis patients from urban compared to rural Tanzania

Background:Differences in rural and urban settings could account for distinct characteristics in the epidemiology of tuberculosis(TB).We comparatively studied epidemiological features of TB and helminth co-infections in adult patients from rural and urban settings of Tanzania.Methods:Adult patients(≥18 years)with microbiologically confirmed pulmonary TB were consecutively enrolled into two cohorts in Dar es Salaam,with~4.4 million inhabitants(urban),and Ifakara in the sparsely populated Kilombero District with~400000 inhabitants(rural).Clinical data were obtained at recruitment.Stool and urine samples were subjected to diagnose helminthiases using Kato-Katz,Baermann,urine filtration,and circulating cathodic antigen tests.Differences between groups were assessed byχ2,Fisher’s exact,and Wilcoxon rank sum tests.Logistic regression models were used to determine associations.Results:Between August 2015 and February 2017,668 patients were enrolled,460(68.9%)at the urban and 208(31.1%)at the rural site.Median patient age was 35 years(interquartile range[IQR]:27-41.5 years),and 454(68%)were males.Patients from the rural setting were older(median age 37 years vs.34 years,P=0.003),had a lower median body mass index(17.5 kg/m2 vs.18.5 kg/m2,P<0.001),a higher proportion of recurrent TB cases(9%vs.1%,P<0.001),and in HIV/TB co-infected patients a lower median CD4 cell counts(147 cells/μl vs.249 cells/μl,P=0.02)compared to those from urban Tanzania.There was no significant difference in frequencies of HIV infection,diabetes mellitus,and haemoglobin concentration levels between the two settings.The overall prevalence of helminth co-infections was 22.9%(95%confidence interval[CI]:20.4-27.0%).The significantly higher prevalence of helminth infections at the urban site(25.7%vs.17.3%,P=0.018)was predominantly driven by Strongyloides stercoralis(17.0%vs.4.8%,P<0.001)and Schistosoma mansoni infection(4.1%vs.16.4%,P<0.001).Recurrent TB was associated with living in a rural setting(adjusted odds ratio[aOR]:3.97,95%CI:1.16-13.67)and increasing age(aOR:1.06,95%CI:1.02-1.10).Conclusions:Clinical characteristics and helminth co-infections pattern differ in TB patients in urban and rural Tanzania.The differences underline the need for setting-specific,tailored public health interventions to improve clinical management of TB and comorbidities.