Accuracy of the kato-katz method in diagnosis of s.mansoni and soil transmitted helminths infection in Zimbabwe.

Abstract

Introduction: Mapping of schistosomiasis and soil transmitted helminths infection in Zimbabwe was prioritized for evidence based treatment control strategy in year 2010. Two diagnostics tests: Kato-Katz (KK) and fomol ether concentration (FEC) were used during the mapping process. Objective: This study aimed to determine the sensitivity and specificity of Kato-Katz technique in the absence of a gold standard using Bayesian modelling for the determination of S. mansoni and soil transmitted helminths infection (STHs) in Zimbabwe. Methods: This is a secondary data analysis based on primary school children (n=15 818) aged 10-15 years who were enrolled in the national mapping of S. mansoni and STHs study, since they were reported to be the most exposed age group. Both parasitic infection by S. mansoni and STHs were diagnosed using a combination of two diagnostic techniques: the Kato Katz technique and the formol-ether concentration technique. A Bayesian approach was used to evaluate the diagnostic performance of the evaluation tool. Results: The formol ether diagnostic technique was generally more sensitive with S. mansoni detection operational characteristics as follows (Sensitivity: 0.995; 95% Bayesian Credible Interval (BCI): 0.989 - 0.999), STHs- Hookworm detection (Sensitivity: 0.991; 95% BCI;0.988 - 0.993 ) , STHs– A. lumbricoides detection (Sensitivity:0.992; 95% BCI;0.989 - 0.995) and STHs– T. trichiuria (Sensitivity:0.988 95% BCI: 0.926 - 1.00); than the Kato- Katz diagnostic technique (for S. mansoni detection (Sensitivity: 0.981; 95% BCI:0.971 - 0.994), STHs - Hookworm detection (Sensitivity:0.966; 95% BCI;0.963 - 0.970) , STHs – A. lumbricoides detection (Sensitivity: 0.967; 95% BCI;0.974-0.981) and STHs – T. trichiuria (Sensitivity:0.988; 95% BCI;0.974 - 0.981). However, specificity is higher for the Kato- Katz technique compared to the formol ether concentration technique. Conclusion: The formol ether concentration technique has better sensitivity compared to the Kato-Katz technique, but however it has less specificity compared to the formol ether concentration technique. been shown for the Kato – Katz technique for all the infections respectively.