Comparison of the Kato-Katz, Wet Mount, and Formol-Ether Concentration Diagnostic Techniques for Intestinal Helminth Infections in Ethiopia

Objective. The aim of this study was to evaluate the operational characteristics (sensitivity and negative predictive value (NPV)) of wet mount, formol-ether concentration (FEC), and Kato-Katz techniques for the determination of intestinal parasitic infections. Method. A total of 354 faecal specimens were collected from students in Northwest Ethiopia and screened with Kato-Katz, wet mount, and FEC for the presence of intestinal parasitic infection. Since a gold standard test is not available for detection of intestinal parasites, the combined results from the three methods were used as diagnostic gold standard. Result. The prevalences of intestinal parasites using the single wet mount, FEC, and Kato-Katz thick smear techniques were 38.4%, 57.1%, and 59%, respectively. Taking the combined results of three techniques as a standard test for intestinal parasitic infection, the sensitivity and negative predictive value of Kato-Katz is 81.0% (confidence interval (CI)？=？0.793–0.810) and 66.2% (CI？=？0.63–0.622), respectively. The FEC detected 56 negative samples that were positive by the gold standard, indicating 78.3% (CI？=？0.766–0.783) and 63.2% (CI？=？0.603–63) sensitivity and NPV, respectively. Furthermore, Kato-Katz detects 113 cases that were negative by a single wet mount. The agreement between the wet mount and Kato-Katz methods for the diagnosis of Ascaris lumbricoides and hookworm was substantial ( for Ascaris lumbricoides, for hookworm). 1. Background Intestinal parasitic infections are among the most common infections worldwide. It is estimated that 3.5 billion people are affected, and 450 million are ill as a result of these infections, the majority being children [1]. In Ethiopia, intestinal parasitic infection is the second most predominant cause of outpatient morbidity. However, there are difficulties in estimating the exact burden of parasitic infections in the country [2]. Although there are several factors that make estimating the number and burden of intestinal parasitic infections difficult, lack of accurate diagnostic tools is the major one [3–9]. Although several diagnostic methods such as Kato-Katz and Formol-Ether Concentration (FEC) techniques are available, direct wet mount is the commonly used as a reliable diagnosis method for the diagnosis of intestinal parasitic infections generally in Africa and particularly in Ethiopia [10–13]. However, low sensitivity of the direct wet mount technique has been reported in the detection of low-intensity infection elsewhere [14]. This shows that the use of direct wet mount as a confirmatory test