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

Abstract

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 κ agreement between the wet mount and Kato-Katz methods for the diagnosis of Ascaris lumbricoides and hookworm was substantial ( κ = 0.61 for Ascaris lumbricoides , κ = 0.65 for hookworm).