Comparison of mini-flotac and Kato-Katz methods for detecting soil-transmitted helminth eggs in 10% formalin preserved stools stored >=12 months

In Soil-Transmitted Helminth (STH) control programs, microscopic examination is applied as a standard method for detecting the presence and the number of STH eggs. The time limitations of fresh specimen processing, especially for an accurate quantitative diagnosis, cause the specimen processing to be delayed or should be performed at a referral laboratory. This deferment requires preservatives to keep the stool integrity without reducing the accuracy. The aims of this study were: 1) to compare the proportion of positive samples and the intensity of A. lumbricoides, T. trichiura, and hookworm infection based on the examination of fresh samples and stool preserved by 10% formalin for >12 months and 2) to determine the most reliably accurate between Kato-Katz and mini-FLOTAC methods in detecting A. lumbricoides, T. trichiura, and hookworm eggs in preserved stools both qualitatively and quantitatively. Seventy-eight (78) stool samples were examined by mini-FLOTAC, and KatoKatz methods. Proportion of positive samples of A. lumbricoides, T. trichiura, and hookworms in fresh and in >=12 months 10% formalin preserved stools had no significant difference. Helminths density (eggs per gram of stool/EPG) in fresh samples was fewer compared to EPG in preserved samples (p <0.05) which leads to a lower proportion of moderate and high level groups in fresh stools samples compared to those in preserved samples (p <0.05). In preserved samples, as qualitative method, mini-FLOTAC detected more A. lumbricoides and T. trichiura eggs than Kato-Katz, while hookworm eggs were detected more by Kato-Katz than the miniFLOTAC. As a quantitative detection, Kato-Katz showed higher calculation of STH EPG than mini-FLOTAC. Using 10% formalin preservation for stool samples, the STH eggs' morphology could still be well identified. Homogenization process and low number of samples tested, were acknowledged as the limitation of this study.