Efficacy of Stool Examination for Detection of Strongyloides Infection

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  • Department of Parasitology, and Research Center of Comprehensive Medicine, School of Medicine, University of the Ryukyus, Izumizaki Hospital, Nishihara, Okinawa, Japan
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To determine the efficacy of stool examination for detection of Strongyloides infection, 1,350 stool samples collected in Japan, Brazil, and Thailand were examined by four different methods (direct fecal smear, formalin-ether concentration, Harada-Mori filter paper culture, and agar plate culture). The newly developed agar plate culture method was highly effective; more than 96% of the positive cases were diagnosed by this method. The coprologic examination, however, was not sensitive enough for detecting chronic infections because more than 40% of the positive cases were overlooked even when persons with proven Strongyloides infection were re-examined several months later without intervening treatment. Therefore, it is essential to examine stool samples repeatedly to achieve a correct diagnosis, and even so, it is important to note that a negative result does not necessarily indicate the unequivocal absence of the infection.