COMPARISON BETWEEN SEROLOGICAL METHOD AND COPROPARASITOLOGICAL METHODS TO DETECT HUMAN STRONGYLOIDIOSIS
Ayman A. El-Badry
Parasitology Department, Faculty of Medicine, Cairo University
The diagnosis of Strongyloides stercoralis infections is routinely made by microscopic observation of larvae in stool samples, a low sensitivity method, or by other, more effective methods, such as the Baermann or agar culture plate methods. Alternatively, several immunological methods for diagnosis of strongyloidiosis have been developed, the most widely used method for diagnosis is the indirect enzyme-linked immunosorbent assay (ELISA). Faecal and serum samples were collected from 406 people attending primary health care centres in Giza province suffering from abdominal pain and/or colic. Faecal samples were analyzed using the direct smear test (DST), modified formalin-ethyl acetate technique (MFECT), agar culture plate technique (ACPT) and the modified Baermann method (MBM). Serum samples from same patients were analysed by ELISA using an antigen obtained from 3rd stage infective larvae of S. stercoralis. Larvae of S. stercoralis were detected in 19 samples (4.7%) by the MBM, 18 samples (4.4%) were positive using the ACPT, 13 samples (3.2%) were positive using the MFECT, and only in 4 samples (0.89%) the larvae were observed using DST of faecal smears. Data obtained suggested that MBM is a simple, easy rapid test and may help to concentrate larvae of S. stercoralis as efficiently or even more than other copro-parasitological methods. Results obtained by ELISA using an antigen obtained from 3rd stage infective larvae of S. stercoralis were useful in diagnosis of human strongyloidiosis, with sensitivity of 94.7% and specificity of 93.7%. ELISA is a highly sensitive test for patients with suspected chronic S. stercoralis infection, however, false positive results and cross reactivity were present. Therefore; MBM and ACPT are recommended as the most efficient methods and the tests of choice for the detection of S. stercoralis larvae and, if feasible, ELISA should be used as supplementary screening test of strongyloidiosis.