The microtest wells were coated with Strongyloides antigen. One hundred microliters of diluted serum (1/64) was dispensed into the wells and incubated for 10min at room temperature. Next the wells were washed three times with the washing buffer provided, 100μl of protein A–peroxidase conjugate was added, and the mixture was incubated for 5min at room temperature. After washing and removing excess moisture, 100μl of tetramethylbenzidine was then dispensed into each well. After incubation at room temperature, the reaction was stopped by the addition of 100μl of 1M phosphoric acid. A negative control and a positive control provided by the manufacturer were included in each assay. The reading of the plates was carried out at 450nm/620nm, subtracting the blank from all wells. In this study we used a cut-off value of 0.200. A test was considered positive if the index (ratio of the OD measure of the sample and OD measure of the cut-off) was >1.1.