Evaluation of three methods for laboratory diagnosis of Strongyloides stercoralis infection

The direct smear, a modified Baermann technique, and the agar plate culture method were compared for cost and efficiency in recovering Strongyloides stercoralis larvae in a hospital setting in Honduras. Of 427 stool samples, 9 were positive by the direct smear and 33 additional ones were detected by the Baermann technique; the agar plate culture method disclosed 28 more cases for a total of 70 S. stercoralis infections. The modified Baermann method was 3.6 times more efficient than the direct smear, and the agar plate culture increased the modified Baermann efficiency by 0.8 times. Cost for materials alone was cheapest for the direct smear; it increased 4 times for the modified Baermann method and 15 times for the agar plate culture method. This last technique required a better equipped laboratory, more time to perform, and the best trained, most skillful laboratory personnel. In field studies, prevalence of infection should determine the cost-effectiveness of the agar plate culture method; in a clinical setting, when S. stercoralis infection must be ruled out, the agar plate culture method should be made available to the medical community.