Screening for schistosomiasis, filariasis, and strongyloidiasis among expatriates returning from the tropics

The clinical utility of eosinophil determinations, stool examinations, and serological studies for detection of parasitic infection was examined in an asymptomatic expatriate population by retrospective chart review. The screened population consisted of 1,605 patients attending a tropical medicine clinic. The sensitivity of eosinophil counts as a screening test for infection with filaria, schistosomes, or Strongyloides stercoralis was 38%, and its positive predictive value was 9%. A cost-efficacy analysis of the use of three diagnostic tests in screening for infection with filaria (n = 23), schistosomes (n = 34), or Strongyloides (n = 7) was performed. The use of stool examination and serological screening together had a sensitivity of 89%, at a total cost similar to that of a conventional strategy involving a stool examination and an eosinophil count, which would have picked up only 61% of our cases. In this population, eosinophil counts contribute little to the diagnostic accuracy obtained with stool examination and serological screening, and the low specificity of eosinophil counts generates high costs.