Volume 7, Issue 2
  • ISSN: 0002-9637
  • E-ISSN: 1476-1645


Summary and Conclusions

Estimations of efficiency of the formalin-ether sedimentation concentration procedure for the detection of ten common intestinal parasites have been determined from an analysis of data obtained in multiple-stool examination series. Approximately 1,000 residents of four, rural, Japanese villages were examined in two five-stool series and findings were analyzed by the maximum-likelihood method of Sawitz and Karpinos. Mean estimates of efficiency for the detection of protozoan cysts were comparable to those computed by other investigators for the ZnSO centrifugation-flotation technic. These estimates, in per cent, for the formalin-ether procedure were 60.2 for ; 75.1 for ; 60.4 for ; 55.7 for ; and 44.5 for . Corresponding figures for helminths were: 91.9 for ; 92.2 for ; 78.9 for hookworm; 41.1 for sp.; and 47.6 for .

The efficiency of the formalin-ether procedure for the detection of some organisms, especially protozoan cysts, was observed to vary and, in some instances, the differences were probably significant. These variations are assumed to be due to a combination of factors including technical error, limitations of the analytical method and the examination procedure itself, possible biologic characteristics of the organisms that might affect their detection, and normal fluctuations in the mean infection intensity in the different population groups.

Re-examination of about one-half of the people within 60 days after the initial examination series permitted a better estimate of the reliability of the technic. The number of additional infections detected in the second examination series was about equal in all instances to the number of cases present in the first series, but absent in the second. The rate of misses for was no greater than the rate for more easily recognized forms. On the basis of the latter data, it was estimated that examination of five separate stools by the formalin-ether technic will detect about 97 per cent of amebiasis cases in a population. Similar data were also obtained for the other nine parasites.


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