The theory of amoebic surveys

Abstract

(i) The theory of amoebic surveys and of related types of pathological surveys is discussed.(ii) An inequality is derived, whereXis the total number of carriers andX₁,X₂are the new carriers found at the first and second examinations.(iii) Demonstrability is defined and several theoretical distributions of it are considered.(iv) Demonstrability is shown not to be a constant in the populations considered.(v) The danger of extrapolation is noted.(vi) Life-table methods are introduced to treat some well-known published series.(vii) A criterion for the adequacy of any estimate of the total carrier rate is given. The mean demonstrability of the outstanding carriers after successive examinations must form a decreasing series.(viii) This criterion usually shows that the method of estimating the carrier rate forEntamoeba histolyticaas three times the proportion of positives at a single examination, or as the total number of positives picked up in six examinations, both give too low a carrier rate.(ix) It is suggested that the investigation of the ‘carrier’ rate may in certain cases be merely a measure of ‘demonstrability’.(x) Possible future lines of investigation of the problem are noted.