Quantification of amebae specific antibodies as "Multiple of normal activity (MONA)" with a standardized enzyme immunoassay (EIA).

Sera of 853 returnees from tropical countries, of 24 cases with amebic liver abscess and of 172 nonexposed German individuals were tested for antibodies to E. histolytica in the enzyme immunoassay (EIA). Antibody results were expressed as "multiple of normal activity (MONA)". The qualification of the EIA as a routine screening procedure for amebae specific antibodies was investigated and compared to that of the complement fixation test. Based on the symmetric frequency distribution of results from the 172 non-exposed controls the upper one sided limits for 95% (less than 2.8 MONA) and 99% (less than 4.2 MONA) specificity were determined. Routine results below the 95% specificity limit were considered "inconspicuous", such between both limits "borderline" and all MONA values exceeding the 99% specificity limit "conspicuous". The intention was to thereby secure a high degree of sensitivity for amebae antibody in the test. Cases with clinically confirmed liver abscess revealed a one sided lower 95% sensitivity limit (greater than or equal to 1.2 MONA), far above the onset of the defined sensitivity thresholds for conspicuous MONA values.