[Study on the mixed testing of serum samples in seroepidemiological survey of parasitic diseases]

In order to accumulate experiences for improving the efficiency in serological tests, the present study on mixed testing of serum samples was performed by taking the serological test of trichinellosis and toxoplasmosis as the examples, and had proved the effects on cost-effectiveness of seroepidemiological survey of parasitic disease with method of mixed-samples test.

According to the binomial distribution principle, to develop an approach to the feasibility of mixed testing of serum samples, and to work on a cost-effectiveness analysis of one-by-one testing and mixed testing using hygienic economic analysis method was performed. For serological test of trichinellosis and toxoplasmosis, 3 kinds of mixed testing methods, namely 3 serum sample mixture, 5 serum sample mixture and 10 serum sample mixture, were performed.

The results showed that all the 3 kinds of mixed tests of trichinellosis and toxoplasmosis showing positive result if only 1 weak positive serum sample were mixed with. When the serum samples being mixed were all negative ones, then among the 24 groups tested with each kind of negative serum sample mixture of trichinellosis (3 serum samples, 5 serum samples and 10 serum samples), they all showed negative. However, among the 12 groups tested with 2 kinds of negative serum mixture of toxoplasmosis (3 serum samples and 5 serum samples), all showed negative while among the 18 groups tested with the 10 serum sample mixture, 16 groups showed negative and 2 were positive. The mixed testing of trichinellosis and toxoplasmosis showed that the efficiency of mixed testing was related to the serological positive rate of the parasitic diseases to be examined. When serological positive rate was 10%, the efficiency of mixed testing was higher in 4 serum sample group. When serological positive rate was 1%, the efficiency of mixed testing was higher in 10 serum sample group and when serological positive rate was 0.1%, the in crease of the size of mixed serum samples could decrease the number of testing, but the prerequisite was that there must be one positive sample, so that the positivity for all the mixed tests could be detected. If mixed testing were performed on all negative samples, no positivity could be detected.

The result of cost-effectiveness analysis demonstrated that for seroepidemiological survey of parasitic diseases, the cost for mixed testing was low, especially when the serological positive rate was expected low (< or = 1%, thus the mixed testing could save a large amount of the cost.