Evaluation of a technique of circumoval precipitin test using blood taken on filter paper and a microtiter technique of complement fixation test of Schistosoma japonicum.

For the circumoval precipitin test (COPT) blood was taken on quantitative blood sampling filter paper by finger prick from outpatients at the Schistosomiasis Control Pilot Project, Palo, Leyte, Philippines. The volume of serum available per strip of filter paper was 0.04 ml and this was extracted at 1:3, 1:5 and 1:8 dilutions. Lyophilized eggs of Schistosoma japonicum were mixed with the diluted serum on a microscope glass slide and incubated at 37 degrees C for 2 days. The reaction was read following the criterion made by Yokogawa et al. [11]. The serum at 1:8 was too dilute to make correct diagnosis; serum at 1:3 dilution contained too much hemoglobin which made microscopic observation difficult and the extract at 1:5 was found to be appropriate. There was no remarkable difference in antigenicity among 3 preparations of lyophilized eggs from Kofu strain, Japan, and those of new and old preparations from Philippine strain. Under the best condition, false negative results appeared in 15.3% of 152 outpatients in Leyte and false positives in 2% of 50 human sera collected in Tokyo. This method of COPT is not satisfactory for the diagnosis of individual cases but is useful in the epidemiological assessment of Schistosoma infections because of the simplicity of blood sampling from dwellers of infested areas and also because it shows nearly the same sensitivity as that of a single fecal examination by the MIFC method. A microtiter technique of complement fixation test (CFT) was also studied. This method, however, was less sensitive than the COPT or a single fecal examination as to give 23.7% false negatives. Frequency distributions of CF and COP titers were analysed among egg positive, egg negative and treated groups. The results showed that treatment with stibophen had little influence in lowering the serum response, especially in COPT.