Diagnostic Evaluation of Complement Fixation Test for Japanese B

Encephalitis Compared with Other Serological Tests

Abstract

Complement fixation test (CF), hemagglutination inhibition test (HI), neutralisation test (NT) and complement fixation inhibition test (CFI) were carried out on the patients admitted in our hospital under suspicion of Japanese B encephalitis (JBE) in 1955 and 1956, in order to know the diagnostic value of CF in comparison with the other tests.
From these patients were naturally excluded the ones diagnosed as non-encephalitic diseases clinically and or bacteriologically. The CF was performed with 143 remaining cases (including 53 mortal cases). Diagnosis of JBE was established on the basis of a 4-fold rise and or a titer 1: 32 or greater in CF test. Eighty one cases were diagnosed in this way out of 95 recovered cases. The HI test, a 4-fold rise of HI antibody being required, was carried out on the sera of 68 patients (including 14 CF negative cases) with the result of 45 positive reactors. The results of both, CF and HI tests coincided in 43 cases except for 13 cases which consisted of 11 HI negative and 2 CF negative ones. The absence of obvious rising of HI antibody titer in many cases was explained from the fact that the titer rose more rapidly than CF. Needless to say, the serological tests were not so effective for mortal cases, although the HI was contrarily of more value than the CF due to the vicissitude of antibody. Namely, diagnosis was serologically established only in 7 of 53 mortal cases, 2 of them with both, 1 with CF and 4 with HI test. NT was carried out with the above mentioned 12 cases which were negative for both CF and HI tests. A rise of NT antibody titer over 1.5 log in convalescence was seen in no case. On the other hand, the rise of titer was found in 3 of 7 cases which were admitted during the same period and were positive reactors for CF. CFI test was also performed with the sera of the same negative reactors. The rise of antibody was not demonstrated.
The clinical aspects of those 12 cases were generally mild in comparison with those of JBE cases. Nine of them did not show any cerebral focus symptom, but might be designated as “aseptic meningitis.” Presumably, some other diseases were mixed in them. Consistently, the reliability of CF test for JBE was confirmed in comparison wtih the other serological tests except for mortal cases, for which HI should be used in combination. Among the recovered patients a negative result of CF would be almost unconceivable, if the sera were examined during a long period (4 weeks after onset)