Abstract:
Objective To confirm the clinical diagnosis of breakthrough mumps cases and evaluate the validity of the clinical diagnosis and the sensitivities of laboratory methods.
Methods For the clinical diagnosed mumps cases reported in Yinzhou district of Ningbo during 2015–2017, the serum IgM against mumps virus was detected with enzyme-linked immunosorbent assay (ELISA) and viral RNA extracted from strains isolated from throat swabs or oral fluids were detected by using reverse transcription-polymerase chain reaction (RT-PCR), the positive rate of samples collected in different time, the positive rates of breakthrough cases and cases without immunization history, and the positive rates of different type samples were compared.
Results The positive rates of IgM were 36.37% (36/99) at 1–7 days after onset and 95.00% (19/20) at 8–32 days after onset, the difference was significant (Fisher’s exact test, P<0.001). For the viral RNA detection, 6.47% (9/139) of breakthrough cases were positive, 16.67% (6/36) of unvaccinated cases were positive, the difference was not significant (χ2=3.79, P>0.05). The positive samples (throat swabs and oral fluids) were mainly collected within 2–3 days after onset. Only 1.39% (1/72) of throat swabs of breakthrough cases were positive, but 11.94% (8/67) of oral fluids of breakthrough cases were positive, the difference was significant(Fisher's exact test, P=0.015) .
Conclusion According to the results of IgM detection, we confirmed most clinically diagnosed breakthrough mumps cases, but the sensitivities of ELISA in detection of IgM and RT-PCR in detection of viral RNA were not high in acute phase (1–7 days). It is suggested to detect IgM 7 days later after onset for confirmation.