Abstract
We retrospectively analyzed serum IgM antibodies (Abs) to influenza viruses from two tertiary hospitals in Beijing from December 2016 to February 2018. Samples from 36,792 patients, aged 0–98 years, were collected and tested. Among the patients, 923 children from two winter flu seasons were assayed with both antigens and IgM Abs to Flu A and Flu B and assigned as paired groups. Another 2,340 adults and 1,978 children with only antigen tested in the 2016 and 2017 winter flu seasons were named as unpaired groups. IgM Abs-positivity rates in children were 0.80% and 36.57% for Flu A and Flu B, respectively, peaking at 4–5 years of age. For adults, the Flu A and Flu B IgM Abs-positivity rates were 10.34% and 21.49%, respectively, peaking at 18–35 years of age. The trend of temporal distribution between the children and the adults was significantly correlated for IgM Abs to Flu B, but not for Flu A. Compared with unpaired groups, the detection rate of Flu A antigen was significantly higher than IgM Abs in children, whereas frequencies of IgM Abs were higher than antigen in adults. Incidence of Flu B antigen was sharply increased in 2017 winter than in the 2016 winter in both children and adults, but no concomitant increase was observed in IgM Abs to Flu B. For paired children groups, incidence of Flu B antigen in the 2017 flu season was significantly higher than that in the 2016 flu season; in contrast, positive rates of IgM Abs in the 2017 flu season were even lower than those in 2016. Considering antigen detection may reflect the Flu A/Flu B epidemic, our results indicate single-assayed IgM Abs were less effective in the diagnosis of acute influenza virus infection, and the use of this assay for epidemiology evaluations was not supported by these findings.
Highlights
The epidemic of influenza is an important public health problem in worldwide [1]
Reverse transcription-polymerase chain reaction (PCR)-based tests, influenza rapid diagnostic test (IRDT), and serological detection of specific antibodies (IgM Abs and IgG Abs) targeting the viruses were recommended to assist with influenza diagnosis from influenza-like illnesses (ILI) cases in the clinical setting [14]
Other 2,340 adults and 1,978 children with Flu A and Flu B antigen tested by an IRDT method during 2016 and 2017 winter flu seasons were included as unpaired groups, with purpose to use the antigen as indicators for virus epidemics (Fig 1)
Summary
Influenza virus genera A (Flu A) or B (Flu B) infections account for a vast majority of influenza cases in humans [2]. Most of these infections are asymptomatic or exhibit relatively mild symptoms, presenting as influenza-like illnesses (ILI). Two major subtypes of Flu A and two lineages of Flu B viruses co-circulate and cause annual epidemics. The epidemics have highlighted the need for simpler and rapider assays to facilitate the diagnosis of influenza infections and differentiate the subtypes/lineages of the viruses. Reverse transcription-polymerase chain reaction (PCR)-based tests, influenza rapid diagnostic test (IRDT), and serological detection of specific antibodies (IgM Abs and IgG Abs) targeting the viruses were recommended to assist with influenza diagnosis from ILI cases in the clinical setting [14]. Frequencies of IgM Abs to Flu A and Flu B were compared with the findings of contemporary antigen tests, providing insights into the use of IgM Abs for influenza diagnosis
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