Research Article: Unreliable usage of a single influenza virus IgM antibody assay in influenza-like illness: A retrospective study of the 2016–2018 flu epidemic

Date Published: April 22, 2019

Publisher: Public Library of Science

Author(s): Yao Yao, Zhao Zhipeng, Song Wenqi, Li Runqing, Zhu Dong, Qin Kun, Zhao Xiuying, Dong-Yan Jin.


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.

Partial Text

The epidemic of influenza is an important public health problem in worldwide [1]. 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). However, some patients with influenza exhibit severe symptoms, leading to hospitalization or even death, particularly in children, the elderly, and those with underlying chronic conditions [3]. Seasonal influenza results in approximately 250,000–500,000 deaths worldwide in each year [4].

In clinical setting, ILI cases might be attributed to seasonal Flu A and Flu B virus infections, newly pandemic viruses, such as p(H1N1), and other respiratory pathogens [11,20]. Rapid and reliable pathogens screening is important for diagnosis and prevention of influenza virus infection. Common detecting methods include IRDT for Flu A and Flu B virus, single or multiplex nucleic acid assays for viral RNA, and serum-specific IgM or IgG Abs to influenza virus [21,22]. To date, many reports have described the development, evaluation, and application of the first two methods, but few reports have documented IgM Abs detection [15,16].




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