Clinical diagnosis of pandemic A(H1N1) 2009 influenza in children with negative rapid influenza diagnostic test by lymphopenia and lower C-reactive protein levels

Authors

  • Lin Wang,

    1. Department of Pediatrics, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine (KCGMH-CGU), Kaohsiung, Taiwan
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    • These two authors contributed equally to this study.
  • Ling-Sai Chang,

    1. Department of Pediatrics, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine (KCGMH-CGU), Kaohsiung, Taiwan
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    • These two authors contributed equally to this study.
  • Ing-Kit Lee,

    1. Department of Internal Medicine, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine (KCGMH-CGU), Kaohsiung, Taiwan
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  • Kuo-Shu Tang,

    1. Department of Pediatrics, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine (KCGMH-CGU), Kaohsiung, Taiwan
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  • Chung-Chen Li,

    1. Department of Pediatrics, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine (KCGMH-CGU), Kaohsiung, Taiwan
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  • Hock-Liew Eng,

    1. Department of Laboratory Medicine, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine (KCGMH-CGU), Kaohsiung, Taiwan
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  • Huey-Ling You,

    1. Department of Laboratory Medicine, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine (KCGMH-CGU), Kaohsiung, Taiwan
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  • Kuender D. Yang

    Corresponding author
    1. Department of Medical Research, Show Chwan Memorial Hospital in Chang Bing, Changhua, Taiwan
    • Correspondence: Kuender D. Yang, Department of Medical Research, Show Chwan Memorial Hospital in Chang Bing, No. 6-1 Lu-Kung Road, Chang Bing Industrial Center, Lu-Kang, Changhua 505, Taiwan. E-mail: yangkd.yeh@hotmail.com

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Abstract

Background

The sensitivity of rapid influenza diagnostic test (RIDT) of children with influenza-like illness (ILI) remains low.

Objective

We compare the parameters between pandemic A(H1N1) 2009 influenza with negative RIDT and ILI not H1N1 for improving the low sensitivity of RIDT for children with ILI.

Methods

In a cohort of consecutive laboratory-confirmed H1N1 influenza, we identified 150 H1N1 children with positive RIDT, 152 H1N1 children with negative RIDT, and 75 children with ILI not H1N1. Viral load in throat, complete blood count (CBC), and C-reactive protein (CRP) levels between H1N1 children with negative RIDT and children with ILI not H1N1 were assessed.

Results

The diagnostic sensitivity of the RIDT was 45·5%. An analysis of CBC and CRP levels indicated that H1N1 children with negative RIDT had lower total leukocyte, neutrophil, lymphocyte, and basophil counts, and serum CRP levels (< 0·01). Lymphocyte counts less than 1500 cells/mm3 and CRP levels <15 mg/l, determined by a receiver operating characteristic curve, showed a diagnostic sensitivity of 52·5% and 80·7%, respectively. Combining the lymphocyte counts and CRP levels provided a diagnostic sensitivity of 91·5%. Moreover, H1N1 children with negative RIDT had a lower viral load than those with positive RIDT (3·33 versus 4·48 log10 copies/ml, < 0·001); the viral load was negatively correlated to the lymphocyte count (< 0·001).

Conclusions

A combination of a low lymphocyte count and a low CRP level could, in the early disease phase, provide a useful screening for H1N1 children with false-negative RIDT, potentially facilitating differential diagnoses.

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