Yonsei Med J.  2010 Nov;51(6):895-900. 10.3349/ymj.2010.51.6.895.

Clinical Predictors of Novel Influenza A (H1N1) Infection in Korea

• Kim CO
• Nam CM
• Lee DC
• Han SH
• Lee JW

• KMID: 1779637
• DOI: http://doi.org/10.3349/ymj.2010.51.6.895

Abstract

PURPOSE
Pandemic influenza A (H1N1) virus has spread rapidly and prompt diagnosis is needed for successful treatment and prevention of transmission. We investigated clinical predictors, validated the use of previous criteria with laboratory tests, and evaluated the clinical criteria for H1N1 infection in the Korean population.
MATERIALS AND METHODS
We analyzed clinical and laboratory evaluation data from outpatient clinics at Severance Hospital in Seoul, Korea between November 11 and December 5, 2009.
RESULTS
This analysis included a total of 828 patients. Of these, 372 (44.9%) patients were confirmed with H1N1 infection by real-time reverse transcriptase-polymerase chain reaction (RT-PCR). The most common and predictive symptom was cough (90.3%, OR 8.87, 95% CI 5.89-13.38) and about 40% of H1N1-positive patients were afebrile. The best predictive model of H1N1 infection was cough plus fever or myalgia. The sensitivities, specificities, positive predictive values, and negative predictive values of our suggested criteria were 73.9%, 69.5%, 66.4%, and 76.6%, respectively.
CONCLUSION
Cough was the most common independent symptom in patients with laboratory-confirmed H1N1 infection, and while not perfect, the combination of cough plus fever or myalgia is suggested as clinical diagnostic criteria. Health care providers in Korea should suspect a cough without fever to be an early symptom of H1N1 infection.

Keyword

Influenza A virus (H1N1 subtype); criteria; diagnosis

MeSH Terms

Adolescent
Adult
Aged
Aged, 80 and over
Female
Humans
Influenza A Virus, H1N1 Subtype/*metabolism
Influenza, Human/*diagnosis/*epidemiology/virology
Male
Middle Aged
Pandemics
Predictive Value of Tests
Republic of Korea
Reverse Transcriptase Polymerase Chain Reaction
Sensitivity and Specificity

Figure

• 

  Fig. 1 Study diagram for influenza A (H1N1) clinical criteria comparisons and suggestions. Clinical and laboratory evaluations were analyzed from all patients who were admitted to the flu center at Severance Hospital. The study period was from November 11 to December 5, 2009. Acute respiratory symptoms were defined as self-reported influenza-like symptoms including chills/feverishness, cough, sore throat, headache, rhinorrhea, and/or myalgia, with or without a documented fever. RT-PCR, reverse transcriptase-polymerase chain reaction.

• 

  Fig. 2 Clinical symptoms and signs of influenza A (H1N1)-positive cases and influenza A (H1N1)-negative cases. Influenza A (H1N1)-positive was defined as a positive result on real-time RT-PCR. Conversely, a negative result on RT-PCR was defined as influenza A (H1N1)-negative. Cough, myalgia, fever (greater than 37.8℃ or antipyretic use), and rhinorrhea are more frequent in the influenza A (H1N1)-positive group. *p < 0.05, calculated by the χ2-test and Fisher exact test (for categorical variables). RT-PCR, reverse transcriptase-polymerase chain reaction.

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