Predicting influenza infections during epidemics with use of a clinical case definition.
Combined pharyngeal and nasal swab specimens were collected from 100 subjects who presented with a flu-like illness (fever >37.8 degrees C plus 2 of 4 symptoms: cough, myalgia, sore throat, and headache) of <72 hours' duration at 3 different clinics in the province of Quebec, Canada, during the 1998-1999 flu season. The rate of laboratory-confirmed influenza infection was 72% according to cell culture findings and 79% according to the results of multiplex reverse-transcription polymerase chain reaction (RT-PCR) analysis (85%, influenza AH3; 15%, influenza B). All subjects for whom these results were discordant (negative culture and positive PCR) presented with a temperature > or =38.2 degrees C as well as 3 or 4 of the symptoms in the clinical case definition. Stepwise logistic regression showed that cough (odds ratio [OR], 6.7; 95% confidence interval [CI], 1.4-34.1; P=.02) and fever (OR, 3.1; 95% CI, 1.4-8.0; P=.01) were the only factors significantly associated with a positive PCR test for influenza. The positive predictive value, negative predictive value, sensitivity, and the specificity of a case definition including fever (temperature of >38 degrees C) and cough for the diagnosis of influenza infection during this flu season were 86.8%, 39.3%, 77.6%, and 55.0%, respectively.
Boivin
G
G
Research Center in Infectious Diseases and Centre Hospitalier Universitaire de Québec, Quebec City, Quebec, Canada. Guy.Boivin@crchul.ulaval.ca
Hardy
I
I
Tellier
G
G
Maziade
J
J
D000328:Adult; D000368:Aged; D000818:Animals; D002460:Cell Line; D003371:Cough; D004196:Disease Outbreaks; D005260:Female; D006261:Headache; D006801:Humans; D007251:Influenza, Human / Q000175:diagnosis* / Q000453:epidemiology / Q000821:virology; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009135:Muscular Diseases; D009975:Orthomyxoviridae / Q000235:genetics / Q000302:isolation & purification*; D010146:Pain; D010612:Pharyngitis; D011237:Predictive Value of Tests; D011792:Quebec / Q000453:epidemiology; D012367:RNA, Viral / Q000032:analysis / Q000235:genetics
D012367:RNA, Viral