Influenza-like illness criteria were poorly related to laboratory-confirmed influenza in a sentinel surveillance study.
OBJECTIVE
To analyze the most related clinical data for influenza and the utility of influenza-like illness criteria as the clinical threshold for sampling in an influenza sentinel surveillance over a 3-year period.


METHODS
Sentinel physicians collected throat specimens and data from outpatients with acute respiratory infection (< or = 72 hours duration). Laboratory-confirmed influenza infection was compared with independent symptoms and the influenza-like illness criteria, as defined by the Classification Committee of the World Organization of Family Doctors.


RESULTS
From 1934 patients, 359 (18.56%) yielded positive results for influenza viruses. Only 199 (55.4%) of laboratory-confirmed cases fulfilled clinical criteria of influenza-like illness: positive and negative predictive value (PPV and NPV) of 0.36 and 0.88, respectively. Fever, cough, and rhinorrhea individually correlated with influenza infections (PPV: 0.30, 0.20, and 0.20, respectively; NPV: 0.92, 0.87, and 0.85, respectively). Multivariate analysis demonstrated that the correlation of influenza infection with the presence of fever and cough was similar to the correlation between influenza infection and influenza-like illness criteria (odds ratio 2.24 vs. 2.71, respectively).


CONCLUSIONS
Influenza-like illness criteria are poorly related to laboratory-confirmed influenza. For early detection of influenza viruses in surveillance systems, a less restrictive clinical criterion (specifically, acute respiratory infection) perhaps should be followed.
Navarro-Marí
José María
JM
Servicio de Microbiología, Hospital Universitario Virgen de las Nieves, Granada, Spain. josem.navarro.sspa@juntadeandalucia.es
Pérez-Ruiz
Mercedes
M
Cantudo-Muñoz
Purificación
P
Petit-Gancedo
Carmen
C
Jiménez-Valera
María
M
Rosa-Fraile
Manuel
M
D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D003371:Cough / Q000821:virology; D005194:Family Practice; D005260:Female; D005334:Fever / Q000821:virology; D006801:Humans; D007223:Infant; D009980:Influenza A virus / Q000302:isolation & purification; D009981:Influenza B virus / Q000302:isolation & purification; D007252:Influenza Vaccines / Q000008:administration & dosage; D007251:Influenza, Human / Q000150:complications / Q000175:diagnosis* / Q000453:epidemiology*; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D010614:Pharynx / Q000821:virology; D012141:Respiratory Tract Infections / Q000175:diagnosis; D018571:Sentinel Surveillance; D013030:Spain / Q000453:epidemiology
D007252:Influenza Vaccines