Key Point:

In a febrile child, the clinical triad of cough, headache, and pharyngitis can accurately predict influenza infection.

PHILADELPHIA—Influenza is a common seasonal illness in children. Unfortunately, the classic flu symptoms in adults are not as readily identifiable in younger patients. Furthermore, viral cultures take too long, and rapid tests for influenza have limited sensitivity and specificity. So, how can you diagnose the flu in children quickly and accurately? A recent study found that three clinical findings—headache, cough, and pharyngitis—in a febrile child are highly predictive of influenza.[1]

The study included 128 children who were seen in the emergency department of a single hospital during the 2002 flu season (January through March). The children had fever and at least one of the following symptoms: runny/stuffy nose, cough, headache, sore throat, or muscle aches.

All patients were given nasal washes for viral culture, and a standard data collection form was completed by the attending physician. The form included questions about the presence or absence of 24 clinical features—12 historical and 12 physical findings. The primary outcome was which clinical features were most predictive of influenza in children.

Of the 128 children, 45 had viral cultures that were positive for influenza A and 13 tested positive for influenza B. Ten children had respiratory viral pathogens other than influenza, and 60 cultures were negative. Influenza patients all had higher respiratory rates than did those without a viral infection (28 breaths per minute vs 21 breaths per minute, respectively). They were also more likely to have a higher fever, along with cough, headache, abdominal pain and/or nausea, and pharyngitis. Of these features, only cough, headache, and pharyngitis were found to independently predict an increased likelihood of influenza.

Most physicians usually rely on clinical symptoms to diagnose influenza. However, studies comparing the diagnostic accuracy of clinical symptoms with laboratory-confirmed viral cultures have found that the positive predictive values for these symptoms were highly variable, ranging from 18% to 87%. In addition, no study has ever focused solely on children.

In the current study, the posttest probability that a febrile child with cough, headache, and pharyngitis had influenza was 77%—significantly better than the pretest probability of 45% using a list of all possible influenza symptoms. These three symptoms had a sensitivity of 80%—comparable to available rapid influenza tests.

Acknowledging the limitation of using a single hospital for the study, the authors maintained that the triad of cough, headache, and pharyngitis in a febrile child accurately predicts influenza infection and can be used for diagnosis during community outbreaks.

—Gale Jurasek