Evaluation of Clinical Case Definitions of Influenza: Detailed Investigation of Patients During the 1995‐1996 Epidemic in France

Abstract

Using clinical predictors, we evaluated clinical case definitions of influenza during the 1995-1996 outbreak in France. Thirty-five general practitioners collected virological specimens and clinical data. Predictors of influenza virus infection were selected with logistic regression models. The results varied with the influenza virus subtype: temperature of >38.2 degrees C, stiffness or myalgia, rhinorrhea, and cough were predictive of influenza A/H3N2, whereas fatigue, lacrimation or conjunctival injection, and the absence of stiffness or myalgia were predictive of influenza A/H1N1. On the basis of this analysis and data from the literature, 12 clinical case definitions were evaluated for their abilities to diagnose influenza virus infection. They were associated with positive predictive values of 27% to 40% and negative predictive values of 80% to 91%. We conclude that focused studies evaluating clinical case definitions of influenza with use of subsets of patients should accompany population-based disease surveillance for optimal estimates of the disease burden associated with influenza epidemics.

Performance of rapid influenza testing in hospitalized children

“…Specifically, the detection of influenza infection presenting with both fever and cough was observed to have sensitivities ranging between 64 and 86%, specificities between 55 and 67%, and PPVs ranging between 48 and 87% [5,6,19,20]. This contrasts other studies which reported that no clinical signs or symptoms are specific for influenza virus infection [21,22]. The present study indicates that the clinical diagnosis of influenza, based on the combined presence of fever and cough, is difficult among children in everyday clinical practice.…”

Is Influenza an Influenza-Like Illness? Clinical Presentation of Influenza in Hospitalized Patients

“…In outpatient studies, many recruitment strategies involve evaluating patients when they report ILI symptoms, such as fever and respiratory symptoms. [2][3][4][5][6] Not surprisingly, these studies observed high rates of fever and respiratory symptoms. Several reports have documented shortcomings of the definition of ILI in long-term care facilities, specifically because many patients did not have documented fever.…”

“…The difficulties of identifying influenza virus infection on the basis of clinical characteristics have been well described for outpatients, [2][3][4][5][6][7] patients in the emergency department, 8,9 and residents of nursing homes. 10 There are fewer recent data regarding the clinical presentation of hospitalized patients with influenza.…”

Risk factors of influenza transmission in households

“…Indeed, 38% of contacts classified as secondary patients did not report a fever. In patients consulting physicians for a respiratory illness during an influenza epidemic period, the relative risk that fever >37.8°C is associated with an influenza diagnosis was 2.5 in one study (4.6 for influenza A [H3N2] specifically), 20 and 3.3 in another. 16 However, syndromes associated with true influenza infection do not necessarily always include fever.…”