Initial clinical management of symptomatic adult patients during influenza A (H1N1) epidemics

Pandemic influenza A (H1N1) has emerged rapidly in Argentina since May 2009. Preliminary comparisons with seasonal influenza suggest that H1N1 disproportionately affects younger patients, generally causing mild disease, but in a minority of cases can be lethal.

The aim of this study was to develop a clinical tool for the initial management of patients with influenza-like syndrome, within the context of the novel H1N1 virus epidemic, to detect patients who need further investigation (e.g., chest X-ray study) for the diagnosis of pneumonia.

We prospectively studied 1090 consecutive patients with influenza-like syndrome for a period of 15 days. Based on the presence of inspiratory crackles and the level of transcutaneous pulse oximetry, we selected 217 patients requiring chest X-ray study, and pneumonia was confirmed in all of these patients.

Among the patients with pneumonia, 132 viral diagnostic tests were available, from which specimens tested by real-time reverse-transcriptase polymerase-chain reaction (RTPCR) were positive for H1N1 in 61 patients (46%). Comparison between RTPCR-positive and RTPCR-negative patients did not show any significant difference. Eighty-seven randomly selected patients with influenza-like syndrome, but without crackles and with O(2) saturation>96%, received chest X-ray studies; none demonstrated pulmonary infiltrates.

Within the context of an influenza epidemic with the new H1N1 virus, the use of two simple and accessible clinical signs permits a rapid differentiation between those patients requiring close monitoring vs. those with mild and self-resolving disease.