Time course of RT-PCR positivity in H1N1-induced ARDS

Introduction

The aim of this study was to analyze the correlation between antiviral therapy efficacy and the negative profile of the RT-PCR made on pharyngeal swab, subglottic aspiration, and bronchoalveolar lavage in patient affected by ARDS caused by H1N1 infection.

Methods

A prospective analysis was performed on 11 patients admitted to the ICU of a tertiary referral center (Careggi Teaching Hospital, Florence, Italy). All patients underwent daily RT-PCR monitoring on pharyngeal swab, subglottic aspiration, and bronchoalveolar lavage. All patients were treated with oral administration of oseltamivir (75 mg twice daily) and inhaled zanamivir (10 mg twice daily) since ICU admission. Six patients were treated with extracorporeal membrane oxygenation (ECMO) due to their critical respiratory conditions. Two of them resulted co-infected by legionella pneumophila.

Results

As shown in Figure 1, RT-PCR from pharyngeal swab at ICU admission failed to demonstrate the viral infection in four patients, whereas RT-PCR from bronchoalveolar lavage had a sensibility of 100%. Similarly, the time course showed that RT-PCR from pharyngeal swab resulted negative in an average time of 3 days after therapy start, while RT-PCRs from bronchoalveolar lavage continued to permit infection monitoring and therapy regimen conduction. None of RT-PCRs on subglottic aspiration samples resulted positive. All patients recovered and were discharged alive from ICU in spontaneous breathing.

Figure 1

Time course of RT-PCR positivity for H1N1 infection.

Conclusions

In our experience, the most reliable method to diagnose and monitor H1N1 infection was RT-PCR from bronchoalveolar lavage, since pharyngeal swab do not offer enough sensibility, either for antiviral therapy initiation or for antiviral therapy management. Samples from subglottic aspiration can be avoided due to a low sensibility.