Results of a pilot study using self-collected mid-turbinate nasal swabs for detection of influenza virus infection among pregnant women

Abstract

Background: We evaluated the feasibility of asking pregnant women to self-collect and ship respiratory specimens.

Methods: In a preliminary laboratory study, we compared the RT-PCR cycle threshold (CT) values of influenza A and B viruses incubated at 4 storage temperatures (from 4 to 35°C) for 6 time periods (8, 24, 48, 72, and 168 hours and 30 days), resulting in 24 conditions that were compared to an aliquot tested after standard freezing (-20°C) (baseline condition). In a subsequent pilot study, during January-February, 2014, we delivered respiratory specimen collection kits to 53 pregnant women with a medically attended acute respiratory illness using three delivery methods.

Results: CT values were stable after storage at temperatures <27°C for up to 72 hours for influenza A viruses and 48 hours for influenza B viruses. Of 53 women who received kits during the pilot, 89% collected and shipped nasal swabs as requested. However, 30% (14/47) of the women took over 2 days to collect and ship their specimen. The human control gene, ribonuclease P (RNase P), was detected in 100% of nasal swab specimens. However, the mean CT values for RNase P (26.5, 95% confidence interval [CI] = 26.0-27.1) and for the 8 influenza A virus positives in our pilot (32.2, 95% CI = 28.9-35.5) were significantly higher than the CTs observed in our 2010-2012 study using staff-collected nasal pharyngeal swabs (P-values < 0.01).

Discussion: Self-collection of respiratory specimens is a promising research method, but further research is needed to quantify the sensitivity and specificity of the approach.

Keywords: Acute respiratory illness; influenza; nasal swab; pregnancy; self-collection.

Figure 1

Cycle threshold from rRT-PCR of four influenza viruses stored for 72 hours at five temperatures.

Figure 2

Cycle thresholds (and 95% confidence intervals) from rRT-PCR of ribonuclease P (RNase P) and influenza A viruses collected from pregnant women with acute respiratory illness during a pilot study of nasal swab self-collection (2013–2014) and a prior study with staff-collected nasal pharyngeal swabs (2010–2012).