Influenza B false-positive results by rapid molecular tests Alere™ i Influenza A&B 2 in France

Diagnostic Accuracy of an At-Home, Rapid Self-test for Influenza: Prospective Comparative Accuracy Study

Background

Rapid diagnostic tests (RDTs) for influenza used by individuals at home could potentially expand access to testing and reduce the impact of influenza on health systems. Improving access to testing could lead to earlier diagnosis following symptom onset, allowing more rapid interventions for those who test positive, including behavioral changes to minimize spread. However, the accuracy of RDTs for influenza has not been determined in self-testing populations.

Objective

This study aims to assess the accuracy of an influenza RDT conducted at home by lay users with acute respiratory illness compared with that of a self-collected sample by the same individual mailed to a laboratory for reference testing.

Methods

We conducted a comparative accuracy study of an at-home influenza RDT (Ellume) in a convenience sample of individuals experiencing acute respiratory illness symptoms. Participants were enrolled in February and March 2020 from the Greater Seattle region in Washington, United States. Participants were mailed the influenza RDT and reference sample collection materials, which they completed and returned for quantitative reverse-transcription polymerase chain reaction influenza testing in a central laboratory. We explored the impact of age, influenza type, duration, and severity of symptoms on RDT accuracy and on cycle threshold for influenza virus and ribonuclease P, a marker of human DNA.

Results

A total of 605 participants completed all study steps and were included in our analysis, of whom 87 (14.4%) tested positive for influenza by quantitative reverse-transcription polymerase chain reaction (70/87, 80% for influenza A and 17/87, 20% for influenza B). The overall sensitivity and specificity of the RDT compared with the reference test were 61% (95% CI 50%-71%) and 95% (95% CI 93%-97%), respectively. Among individuals with symptom onset ≤72 hours, sensitivity was 63% (95% CI 48%-76%) and specificity was 94% (95% CI 91%-97%), whereas, for those with duration >72 hours, sensitivity and specificity were 58% (95% CI 41%-74%) and 96% (95% CI 93%-98%), respectively. Viral load on reference swabs was negatively correlated with symptom onset, and quantities of the endogenous marker gene ribonuclease P did not differ among reference standard positive and negative groups, age groups, or influenza subtypes. The RDT did not have higher sensitivity or specificity among those who reported more severe illnesses.

Conclusions

The sensitivity and specificity of the self-test were comparable with those of influenza RDTs used in clinical settings. False-negative self-test results were more common when the test was used after 72 hours of symptom onset but were not related to inadequate swab collection or severity of illness. Therefore, the deployment of home tests may provide a valuable tool to support the management of influenza and other respiratory infections.

Impact of decreasing cerebrospinal fluid enterovirus PCR turnaround time on costs and management of children with suspected enterovirus meningitis

To estimate the impact of implementing in-hospital enterovirus (EV) polymerase chain reaction (PCR) testing of cerebrospinal fluid (CSF) with same-day turn-around-time (TAT) on length-of-stay (LOS), antibiotic use and on cost per patient with suspected EV meningitis, compared with testing at an outside reference laboratory. A model-based analysis using a retrospective cohort of all hospitalized children with CSF EV PCR testing done between November 2013 and 2017. The primary outcome measured was the potential date of discharge if the EV PCR result had been available on the same day. Patients with positive EV PCR were considered for potential earlier discharge once clinically stable with no reason for hospitalization other than intravenous antibiotics. Descriptive statistics and cost-sensitivity analyses were performed. CSF EV PCR testing was done on 153 patients, of which 44 (29%) had a positive result. Median test TAT was 5.3 days (IQR 3.9–7.6). Median hospital LOS was 5 days (IQR 3–12). Most (86%) patients received intravenous antibiotics with mean duration of 5.72 ± 6.51 days. No patients with positive EV PCR had a serious bacterial infection. We found that same-day test TAT would reduce LOS and duration of intravenous antibiotics by 0.50 days (95%CI 0.33–0.68) and 0.67 days (95%CI 0.42–0.91), respectively. Same-day test TAT was associated with a cost reduction of 342.83CAD (95%CI 178.14–517.00) per patient with suspected EV meningitis. Compared with sending specimens to a reference laboratory, performing CSF EV PCR in-hospital with same-day TAT was associated with decreased LOS, antibiotic therapy, and cost per patient.