Clinical performance of the Sofia™ Influenza A+B FIA in adult patients with influenza-like illness

Diagnostic Accuracy of the Quidel Sofia Rapid Influenza Fluorescent Immunoassay in Patients with Influenza-like Illness: A Systematic Review and Meta-analysis

Background

Although the Quidel Sofia rapid influenza fluorescent immunoassay (FIA) is widely used to identify influenza A and B, the diagnostic accuracy of this test remains unclear. Thus, the objective of this study was to determine the diagnostic performance of this test compared to reverse transcriptase-polymerase chain reaction.

Methods

A systematic literature search was performed using MEDLINE, EMBASE, and the Cochrane Central Register. Pooled sensitivity, specificity, diagnostic odds ratio (DOR), and a hierarchical summary receiver-operating characteristic curve (HSROC) of this test for identifying influenza A and B were determined using meta-analysis. A sensitivity subgroup analysis was performed to identify potential sources of heterogeneity within selected studies.

Results

We identified 17 studies involving 8,334 patients. Pooled sensitivity, specificity, and DOR of the Quidel Sofia rapid influenza FIA for identifying influenza A were 0.78 (95% confidence interval [CI], 0.71–0.83), 0.99 (95% CI, 0.98–0.99), and 251.26 (95% CI, 139.39–452.89), respectively. Pooled sensitivity, specificity, and DOR of this test for identifying influenza B were 0.72 (95% CI, 0.60–0.82), 0.98 (95% CI, 0.96–0.99), and 140.20 (95% CI, 55.92–351.54), respectively. The area under the HSROC for this test for identifying influenza A was similar to that for identifying influenza B. Age was considered a probable source of heterogeneity.

Conclusion

Pooled sensitivities of the Quidel Sofia rapid influenza FIA for identifying influenza A and B did not quite meet the target level (≥80%). Thus, caution is needed when interpreting data of this study due to substantial between-study heterogeneity.

Detection and characterization of type B influenza virus from influenza-like illness cases during the 2017-2018 winter influenza season in Beijing, China

In the winter of 2017-2018, there was significant influenza activity in China, resulting in unprecedented usage of influenza rapid antigen tests (IRAT) and neuraminidase inhibitors (NAIs). The aim of this study was to characterize the most prevalent influenza virus type in a clinical setting with respect to diagnosis and concomitant NAI treatment. From Dec 2017 to Jan 2018, 3257 patients with influenza-like illness (ILI) were screened using IRAT. We summarized and compared the results with the last influenza season. Subtyping of influenza B viruses and identification of NAI drug resistance mutations were carried out by sequencing the HA and NA genes and aligning these with genetic isotypes. The performance of IRAT and RT-PCR was compared. Screening results indicated that influenza B virus was the leading cause of this influenza epidemic, with children being more susceptible to infection than adults. Phylogenetic analysis revealed that the prevailing influenza B virus belonged to the Yamagata lineage and were genetically similar to strains isolated from North America in the same influenza season. Cross-continental spread of influenza/B/Yamagata occurred. NAI resistance mutations were not identified in the 18 samples analyzed. The current antiviral protocol was still effective for influenza B control. RT-PCR positivity was significantly higher than that of IRAT (P = 0.004). IRAT and RT-PCR had a consistency rate of 86.9%, with the consistency rates of the positive and negative cases being 54.3% and 97.3%, respectively. Clinicians should be alert to the possibility of obtaining false negative results when using IRAT, and RT-PCR is recommended to improve the accuracy of pathogen detection.

Diagnostic performance of the Sofia® influenza A+B fluorescent immunoassay in adult outpatients in Northern Taiwan

To evaluate the diagnostic performance of the Sofia influenza A+B fluorescent immunoassay (Sofia FIA), we performed a prospective study at the Chang Gung Memorial Hospital in Taiwan from January 2012 to December 2013. Patients who presented at out-patient clinics or the emergency department with influenza-like illness were included. Upper respiratory tract specimens were collected from oropharynx or nasopharynx. Performance of the Sofia FIA was compared to that of the Formosa One Sure Flu A/B Rapid Test. A Real-time reverse transcriptase-polymerase chain reaction assay (RT-PCR) and/or virus culture were used as reference standards. Of the 109 enrolled patients, the sensitivity, specificity, positive, and negative predictive values of the Sofia FIA to detect influenza A virus were 82%, 89%, 77%, and 89%, respectively. These parameters were 100% when the samples were from nasopharynx. The positive predictive value for influenza B virus detection was 29%. The sensitivity of the Sofia FIA for detection of influenza A virus was 93% between days 2 and 4 after onset of symptoms. For specimens with low viral loads (RT-PCR cycle threshold between 30 and 34.9), the sensitivity of The Sofia FIA was 83% (10/12). The Sofia FIA performed effectively in detecting influenza A virus infection. With nasopharyngeal samples, the performance was comparable to RT-PCR. Although influenza viral load typically decreases with time, the Sofia FIA was sensitive enough to identify influenza infecting patients presenting after several days of illness. However, a high false positive rate limits the assay's usefulness to identify influenza B virus infection.

Evaluation of a two-stage testing algorithm for the diagnosis of respiratory viral infections

New on-demand multiplex molecular respiratory viral diagnostics offer superior performance although can be expensive and some platforms cannot process multiple specimens simultaneously. We performed a retrospective study reviewing results of patients tested for respiratory viruses following introduction of a two-stage testing algorithm incorporating an initial screen with Sofia® immunoassay then secondary Biofire Filmarray®, and compared to a period when only Filmarray® was used. Of 2976 testing episodes, 1814 underwent initial Sofia® then follow-up FilmArray®. A diagnosis of influenza was made by Sofia® in 282 patients, and by FilmArray® in an additional 163 (median time to result 1.12 hours versus 3.46 hours, P < 0.001). Significantly more patients received their diagnosis within 90 minutes in winter despite testing more samples (11.1% versus 3.4%, P < 0.001), and approximately $36,000 was saved. An algorithmic approach to respiratory viral diagnosis can combine the advantages of accuracy and speed and be cost saving.