Elsevier

Journal of Virological Methods

Volume 213, 1 March 2015, Pages 131-134
Journal of Virological Methods

Evaluation of respiratory syncytial virus (RSV) direct antigen detection assays for use in point-of-care testing

https://doi.org/10.1016/j.jviromet.2014.11.016Get rights and content

Highlights

  • RSV Antigen detection assays with objective results.

  • Useful for point-of-care RSV testing.

  • Walkaway testing mode allows workflow flexibility.

Abstract

RSV infections cause lower respiratory tract infections and result in surges in physician's office, emergency department visits and hospitalizations, especially in infants and toddlers. Point-of-care (POC) testing reduces healthcare costs and permits informed decisions on treatment, however, optimal POC assays must be sensitive, easy to perform and provide rapid results.

A prospective study tested 230 patient nasopharyngeal specimens using 4 RSV direct antigen detection assays (Directigen, Quickvue, Sofia and Veritor) and RT-PCR. A RSV dilution study was also performed to evaluate sensitivity. RSV fluorescent antibody testing in 46/230 patients was also evaluated.

Sensitivity values obtained for the Sofia, Veritor, Directigen and Quickvue assays (%) were 85, 72.5, 70 and 57.5, respectively. Fluorescent result interpretation may account for Sofia's enhanced sensitivity. Specificity (%) was 97–100 among assays. Sensitivity data were confirmed in the dilution studies. Fluorescent antibody testing demonstrated 64% sensitivity compared with RT-PCR.

Objective result reporting, walk away testing and high sensitivity make the Sofia a valuable choice for POC testing. Veritor's sensitivity may also render it acceptable in POC. Lack of objective results by Directigen and the poor sensitivity observed by Quickvue may preclude their value in diagnostic testing.

Introduction

Respiratory syncytial virus (RSV) is recognized as the most important cause of severe respiratory tract infection in infants and young children. The virus co-circulates in the Northern Hemisphere with other respiratory pathogens producing substantial morbidity in children under 5 years of age during the fall and winter months. In one study, estimates of hospitalization (20%), emergency department visits (18%) and physician office visits (15%) were attributed to RSV infection from November through April (Hall et al., 2009). RSV is not limited to the pediatric population; reinfection occurs throughout life and RSV is regarded as an important pneumonial agent in long-term care facilities (Collins and Melero, 2011).

RSV point-of-care (POC) diagnostic testing enhances patient care and reduces overall healthcare costs by allowing decisions regarding the need for hospitalization, administration of antimicrobial therapy or further diagnostic testing to be made during the physician-patient encounter. Rapid diagnostic testing for respiratory viruses has been demonstrated to reduce both patient hospitalization time and its associated financial costs (Barenfanger et al., 2000). The ideal diagnostic assay for use at the POC must be easy to use, provide rapid results, demonstrate a high degree of sensitivity, allow easy result interpretation and be cost effective.

To that end, substantial research efforts have attempted to develop molecular-based, multiplex PCR assays to identify numerous viral and bacterial pathogens. Although these efforts have produced some success to date, technical pitfalls (e.g. the need for miniaturization) and cost have hindered POC integration (Ince and McNally, 2009, Kiechle and Holland, 2009). Consequently, rapid antigen detection assays remain the predominant, whilst imperfect tool utilized in POC testing.

One drawback to antigen detection assays has been the requirement for subjective result reporting. Nursing staff, who may not have substantial training or experience with these assays, can find interpretation of colorimetric “lines or triangles” difficult. Further, the requirement to interpret assay results within a rigid time frame places an extra burden on emergency department or physician's office nurses who are usually overwhelmed during the respiratory virus season.

Recently, newer RSV antigen detection assays have incorporated instrumentation providing objective colorimetric (Veritor system, Becton Dickinson, Sparks, USA) or fluorescent (Sofia, Quidel, San Diego, USA) results. We examined the performance of these assays along with their subjective-result predecessor assays (Directigen EZ RSV, Becton Dickinson, Sparks, USA and Quickvue, Quidel, San Diego, USA RSV) to fulfill a potential POC role in RSV testing.

Section snippets

Patient study design

A total of 230 patient nasopharyngeal specimens were collected using flocked swabs and placed into 3 mL of viral transport medium (Copan Inc, Merita, CA). These specimens were received by physicians requesting laboratory testing in patients who were symptomatic for respiratory illness including flu-like symptoms, fever, wheezing, bronchiolitis and pneumonia. This study used the remnant specimen destined for disposal and did neither require informed patient consent nor institutional IRB review.

Results

A total of 230 patient nasopharyngeal specimens were tested by the four antigen detection assays and RT-PCR. Of these, 40 patient specimens were RSV-positive by RT-PCR. The majority of positive patients were under 5 years of age (31/40), but RSV was also identified in adults, including 2 patients greater than 65 years of age. Reported symptoms with illness included fever, rhinitis, bronchiolitis, wheezing, croup and pneumonia.

Using RT-PCR as the gold standard, sensitivity/specificity values (%)

Discussion

Respiratory viruses, including RSV, are responsible for substantial disease outbreaks during winter in temperate climate regions. Infections among children, the elderly and profoundly immunosupressed patients place severe pressures on physician offices and hospital resources. RSV control strategies targeting high-risk children have limited effect on the total disease burden because most children are healthy prior to infection (Hall et al., 2009). POC testing for respiratory viruses may directly

Funding

None.

Ethical approval

Not required.

References (12)

There are more references available in the full text version of this article.

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