Rapid Diagnostic Testing for Seasonal Influenza: An Evidence-Based Review and Comparison with Unaided Clinical Diagnosis

Background: Worldwide, seasonal influenza imposes a considerable health and economic burden. Clinical diagnosis of influenza-like illness (ILI) is complicated by non-specific symptomatology. Rapid flu tests (RFTs) impact treatment decisions and may improve patient care; yet, recommendations for RFT use are broad, and the performance of unaided clinical diagnosis relative to RFTs is unclear. Objectives: To determine age-stratified, overall sensitivities and specificities of the widely studied RFT, QuickVue® (Quidel Corporation, San Diego, CA), and clinical diagnosis of ILI by meta-analysis and to seek factors associated with poorer clinical diagnostic discrimination. Methods: A systematic literature review was conducted using article selection criteria identifying studies indexed in PubMed/MEDLINE, the Cochrane Library, and other pertinent sources of studies reporting sensitivity, specificity, and effects of RFTs and clinical diagnosis on decision-making for patients with ILI. Results: QuickVue's® diagnostic specificity exceeds that of unaided clinical diagnosis by 29-31%. False-positive results occur approximately 8.2 times more frequently by unaided clinical diagnosis than by the RFT alone. These findings were unaffected by seasonal variations in disease prevalence. RFTs reduce diagnostic testing, antibiotic use, and emergency department utilization while increasing antiviral prescription rates. No systematic relationship between the broadness of clinical diagnostic criteria for influenza and diagnostic performance was observed across studies included in this review. Conclusions: Use of RFTs improves seasonal influenza diagnostic specificity above that based on unaided clinical diagnosis irrespective of the broadness of clinical diagnostic criteria, and affects clinical decision-making. These results provide an improved framework upon which to diagnose influenza, design future RFT studies, and modify existing recommendations for improved ILI patient management.