Review of Rapid Diagnostic Tests for Influenza

Abstract

Influenza is unique among viral infections because of its propensity for seasonal epidemics and occasional pandemics, and because of the morbidity and mortality that result from its pulmonary complications. In contrast to the majority of viruses, effective well-tolerated influenza vaccines, antivirals and chemoprophylaxis are available. The need for a timely diagnosis, which allows for optimal use of these treatments, led to the introduction of numerous rapid diagnostic tests (with turnaround times of less than 30 minutes). However, during influenza season, clinical diagnosis (based on cough and high fever of acute onset) can be highly predictive of influenza. Thus diagnostic tests are not required for all patients with suspected influenza but may be of value if the clinical diagnosis is unclear and if antiviral or antibiotic treatment is a consideration. When evaluating performance of various rapid diagnostic tests for influenza, it is important to consider the type and quality of specimen and type of patient to be tested. Specimen-type drives performance of the rapid diagnostic tests. Swab specimens, particularly throat swabs are the most frequently submitted but least desirable specimen-type. Thus, although current rapid diagnostic tests are specific for influenza, sensitivity is highly variable. To improve diagnostic accuracy, a nasal/nasopharyngeal aspirate or sputum specimen should be obtained. Because of their highly variable sensitivity and negative predictive value, it is our opinion, that rapid diagnostic tests should only be used in influenza season and that results should be confirmed with virus culture. Despite these reservations, during influenza-season, detection of influenza by rapid diagnostic test may, potentially, be of great benefit to the patient and public health.