Rapid influenza diagnostic tests can accurately identify the infection in adults and children presenting with flulike symptoms (fever, cough, sore throat), but are not as accurate at ruling it out, meaning a negative result should be followed up with a culture or reverse transcriptase-polymerase chain reaction (PT-PCR) test.
Simple to use, RIDTs give results in 15 to 30 minutes. In some cases, they can be used at the point of care in a routine clinical setting, such as a primary-care office. However, RIDTs may have inconsistent accuracy, with reported sensitivity ranging from 10% to 80%, an investigative team led by Caroline Chartrand, MD, MSc, cautioned in Annals of Internal Medicine.
The researchers conducted a systematic review of 159 studies involving 26 RIDTs. The data yielded pooled sensitivity and specificity of 62.3% and 98.2%, respectively. The positive and negative likelihood ratios were 34.5 and 0.38, respectively.
RIDTs were more sensitive for influenza A than for influenza B. The tests also were more sensitive in children than in adults (66.6% vs. 53.9%). “This is plausible because children have higher viral loads and longer viral shedding than adults,” the researchers wrote.
“RIDTs fill a void at the point of care that no other test is likely to fill in the near future: as a first-line test to be confirmed (especially if negative) by more time-consuming, definitive testing,” they added. “As long as clinicians understand the limitations of RIDTs, namely that a negative result is unreliable and should be confirmed by using culture or RT-PCR, RIDTs could enable clinicians to institute prompt infection-control measures, begin antiviral treatment in high-risk populations and make informed decisions about further diagnostic investigations.”