# 4686
Of primary interest to clinicians, I suppose, but we’ve a new study showing the wide divergence of sensitivity of RIDTs (Rapid Influenza Detection Tests) sometimes called IRDTs to various strains of influenza A and B – including avian strains.
These tests are generally used in doctor’s offices, clinics, and ERs to quickly (less than 30 minutes) test for the influenza virus.
Their accuracy has come under increasing fire over the past couple of years, however.
A few blogs on the subject include:
A Tale of Two Headlines
PLoS Currents: Improving Diagnostic Efficiency Of H1N1
No Doesn’t Always Mean No
The rapid tests vary in terms of sensitivity and specificity when compared with viral culture or RT-PCR. Product insert information and research publications indicate that:
- Sensitivities are approximately 50-70%
- Specificities are approximately 90-95%
The two main measures of the accuracy of a diagnostic test are sensitivity and specificity.
- Sensitivity is defined as the ability of a test to correctly identify individuals who have a given disease or condition.
- Specificity is defined as the ability of a test to exclude someone from having a disease or illness.
The various RIDTs are designed to show if someone tests positive for the Influenza A or B virus, but not the strain of flu.
Today from the Journal of Microbiology, we look at a side-by-side comparison of 20 different IRDTs available in Japan.
Sensitivity of influenza rapid diagnostic tests to H5N1 and 2009 pandemic H1N1 viruses
Yuko Sakai-Tagawa, Makoto Ozawa, Daisuke Tamura, Quynh Mai Le, Chairul A. Nidom, Norio Sugaya, and Yoshihiro Kawaoka
J. Clin. Microbiol. published ahead of print on 16 June 2010, doi:10.1128/JCM.00439-10
Abstract
Simple and rapid diagnosis of influenza is useful to treatment decision-making in the clinical setting. Although many influenza rapid diagnostic tests (IRDTs) are available for the detection of seasonal influenza virus infections, their sensitivity for other viruses, such as H5N1 viruses and the recently emerged swine-origin pandemic (H1N1) 2009 virus, remains largely unknown.
Here, we examined the sensitivity of 20 IRDTs to various influenza virus strains, including H5N1 and 2009 pandemic H1N1 viruses. Our results indicate that the detection sensitivity to swine-origin H1N1 viruses varies widely among IRDTs, with some tests lacking sufficient sensitivity to detect the early stages of infection when the virus load is low.
Viruses tested include seasonal H1N1, seasonal H3N2, seasonal Type B, 16 different (human and avian) H5N1 viruses, H5N2, H5N3, H9N2, H7N7, and 3 clades of pandemic H1N1.
You’ll find that that these tests all are not created equally, and that it is important to match the test to the virus you are testing for. As stated in the report:
Our findings emphasize the importance of selecting the right IRDT for rapid diagnosis of non-seasonal
influenza viruses, since the sensitivity of the IRDTs we tested varied by as much as 100-fold.
Obviously, we are in need of better, more accurate, rapid influenza tests – particularly when it comes to picking up novel or avian strains of the virus.
This is a detailed report and well worth reading, particularly if you are involved in the selection of RIDTs for your practice.
