Accurate Diagnosis of Influenza Critical for Better Treatment/Control

Two new metaanalyses published online in the Annals of Internal Medicine on February 21, 2012, and February 27, 2012, highlight the importance of rapid diagnosis and treatment of flu.

In the first Annals article Mudhukar Pai, MD, PhD, from the University of Alberta (Edmonton, Canada) and colleagues reviewed 159 published studies to determine the accuracy of rapid influenza diagnostic tests (RIDTs) in diagnosing flu in adults and children presenting with flu-like symptoms. In all studies, RIDTs were tested against one of two accepted reference standards.

The scientists found that RIDTs were accurate at diagnosing the flu, but not as accurate at ruling it out, meaning that patients with a negative result would need to follow up with a culture or RT-PCR. RIDTs had an approximately 13 % higher sensitivity in children compared to adults, and were more accurate at detecting the more common influenza virus A compared to influenza virus B. According to the authors, the study results support implementing RIDTs in clinical practice, especially when treating children and other patients at risk for flu-related complications.

In the second Annals study Holger Ishüneman from the Iberamerican Cochrane Center (Barcelona, Spain) and colleagues cited evidence that early treatment with antivirals (within 48 hours) may be of greater benefit than later treatment. The scientists reviewed 74 published observational studies to determine the benefits and harms of four commonly prescribed antivirals: oseltamivir, zanamivir, amantadine, and rimantadine. The investigators found that oral oseltamivir and inhaled zanamivir might provide a net benefit over no treatment for patients with known flu.

Currently used viral cultures are accurate, but turnaround from culture to lab result can take up to 10 days. Newer reverse transcriptase-polymerase chain reaction (RT-PCR) tests are much quicker than viral cultures, but are very expensive and require specialized equipment. RIDTs are inexpensive and simple to use in the physician's office. The two studies described in the Annals of Internal Medicine give more information about their advantages for diagnosing flu, and the antivirals that are most effective.

Related Links:
University of Alberta
Iberamerican Cochrane Center