H1N1 pandemic shed light on ineffectiveness of some viral diagnostics

Issue: February 2011

ARLINGTON, Va. — The 2009 H1N1 pandemic allowed a unique opportunity to review viral diagnostic testing for influenza. Depending on the diagnostic method, clinicians should remember that performance may vary depending upon the patient’s age, test type, laboratory, or issues with specimen collection and transport, according to Richard L. Hodinka, PhD.

“The pandemic highlighted the good, the bad, and the ugly in viral diagnostics,” Hodinka, of The Children’s Hospital of Philadelphia, said during a presentation at Infectious Diseases Society of America’s Seasonal and Pandemic Influenza Meeting, held here. “The pandemic has really taught us from a diagnostic standpoint that we can do better.”

Because the accuracy of an influenza diagnosis on the basis of symptoms alone is unreliable, diagnosis requires the help of the laboratory and must be rapid and reliable to have a significant effect on patient care and management, he said.

Hodinka presented an overview of issues associated with the diagnosis of influenza. Culture-based assays and rapid diagnostic tests are two of the most commonly used assays and were considered the gold standard in the past. However, Hodinka said molecular testing is the new gold standard for detecting influenza and other respiratory viruses because of their high sensitivity and specificity.

“Molecular testing is now widely recognized, and manufacturers are motivated to develop fully automated, simple molecular systems. The relevance of traditional methods is now being questioned,” he said.

Some of the advantages of using this type of test include: compatibility of expense, labor and time; the ability to detect coinfections; and quick turn-around times. Yet, Hodinka said there are some concerns:

Few available, but many in the pipeline.
Lack of point-of-care molecular technology for rapid results in clinics, ED, physician offices.
How fast and how often can testing be done?
Is the diagnosis of coinfections relevant?
Does detection of nucleic acid always correlate with transmission and disease?
Does the benefit outweigh the cost?

Despite these concerns, Hodinka said advances in molecular technology will be seen soon.

“Pandemics allowed us a unique opportunity to utilize our labs. Like all diagnostic tests, evaluate influenza tests in the context of available clinical and epidemiologic information. We need to remember that regardless of the method, performance can vary,” he said. – by Jennifer Henry

One of the lessons learned during the recent influenza pandemic is the diagnostic value of molecular tests for influenza virus and other respiratory pathogens. In fact, molecular testing has replaced culture as the gold standard for influenza diagnosis. Molecular tests have many potential advantages; they are more accurate and more sensitive than other available tests and have the potential to simultaneously detect multiple viruses. Some tests can also detect other respiratory pathogens including Mycoplasma pneumoniae and Chlamydophila pneumoniae. With some of the newer platforms results can also be rapidly available. The potential clinical advantages include more appropriate use of antivirals and avoidance of unnecessary antibiotics and additional diagnostic testing, reducing costs and reducing selective pressure for development of antimicrobial resistance. In addition, knowing exactly what infection a patient has facilitates the implementation of appropriate infection control measures to reduce the risk for transmission. Some preliminary data show these positive impacts, but more studies are needed. Some challenges remain. These tests are still more expensive and require a modern laboratory, so they are not available in the office or in smaller hospitals. New technology in advanced development may address these issues. The goal should be the development of sensitive, specific, inexpensive tests that the clinician can use at the bedside or in the clinic for diagnosis and the identification of drug-resistant organisms when they are present.

–James M. Hughes, MD

Infectious Disease News Editorial Board member

President, Infectious Diseases Society of America

For more information:

Hodinka RL. Presented at: the IDSA’s Seasonal and Pandemic Influenza Meeting; Jan. 27-28, 2011; Arlington, Va.

Follow InfectiousDiseaseNews.com on Twitter.