Influenza A Test Is a Help When Screening for H1N1

In anticipation of the next flu season, some labs are expanding flu test capacity and capabilities

CEO SUMMARY: Viracor Laboratories is preparing to handle expanded volumes of influenza testing prior to the start of the next flu season. It will use added instrumentation and expanded working hours to expand capacity. Another strategy is to use influenza A testing as a way to reduce the overall number of influenza specimens that might need to be referred for additional testing. New molecular tests offering better sensitivity for influenza are also entering the clinical marketplace.

SO FAR, INFLUENZA A/H1N1 has not been the public health threat long predicted by experts. It arrived at the very end of the flu season and has not proved to be as lethal as originally feared. But this is only the first chapter in the A/H1N1 story.

“Fortunately, this influenza virus has not been highly lethal or highly virulent and standard flu treatments work well,” stated Steven B. Kleiboeker, DVM, Ph.D., Vice-President and Chief Scientific Officer at ViraCor Laboratories in Lee’s Summit, Missouri. “It did spread rapidly, spanning the globe in a short period of time. But the number of deaths has been moderate. That can all change because flu viruses often pick up virulence. Thus, we are not yet finished with this virus.

“So, will clinical laboratories heed the lesson and develop the requisite testing capacity?” Kleiboeker asked. “As a company, we are planning to expand our capacity to handle a surge, by this fall, of around 2,000 flu samples a day. We can get to that level by having our staff work up to 70 hours per week and by operating double shifts of 10 or 11 full capacity hours per day. That would require us to operate the lab for 20 to 22 hours per day.

“It’s my belief that all labs should consider ways that they can get more capacity,” Kleiboeker continued. “But having the laboratory capacity is only the first step. The second step is to have a validated assay ready to go. Here in Missouri, our public health lab didn’t have such an assay in hand until the second full week of the outbreak. That’s very late.

Reagent Licensing Issues

“Another issue is that the CDC and the state health laboratories have been unwilling to supply private laboratories with reagents,” he said. “Even though the assay is in the public domain, licensing issues create difficulties in making these reagents available.

“It is now recognized that a general influenza A assay is useful,” he added. “At a minimum, it allows the laboratory to identify the 5% or 10% of the flu samples that are positive for this factor. These influenza A tests have great sensitivity and reasonably good throughput. Thus, for labs lacking a true definitive assay, those specimens could be reflexed to another lab.

“That arrangement alone would reduce reflexive testing by 90%,” said Kleiboeker. “Public health labs need to have a certain number of flu strains that we can identify today and be ready to run them in case of a future similar epidemic.”

Another laboratory professional who agrees with the value of using an influenza A test is Jeremy Bridge-Cook, Ph.D., Vice President of Luminex Molecular Diagnostics, based in Toronto, Ontario. “It was the ability of the Luminex test to quickly and accurately recognize and sub-type influenza A that helped our customers during this outbreak,” observed Bridge-Cook.

“Because the Luminex test identifies subtypes, the lab does not have to send out every flu A sample,” he explained. “It only needs to refer the specimens which are negative for a subtype result because that indicates that the sample may contain a novel flu A that should be investigated by a public health lab. This benefits hospital labs and public health labs because it greatly reduces the number of flu samples that require follow up testing.

Labs Asked To Report Flu A

“Currently the CDC and the FDA are requesting that labs report all flu A samples that are unsubtyped and provide those samples to a public health lab,” noted Bridge-Cook. “Thus, labs using a rapid EIA (enzyme immunoassay), DFA (direct immunofluorescent antibody), culture, or any method that does not sub-type, must send every positive flu A result to a public health lab to be analyzed. “Currently, that volume of referral specimens is manageable because it is not peak flu season,” he stated. “But, were we to be in the middle of the flu season, it is likely that public health labs would be inundated with flu A-positive specimens that need subtyping.”

Molecular Analysis of H1N1 Proved Fast and Accurate

WITH THE EMERGENCE of the influenza A/H1N1 strain, new molecular testing technologies faced a major public health challenge and played new roles in helping health officials understand and react to the outbreak.

“To my knowledge, this is the first time where large scale molecular testing was helpful and necessary to understanding the spread of the A/H1N1 influenza,” said Steven B. Kleiboeker, DVM, Ph.D., the Chief Scientific Officer and a Vice-President of ViraCor Laboratories.

“The rapid flu tests in common use by most clinical labs don’t have great sensitivity or specificity and were not designed to distinguish between the different strains of the influenza virus,” he noted. “Rapid flu tests are useful for screening. However, when public health considerations become important, a more accurate screening test is needed to identify the genealogy of a virus strain like A/H1N1.

“That’s where PCR (polymerase chain reaction) testing has a role,” Kleiboeker continued. “PCR testing runs on a robust platform and one scientist with the appropriate instrumentation should be able to process 100 samples every three to four hours.”

“This is still a relatively new technology. Many labs that have molecular testing have a narrow spectrum of capability,” he added. “The laboratory also needs an assay that has been developed and validated.”

“This new H1N1 strain returns a negative resolution H1 assay and a flu A positive,” said Kleiboeker. “The H1 component turns out to be significantly different than the seasonal swine A/H1N1. That makes it easy to distinguish from other strains of the influenza virus. It also shows how molecular testing has been an effective tool to help labs identify the new A/H1N1 strain of influenza.”

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