An influenza diagnosis for people 65 and older is serious. Up to 85 percent of influenza-related deaths occur in older adults, the Centers for Disease Control and Prevention (CDC) reports.
However, according to a new Vanderbilt study, doctors are less likely to test this age group of hospitalized patients.
“We thought many adults might not be tested because older adults often do not present with high fever. We were very surprised to find that even if they presented with the classical signs of influenza, they might not be tested,” said Dr. Keipp Talbot, associate professor of infectious diseases and senior author of the study, which was recently published online in the Journal of the American Geriatrics Society.
From November 2006 through April, 2012, 1,422 adults, 18 and older, who had a respiratory illness or fever took part in the study. Only 48 percent of the participants were age 65 and older. The patients were treated in four Davidson County hospitals.
“The only (previous) test that we had readily available to test for influenza had very poor sensitivity in older adults — the test was often negative even when the patient had influenza. It is very possible that physicians ‘gave up’ testing.
“There is much better testing available now that is much more sensitive,” Dr. Talbot said.
Researchers obtained nose and throat swabs from the patients, then used the real-time reverse-transcriptase polymerase chain reaction (RT-PCR) test, which is more sensitive than the commonly used rapid antigen influenza test. They ordered the tests for all patients, regardless of whether their providers ordered flu testing.
The study found 136 participants tested positive for flu, but overall only 399, or 28 percent, had been tested for influenza.
The team involved in this research wrote: “a major concern regarding lower rates of influenza testing in older adults is that clinicians are underdiagnosing influenza in a population with substantial morbidity and mortality that could be mitigated by early antiviral treatment.”
Dr. Talbot said if these older patients are not diagnosed with influenza there is the potential for the virus to spread.
“It is likely that their housemates, family members or caregivers are not given prophylaxis to prevent spread of disease if no one considers influenza as the cause for hospitalization. This is key for preventing outbreaks in senior centers, nursing homes and assisted living facilities,” Dr. Talbot said.
Other findings in the study include:
Younger patients — 58 years old on average — were more likely to be tested for influenza than older patients — 66 years and older.
Those with cardiac and/or pulmonary disease were also less likely to be tested for flu.
Dr. Lauren Hartman, an internal medicine resident; Dr. Yuwei Zhu, senior associate in biostatistics; Dr. Kathryn Edwards, Sarah H. Sell and Cornelius Vanderbilt Chair in Pediatrics; and Dr. Marie Griffin, professor of health policy and medicine, also contributed to the study, which was funded by multiple sources: the Vaccine and Treatment Evaluation Units, the CDC, and the National Institutes of Health (NIH).
It was also supported in part by Vanderbilt CTSA Grant 1UL1RR024975 from the National Center for Research Resources, NIH.