TUESDAY, Sept. 23, 2014 (HealthDay News) -- A test used to diagnose lung cancer may not be as reliable in geographic regions where certain lung infections are more common, a new analysis says.
One noninvasive way of detecting lung cancer is through the use of what's known as functional imaging. For lung cancer, a specific type of functional imaging called FDG-PET is used, according to the study authors.
Cancerous tumors generally look different on FDG-PET images than do parts of the lungs that don't have cancer, according to background information in the study. But, it can be difficult to tell the difference between lung cancer and some lung infections, according to the study.
Lung conditions that might affect the accuracy of the functional imaging tests include tuberculosis and fungal infections, the study authors said.
Geographic regions in the new analysis where tuberculosis is common include China, Japan and South Africa. Areas where fungal lung infections occur frequently include the Mississippi, Missouri and Ohio river valley regions, as well as the U.S. Southwest, and Ontario, Canada, according to the analysis.
The analysis looked at the results of 70 studies.
Overall, the imaging test's ability to correctly identify people with lung cancer was 89 percent, the study found. And, the test's ability to correctly identify patients without lung cancer (called "specificity") was 77 percent in the adjusted analysis.
The researchers said that when they examined only geographic areas with a high prevalence of infectious lung diseases, FDG-PET scans had a 16 percent lower average specificity. That means the lung diseases common in those regions may have sometimes been mistaken for lung cancer on the imaging tests, the researchers said.
"Knowledge of this reduction in specificity should limit the use of FDG-PET to diagnose lung cancer," the study authors, from Vanderbilt University Medical Center in Nashville, said in the report.
They suggested that only institutions with proven expertise in interpreting these scans in geographic areas where lung infections are common should use them for diagnosing lung cancer.
The findings were published Sept. 23 in the Journal of the American Medical Association.
The American Lung Association provides more information on diagnosing lung cancer.