Understanding High False-Positive Rates Among VA Lung Cancer Screenings

01/30/18

A recent lung cancer screening demonstration project by the Veteran’s Health Affairs (VHA) identified a high false-positive rate following initial low-dose computed tomographic screening. Researchers examined how a high false-positive rate influences the harm-to-benefit ratio for higher- versus lower-risk patients.

  • Researchers screened 2106 patients across 8 academic VAs from March 31, 2015 through June 30, 2015, in order to measure screening effectiveness; and screening efficiency.
  • Patients in higher quintiles of lung cancer risk had more lung cancers diagnosed during the project. The authors noted that this supports the Bach model’s ability to identify risk stratify in this population.
  • Initial screenings were least effective for veterans in quintile 1—the lowest lung cancer risk—and most effective for veterans in quintile 5.
  • Rates of false-positive results and downstream evaluations did not differ significantly across quintiles, meaning the overall 56.2% rate of false-positive results requiring tracking remained relatively stable across risk quintiles.
  • As for harm versus benefit balance for higher-risk versus lower-risk participants, the initial screen was least efficient for patients in quintile 1, and most efficient for those in quintile 5.

Offering insight into these findings, Tanner Caverly, MD, MPH, clinical lecturer of learning health sciences and internal medicine at the University of Michigan, lead study author, recently explained the impact of these high false-positive rates and the associated cost implications.

Insight From The Author

Were false positive rates higher or lower than you anticipated? 

These false positive rates were from a previous study that received a lot of press because the rates were much higher than expected (higher than reported in the controlled trial setting). We did our study, which was a re-analysis of the prior study, because this prior study put a lot of focus on the downsides of screening, such as a potentially high false-positive rate.

Screening is a balance of pros and cons, so we wanted to look at that balance. We found that the high rates of false positive findings are a major concern for some people eligible for screening (who have smaller benefit because of lower lung cancer risk), but the false positive rates are much less of a concern for eligible people at very high lung cancer risk (with a lot to potentially gain from screening).

Was lung cancer screening more prevalent among the VA Health System compared to the general health system? 

In this VA study population, the lung cancer rate was pretty similar to what was seen in the larger trial, which included VA sites but also many non-VA sites across the nation. But, there is other evidence that lung cancer is a relatively larger problem in the VA population because of higher rates of smoking and heavier smoking.

What kind of cost implications are associated with your findings? 

You get a lot more bang for your buck screening higher risk persons. The false-positive rates are less of a concern in very high-risk folks because the potential benefits of screening are so large. At very high-risk the chances of avoiding a lung cancer death with screening are so large that this benefit becomes the dominant factor.


To read the original article from First Report Managed Care, click here.