False-Positives Not a Concern for Lung Screening Trial Participants

A new study of National Lung Screening Trial (NLST) participant responses to false-positive diagnoses finds that those who received false-positive screening results did not report increased anxiety or lower quality of life compared with participants who received negative screen results.

This research comes after the US Preventive Services Task Force recently recommended CT lung screening for people at high risk of cancer despite many policymakers expressing concern that a high false-positive rate will cause patients to become needlessly upset.

“Most people anticipated that participants who were told that they had a positive screen result would experience increased anxiety and reduced quality of life. However, we did not find this to be the case,” says Ilana Gareen, PhD, an assistant professor of epidemiology research in the Brown University School of Public Health and lead author of the study published in the journal Cancer.

The NLST’s central finding, announced in 2010, was that screening with helical CT scans reduced lung cancer deaths by 20% compared with screening with chest X-rays. The huge trial spanned more than a decade, enrolling more than 53,000 smokers at 33 sites.

In the new study, Gareen and coauthors followed up with a subset of participants at 16 sites to assess the psychological effects of the CT and X-ray screenings compared in the trial.

“In the context of our study, with the consent process that we used, we found no increased anxiety or decreased quality of life at one or six months after screening for participants having a false-positive,” Gareen says. “What we expected was that there would be increased anxiety and decreased quality of life at one month and that these symptoms would subside by six months, which is why we measured at both time points, but we didn’t find any changes at either time point.”

The unexpected similarity between the participants with a negative and a false-positive screen result is not because getting a false-positive diagnosis is pleasant, Gareen says, but presumably because study participants understood that there was a high likelihood of a false-positive screen result.

“In advance of any screening, participants were advised that 20% to 50% of those screened would receive false-positive results, and that the participants might require additional work-up to confirm that they were cancer-free,” Gareen says.

To make its assessments, Gareen’s team surveyed 2,812 NLST participants for the study. Patients responded well, with 2,317 returning the survey at one month after screening and 1,990 returning the survey at six months. The survey included two standardized questionnaires: the 36-question Short Form SF-36, which elicits self-reports of general physical and mental health quality, and the 20-question Spielberger State-Trait Anxiety Inventory.

In the study analysis, the researchers divided people into groups based on their ultimate accurate diagnoses: 1,024 participants were false-positive, 63 were true positive, 1,381 were true negative, and 344 had a significant incidental finding, meaning they didn’t have cancer but instead had another possible problem of medical importance.

The results were clear after statistical adjustment for factors that could have had a confounding influence. Whether participants received X-rays or the helical CT scans, the questionnaire scores of those with false-positive diagnoses remained similar to those who were given true negative diagnoses.

Meanwhile, the scores of the true positive participants who were diagnosed with lung cancer markedly worsened over time as their battle with the disease took a physical and psychological toll.

Because participants received the questionnaires at one and six months, it is possible that study participants receiving a false-positive screen result experienced anxiety and reduced quality of life for a short time after receiving the result, Gareen says. But by one month after their screening, there was no evidence of a difference between the screen result groups.

Gareen says the results should encourage physicians to recommend appropriate screenings, despite their high false-positive rates so long as patients are properly informed of the likelihood of a positive screen result and its implications. The data provide evidence that the NLST consent process provided a good model for advising those undergoing screening, she says.

Source: Brown University