Study questions evidence that screening reduces mortality

Randomized controlled trials (RCTs) show that few of the currently available screening tests for major diseases where death is a common outcome have documented reductions in disease-specific mortality, according to a new study published online in the International Journal of Epidemiology.

Senior author Dr. John Ioannidis, of Stanford University, and colleagues examined evidence for 39 screening tests from 48 RCTs and nine meta-analyses identified via the Cochrane Database of Systematic Reviews and PubMed. Their goal was to determine whether screening asymptomatic adults for major disease led to a decrease in disease-specific and all-cause mortality.

Randomized controlled trial data were available for 19 tests for 11 diseases, including abdominal aortic aneurysms, breast cancer, cervical cancer, colorectal cancer, hepatocellular cancer, lung cancer, oral cancer, ovarian cancer, prostate cancer, type 2 diabetes, and cardiovascular disease (Int J Epidemiol, January 15, 2015).

There was evidence of a reduction in mortality in only 30% of the disease-specific mortality estimates and 11% of the all-cause mortality estimates from the RCTs evaluated, according to Ioannidis and colleagues. Findings from the individual RCTs for disease-specific mortality were supported by evidence from four meta-analyses, but none of the six meta-analyses that included estimates of all-cause mortality showed evidence of a reduction in mortality.

RCT evidence should be considered on a case-by-case basis, depending on the disease, Ioannidis and colleagues concluded. They noted that screening is likely to be effective and justifiable for a variety of other clinical outcomes besides mortality.