Chest X-rays are not effective in preventing lung cancer deaths involving both smokers and non-smokers, according to a government study involving over 150,000 Americans.

The 13-year study followed around 154,000 participants, with 10 percent current smokers and the rest former smokers and non-smokers. Despite having four annual chest X-rays, patients in the intervention group were just as likely to die from lung cancer as patients who do not have tests. After four years, more cases of cancers were found in the group that had used X-rays, while deaths were similar, with 1,213 in the X-ray group and 1,230 in the control group.

Martin Oken of the University of Minnesota led the study, to be published in The Journal of the American Medical Association next month. The large-scale study confirms previous, smaller studies.

CT scans, which provide more detailed views of the lungs, have been found to be more effective for radiologists to diagnose the diseases. A study released in August in the New England Journal of Medicine found patients were 20 percent less likely to die from lung cancer after receiving a CT Scan.