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To assess the risks of leukemia for individuals participating in a gastric mass screening program using barium photofluorographic examination in Japan, a population-based, case-control study was carried out. The histories of participation in the last 10 years of 79 leukemia cases diagnosed between 1978 and 1985 and twofold controls matched for sex, age (+/- 5 years), and residence were investigated using the records of the gastric mass screening program. The odds ratio of any type of leukemia for those participating at least once in the last 10 years was 1.09 (95% confidence interval, 0.61-1.96) and that of myeloid type was 0.88 (95% confidence interval, 0.38-2.27). Even when the histories of the preceding 5 years were ignored, no significant excess risks were found among patients with any type and myeloid type of leukemia. These results suggest that there is insufficient evidence to support the positive association between the incidence of leukemia and participation in gastric mass screening. The limitations and implications of this analysis are discussed.

The incidence of postoperative deep venous thrombosis was compared between patients who had or had not received a preoperative screening venogram. No statistically significant difference in the deep venous thrombosis rate was noted postoperatively. Thirty percent of patients who received a preoperative venogram developed postoperative deep venous thrombosis, and 28% of those who did not have a preoperative venogram developed postoperative deep venous thrombosis. These results suggest that an orthopaedic surgeon may order a preoperative venogram for a patient at potential high risk of thromboembolic complications without predisposing the patient to an increased risk of postoperative deep venous thrombosis.

Doses to the salivary glands, thyroid gland, breast, lung, stomach and colon during mass radiological gastric screening, mass radiographic chest screening, upper gastrointestinal series and computed tomography were determined by exposing a female human phantom to simulated radiological X-ray examinations as performed in community hospitals. The doses were measured using thermoluminescent dosimeters, and the results will be used to document organ doses received by participants in the Atomic Bomb Casualty Commission/Radiation Effects Research Foundation Adult Health Study.

Can routine digital rectal examinations, transrectal ultrasound studies, and prostate-specific antigen determinations reduce deaths from prostatic carcinoma? The evidence is that the benefits of early diagnosis and treatment are at least neutralized by the limited reliability and high monetary and human costs of the test and by the lack of proof that treatment is effective for those tumors detected. One must conclude that universal screening is not now warranted and will await demonstration of effectiveness by controlled studies.

Routine testing for prostatic carcinoma by digital rectal examination, transrectal ultrasonography and prostate specific antigen determination has been proposed to reduce deaths by earlier diagnosis. The questionable reliability of results, cost of screening, and inability to establish a balance between the benefits of treatment and the adverse effects on the quality of life of the men screened make screening experimental until controlled studies prove its value.

The adverse effects of screening are not commonly studied. False-positive tests lead to discomfort, costs, and risks from additional diagnostic and therapeutic procedures. False-negative tests lead to a sense of security and delays in seeking medical help when symptoms develop. Labeling an individual with a false-positive test, or with a true-positive test for which there is no evidence that intervention makes a difference, e.g., intervention on an 80-year-old asymptomatic woman with hypercholesterolemia, can have a markedly negative impact on the quality of life. Interpreting statistical abnormalities out of clinical context, e.g., lending importance to a multiphasic blood screen showing "high" alkaline phosphatase in a teenager, leads to unnecessary costs and anxiety. The cost of screening programs that may not have been shown to do more good than harm is already having an impact on the resources available to diagnose and treatment symptomatic persons. Premature implementation of unproved screening programs will continue to decrease physician and public confidence in prevention.

The potential risk of a radiologic procedure often is compared with the potential benefit of the procedure. While risk vs. benefit analysis has been useful as a step toward increased communication and understanding among radiologists, referring physicians, and the general public, it has the disadvantage that risk and benefit are fundamentally different quantities. Hence, their juxtaposition for purposes of comparison presents contextual difficulties. In this article, the concept is presented of comparing the risk of doing a procedure with the risk of choosing not to do the procedure. An example of risk vs. risk analysis of screening mammography for women over the age of 50 is given, with the conclusion that the risk of having yearly mammograms is less than 1/10 the risk of early death caused by failure to diagnose breast cancer by x-ray mammography. This approach to risk analysis would yield interesting data for examinations that are part of more complicated diagnostic pathways.