Is there a ‘cascade effect’ generated by predictive genetic testing? Some evidence from Italy

Background The term ‘‘cascade effect’’ of medical technology refers to a chain of events initiated by an unnecessary test, an unexpected result, patient or physician anxiety, which results in inappropriate tests or treatments that may cause avoidable morbidity and unnecessary costs. Although the cascade effect of predictive genetic testing is a matter of concern, the problem is still under-investigated in the medical literature. Methods The estimation of the actual health care pathways triggered by three selected genetic tests (APC test, BRCA1/2 test and genetic tests for thrombophilia) is currently being developed through three different approaches: experts interviews (a total of nine experts were interviewed); physicians survey (a cross-selection survey of 331 general practitioners was carried out, with a response rate of 70%); patients survey (a survey involving at least 230 patients who performed a genetic test two or three years ago is in process). Results A comparative evaluation between the recommended health care pathways subsequent to predictive genetic testing (identified through an extensive review of national and international guidelines) and the actual pathways indicated by physicians was performed. Physicians are more comfortable to identify the recommended pathways for individuals undergoing genetic testing for breast cancer (28% of the sample) or colorectal cancer (21%), while recommendations about the subsequent paths to genetic tests for thrombophilia are poorly followed (10%). Patients interviews suggest that individuals undergoing genetic tests for breast or colorectal cancer are managed more appropriately than those after genetic testing for thrombophilia. These results are in line with the information provided by the experts panel. Conclusions The cascade effect generated by predictive genetic testing seems to be greater for tests of unproven efficacy (such as tests for thrombophilia) compared to those with some evidence of effectiveness and cost-effectiveness (BRCA1/2 and APC tests). Proper dissemination of authoritative guidelines, as well as training and education initiatives of physicians and of the public are needed for the appropriate use of predictive genetic testing and to contain the cascade effect. Key messages Physicians surveys, patients interviews and experts consultation suggest that the cascade effect is more relevant for predictive genetic tests without evidence of efficacy and cost-effectiveness. Dissemination of guidelines, training of physicians and education of the public are needed for the appropriate use of predictive genetic testing and to contain the cascade effect.