The withholding of test results as a means of assessing the effectiveness of treatment in test-positive persons.

In recent years, a number of studies have achieved randomization of patients to alternative management strategies by blinding some patients (and their providers of medical care) to the results of tests that guide such strategies. Although this research approach has the potential to be a powerful means of measuring treatment effectiveness, the interpretation of the results may not be straightforward if the treatment received by test-positive persons is variable or not well documented, or if the analysis is not restricted to outcomes in test-positive persons. Studies in which the test results are withheld at random may face ethical issues that, to date, have received little discussion.