Health impact (zero): estimating the proportion and number of vitamin D tests with no net health benefit (unnecessary tests) To estimate the proportion (percentage) of vitamin D tests that provide no net health benefit, we conducted a rapid evidence review of peer-reviewed studies which provided an estimate of the proportion of inappropriate or unnecessary vitamin D tests (see table 1 for how this was defined by each study). We searched the following databases: Scopus, ScienceDirect and PubMed.