The PhenX Toolkit is designed to help investigators effectively expand their studies, but there are limitations. Each working group is asked to balance multiple criteria for selecting measures (defined by the Steering Committee) as they decide what measures to include in the Toolkit. Current limitations are: 1) the Toolkit does not necessarily include the gold standard for each research domain, as these measures are often quite burdensome to administer; 2) promising but relatively new measures are not included in the Toolkit because they are not yet well established; and 3) established protocols are not modified (although some working groups indicated that this could be beneficial).
