However, as discussed in Section 5.1, the writing committee did elect to include documentation of preprocedural estimated GFR and contrast dose as in- ternal quality-improvement measures in this set. There is a tight linkage between GFR and contrast dose and devel- opment of contrast-related nephropathy. The writing committee felt that these measures should capture, with suf cient granularity, important data to guide local improvement efforts. As the evidence base to guide the management of contrast-related nephropathy continues to evolve, consideration for inclusion might be appropriate in future iterations of this measure set. 7. Areas for Further Research The writing committee identi ed 4 areas of interest for further investigation. Although the areas are relevant to performance measures in general, the writing committee felt they would have particularly important implications for measurement with regard to PCI. Some of these have been discussed throughout the present document in relevant sections but are highlighted here for additional emphasis. 7.1. Documentation of Prescription of Drugs Versus Filling of Drug Prescriptions and Optimal Dosing of Drugs The writing committee felt that it will be important in future work to examine moving beyond documentation of only the prescription of drugs to the actual lling of drug prescriptions and the optimal dosing of drugs. Unfortu- nately, using existing data collection systems to measure these is currently too dif cult, expensive, and prone to error to serve as a useful quality measure. Additionally, a patient could be seen by several practitioners who have different standards for optimal dosing. 7.2. Limitations of Current Data Systems for PCI Administrative claims data are used for a large number of analyses focused on PCI utilization. Although valuable for capturing use and costs, these data are inadequate as a source for quality measures. 