In the future, broadening this measure to assess levels of participation on the basis of attendance, rather than simply referral, might be examined. 5.9. Regional or National PCI Registry Participation The writing committee believed strongly that every catheter- ization laboratory should participate in a national or regional PCI registry for benchmarking purposes. The benefits of participating in a registry include the ability to compare the catheterization laboratory s outcomes with those of similar laboratories of comparable volumes, so that the laboratory staff understands their outcomes in relation to national or regional standards. We believe this measure will encourage more cardiac catheterization laboratories to participate in large multicenter databases and collaboratives to improve the evidence base to support quality efforts in PCI. 5.10. Annual Operator and Hospital PCI Volume The writing committee designated the operator procedure volume as appropriate for internal quality improvement only, as indicated inAppendix C. It is well recognized that operator volume, though useful, is a limited surrogate for quality. This is due partly to the difficulty of collecting volume data for individual operators, who can practice across numerous facilities and even states. The vol- ume of the catheterization laboratory in which an operator works seems to be a more trustworthy surrogate for quality than does individual operator volume.Although updated recommendations exist for operator and institutional volumes,24 they are still based on observational studies that looked at a variety of facility vol- ume thresholds. However, the preponderance of evidence sug- gests that facilities that perform <200 PCIs per year have worse outcomes than facilities that perform more procedures. Given the limitations of the evidence base, the writing committee felt strongly that no specific threshold should be required for these measures, though it did see value in collecting these data for institutional and operator quality assurance. 