Quality improvement (QI) projects are now an integral part of the strategy of healthcare systems towards accountability. While the immediate audience of the outcomes of such projects is internal to the care providing organization, accountability to external audiences (communities, government, payers, business coalitions) is increasingly demanded.¹ Indeed, while in the past decade outcomes research was primarily the domain of healthcare professionals, now it seems the cornerstone of any accountability strategy. In the US such strategies are translated into “report cards”, in the UK to “league tables”, and elsewhere to “hospital ranking reports”. Even when the methods of analysis have not changed—variation, observed to expected ratios, statistically significant differences in utilization or outcomes rates—the landscape has been expanded to encompass numerous groups asking for accountability.²

To achieve responsiveness to various audiences, QI projects should measure temporal trends in performance, link outcomes to processes, and ascertain the extent of organizational readiness for promoting higher quality and safer systems of delivery. Epidemiological methods of measurement and analysis, specially based on rates, are necessary for a successful QI …