Using centrally held data to validate carotid surgery outcome data

Outcome audit data for peer group comparison must be transparent, objective, and independently reproducible. Personal data sets are difficult to maintain and often lack complete follow-up. Local coding difficulties make initial retrieval of centrally held data unreliable. However starting with a complete list of interventions, reliable identification of patients who have experienced an adverse postoperative event may be possible using record linkages.

A surgical database, augmented by a hand-search of all theater registries and personal logbooks, identified 378 carotid endarterectomies performed for stroke prevention in symptomatic patients, in a single hospital between 2002 and 2009. A list of the names, unique patient identifiers, and operation dates was sent to the Information Services Division of National Health Service Scotland. Data were requested pertaining to all deaths and potential diagnoses of stroke after surgery. Every identified case was scrutinized.

There were 30 (8%) readmissions or transfers of care identified within 30 days of surgery. From this, 12 strokes were identified with another 2 strokes, occurring without readmission, diagnosed in the outpatient clinic. Only 6 of the postoperative strokes were identified during the index admission. There were 2 early deaths resulting in a combined stroke and death rate of 4.2% (95% confidence intervals, 2.4%-6.9%).

These outcome data are similar to the outcomes of the major carotid surgery trials. Record-linked data retrieval seems to be an appropriate starting point for outcome-based audit. This has the potential to generate robust, transparent data for comparison between individuals and centers for a specific procedure.