Validation of surgical site infection surveillance data in Scotland

Validation of surveillance data is necessary to ensure its scientific credibility, to identify methodological problems within the surveillance programme, to help increase compliance and participation in the surveillance programme, and to identify data quality issues at local level. Surgical site infection surveillance (SSIS) in Scotland has been implemented in collaboration between Health Protection Scotland (HPS) and staff in acute divisions in Scotland. A team at HPS carried out a study to validate the SSIS data reported to them. The aims of the validation study were: (i) to measure the completeness of the denominator data; (ii) to measure the accuracy of all SSIS data items reported to HPS; and (iii) to determine the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the SSIs reported to HPS against the SSIs validated as part of this study. The methodology utilized for validation of SSIS data was based on an evaluation research approach. The evaluation research approach involves a range of investigative activities, aimed at judging the worth of a programme or practice, and measures SSIS in terms of structure, process and outcome. The completeness of the denominator and the means of identifying eligible patients was identified. Descriptive information about how SSIS data were collected and managed at hospital level was collated, and the accuracy and completeness of the reported SSIS data were measured by case note review of selected cases. SSIS data from 27 hospitals in 15 acute divisions and one special health board were validated. The results indicated that a total of 91% of the procedures carried out (denominator) during a specified three-month period were reported to HPS. The case notes validated over 90% of records reported to HPS; however, there was variation in data quality between hospitals. The sensitivity, specificity, PPV and NPV of the SSIs reported to HPS were 96.7, 99.0, 94.6 and 99.4%, respectively. Where problems with data were identified at local level, hospitals have been offered guidance to improve their data. As a result of this study, HPS are confident that the Scottish SSIS data are reliable and robust.