Sensitivity and positive predictive value of the registration of self-expanding metal stent treatment for obstructive colorectal cancer in two Danish nationwide registries

Background: Randomized controlled trials have not provided clear evidence for the use of self-expanding metal stents (SEMS) for colonic cancer obstruction. Existing observational research mainly originates from highly specialized single-center settings with limited generalizability. The conduct of population-based nationwide studies is possible by using Danish medical databases. However, the quality of the coding of SEMS procedures in these databases is unclear. Methods: From March 1, 2010 through December 31, 2013, we compared the registration of SEMS procedures among obstructive colorectal cancer patients in the Danish National Patient Register (DNPR) and the Danish Colorectal Cancer Group (DCCG) database to the registration in a prospective SEMS database (the reference standard). Results: Ninety-three patients were included in the reference standard for the evaluation of DNPR data. In the DNPR, only two patients were incorrectly registered (positive predictive value [PPV]= 98%, 95% CI: 92%-100%) whereas six patients were not captured by the DNPR (sensitivity = 94%, 95% CI: 87%-98%). For the evaluation of the DCCG database, the reference standard included 54 patients. Only two patients in the DCCG database were incorrectly recorded (PPV = 95%, 95% CI: 82%-99%), whereas 19 patients were not captured by the DCCG database (sensitivity = 65%, 95% CI: 51%-77%). Conclusion: We found high PPV and sensitivity of SEMS coding in the DNPR, supporting the use of these data in future research. The PPV of SEMS data in the DCCG database was high, but the sensitivity was low, suggesting that data on SEMS treatment from this database should be used with caution.