Validity of bariatric surgery codes in the UK Clinical Practice Research Datalink (CPRD) GOLD compared with Hospital Episodes Statistics.

Abstract

To assess completeness and validity of bariatric surgery codes in the UK Clinical Practice Research Datalink (CPRD) GOLD compared with Hospital Episodes Statistics (HES). We conducted a validation study among patients in the UK-based CPRD GOLD with linkage to HES (1998 to 2017). Since the same surgery codes are used for bariatric and other gastrointestinal surgery we assessed code distribution patterns used in patients with bariatric versus other gastrointestinal surgery by presence of other conditions such as obesity and gastrointestinal cancer. We developed algorithms to identify bariatric surgery and calculated validity measures (ie, positive/negative predictive value [PPV/NPV], sensitivity, and specificity) of each in CPRD GOLD compared with HES (gold standard). Among 7 357 007 available patients we identified 10 190 patients who had a total of 14 046 potential bariatric surgery codes in CPRD GOLD and/or HES. Surgery code patterns differed between bariatric surgery and assumed other gastrointestinal surgery. The sensitivity of CPRD GOLD bariatric surgery coding improved from an overall of 56% to 69-71% when applying stricter algorithms (ie, in obese patients or obese, gastrointestinal disease/complication free patients) but PPVs remained at 53%-55%. NPVs and specificities of CPRD GOLD bariatric surgery coding achieved ≥99.8% for all algorithms. Our results suggest that using CPRD GOLD and HES data and a wide selection of surgery codes will result in the most complete and accurate capture of bariatric surgery events. Validity measures of CPRD GOLD bariatric surgery codes were identical in obese patients and more restrictive populations.