Using linked administrative data to study periprocedural mortality in obesity and chronic kidney disease (CKD)

Both obesity and chronic kidney disease (CKD) are associated with adverse periprocedural outcomes, but it is unknown how these two common conditions interact to influence risk. We examined the feasibility of combining a new procedure-related, obesity-specific flag with administrative and laboratory data and assessed the joint association between obesity and CKD with mortality. Since 2007, Alberta physicians may claim a fee supplement for performing eligible surgical and non-surgical procedures on patients with documented BMI ≥ 35 kg/m(2). We linked this information to the Alberta Kidney Disease Network registry. Participants were classified into four mutually exclusive groups based on the presence/absence of both obesity (BMI ≥ 35 kg/m(2)) and CKD (eGFR < 60 mL/min/1.73 m(2)). Mortality was assessed at 30 days following the index procedure. Of 393 659 participants, 9% were obese. Overall, 8% had obesity only, 78% neither obesity nor CKD, 13% CKD only and 1% both obesity and CKD. Unadjusted risks of mortality at 30 days were 0.3, 0.4, 2.0 and 2.1%, respectively--but decreased to 0.1, 0.2, 0.3 and 0.3%, respectively, after adjustment for age, sex, socioeconomic status, procedure type and other comorbidities. Administrative data can be feasibly combined with disease registries to study obesity-related outcomes. Results from the linked dataset demonstrated face validity--subjects with both obesity and CKD were at increased risk of periprocedural mortality, and this was driven in part by differences in age and comorbidity.