Simple Laboratory Test-Based Risk Scores in Coronary Catheterization: Development, Validation, and Comparison to Conventional Risk Factors

Abstract

Background: We developed and validated laboratory test-based risk scores (i.e., lab risk scores) to reclassify mortality risk among patients undergoing their first coronary catheterization. Methods: Patients were catheterized between 2009 and 2015 in Calgary, Alberta, Canada (n = 14 135, derivation cohort), and in Edmonton, Alberta, Canada (n = 12 143, validation cohort). Logistic regression with group LASSO (least absolute shrinkage and selection operator) penalty was used to select quintiles of the last laboratory tests (red blood cell count, mean corpuscular hemoglobin concentration, mean corpuscular hemoglobin, mean corpuscular volume, red cell distribution width, platelet count, total white blood cell count, plasma sodium, potassium, chloride, CO2, international normalized ratio, estimated glomerular filtration rate) performed <30 days before catheterization and by age and sex that were significantly associated with death ≤60 and >60 days after catheterization. Follow-up was until 2016. Risk scores were developed from significant tests, internally validated in Calgary among bootstrap samples and externally validated in Edmonton after recalibration using coefficients developed in Calgary. Interaction tests were performed, and net reclassification improvement vs conventional demographic and clinical risk factors was determined. Results: Lab risk scores were strongly associated with mortality (29-40× for top vs bottom quintile, P for trends <0.01), had good discrimination and were well calibrated in Calgary (C = 0.80-0.85, slope = 0.99-1.01) and Edmonton (C = 0.80-0.82; slope = 1.02-1.05) - similar to demographic and clinical risk factors alone. Associations were attenuated by several comorbidities; however, scores appropriately reclassified 11%-20% of deaths (both follow-up periods) and 6%-9% of survivors (>60 days) after catheterization vs demographic and clinical risk factors. Conclusions: In 2 populations of patients undergoing their first coronary catheterization, risk scores based on simple laboratory tests were as powerful as a combination of demographic and clinical risk factors in predicting mortality. Lab risk scores should be used for patients undergoing coronary catheterization.