Development and external validation of tools for categorizing diagnosis codes in international hospital data.

BACKGROUND: The Clinical Classification Software Refined (CCSR) is a tool that groups many thousands of International Classification of Diseases 10th Revision (ICD-10) diagnosis codes into approximately 500 clinically meaningful categories, simplifying analyses. However, CCSR was developed for use in the United States and may not work well with other country-specific ICD-10 coding systems. METHOD: We developed an algorithm for semi-automated matching of Canadian ICD-10 codes (ICD-10-CA) to CCSR categories using discharge diagnoses from adult admissions at 7 hospitals between Apr 1, 2010 and Dec 31, 2020, and manually validated the results. We then externally validated our approach using inpatient hospital encounters in Denmark from 2017 to 2018. KEY RESULTS: There were 383,972 Canadian hospital admissions with 5,186 distinct ICD-10-CA diagnosis codes and 1,855,837 Danish encounters with 4,612 ICD-10 diagnosis codes. Only 46.6% of Canadian codes and 49.4% of Danish codes could be directly categorized using the official CCSR tool. Our algorithm facilitated the mapping of 98.5% of all Canadian codes and 97.7% of Danish codes. Validation of our algorithm by clinicians demonstrated excellent accuracy (97.1% and 97.0% in Canadian and Danish data, respectively). Without our algorithm, many common conditions did not match directly to a CCSR category, such as 96.6% of hospital admissions for heart failure. CONCLUSION: The GEMINI CCSR matching algorithm (available as an open-source package at https://github.com/GEMINI-Medicine/gemini-ccsr) improves the categorization of Canadian and Danish ICD-10 codes into clinically coherent categories compared to the original CCSR tool. We expect this approach to generalize well to other countries and enable a wide range of research and quality measurement applications.

Treatment with prophylactic oral anticoagulants and the risk of mortality in COVID-19 patients: a nationwide cohort study.

Background: Venous thromboembolism has been reported in patients with coronavirus disease 2019 (COVID-19). It remains unclear if premorbid use of prophylactic oral anticoagulation, for reasons other than COVID-19, protects against death in patients with COVID-19. The aim of this study was to estimate if the risk of all-cause mortality, hospital admission or intensive care unit (ICU) admission for individuals with verified SARS-CoV-2 was lower if patients used oral anticoagulant (OAC) therapy prior to a positive COVID-19 status. Methods: Data were obtained using national health registries. Cohort entry was the day of a positive SARS-CoV-2 test, and individuals were followed for 14 days or until death or hospital admission. Adjusted Cox proportional hazard regressions and competing risk analyses were used to estimate the risk of all-cause mortality, hospital admission and ICU admission in OAC users compared with patients with no use of OAC. Results: In this nationwide cohort study a total of 244 522 individuals were included (median age 35 years (interquartile range 21-52); 124 095 (51%) female), among whom 3710 (1.5%) were OAC users. In the adjusted Cox regression cohort, there was no difference in risk of all-cause mortality in OAC versus non-OAC users. (hazard ratio (HR) 1.13, 95% CI 0.99-1.30). Hospital admission risk (HR 1.11, 95% CI 1.02-1.20) was slightly increased in OAC users, and there was no difference between the groups regarding the risk of ICU admission (HR 0.96, 95% CI 0.74-1.24). Conclusions: In individuals with confirmed SARS-CoV-2, pre-existing treatment with OAC was not associated with prophylactic benefits in the prevention of hospital admission, ICU admissions or death. Prescription patterns should remain unchanged.