Assessing the accuracy of ICD-10 coding for measuring rates and mortality from Acute Kidney Injury and the impact of electronic alerts:An observational cohort study

Background: The application of a uniform definition for Acute Kidney Injury (AKI) is vital in order to advance understanding and management of AKI. ICD-10 coding is frequently used to define AKI but its accuracy in unclear. The aim of this study was to determine whether ICD-10 coding is a reliable method of monitoring rates and outcomes of AKI in inpatients compared to biochemically-defined AKI and whether electronic alerts for AKI affects ICD-10 AKI coding.Methods: An observational cohort study of all 505,662 adult admissions to acute hospitals in two Scottish Health Boards (NHS Tayside and NHS Fife) January 2013 – April 2017 was performed. AKI e-alerts were implemented in NHS Tayside in April 2015. Sensitivity, specificity, positive and negative predictive values of ICD-10 coding for AKI compared to biochemically-defined AKI using the Kidney Disease Improving Global Outcomes definition and relative risk of 30-day mortality in people with ICD-10 and biochemically-defined AKI before and after AKI e-alert implementation was performed.Results: Sensitivity of ICD-10 coding for identifying biochemically-defined AKI was very poor in both health boards for both all AKI (Tayside 25.7%, Fife 35.8%) and for stage 2 and 3 AKI (Tayside 43.8%, Fife 53.8%). Positive predictive value was poor for both all AKI (Tayside 76.1%, Fife 45.5%) and for stage 2 and 3 AKI (Tayside 45.5%, Fife 36.8%). Measured mortality fell following implementation of AKI e-alerts in the ICD-10 coded population but not in the biochemically-defined AKI population, reflecting an increase in the proportion of stage 1 AKI in ICD-10 coded AKI. There was no evidence that the introduction of AKI e-alerts in Tayside improved ICD-10 coding of AKI.Conclusion: ICD-10 coding should not be used for monitoring of rates and outcomes of AKI for either research or improvement