Validation of ICD-10 Codes for Identifying Acute Chest Syndrome in Patients with Sickle Cell Disease

Introduction: Claims data with International Statistical Classification of Diseases, Tenth Revision (ICD-10) codes are routinely used in clinical research. Acute chest syndrome (ACS) is the 2^nd most common cause of hospitalization in patients with sickle cell disease (SCD), yet our understanding of risk factors, severity classification, and the impact of supportive therapies on clinical outcomes is limited. Real-world data utilizing electronic health records offer an opportunity to study current management practices. However, ICD-10 codes to identify Acute Chest Syndrome (ACS) in patients with sickle cell disease (SCD) have yet to be validated. Our objective was to understand if ICD-10 coding was reliable in real-world datasets to correctly identify patients with SCD diagnosed with ACS.

Methods: This study identified consecutive patients 18 years of age and older listed in the patient registry of Boston Medical Center who were hospitalized between 1/1/2021 and 12/31/2022. Primary and secondary ICD-10 diagnosis codes for ACS (D57.01, D57.211, D57.411, D57.431, D57.451, D57.811). Manual chart abstraction identified patients with ACS according to the diagnostic criteria of a new infiltrate involving at least one lung segment on chest imaging, not due to atelectasis, associated with chest pain, dyspnea, fever, and signs of respiratory compromise. We calculated the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for any (1) ACS diagnostic code and (2) Primary diagnosis of ACS. For patients, with multiple hospitalizations, each one was included in the analyses. In a sensitivity analysis, we studied only patients with hemoglobin (Hb)SS disease.

Results: 125 of 404 patients in the registry had at least one hospitalization during the study time period (542 hospitalizations). The median age was 30 years (20-67), 51% were female, and 72% had HbSS disease. Fifty-four (9%) of patients required the intensive care or step-down unit during their hospitalization. 119 (22%) hospitalizations met diagnostic criteria for ACS and 88 (16.2%) had a discharge ICD-10 diagnostic code for ACS. The presence of any ACS ICD-10 code had a sensitivity of 65.8% (95% CI 57.3-74.3%), specificity of 97.6% (95% CI 96.4-99.2%), PPV of 89.8% (95% CI 84.3-96.1% and NPV of 90.7% (95% CI 88.3-93.6%). The presence of a primary diagnosis code for ACS had a sensitivity of 55% (95% 46.2-63.9%), a specificity of 98.3% (95% CI 93.6-97.2%), a PPV of 90.4% (95% 83.6-97.2%), and a NPV of 86.5% (95% CI 85.6-91.4%). In those with HbSS disease (192 hospitalizations), the results were similar: the presence of any acute chest syndrome ICD-10 code sensitivity 68.7% (95% CI 59.5-78%), specificity 98.4% (95% CI 97-99.8%), PPV 92.9% (95% CI 87-98.9%) and NPV 91.2% (95% CI 88.1-94.2%).

Conclusions: In this single-center study, ICD-10 diagnostic codes for ACS had moderate sensitivity and high specificity, with high positive and negative predictive values. These findings suggest that ICD-10 codes for ACS in electronic health record-based datasets could be utilized to better understand ACS epidemiology and clinical outcome.