Presentation (CTI)

OBJECTIVES: Little is known about the accuracy of International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) codes on detailed conditions of asthma, such as severity level and exacerbation episodes. We aimed to evaluate the validity and accuracy of asthma-related ICD-10-CM codes against clinical indications.
METHODS: This retrospective observational study used Premier Healthcare Database (PHD)-linked administrative claims (10/01/2021-09/30/2022) for US patients aged ≥ 18 years with asthma, a short-acting beta₂-agonist (SABA) fill, and a history of asthma exacerbation. True asthma severity levels were categorized as mild intermittent, mild persistent, moderate persistent, and severe persistent based on the presence and type of asthma maintenance medication fills during 12-month baseline period. True asthma exacerbation episode was defined using asthma-related visit plus systemic corticosteroid fills during 12-month follow-up period.
RESULTS: Among 12,693 eligible patients, 40.2% (n=5,101) had mild intermittent asthma, 5.4% (n=682) had mild persistent asthma, 17.4% (n=2,209) had moderate persistent asthma, and 37.0% (n=4,700) had severe persistent asthma. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were 27.5%, 67.5%, 36.3%, and 58.1% for mild intermittent asthma; 11.9%, 85.9%, 4.6%, and 94.5% for mild persistent asthma; 35.7%, 69.3%, 19.7%, and 83.6% for moderate persistent asthma; and were 22.1%, 95.5%, 74.2%, and 67.6% for severe persistent asthma. Among asthma patients who were not assigned the correct diagnosis codes, 60-75% were coded as unspecified asthma across the four asthma severity groups. During follow-up period, 30.6% (n=3,889) patients had an asthma exacerbation. The sensitivity of ICD-10-CM codes for asthma exacerbation was 59.0%, specificity 79.8%, PPV 56.4%, and NPV 81.5%.
CONCLUSIONS: Asthma severity levels, especially mild persistent asthma, are not accurately captured using diagnosis codes. Asthma exacerbation episodes were captured better with ICD-10-CM codes. Codes for unspecified asthma were widely used. Caution is warranted for using diagnosis codes to assess prevalence of different asthma severity levels.