Use of the Postacute Sequelae of COVID-19 Diagnosis Code in Routine Clinical Practice in the US

Question  How is the International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) code for postacute sequelae of COVID-19 being used in clinical practice?

Findings  In this cohort study, 56 143 patients had an ICD-10-CM code for post–COVID-19 conditions; among patients with 3 months of preindex continuous enrollment, 1080 (8.6%) were children. Only 698 patients (5.5%) had at least 1 of the 5 codes listed as possible concurrent conditions in the coding guidance.

Meaning  These findings suggest the diagnosis code is being used to identify patients of all ages with continuing illness following the acute phase of disease; however, the clinical presentation of postacute COVID-19 spans a range of conditions.

Importance  A new International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) diagnosis code (U09.9 Post COVID-19 condition, unspecified) was introduced by the Centers for Disease Control and Prevention on October 1, 2021.

Objective  To examine the use of the U09.9 code and describe concurrently diagnosed conditions to understand physician use of this code in clinical practice.

Design, Setting, and Participants  This cohort study of US patients with an ICD-10-CM code for post–COVID-19 condition used deidentified patient-level claims data aggregated by HealthVerity. Children and adolescents (aged 0-17 years) and adults (aged 18-64 and ≥65 years) with a post–COVID-19 condition code were identified between October 1, 2021, and January 31, 2022. To identify a prior COVID-19 diagnosis, 3 months of continuous enrollment (CE) before the post–COVID-19 diagnosis date was required.

Main Outcomes and Measures  Presence of the ICD-10-CM U09.9 code.

Results  There were 56 143 patients (7723 female patients [61.2%]; mean [SD] age, 47.6 [19.2] years) with a post–COVID-19 diagnosis code, with cases increasing in mid-December 2021 following the trajectory of the Omicron case wave by 3 to 4 weeks. The analysis cohort included 12 622 patients after the 3-month preindex CE criteria was applied. Among this cohort, the median (IQR) age was 49 (35-61) years; however, 1080 (8.6%) were pediatric patients. The U09.9 code was used most often in the outpatient setting, although 305 older adults (14.0%) were inpatients. Only 698 patients (5.5%) had at least 1 of the 5 codes listed as possible concurrent conditions in the coding guidance. Only 8879 patients (70.4%) had a documented acute COVID-19 diagnosis code (569 [52.7%] among children), and the median (IQR) time between acute COVID-19 and post–COVID-19 diagnosis codes was 56 (21-200) days. The most common concurrently coded conditions varied by age; children experienced COVID-19–like symptoms (eg, 207 [19.2%] had cough and 115 [10.6%] had breathing abnormalities), while 459 older adults aged 65 years or older (21.1%) experienced respiratory failure and 189 (8.7%) experienced viral pneumonia.

Conclusions and Relevance  This retrospective cohort study found patients with a post–COVID-19 ICD-10-CM diagnosis code following the acute phase of COVID-19 disease among patients of all ages in clinical practice in the US. The use of the U09.9 code encompassed a wide range of conditions. It will be important to monitor how the use of this code changes as the pandemic continues to evolve.