(413) The most common comorbidities leading to a diagnosis of chronic lung allograft dysfunction (CLAD)-bronchiolitis obliterans syndrome (BOS) subsequent to lung transplant (LTx) using an open administrative claims database in the United States (US)

Background: : Chronic lung allograft dysfunction (CLAD)-bronchiolitis obliterans syndrome (BOS) is a rare disease and severe form of chronic rejection after lung transplantation (LTx) affecting an increasing proportion of LTx recipients after transplant. CLAD-BOS is characterized by airflow restrictions and progressive shortness of breath resulting in increased morbidity and mortality after LTx. Recent updates to the ICD-10-CM for the US now include BOS (J44.81), CLAD (J4A8, J4A9), and restrictive allograft syndrome (RAS, J4A.0), effective 10/1/2023. CLAD-BOS previously had no specific ICD-10-CM codes thereby making claims-based analysis difficult.

Objective: : Our analysis was designed to assess the most frequent comorbidities associated with a CLAD-BOS diagnosis using open administrative claims as the data source.

Methods: : We used a licensed open administrative claims database (Ambit, Inc.) to build a cohort of CLAD-BOS patients after LTx. The cohort was indexed to a claim for LTx (diagnosis and procedure claims) between 11/01/2017 and 10/31/2022. The second index event was a CLAD-BOS diagnosis ≥12 months post-LTx possible in two ways: 1) having a code for BOS, CLAD or RAS; 2) having two CLAD symptom codes and a pulmonary evaluation (i.e., CT, lung biopsy, or bronchoscopy) in a pre-specified sequence. We then assembled time aligned cohorts of LTx patients without CLAD-BOS for all comparisons.

Results: : The open claims database yielded a large LTx population (n=7440) with sufficient CLAD-BOS or RAS patients (n=204) forming the basis for all analyses. We further subdivided the CLAD-BOS or RAS groups into faster (1-2 years, n=116) and slower (>2 years, n=88) development subgroups. The top four comorbidities demonstrating differences were identical in the faster and slower CLAD-BOS or RAS development subgroups, respectively, including bronchitis (2.5x and 1.7x), interstitial lung disease (ILD)/fibrosis (2.2x and 1.6x), gastroesophageal reflux disease (GERD, 1.6x and 1.2x), and infection (1.4x and 1.1x).

Conclusions: : Comorbid conditions most closely associated with CLAD-BOS development after LTx were bronchitis, interstitial lung disease (ILD)/fibrosis, gastroesophageal reflux disease (GERD) and infection in our analysis utilizing open claims data. These data represent an opportunity for intervention when these comorbid conditions are present prior to CLAD-BOS diagnosis.

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