Chronic lung allograft dysfunction (CLAD)-bronchiolitis obliterans syndrome (BOS) is a progressive, irreversible pulmonary disease where the immune system attacks airways in transplanted lungs leading to graft failure and death. CLAD-BOS severity is measured using CLAD stages 0-4 based on decreased forced expiratory volume in one second (FEV-1). Previous claims analyses were limited by the inability to identify CLAD stages due to the absence of an ICD-10 code and linkage to clinical measures. This analysis estimated costs by CLAD stage using claims data arising from a presumptive BOS diagnosis.