BACKGROUND:In the United States, chronic obstructive pulmonary disease (COPD) diagnosis is often a lengthy process, and consequently results in delays in treatment in early stages. Disease progression and complication may result in increased levels of healthcare service use. To understand the economic burden of COPD prior to diagnosis in the U.S., trends in utilization and costs during the period before initial COPD diagnosis were compared with matched controls. METHODS:A retrospective case-control study was conducted using medical and pharmacy claims data from a large managed care health plan representing a base population of over 30 million covered lives in the U.S. COPD patients with at least 12 months of continuous enrollment and aged 40 years or older were identified (n=28,968) and matched to up to three random controls (n=81,322) by age, gender, region of plans and index date. Multivariate regression models were used to estimate average incremental service use and cost between COPD patients and controls. Moreover, trends in utilization and costs for the COPD patients were examined over 36 months before diagnosis. RESULTS:COPD patients used 1.5-1.6 times more inpatient/emergency department (IP/ED) services and office visits compared to control patients. The average incremental annual costs for IP/ED services, office visits, and medical and pharmacy services were estimated at $550, $238, $1438 and $401, respectively, after adjusting for age, gender, region and comorbid conditions. The 36-month trend analysis showed that COPD patients' healthcare utilization and costs increased gradually over time, often with a marked increase in the month before COPD diagnosis. CONCLUSIONS:COPD patients in the U.S. consumed substantial healthcare services and costs prior to diagnosis. More timely diagnosis and subsequent treatment may avoid costly healthcare utilization and unnecessary mortality and morbidity post-diagnosis.