Background/Purpose: Osteoarthritis (OA) is a disease with complex pathogenesis, and it is important to understand a patient’s level of severity in order to plan and stage treatment interventions. Prior studies have documented the health and economic burdens of patients with OA compared to those without OA. The goal of our study was to further stratify OA patients based on pain severity and compare healthcare utilization and cost.

Methods: This was a retrospective study using electronic health records and insurance claims from 2001-2018 at Geisinger, an integrated health system in Pennsylvania serving over 500,000 patients per year. Patients age 18 or older were included if they had ≥1 month of insurance coverage and ≥1 numerical pain score (NPS) after receiving a diagnosis code for OA (ICD-9: 715.*, ICD-10 M15-19) on an encounter, problem list, or OA-related procedure (hip/knee replacement, arthroscopy or injection). Pain episodes were defined as periods of time starting with an NPS (mild pain 0-3, moderate 4-6, severe 7-10) and ending when 90 days had elapsed with no new NPS. For each episode, claims were examined for the number of all-cause outpatient visits (OP), emergency department visits (ED) and inpatient days hospitalized (IP), total allowed medical cost, and total allowed pharmacy cost; these were converted to per-member-per-year (PMPY) rates or means. These statistics were compared among mild, moderate and severe pain episodes to look for differences, using generalized linear regression models adjusting for age and sex, with p< 0.05 considered statistically significant. Costs were normalized to 2010 US$ based on the Consumer Price Index. Claims containing a diagnosis, procedure, or national drug code related to OA were classified as OA-related and re-analyzed as a subset to examine OA-related utilization and cost.

Results: We identified 92,576 eligible patients with 306,200 pain episodes (43% mild, 32% moderate, 25% severe). For all types of OA-related utilization, moderate and severe pain episodes were associated with significantly higher rates relative to mild pain episodes (OP: 0.84 vs. 1.39 vs. 1.70 visits PMPY for mild, moderate and severe, respectively; ED: 0.13 vs. 0.21 vs. 0.41; IP: 0.10 vs. 0.22 vs. 0.26). All-cause OP and ED utilization also significantly increased with increased pain severity, but IP days did not (OP: 11.09 vs. 11.98 vs. 13.71; ED: 1.05 vs. 1.12 vs. 1.89; IP: 2.77 vs. 2.57 vs. 3.39). Similarly, we observed significant increases in OA-related costs for every category during moderate and severe pain episodes relative to mild pain (pharmacy: $669 vs. $943 vs. $1,207; medical: $1,345 vs. $2,320 vs. $2,429). Increasing pain severity was positively associated with all-cause pharmacy costs, but not all-cause medical costs (pharmacy: $7,729 vs. $9,143 vs. $10,068; medical: $27,571 vs. $22,802 vs. $20,876).

Conclusion: We observed that pain, an important symptom of OA, was strongly associated with patients’ OA-related utilization and costs, and to a lesser extent, all-cause utilization and costs. With a better understanding of when and how patients become more expensive and challenging, we can develop better approaches for managing disease burden in the future.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/association-of-healthcare-costs-and-utilization-with-increasing-severity-of-pain-in-osteoarthritis-patients-an-18-year-retrospective-study/