Background/Purpose: The economic burden of psoriatic arthritis (PsA) and ankylosing spondylitis (AS) in the biologics era is not well understood in the US population.  Using a large US medical and pharmacy claims database, we investigated the characteristics, healthcare utilization, costs and treatments of PsA patients with high medical costs.  

Methods: Claims data from the MarketScan Commercial and Medicare Supplemental Databases were used to stratify PsA and AS patients into 2 groups based on overall costs: ≥90% quantile (top 10% cost group) and <90% quantile (bottom 90% cost group). Patients included were aged: ≥18 years with ≥2 diagnostic claims for PsA (n=10,832) or AS (n=4,288) between October 1, 2011, and September 30, 2012 (first diagnosis is index date) and were continuously enrolled with medical and pharmacy benefits for 12 months before and after the index date. Baseline demographics, individual comorbidities and an elixhauser comorbidity score were captured. Direct costs included hospitalizations, emergency room and office visits, and pharmacy costs. The Wilcoxon rank sum test was conducted on continuous variables and the chi-square test on categorical variables.

Results: The study included 10,832 PsA patients and 4,388 AS patients.   For the PsA top 10%  (N=1,083) and bottom 90% groups (N=9,740), mean all-cause medical costs were about 13 times higher $30,591±$51,862 vs.  $2,277±$4,138 respectively.   Biologics costs were only about 2 times higher $27,254±$18,026 and $12,595±$14,581, respectively. For the AS top 10% (n=428) and bottom 90% groups (n=3,860), mean all-cause medical costs were 20 times higher $42,703±$78,942 vs.  $2,491±$4,561, respectively; mean biologics costs were 2 times higher $18,261±$16,048 vs.  $10,373±$13,552, respectively. In the PsA cohort, the top 10% cost group was older (mean age 54.7±10.8 y vs 51.6±11.9 y; P<0.01), had higher rates of diabetes mellitus (26.5% vs 15.2%, P<0.01), hypertension (43.2% vs 31.4%), hyperlipidemia (29.8% vs 23.8%), and ischemic heart disease (14.4% vs 5.8%) all P<0.01.  The high cost group also had a higher rate of biologics use (83.4% vs 58.7%; P<0.01), compared with the bottom 90% cost group, respectively. The top 10% AS cost group, similarly, was older (mean age 52.1±12.6 y vs 48.7±13.4 y; P<0.01) and had higher Elixhauser comorbidities scores (mean, 2.9±2.3 vs 1.8±1.5; P<0.01) compared to the bottom 90% cost group, respectively.  They also had higher biologics (70.4% vs 50.5%) and oral DMARDS (26.6% vs 21.3%) use all P≤0.01, compared with the bottom 90% cost group, respectively. 

Conclusion: PsA and AS patients with high costs of care were generally older and more affected by comorbidities than their counterparts with lower costs.  Medical costs seem to be the biggest drivers in the high cost subgroup of patients.  In AS patients medical costs were almost 20 times higher in the high cost group.  PsA high cost patients had 13 times higher medical costs.  This study highlights that the majority of patients with AS and PsA have relatively low disease management costs, however there are a subgroup of more costly patients that may require more individual management due to high comorbidity and biologic use.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/identifying-psoriatic-arthritis-and-ankylosing-spondylitis-patients-responsible-for-the-highest-costs-of-care-data-from-a-large-us-cohort/