Background Reviews have shown that 49% to 99% of the patients with rheumatoid arthritis (RA) are adherent to their medication, depending on the measurement method. Non-adherence is associated with worse clinical outcome, more work disability and more health care costs. Up till now, the actual impact of non-adherence to DMARDs on hospital related health care costs has not been investigated.
Objectives The aim of this study is 1) to examine the direct hospital-related health care costs for inflammatory arthritis in the first year after diagnosis and 2) to determine whether non-adherence to DMARDs and other variables are predictors of direct hospital related health care costs.
Methods DMARD naïve patients diagnosed with inflammatory arthritis were invited for a one year cohort study. Cost measurement comprised hospital-related costs in the first year: consultations, emergency room visits, hospitalization, medical procedures, imaging modalities, medication costs, and laboratory tests. Cost volumes were registered from patient medical files. Non-adherence was continuously measured using electronic monitored medication containers and was defined as the number of days when the amount of observed openings of the container was lower than the amount of expected days with openings. Spearman rank correlations of potential predictors of hospital related costs were calculated. Possible predictors were non-adherence, age, sex, center, baseline disease activity, diagnosis, education level, symptoms of anxiety and depression as measured with the Hospital Anxiety and Depression Scale (HADS), number of comorbidities, and all subscales from the Beliefs About Medication Questionnaire (BMQ); necessity, concerns, general harm and general overuse.
Results Of the 275 invited patients, 202 were willing to participate. Six patients were either lost to follow up in the clinic or lost to follow up in the study, which left 194 patients. 74.7% had RA, 20.6% had psoriatic arthritis and 4.6% undifferentiated arthritis. 30.9% of the patients were more than 20% non-adherent over the one-year follow up period to at least one DMARD. The mean (median) rheumatology-related costs per year were € 1714.42 (SD € 2489.20) (median € 976.44 IQR € 615.37–€ 1590.22). The mean (median) total costs per year were € 2211.05 (SD € 3033.35) (median € 1189.99 IQR € 674.95–€ 2043.58). Table 1 shows the mean cost volumes and costs per category. Table 2 shows the Spearman rank correlations of eligible predictors of costs. There were interactions between age and comorbidity; anxiety and depression with baseline DAS28; comorbidity and anxiety. Non-adherence, anxiety and depression and baseline DAS28 contribute to rheumatology hospital costs univariately.
Conclusions There is an association between non-adherence and hospital costs, which suggests that applying non-adherence interventions reduces rheumatology costs.
Disclosure of Interest None declared