Burden of rheumatoid arthritis in the private health sector : medicine cost and comorbidities

Abstract

The purpose of the study was to determine the prevalence of rheumatoid arthritis (RA) and associated comorbidities, as well as to investigate antirheumatic prescribing patterns, direct medicine treatment cost and the impact of comorbidities on the total annual direct medicine cost per patient diagnosed with RA in the private healthcare sector of South Africa. The study consisted of two phases: a literature review and an empirical investigation. The objective of the literature review was to provide an overview of RA, including the burden of the disease (i.e. its prevalence, comorbidities and economic impact). The empirical investigation (a drug utilisation review (DUR) study) followed a quantitative, non-experimental (descriptive), cross-sectional design. Retrospective medicine claims data provided by a South African Pharmaceutical Benefit Management (PBM) company for the period 1 January 2014 to 31 December 2014 were analysed. Data for a total of 4 352 patients with an International Statistical Classification of Diseases and Related Health Problems 10th Revision (ICD-10) diagnosis code for RA (e.g. M05, M06 and M08) in conjunction with a claim for medicine paid from a patient's prescribed minimum benefits (PMBs) was analysed. Patients with RA represented 0.5% of the total number of beneficiaries registered on the database during 2014 (N = 838 618). A total of 3 016 (69.3%) patients had RA and at least one other chronic disease list (CDL) condition. The gender ratio of female to male was 3:1 in the study population as a whole and also in both respective disease groups (i.e. patients with RA only and patients with RA and other coexisting CDL conditions). The study population had a mean age of 60.32 ± 14.29 years (95% CI 59.90-60.75); however, patients with RA and other CDL conditions (mean age 63.59 ± 12.26; 95% CI 63.15-64.02) were meaningfully older than those patients with RA only (mean age 52.96 ± 15.76; 95% CI 52.11-53.80). Hypertension was the most prevalent CDL condition, recorded in 47.5% of RA patients. Other CDL conditions that coexisted with RA the most often were hyperlipidaemia (25.9%), hypothyroidism (19.7%), type 2 diabetes mellitus (11.4%), asthma (7.8%), cardiac failure (3.8%), glaucoma (2.5%), dysrhythmias (2.2%), epilepsy (2.1%) and bipolar mood disorder (1.9%). The odds of having cardiovascular disease (CVD) risk factors (i.e. a combination of hyperlipidaemia, hypertension and type 2 diabetes mellitus) co-occur with hypothyroidism were 2.5 times lower among men than among women. The total annual direct medicine treatment cost of RA summed to R59 264 203.68 for the study population in 2014. The mean (median) cost per medicine item for patients with RA only was R746.36 ± 3 846.09 (R127.21) whereas that for patients with RA and coexisting CDL conditions was R623.27 ± 3 494.73 (R130.33); as such, there was no practical significant difference in the mean cost per medicine item for patients with RA only and for those with RA and coexisting CDL conditions (Cohen's d ? 0.1). The drugs representing the 90% drug utilisation (DU90%) segment for phase one treatment were celecoxib (26.6%), meloxicam (24.4%), prednisone (20.5%), diclofenac (7.7%), etoricoxib (7.3%), piroxicam (2.9%) and diclofenac/misoprostol (2.2%), these drugs accounting for 92.8% of the total annual medicine cost. The DU90% for phase two treatment consisted of methotrexate (26.5%), prednisone (14.7%), sulphasalazine (10.2%), chloroquine (9.8%), meloxicam (8.9%), celecoxib (7.2%), diclofenac (3.8%), leflunomide (3.2%), etoricoxib (3.0%), naproxen/esomeprazole (1.3%), betamethasone (1.2%) and methylprednisolone (1.2%), these drugs accounting for only 34.7% of the total annual medicine cost. Rheumatoid arthritis patients with coexisting hypertension generated the highest total annual direct medicine treatment cost among patients with RA and other coexisting CDL conditions at R9 124 831.15, accounting for 15.4% of the total cost of RA for 2014. However, analysis showed no practical significant difference in the mean cost per item of patients with RA only (R746.36 ± 3 846.09) and those with RA plus hypertension (R544.38 ± 2 983.08) (Cohen's d ? 0.1). The presence of coexisting CDL conditions showed no practical significant impact on the total direct medicine cost of RA in patients from the study population. In conclusion, this study established base-line estimates of the prevalence of RA and coexisting CDL conditions and of the direct medicine treatment costs, and investigated antirheumatic medicine prescribing patterns of patients with RA in a section of the private healthcare sector of South Africa.