A drug utilisation review of the concept of metabolic syndrome using a South African medicines claims database

Abstract

The aim of the study was to determine the prevalence, medicine prescribing patterns and direct treatment cost associated with the metabolic syndrome and its components in the private health care sector of South Africa. A two–dimensional research method was employed, consisting of a literature review and an empirical investigation. The objective of the literature review was to provide background to the study by conceptualising the metabolic syndrome and the components forming part thereof. The empirical investigation consisted of a descriptive, quantitative, retrospective drug utilisation review study, utilising medicine claims data sourced from a South African Pharmaceutical Benefit Management (PBM) company for the period January 1, 2005 to December 31, 2008. Data for a total 246 122 patients from 2005, 252 080 from 2006, 208 632 from 2007 and 196 242 from 2008, receiving at least one medicine item from the pharmacological medicine classes of antihypertensives (including diuretics, MIMS® classifications 7.3 and 16.1), hipolipidaemics (MIMS® classification 7.7) and antidiabetics (MIMS® classification 19.1) were analysed. Metabolic syndrome was defined according to the American Heart Association/National Heart, Lung and Blood Institute criteria, as patients with claims for 1 medicine item(s) per year from each of these drug classes. Seventy one per cent (n = 261 036) of patients from 2005 met one risk selection criterion for the metabolic syndrome, compared with 69.9% from 2006 (n = 269 452), 66.6% (n = 226 264) from 2007 and 64.9% (n = 214 109) from 2008 (male:female ratio 1:1.5 for 2005–2008; age peak >45,60 year). A total 60 683 (4.0%, n = 1 509 621) of patients from the 2005 data set met at least two risk criteria for the metabolic syndrome. This number of patients increased to reach 63 835 (4.1%, n = 1 558 090) in 2006, thereafter decreasing to 57 992 (4.9%, n = 1 178 596) in 2007 and 57 220 (5.9%, n = 974 497) in 2008. A total 5.7% (n = 246 122) of patients in 2005 met inclusion criteria for the metabolic syndrome, increasing to 6.5% (n = 252 080) in 2006, 7.8% (n = 208 632) in 2007 and 8.3% (n = 196 242) in 2008 (male to female ratio for 2005 – 2008:1.2:1). In general, prevalence increased from ~0.1% of patients aged >0,15 years to ~0.3% in those >15,30 years, ~6% in patients >30,45 years, ~40% in patients aged >60,75 years and ~20% in patients >75 years. The average prevalent age appeared earlier in males than in females by 2 years. The average pill burden per prescription for patients from the 2005–metabolic syndrome category was 2.6 ± 1.43, compared with 2.6 ± 1.47 in 2006, 2.7 ± 1.52 in 2007 and 2.7 ± 1.53 in 2008, with a maximum of 16 items claimed per patient in 2005, 14 in 2006 and 2007, respectively and 19 in 2008. Antidiabetics, hipolipidaemics and antihypertensives were claimed in a ratio of 1:1:2 across the 4–year study period. A prescribing index of 20 medicine items (active substances) based on prescribing volume was established for metabolic syndrome patients; the 5 most claimed medicine items on this index was metformin, simvastatin, atorvastatin, insulin and gliclazide. A total of 17 716 different treatment regimens was identified for patients from the 2008–metabolic syndrome category, containing from one to 12 different active substances per regimen. Overall 90.7% (n = 17 716) of treatment regimens contained between 3 and 7 different active substances per prescription; a further 3.3% contained 8 active substances each. The combination of indapamide and perindopril with amlodipine, or simvastatin and/or metformin had the highest prevalence among those regimens containing 3 active substances. The total direct medicine treatment cost from the metabolic syndrome category amounted to R71.7 million in 2005, increasing to R94.7 million in 2008. Medical aid schemes contributed 90.0% (n = R71 724 445.88) towards these costs in 2005, decreasing to 86.0% (n = R94 690 393.54) in 2008. The average scheme contribution was R131.14 ± 135.64 (median R103.12) per medicine item in 2005, compared with R126.63 ± 133.65 (median R101.24) in 2006, R128.39 ± 141.69 (median R101.35) in 2007 and R122.45 ± 143.97 (median R94.27) in 2008. Patients paid the excess 10% (2005) to 14% (2008) of costs out–of–pocket for co–payments on medicine items at an average cost of R14.55 ± 34.26 (median R0.00) per item for 2005, compared with R15.80 ± 38.04 (median R0.00) during 2006, R16.61 ± 38.01 (median R0.00) in 2007 and R19.95 ± 40.06 (median R2.28) in 2008. The average annual direct medicine treatment cost for a patient from the metabolic syndrome category summed to R4 809.20 ± 4 057.46 (median R3 850.67) in 2005, compared with R5 053.34 ± 4 033.85 (median R4 041.16) in 2006, R5 503.88 ± 4 348.67 (median R4 357.79) in 2007 and R5 300.03 ± 4 433.93 (median R4 100.06) in 2008. A total 7 050 patients (39.5%, n = 17 866) or approximately every third patient from the metabolic syndrome category had at least one other Chronic Disease List (CDL) condition during 2008. An average chronic disease count of 1.4 ± 0.63 (median 1) (range: 1–5) per patient was calculated. Diseases that co–occurred most were hypothyroidism (22.7%, n = 7 050), coronary artery disease (13.6%, n = 7 050), cardiac failure (10.7%, n = 7 050), asthma (7.3%, n = 7 050) and glaucoma (4.5%, n = 7 050). In conclusion, this study established base–line estimates on the prevalence, medicine prescribing patterns and associated direct medicine treatment cost of patients with metabolic syndrome and/or those at risk for the development thereof in the private health care sector of South Africa, as defined by surrogate measures of criteria from the American Heart Association and National Blood Institute. Recommendations for future extensions and diversifications to the study were made.