Research methods for conducting pharmacoepidemiological studies using medicines claims data
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This study aimed to evaluate the appropriate use of various research methods in pharmacoepidemiological studies using a South African medicines claims database. A literature review was carried out to conceptualise pharmacoepidemiology and the study designs, data sources as well as methods employed in performing pharmacoepidemiological studies. The empirical investigation utilised a quantitative, cross-sectional approach. Medicines claims data covering the period between January 2006 and December 2015 were supplied by a privately-owned Pharmaceutical Benefit Management company (PBM) for analyses in this study. The objectives of the empirical study were to: (i) Determine the time to onset of treatment of hypertension and hyperlipidaemia in patients with type 2 diabetes mellitus using survival analysis. (ii) Compare different adherence measures, by determining adherence to montelukast among asthma patients, using data from a medicines claims database in South Africa. Survival analysis and methods for the determination of adherence were the methods assessed in this study. Manuscript 1 presented the results of a survival analysis conducted to determine the time to onset of treatment of hyperlipidaemia and hypertension among diabetes patients using a South African medicines claims database. Patients with ICD-10 codes I10, I11, I12, I13, I15, O10 and O11 for hypertension and E78.5 for hyperlipidaemia, who were receiving medications for these conditions according to the National Pharmaceutical Product Index (NAPPI) codes provided by the Monthly Index of Medical Specialities (MIMS), were selected among patients with ICD-10 code E11 for diabetes in conjunction with the NAPPI codes for antidiabetic medications for this study. Retrospective data of patients continuously enrolled with a Pharmaceutical Benefit Management company in South Africa from 1st January 2008 to 31st December 2016 (N = 494) were analysed and the Kaplan-Meier approach was used to compare the survival experience of subjects who developed hypertension and hyperlipidaemia. The mean age of the population was 53.5 ± 11.4 years, with 34.8% (N = 494) being females. Prevalence of hyperlipidaemia and hypertension among diabetic patients were 35.0% and 45.6%, respectively. The mean time to onset of treatment of hyperlipidaemia was 2684.4 ± 42.2 days compared to 2434.2 ±47.6 days for hypertension. There was no statistically significant difference in age and sex among subjects who developed either of these conditions during the study. This study showed that survival analysis can successfully be conducted using secondary data, provided data fields are accurately documented. Manuscript 2 reported the findings of the investigation into the methods for the determination of adherence. Six different measures of adherence were compared to the medication possession ratio (MPR), as the reference adherence measure, by analysing claims made for montelukast. Data of patients continuously enrolled with a South African PBM from 1st January 2006 to 31st December 2015 were obtained and analysed to determine the adherence to montelukast. Patients with ICD-10 code J45 for asthma who made at least two consecutive claims for montelukast based on the NAPPI code 10.4.2 were selected and included in this study. Of the total of 9 141 patients with a median age of 13.3 (5.2 – 49.2) years, 52.8% (n = 4 825) were females. These women were significantly older than their male counterparts (p < 0.0001; Cohen’s d = 0.5). Compared to the MPR, continuous multiple interval measures of oversupply (CMOS) and compliance ratio (CR) were found to be equivalent, each producing an adherence value of 86.0%. Higher adherence values of 96.9%, 117.2% and 129.0% were produced by the modified medication possession ratio (MPRm), refill compliance rate (RCR) and mean continuous single interval measure of medication acquisition (CSA), respectively, whereas the proportion of days covered (PDC) capped at 1 yielded a lower adherence value of 76.0%. This study showed that compared to the measures that used the difference between claims dates as denominator, those that had the entire investigation period as the denominator produced consistent results. From the study, it can be concluded that medicines claims data are vital in in pharmacoepidemiological studies since they provide large and readily available data over a wide period for research. Research methods, such as measures for determining adherence and survival analysis can be effectively conducted using medicines claims data when all relevant data fields are accurately recorded. In carrying out research using medicines claims data, availability of specific parent and medication information determines the methods to be used and the extent of data analysis and interpretation.
- Health Sciences