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Objectives: To determine the frequency of lipid testing and to identify the factors predictive of lipid-testing frequency over a 1-year period in patients beginning statin treatment.
Methods: Retrospective cohort study performed using the UK General Practice Research Database. The patients were selected if they were ≥35 years of age, received first-ever statin between January 2000 and December 2004, had at least one total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), or triglyceride (TG) test conducted in the 1-year period before statin initiation, and had at least 1 year of follow-up data. The main outcome measures were TC, HDL-C, and TG testing frequencies in the year after initiating statins. Poisson regression was used to assess baseline factors associated with testing frequency for each lipid.
Results: In the year after initiating statins, the patients received a mean (±SD) of 1.3 (±1.0) TC tests, 0.9 (±1.0) HDL-C tests, and 0.9 (±1.0) TG tests; however, 22.7%, 44.3%, and 39.1% of the patients did not receive any TC, HDL-C, and TG tests, respectively. In multivariate analyses, a high coronary heart disease (CHD) risk (odds ratio [OR] 1.04; 95% confidence interval [CI] 1.01–1.07) and elevated baseline TC (≥6.2 vs. <5.0 mmol/L; OR 1.12; 95% CI 1.06–1.18) were significantly associated with greater TC testing frequency.
Conclusions: High risk of CHD and elevated baseline TC were associated with greater rates of TC testing in the year after statin initiation. Lack of TC testing in approximately one in five patients, and infrequent HDL-C and TG testing may be barriers to comprehensive lipid management.
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Monitoring lipid levels in the year after beginning lipid-modifying drug therapy is important to determine whether treatment goals are being met. The UK guidelines for the prevention of cardiovascular disease set minimum benchmark targets for low-density lipoprotein cholesterol (LDL-C), which is the primary target of statins (the usual initial cholesterol-lowering drug), and for total cholesterol (TC) [1–3]. Treatment recommendations, however, are based on the 10-year risk of coronary heart disease (CHD), which is calculated from the ratio of TC and high-density lipoprotein cholesterol (HDL-C) [1,3]. These guidelines also recognize that elevated triglyceride (TG) levels increase the risk of CHD. Consequently, decisions on whether to modify treatment in the year after initiation of drug therapy should be informed by measurements of TC, HDL-C, and TG. There is, however, relatively little information about the type and frequency of lipid testing after the initiation of lipid drug treatment in the United Kingdom. The objectives of this study were to examine the frequency of lipid testing and to identify variables predictive of the frequency of lipid testing in the year after patients began their first-ever statin treatment in the United Kingdom.
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The study population consisted of 57,296 patients, with a mean age of 65.4 years and a slight preponderance (52.3%) of men (Table 1). The patients received a mean of 1.3 TC tests, and 0.9 HDL-C and TG tests in the year after beginning statin treatment (Table 2). Nevertheless, 22.7% of the patients did not receive a TC test in the follow-up period, and 44.3% and 39.1%, respectively, of the patients did not receive an HDL-C or TG test (Fig. 2).
Table 1. Sociodemographic and clinical characteristics
|Characteristic||Percent patients (N = 57,296)|
|Age category|| |
| <55 years||18.3|
| 55–64 years||28.1|
| 65–74 years||33.6|
| 75+ years||20.0|
| East England||8.9|
| South England||41.7|
| North England||24.9|
|Smoking status*|| |
| Current smoker||19.0|
| ≥24 to <26||15.7|
| ≥26 to <28||16.6|
| ≥28 to <30||13.6|
|Concomitant conditions|| |
| Peripheral arterial disease||5.0|
| High-risk CHD||61.2|
|Number of patients with at least one test at baseline|| |
| TC or HDL-C or TG||57,296|
|Lipid parameters (mmol/L)|| |
| TC||6.4 ± 1.2|
| LDL-C||4.1 ± 1.0|
| HDL-C||1.4 ± 0.4|
| TG||2.2 ± 1.5|
Table 2. Number of lipid tests conducted in the year after statin initiation
|Test||Mean ± SD||Median|
|TC||1.3 ± 1.0||1.0|
|HDL-C||0.9 ± 1.0||1.0|
|TG||0.9 ± 1.0||1.0|
Figure 2. Frequency of lipid testing in the year after statin initiation. HDL-C, high-density lipoprotein cholesterol; TC, total cholesterol; TG, triglyceride.
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In multivariate analyses, a high risk of CHD and elevated baseline TC were predictive of TC testing, and elevated baseline TG (≥2.2 to <5.6 mmol/L) was predictive of TG testing (Table 3). Age (≥75 years), region (East England vs. Wales), hypertension, and smoking status were significantly associated with 3% to 10% lower frequencies of TC, HDL-C, and TG testing, and male sex was associated with 3% lower frequencies of HDL-C and TG testing (Table 3).
Table 3. Significant predictors of TC, HDL-C, and TG testing frequencies
|Variable*||TC Risk ratio (95% CI)||HDL-C Risk ratio (95% CI)||TG Risk ratio (95% CI)|
|Baseline TC ≥6.2 mmol/L||1.12 (1.06–1.18)||—||—|
|Baseline TG ≥2.2 to <5.6 mmol/L||—||—||1.04 (1.01–1.07)|
|High-risk CHD||1.04 (1.01–1.07)||NS||NS|
|Male sex||NS||0.97 (0.94–0.99)||0.97 (0.94–0.99)|
|Age ≥75||0.94 (0.90–0.99)||0.94 (0.90–0.99)||0.95 (0.90–0.99)|
|Region (East England)||0.91 (0.85–0.97)||0.90 (0.84–0.97)||0.90 (0.84–0.97)|
|Smoking||0.96 (0.92–0.99)||0.96 (0.93–0.99)||0.96 (0.92–0.99)|
|Hypertension||0.97 (0.94–0.99)||0.97 (0.94–0.99)||0.96 (0.94–0.99)|