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Management of Hypertension and Hypercholesterolaemia in Primary Care in the Netherlands*

Posted on: Wednesday, 13 July 2005, 03:00 CDT

Key words: Hypercholesterolaemia - Hypertension - Patient management - Primary care - Screening - Treatment - Undertreatment

ABSTRACT

Objective: Screening, treatment and monitoring guidelines for hypertension and hypercholesterolaemia have been developed to assist physicians in providing evidence-based health care. We conducted a retrospective study to assess the management of patients with these single or combined conditions.

Research design and methods: This was a retrospective cohort study conducted using data from the Integrated Primary Care Information (IPCI) project based in the Netherlands. Management of hypertension and hypercholesterolaemia was assessed from 2000-2003 by measuring the numbers of patients screened for these conditions, treated pharmacologically and monitored for treatment success.

Results: Approximately 11%, 3% and 10% of participants were eligible for screening for hypertension alone, hypercholesterolaemia alone and both conditions, respectively. Blood pressure screening was high in patients eligible for both blood pressure and cholesterol screening (> 86%), whereas cholesterol screening was low (< 56%). Among patients newly identified with hypertension or hypercholesterolaemia who were eligible for pharmacotherapy, 29% and 43% respectively were not treated within one year of diagnosis. Undertreatment was significantly lower in patients with both conditions (24% and 37% for antihypertensive and lipid-lowering treatment, respectively and 28% were not treated for both). Among newly treated patients, in the first year of treatment there was no record of a blood pressure or cholesterol assessment, for 35% and 72%, respectively.

Conclusion: Management was sub-optimal in patients with hypertension or hypercholesterolaemia as well as in those with both of these conditions. The results of this study are likely to be widely applicable, particularly to other European and industrialised countries that have similar free-access health care systems to the Netherlands.

Introduction

Hypertension and hypercholesterolaemia are common, modifiable risk factors for cardiovascular disease (CVD), which is a leading cause of morbidity and mortality in industrialised countries1. The level of cardiovascular (CV) risk associated with concurrent hypertension and hypercholesterolaemia is far greater than the risk associated with either condition in isolation2. Long-term treatment of hypertension may substantially reduce the risk of myocardial infarction and stroke3; long-term use of lipid-lowering medications reduces the risk of coronary heart disease (CHD)4. Despite abundant evidence of the risks associated with hypertension and hypercholesterolaemia, and the proven efficacy of available treatments for these conditions, there is considerable underdiagnosis and undertreatment of these conditions5-13.

The majority of previous studies have not addressed the overall management of hypertension and hypercholesterolaemia, and instead have focused on one aspect, such as screening or treatment. Furthermore, many of these studies have not assessed the concomitant management of patients with both conditions56,8,10-14. Moreover, studies examining the undertreatment of hypercholesterolaemia have often been based on selected secondary prevention populations or on self-reported information11,12,15. Previous studies in the Netherlands did not distinguish between undertreatment due to lack of prescribing or undertreatment due to lack of persistence in taking medications5,6,11.

We conducted a retrospective study using a database containing general practitioner (GP) medical records. Our aims were to assess the extent of screening for, and pharmacological treatment of, hypertension and hypercholesterolaemia, and the extent of blood pressure (BP) and cholesterol monitoring in patients initiating treatment for one or both of these conditions. We then compared these findings with the recommendations of the national guidelines for hypertension and cholesterol management16-18. Furthermore, we assessed the impact of the presence of concomitant hypertension and hypercholesterolaemia, versus either condition alone, on the management of these conditions.

Patients and methods

Database and study population

Patient data were retrieved from the Integrated Primary Care Information (IPCI) project. The IPCI is a GP research database, containing longitudinal computer-based patient records (more than 500000 patients in total) from 150 GPs in the Netherlands19,20. The electronic records contain coded and anonymous data on patient demographics, symptoms (in free text), diagnoses by GPs and specialists (using the International Classification for Primary Care21 and free text], referrals, laboratory findings, clinical assessments, hospitalisations and prescribed medications (including indications and dosage regimens). The IPCI system complies with the European Union guidelines on the use of medical data for research and has been proven valid for pharmacoepidemiological research20. The study was approved by the Scientific and Ethical Advisory Board of the IPCI project.

The study population comprised subjects aged ≥ 16 years, who had been registered for at least 1 year with their GP and whose GP had participated in the IPCI project for at least 1 year. The study period was from January 2000 to September 2003. Patients were followed until their death, transfer from the GP's practice or the end of the study period.

Screening

Patient eligibility for, and the prevalence of, BP and cholesterol screening were assessed as of 1 January 2000 and 1 January 2002. Patient eligibility for screening was determined according to the 1999 Dutch College of General Practitioners (DCGP) clinical guidelines (Table 1)16,17. Patients were considered to have had their BP screened if they had a previous record of at least one BP measurement, a prescription for an antihypertensive medication or a diagnosis of hypertension. Recommendations of current DCGP cholesterol guidelines include the screening of individuals with familial hypercholesterolaemia17. However, since this condition could not be assessed reliably for all subjects, it was not included in the analyses. Patients were considered to have had their cholesterol level screened if they had a previous record of at least one total cholesterol or total cholesterol/high-density lipoprotein (HDL) cholesterol ratio measurement, a prescription for statin treatment or a diagnosis of hypercholesterolaemia.

Identification of hypertension and hypercholesterolaemia

Hypertension was defined as: a recorded diagnosis by the patient's GP or specialist; ≥ 2 BP measurements > 160/95 mmHg (in accordance with the 1999 DCGP guidelines); or antihypertensive pharmacotherapy (thiazide, β-blocker, calcium channel blocker, angiotensin-converting enzyme inhibitor or angiotensin II antagonist).

Hypercholesterolaemia was defined as: a recorded diagnosis by the patient's GP or specialist; total cholesterol > 5mmol/L (193mg/dL); or treatment with a statin. The prevalence of hypertension alone, hypercholesterolaemia alone and concurrent hypertension and hypercholesterolaemia, was determined on 1 January of 2000, 2001 and 2002.

Table 1. Summary of the DCGP guidelines for managing hypertension and hypercholesterolaemia

Newly identified patients had no recorded evidence of hypertension and hypercholesterolaemia in their history. The earliest date that one of the hypertension criteria was identified was considered as the index date for the onset of hypertension. Newly identified patients with hypercholesterolaemia were determined in a similar manner. Among these cohorts, subgroups were identified as: patients who were known to have hypertension at the first diagnosis of hypercholesterolaemia, patients who had hypercholesterolaemia at the first diagnosis of hypertension and patients who were identified with hypercholesterolaemia and hypertension within a period of 30 days.

Pharmacological treatment

Only individuals with at least 1 year of follow-up data after the onset of hypertension or hypercholesterolaemia were included in the evaluation of treatment. At the index date, we assessed whether the patient was eligible for treatment, and if the patient was prescribed pharmacological treatment within 1 year after the index date. The 1999 DCGP guidelines16,17, which use the Framingham risk function to estimate CV risk22, were used to determine treatment eligibility (Table 1). The presence of concomitant CVD was determined from coded diagnoses. Risk factors for CVD were obtained from patients' medical records and CV risk profiles. In the absence of total cholesterol/HDL cholesterol ratios, which are necessary to calculate the Framingham risk score, gender and age-specific reference values were imputed23. Also, since the thresholds for treatment eligibility in the Dutch guidelines omit left ventricular hypertrophy, this condition was not considered in this calculation.

Table 2. Blood pressure and cholesterol measurements: eligibility for screening and screening rates as of 1 January 2000 and 1 January 2002

The number of patients eligible for treatment at the index date, the proportion who received treatment within 1 year and the proportion monitored for BP and cholesterol during the first year following tr\eatment initiation, were estimated.

Statistical analysis

Descriptive statistical analyses were performed with SPSS version 11 (SPSS Inc., Chicago, IL, USA). Patient characteristics were summarised by mean and standard deviation (SD) for continuous variables and by percentage for categorical variables. Prevalences were summarised by mean and 95% confidence intervals (CI). Chi- square tests were used to assess differences in the treatment and monitoring rates of patients with and without prevalent concomitant conditions.

Results

The source population with 1 year of valid history comprised 250 210 subjects aged ≥ 16 years (mean age 42.6 years, 50.6% female).

Screening

Overall, the proportion of the population who were eligible for BP screening as of 1 January 2000 and 1 January 2002 was slightly above 20% (Table 2). Fewer patients (approximately 13%) were eligible for cholesterol screening. The BP screening rate for patients who were eligible for both cholesterol and BP screening was considerably higher than in those patients eligible for BP screening alone (86.2% vs. 50.8% in 2000). Also, the rate of cholesterol screening was higher in patients eligible for both types of screening compared with those eligible for cholesterol screening alone (50.2% vs. 38.0% in 2000).

Despite little change in the proportion of patients who were eligible for screening from 2000 to 2002, the proportion of patients who were screened increased slightly over this time period (Table 2).

Prevalence

The prevalence of concomitant hypertension and hypercholesterolaemia increased from 6.5% in 2000 to 8.1% in 2002 (Figure 1).

Pharmacological treatment

We identified 8495 new patients with hypertension and 10451 new patients with hypercholesterolaemia. Among these patients, there were 964 in whom hypertension and hypercholesterolaemia were identified within a period of 30 days. Clinical and demographic characteristics at the index date are presented in Table 3. It is noteworthy that 23.6% of newly identified patients with hypertension were known to have existing hypercholesterolaemia, and 45.9% of newly identified patients with hypercholesterolaemia were known to have existing hypertension. The estimated 10-year risk of CHD was, on average, 10.5%, 14.7% and 12.9% among patients with newly identified hypertension, hypercholesterolaemia and both conditions newly identified, respectively.

Figure 1. Prevalence of hypertension, hypercholesterolaemia and concomitant hypertension and hypercholesterolaemia. Dotted lines indicate the prevalences based on the 2003 hypertension guidelines. Vertical bars represent 95% confidence intervals. Data labels show mean values

The numbers of patients who were eligible for antihypertensive or lipid-lowering pharmacotherapy based on the 1999 guidelines (Table 1) and the proportions of these patients who received treatment within 1 year of diagnosis are shown in Table 4. Overall, undertreatment was substantial, with 28.7% and 43.1% of treatment- eligible patients not receiving treatment for hypertension and hypercholesterolaemia, respectively (Figure 2A,B). Moreover, 27.9% of treatment-eligible patients who were identified with both hypertension and hypercholesterolaemia within 30 days did not receive treatment for both conditions (Figure 2C). Undertreatment rates for patients with prevalent concomitant hypertension and hypercholesterolaemia were significantly lower than undertreatment rates in persons with a single condition (p < 0.001) (Table 4).

Table 3. Baseline characteristics of patients with newly identified hypertension, newly identified hypercholesterolaemia or both conditions

Table 4. Treatment and monitoring rates in patients with newly identified (A) hypertension, (B) hypercholesterolaemia and (C) concomitant hypertension and hypercholesterolaemia

Figure 2. (A) Antihypertensive treatment and blood pressure monitoring rates in patients with newly identified hypertension. (B) Lipid-lowering treatment and cholesterol monitoring rates in patients with newly identified hypercholesterolaemia, (C) Antihypertensive and lipid-lowering treatment rates, and blood pressure and cholesterol monitoring rates, in patients with newly identified concomitant hypertension and hypercholesterolaemia. *Treatment eligibility is based on the 1999 DCGP guidelines. [dagger]The treatment rate is calculated as the percentage of treatment-eligible patients (with ≥ 1 year of follow-up data from diagnosis) who had a record of treatment within 1 year of diagnosis. [double dagger]The monitoring rate is calculated as the percentage of treated patients (with ≥ 1 year of follow-up data from treatment initiation) who had a record of at least one measurement during the first year of treatment

Monitoring during initial treatment

Overall, 90% of the patients had at least one visit to their GP during the first year of treatment. Approximately 65% of patients treated for hypertension had a BP measurement recorded in their first year of treatment. Only 27.6% of patients treated for hypercholesterolaemia, irrespective of the type of statin used, had a cholesterol level measurement recorded during their first year of treatment (Table 4; Figure 2A,B). Among patients taking simvastatin (the only drug for which cholesterol monitoring is recommended [Table 1]), 25.4% had one or more recorded cholesterol measurements for this time period. Among patients newly identified with both hypertension and hypercholesterolaemia and who were treated for both conditions, only 16.7% had both their BP and cholesterol recorded (Figure 2C). Blood pressure and cholesterol monitoring rates did not differ significantly between patients with one condition only versus patients with both conditions (Table 4).

Discussion

This study demonstrates that the management of hypertension and hypercholesterolaemia is far from optimal across the entire management process (screening, treatment and treatment monitoring) in primary care in the Netherlands. The prevalence of these conditions, as well as the prevalence of concomitant hypertension and hypercholesterolaemia, is substantial and increased between 2000 and 2002. Furthermore, we observed that these two CV risk factors commonly coexisted. The reasons for this increase in the prevalence of hypertension and hypercholesterolaemia are uncertain, but could be related to increased screening for these conditions and ageing of the population.

Many patients who were eligible for BP and cholesterol screening were not screened. For example, by 2002 almost 30% of those eligible did not have their BP screened, and over 45% of those eligible failed to have their cholesterol levels screened. These observations are surprising considering the extent of information regarding CV risk factors and events that was available in the patients' medical records. However, the small increase in screening from 2000 to 2002 and the increased levels of screening of patients with concomitant hypertension and hypercholesterolaemia (compared with those with just one of these conditions) indicates one area of improvement. Nevertheless, the reasons for this poor performance should be identified and addressed.

Among treatment-eligible patients with newly identified hypertension or hypercholesterolaemia, many did not receive pharmacotherapy for their condition within 1 year of their initial diagnosis (hypertension 29%; hypercholesterolaemia 43%). Monitoring rates among those initiating antihypertensive or lipid-lowering pharmacotherapy were also low (65% and 28%, respectively). The presence of concomitant hypertension or hypercholesterolaemia in these patients resulted in a small improvement in the rate of treatment but had no significant effect on monitoring rates. Among patients newly identified with both hypertension and hypercholesterolaemia who were eligible for treatment, 28% did not receive pharmacotherapy for both conditions. In those initiating treatment for both conditions, only 17% had both their BP and cholesterol measured during the first year of treatment.

Since GPs participating in IPCI are not allowed to maintain additional paper records, the low treatment and monitoring rates that we have observed here are likely to represent an accurate view of the state of management of hypertension and hypercholesterolaemia in the Netherlands.

Our study used the 160/95 mmHg cut-off points of the 1999 DCGP guidelines16 to define hypertension. In the 2003 DCGP hypertension guidelines18, the cut-off point was lowered to 140/90mmHg (Table 1), in accordance with World Health Organization/International Society of Hypertension (WHO/ISH) recommendations24. Therefore, while our assessment of patient management was based on the guidelines that were in place at the time of the study, the actual prevalence of hypertension and concomitant hypertension and hypercholesterolaemia using the current definition (140/90 mmHg)18 was higher in this population (Figure 1). This suggests that there were many patients who potentially could have benefited from pharmacotherapy but who were not recognised as being in need of treatment.

Despite a generally high acceptance rate of the DCGP guidelines among GPs25, low adherence to these guidelines has previously been recognised. Grol et al. found that many of the DCGP recommendations were followed in only 61% of clinical decisions26. Aside from the issue of cost-effectiveness, which forms part of the DCGP cholesterol guidelines, there are a number of barriers that may prevent physicians from adhering to guidelines. These barriers may relate to a general lack of familiarity, awareness or agreement with the guidelines, or a lack of outcome expectancy, self-efficacy or motivation27-29. We expect that our results are influenced by all of these factors, but that certain aspects are more pertinent. For example, hypertension guidelines generally are easier to implement, because of the less invasive \nature of the procedures involved, which may improve adherence. Efforts to facilitate the implementation of guideline recommendations, particularly those for hypercholesterolaemia, are required urgently.

Previous studies conducted in a variety of locations and settings have assessed the extent of undertreatment of hypertension, hypercholesterolaemia or both conditions5-14,30-41, and our results point to the same conclusion: undertreatment is extensive, even in patients who have both conditions and are therefore at increased risk of developing CVD. For example, similarly high rates of undertreatment of hypertension (30% for females and 47% for males) have been observed in a Dutch population-based survey conducted between 1987 and 1995 among individuals aged 20-59 years of age5. In our study, 31% of treatment-eligible patients over the same age range were undertreated. This level of undertreatment for hypertension at the 160/95 mmHg threshold is greater than that observed in the US in a survey completed in 1994 (22%), but less than that seen in surveys conducted in Canada (1986-92; 38%), England (1998; 48%), Italy (1998; 46%), Spain (1990; 54%), Sweden (1999; 51%) and Germany (1997-99; 59%)13.

Recent studies conducted in the United Kingdom (UK) have indicated that secondary prevention patients who are at high risk of further CVD events often do not have their cholesterol levels recorded (17% in a small study [n = 300] and 51.7% for a much larger study [n = 89422])12,38. Among patients who had their cholesterol levels recorded, only half were receiving statin therapy12,38. Furthermore, evidence from a range of studies conducted in both primary and secondary prevention populations suggests that patients receiving statin therapy are rarely titrated to the doses required to attain lipid treatment goals7,12,35,38.

The treatment rates for hypercholesterolaemia in the present study are much higher than the results of the MORGEN (Monitoring Project on Risk Factors for Chronic Diseases) study, a 1987-1997 Dutch population-based, cross-sectional study of individuals aged 20- 59 years11. In the MORGEN study, 32% of individuals who were eligible for treatment (accounting for 5.5% of the total population with suboptimal cholesterol levels) were aware of their high cholesterol levels, and only 16.3% of these treatment-eligible individuals were treated. Our higher treatment rates (60.9% when restricted to the same age range as the MORGEN study) might point to an improvement in cholesterol management with time. Mantel- Teeuwisse15 observed a comparable increase in treatment rates with time, from 10% (1987-1992) to 45.9% (1998-2002). This increase in treatment rates for hypercholesterolaemia has been reported in studies across Europe and Australia7,35,36,38,39. A slight increase in the use of antihypertensive medications was also reported between 1995-6 and 1999-2000 across 15 European countries8. However, unlike the results for hypercholesterolaemia, this increased utilization of antihypertensives was not associated with a decrease in the prevalence of hypertension8.

Blood pressure monitoring is recommended by the DCGP guidelines in patients starting antihypertensive therapy16,18. However, in this study, the rate of BP monitoring (65%) was lower than the 81% rate found in a similar observational setting in the United States42.

The DCGP guidelines also advise that cholesterol should be tested 3 months after initiating treatment with simvastatin17. For statins other than simvastatin, cholesterol monitoring is not an explicit recommendation of the DCGP guidelines17. However, the rate of cholesterol monitoring in patients on simvastatin treatment was very low and was similar to the rate of monitoring among patients treated with other types of statins. Most current international guidelines recommend the monitoring of hepatotoxicity in patients administered statin therapy, but not of cholesterol levels. This is inconsistent with the approach advocated regarding the monitoring of BP during antihypertensive treatment. As acknowledged in the DCGP cholesterol guidelines, persistence with therapeutic regimens is essential for successful treatment. Monitoring of laboratory levels is an effective way of ensuring patient adherence to treatment, and it is likely that the lack of follow-up cholesterol measurements could have a negative impact on persistence with lipid-lowering treatment and the attainment of therapeutic goals. The low recorded monitoring rates observed in patients with both hypertension and hypercholesterolaemia suggest that there may be many missed opportunities to assess the status of these conditions and to provide appropriate follow-up care.

Limitations and validity

Our study benefits from the fact that it used an observational database, which reflects the GP's daily actions without any intervention by researchers. However, our choice of working from the perspective of the GP also confers some limitations. For example, GPs do not screen or record all CV risk factors in all patients. Therefore, the number of patients eligible for screening and the number of patients with hypertension and/or hypercholesterolaemia will probably have been underestimated. Furthermore, the absence of data on patient smoking habits, the imputation of reference values on the total cholesterol/HDL cholesterol ratio and assumptions regarding the presence of familial hypercholesterolaemia will have resulted in an underestimation of the number of patients eligible for treatment. Because of this, and the fact that there may be patients with elevated cholesterol and/or BP levels whose condition has not been recognised by their GP or who have not visited their GP, the rate of undertreatment may be considerably higher.

The results of this study should be widely applicable, particularly to other European and industrialised countries that have free-access health care systems.

Conclusion

Our study demonstrates the systematic underperformance that is present in the overall management of hypertension and hypercholesterolaemia in the Netherlands. Considering the high level of CV risk that is commonly observed in patients with both hypertension and hypercholesterolaemia, the latest DCGP guidelines provide a significant opportunity to improve the management of patients with these conditions. Our approach has been to examine the management process using the information available to GPs, which has enabled us to highlight the disparity between guideline recommendations and actual practice. It is clear that a much greater effort is needed in finding ways to help physicians provide optimal screening, pharmacotherapy and monitoring of patients with hypertension, hypercholesterolaemia and, in particular, both of these conditions.

Acknowledgements

This study was supported by a grant from Pfizer Inc.

* Data described in this paper were presented at the 19th Annual Scientific Meeting and Exposition of the American Society of Hypertension, New York, May 18-22, 2004

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CrossRef links are available in the online published version of this paper: http://www.cmrojournal.com

Paper CMRO-2982_3, Accepted for publication: 15 April 2005

Published Online: 05 May 2005

doi:10.1185/030079905X46368

Jacobus T. van Wyk(a), Gino Picelli(b), Jeanne P. Dieleman(a), Essy Mozaffari(c), Piotr Kramarz(d), Marc A. M. van Wijk(a), Johan van der Lei(a) and Miriam C. J. M. Sturkenboom(a,e)

a Department of Medical Informatics, Erasmus MC University Medical Centre, Rotterdam, The Netherlands

b International Pharmacoepidemiology and Pharmacoeconomics Research Centre, Desio, Italy

c Worldwide Outcomes Research, Pfizer Inc, New York, NY, USA

d Outcomes Research Europe, Pfizer Ltd, Walton Oaks, UK

e Department of Epidemiology and Biostatistics, Erasmus MC University Medical Centre, Rotterdam, The Netherlands

Address for correspondence: Dr M.C.J.M. Sturkenboom, Erasmus University Medical Center, Department of Medical Informatics, PO BOX 1738, 3000 DR Rotterdam, The Netherlands. Tel.: +31-10-4088123; Fax: +31-10-4089447; email: m.sturkenboom@erasmusmc.nl

Copyright Librapharm Jun 2005

Source: Current Medical Research and Opinion

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