Impact of ethnic-specific guidelines for anti-hypertensive prescribing in primary care in England: a longitudinal study

Observational studies have consistently shown that fewer than 40% of hypertensive patients worldwide have controlled blood pressure [1]. Hypertensive patients either without treatment or with inappropriate therapy are an important cause of the current low rates of blood pressure control [1, 2]. Lack of treatment intensification or ‘clinical inertia’ has been recognized as a frequent cause of uncontrolled blood pressure in hypertensive patients managed in primary care [3]. Clinical guidelines are produced, and frequently updated, to guide physicians on choosing optimal antihypertensive therapy as a strategy to reduce clinical inertia [4, 5].

Physician criteria for antihypertensive prescribing may differ from that established in clinical guidelines. Surveys have revealed sub-optimal use of clinical guidelines by physicians for prescribing antihypertensive drug therapy [6‐15]. This may be due to concerns among physicians that the clinical guideline recommendations may not apply to all hypertensive patients in primary care [12, 16‐19]. Variations in hypertension treatment across primary care practices have additionally documented the gap between guidelines and physician antihypertensive drug preferences [20].

In England, the National Institute for Health and Care Excellence (NICE) is the authoritative body for the production of clinical guidelines [4]. The NICE guidelines are also used as reference to measure the performance of primary care services [21]. Until the last NICE hypertension guidelines published in 2011 [4], the management of hypertension in England primary care was based on the recommendations established in the 2004 NICE hypertension guidelines [22]. In 2006, an NICE guidance update was introduced advising that those patients of black ethnicity and those aged 55 years or over should be treated differently to the rest of the population in terms of the first line antihypertensive monotherapy. Between January and April NICE extensively promoted that guideline and it was finally adopted in June 2006.

In England increases in antihypertensive prescribing for hypertensive patients have been documented; however the use of antihypertensive treatments established in the guidelines has been less explored. Because the antihypertensive treatment established in the 2006 updated NICE guidelines was based on the 2004 BHS (British Hypertension Society) guidelines and studies already published, these recommendations may have already been used before the introduction of that guideline. To assess the use of the NICE hypertension guideline recommendations by general practitioners, we examined variations in drug antihypertensive prescribing among hypertensive patients managed in England primary care over a 10 years follow-up period. The recommended treatment established in the 2006 updated NICE guidelines was used as the reference guideline. The impact of the introduction of this guideline on antihypertensive prescribing was also assessed.

The data used for this study was derived from 28 general practices located in Wandsworth, Southwest London. We identified all patients with essential hypertension that had a clinical record in 2007 using diagnostic READ codes in computerized general practice records. READ codes are the clinical classification system used in primary care in the United Kingdom (UK). For each patient, we retrospectively extracted data on annual antihypertensive prescribing and clinical variables registered between 2000 and 2007. The study was part of a research programme that received ethics approval from the Wandsworth Local Research Ethics Committee.

We only included patients without missing or unknown record of race/ethnicity and aged 18 years or over during the study period. Patients who were registered for the first time in the respective year were counted as newly hypertensive patients. Data on whether the patient was prescribed the following antihypertensive drug class: angiotensin converting enzyme inhibitors (ACEI), beta-blockers (BB), calcium antagonist blockers (CCB), and diuretics (DD) was extracted annually. We defined a patient with an additional cardiovascular comorbidity as one who had one or more of the following diseases: diabetes mellitus, coronary heart disease, stroke, atrial fibrillation, renal failure and heart failure. Race/ethnicity was based on the information provided by the patient and registered according to that defined in the 2001 UK census [23].

We used the 2006 NICE guidelines as a reference guideline to assess variations in antihypertensive prescribing over the study period. The guideline was reviewed in January 2006 and the updated version was launched in June 2006. Because that guideline established the recommendations on the first line antihypertensive monotherapy based on a patient’s age and race/ethnicity (Table 1), we stratified our hypertensive population such as: black for patients of black ethnicity at all ages, younger non-black for patients of other ethnic origin different from black aged below 55 years and older non-black for patients of other ethnic origin different from black aged 55 years or over. Therefore, the older non-black and younger non-black patient groups include those from white, South Asian, Other Asian and other ethnic origins [24, 25].

To examine variations in antihypertensive prescribing over the study period, we measured the following annual percentages a) the percentage of patients on antihypertensive treatment as the number of patients being prescribed no antihypertensive drug, one antihypertensive drug and two or more antihypertensive drugs over the total number of patients in each NICE patient group; b) the percentage of patients on ACEI, BB, CCB and DD monotherapy as number of patients prescribed each antihypertensive drug class over the number of patients on monotherapy in each NICE patient group; c) the annual percentage of patients on the recommended monotherapy as the number of patients prescribed the recommended monotherapy over the total number of patients on monotherapy in each NICE patient group. Because the recommendations established in the 2006 NICE guidelines applied to hypertensive patients aged 18 years or over without other cardiovascular comorbidity, we included only this hypertensive patient category to calculate the last two percentages [24, 25].

15933 hypertensive patients with a valid ethnicity code were selected from the registers of the participating practices in 2007. Among them, 9085 (57.0%) were white, 3926 (24.6%) were black, 1556 (9.8%) were South Asian, 594 (3.7%) were other Asian and 772 (4.8%) belonged to other ethnic groups. 9261 (58.1%) were over 55 years, 8755 (55%) were female and 6042 (37.90%) had at least one cardiovascular comorbidity. The most frequently associated comorbidity was diabetes, which was present in 3419 (21.5%) of patients, followed by coronary heart disease in 1842 (11.6%), stroke in 1145 (7.2%), atrial fibrillation in 756 (4.7%), renal failure in 670 (4.2%) and heart failure in 395 (2.5%). 4078 (44.3%) of older non-black patients had at least one cardiovascular comorbidity compared to 555 (20.2%) of younger non-black patients (Table 2).

There have been major changes in antihypertensive prescribing between 2000 and 2007 in this UK primary care setting. Over this period, the main changes were an annual decrease in the percentage of all hypertensive patients with no antihypertensive medication. The recommended monotherapy treatment established in the 2006 NICE guidelines for patients of black origin started using before the introduction of this guideline. Black patients were additionally more likely to be prescribed CCB monotherapy after the introduction of 2006 NICE guideline. ACEI was progressively incorporated as antihypertensive monotherapy for younger non-black patients through the study period. The introduction of the 2006 NICE guidelines was associated with an additional increase in the use of ACEI monotherapy in this patient group. There was a slight variation in the monotherapy prescribing pattern used for older non-black patients over the study period. Our analysis suggests that guidelines did not impact equally on all patient groups.

On overall 61.4% of hypertensive patients were on the 2006 NICE first line monotherapy antihypertensive treatment at the end of the study period. The use of this recommended monotherapy seems to start before the introduction of these guidelines particularly in those of black origin. Evidence from clinical trials published before the introduction of these guidelines showing a differential antihypertensive response to CCB in patients of black origin [31] may influenced the early use of this antihypertensive treatment. Although the use of ACEI in younger non-black constantly increased over the period, the introduction of the guideline clearly reinforced its prescribing among general practitioners. Thus, after the implementation of the guidelines younger non-black patients experienced a nearly 50% increase in the odds of being prescribed the recommended monotherapy compared to black patients. Our findings on the use of antihypertensive treatment recommended in the national guidelines look similar to that have been reported. In 2003, Walley et al. reported that 54% of hypertensive patients were on the first line antihypertensive treatment established in the former BHS hypertension guidelines [32]. More recently, in a cohort of patients with stroke, Toshcke et al. found that the use of the antihypertensive recommended treatment established in the 2004 BHS guidelines increased from 24% to 37% between 1997 and 2006 [33]. In a cross-sectional study of 51 general practices located in Lambeth, London, Schofield et al. also found that 44% of hypertensive patients were prescribed the 2006 guidelines recommended antihypertensive treatment [34]. In addition to this overall use, our results remarked the influence of the guidelines on the first line prescribing particularly in younger non-black patients.

The 2006 NICE guidelines recommended that either a CCB or DD should be used as the first line monotherapy in older non-black patients [24], but on overall the percentage of older patients on either CCB or DD slightly decrease from 57.4% to 55.0% over the study period. Moreover, compare to black patients, the odds of being on that recommended monotherapy treatment was significantly lower in older non-black patients (OR 0.49 CI 95% 0.37 – 0.65) and this prescribing pattern did not improve after the introduction of the guidelines. This result differ from that published by NICE in 2010 where an increase in CCB prescribing for newly hypertensive patients aged 55 years and older was found. However, the report did not examine differences between black patients and those of other ethnic origin [35]. Schofield et al. also found that among all 2006 NICE patient groups, older non-black patients had the lowest percentage of those being prescribed the 2006 NICE recommended treatment [34]. Elderly hypertensive patients may be treated differently in routine clinical settings. For these patients the use of higher blood pressure targets and the prescription of few antihypertensive drugs for the treatment of hypertension have been observed in different surveys. This is despite guideline recommendations state that hypertension should be actively managed in older persons [36, 37]. In general practice a low use of DD in elderly hypertensive patients has also been reported [7]. The divergence between the guideline recommendations and the antihypertensive treatment offered to older non-black patients observed in our study may also be due to the effect of other non-cardiovascular comorbidities, side effects or individual physician preferences influencing choice of antihypertensive drug made by general practitioners [7].

The highest percentage of hypertensive patients on CCB monotherapy was in black patients. Moreover the introduction of the 2006 NICE guidelines was associated with an additional increase in the use of CCB for this NICE patient group. They were also more likely to be on the recommended monotherapy (CCB or DD) compared to younger non-black patients and older non-black patients over the study period. In 2005, we had already reported this prescribing pattern in black patients [38]. Similarly, Schofield et al. reported that nearly 90% of black patients were prescribed the 2006 NICE recommended antihypertensive treatment among hypertensive patients treated in primary care [34]. A differential antihypertensive treatment provided to black patients has also been documented elsewhere. In a trend analysis of the National Health and Nutrition Examination Surveys (NHANES) between 2001 and 2010, Gu et al. found that patients of black origin not only were more likely to be prescribed CCB or DD but also the percentage of black patients on CCB or DD therapy increased over the period [39]. The recommendations established in the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure (JNC 7) may have influenced these trends. Hence, it seems that the recommendations on antihypertensive treatment for black patients established in national guidelines have been highly adopted in clinical practice.

For all NICE patient groups there has been a significant reduction in the use of beta blockers as monotherapy antihypertensive treatment. This reduction was significantly intensified by the introduction of the NICE guidelines. Similarly, the 2010 NICE implementation uptake report showed a decline in the percentage of BB usage related to all hypertensive drugs, from nearly 25% in February 2006 to 21% in October 2009. The decline was time-related to the introduction of the 2006 NICE guidelines [35]. In addition to guidelines, general practitioners aware of some evidence that beta blockers may be less effective at reducing blood pressure [40], as well as of their association with new onset diabetes [41] may contribute to the constant reduction in BB use over the period. However opposite trends in BB prescribing have also been observed. Using NHANES data, Gu et al. found an increase in the use BB either as monotherapy or polytherapy between 1998 and 2010 (39). Similarly, in the analysis of the prescribing antihypertensive patters in Canada between 1996 and 2006, Walker et al. found an increase in the BB monotherapy prescribing across all Canadian provinces [20]. That discrepancy may be attributed to variations in the recommendations of BB use established in each guideline. For instance, whereas the 2004 and 2006 Canadian guidelines recommended the use of BB in all hypertensive patients aged below 60 years [42, 43] and the JNV 7 established BB a second line antihypertensive treatment for all patients [44], the 2004 and 2006 NICE guidelines downgraded the BB as an additional therapy for all patients [22, 24]. Hence, these observations may suggest that the local guidelines markedly influence the antihypertensive prescribing patterns among general practitioners.

Among hypertensive patients treated in primary care in Wandsworth, there was a constant increase in the use of 2006 NICE recommended antihypertensive treatment in both younger non-black patients and black patients between 2000 and 2007. The introduction of the 2006 NICE guidelines had the greatest impact on prescribing for younger non-black patients. Lower guideline-associated increases in recommended prescribing among black patients may be due to higher levels of that recommended prescribing in this patient group at baseline. The treatment offered to older non-black patients was less influenced by the 2006 NICE guidelines. Hence, the ethnic-age specific NICE guidelines influence antihypertensive prescribing but the impact of these guidelines can vary across different patient groups.