M A Crilly, P E Bundred*
University of Aberdeen, Department of Public Health, Polwarth Building at Foresterhill, Aberdeen: *University of Liverpool, Department of Primary Care, Whelan Building, Liverpool
Correspondence to: M A Crilly, University of Aberdeen, Department of Public Health, Polwarth Building at Foresterhill, Aberdeen AB25 2ZD. Email: mike.crilly@abdn.ac.uk
SMJ 2005 50(4): 154-158
Abstract
Background and Aims: To determine the extent of gender differences in the routine clinical care of patients with angina pectoris in primary care. Methods: A cross-sectional survey of general practitioner (GP) medical records undertaken by trained data managers in 6 GP practices. 925 adults (489 men) with a clinical diagnosis of angina (prevalence= 2.4%, 95%CI 2.3-2.6). Data extracted included: level of care; risk factor recording; prescribed medication; exercise ECG and coronary revascularisation. Adjusted male-to-female odds ratios (AOR) adjusted for age, angina duration, and previous myocardial infarction, (MI). Results: Women with angina were older than men (71 v 65 years) with a lower prevalence of MI (30% v 45%), but a longer duration of angina (5 v 4 years). Men were more likely to receive once daily aspirin (AOR= 2.07, 95%CI 1.56- 2.74) and be prescribed triple anti-anginal therapy (1.58, 95%CI 1.03-2.42). Men were also significantly more likely to undergo exercise ECG (1.56, 95%CI 1.14-2.15) and surgical revascularisation (1.71, 95%CI 1.03-2.85). Women tended to receive GP care alone (AOR=0.64, 95%CI 0.46-0.89), whilst men received specialist cardiac care (1.47, 95%CI 1.09-2.00). Beta-blocker use following MI was similar (0.99, 95%CI 0.59-1.69). Conclusion: Differences in the management of men and women are unaccounted for by differences in age, previous MI or duration of angina. Gender differences in management of CHD reported from secondary care may also exist in primary care.
Key words: Angina pectoris; cross-sectional survey; gender inequalities; primary health care.
Introduction
Previous studies have suggested that men with known or suspected coronary heart disease (CHD) receive superior medical care to similar women.1-16 Although not all studies have confirmed the existence of such gender differences.17-20 The majority of previous studies have focused on highly selected groups of patients seen in specialist centres in North America.1-11; 17-19 Several studies have attempted to quantify the existence of similar sex differences in the management of CHD in the United Kingdom.12-16,20-22 But despite the fact that CHD is commonly managed in primary care, relatively little attention has been directed towards assessing the existence of such differences in the community setting.21-22
In view of the lack of attention that such gender differences have received in primary care, we have analysed data collected as part of a ‘primary care data project’ to promote the use of once daily aspirin by patients with CHD and their general practitioners. Although the main focus of the ‘primary care data project’ was on general practitioner prescribing (and ‘advising’) of once daily aspirin for their patients with CHD, data was also extracted on several aspects of the evidence-based clinical management of angina pectoris.24,25
The aim of our study was to determine if the sex differences observed in the management of CHD under specialist care also exist for patients with angina pectoris in primary care.
Methods
The study was based in six ‘sentinel general practices’ in Liverpool (UK) serving 38,320 registered patients (the surveillance of illness and the provision of healthcare in the community is often undertaken by collecting data from a number of nominated GP practices - so called ‘sentinel practices’). The six ‘sentinel practices’ are widely distributed geographically across the city, serving a range of patients from the most deprived to the most affluent areas of Liverpool. All the ‘sentinel practices’ issued repeat prescriptions by computer.
Data was collected from a cross-sectional survey of the medical records of patients labelled by their physicians as having angina pectoris. Information was extracted retrospectively (from both written and computerised medical records) by specially trained and supervised ‘primary care data managers’ attached to each practice. Data extraction was undertaken in March 1995.
The clinical computer systems of the six sentinel GP practices were systematically searched for any registered patients ever previously prescribed any nitrate preparation (as listed in the British National Formulary, BNF). Such patients were considered ‘labelled with a diagnosis of angina pectoris’ if any of a series of ‘allowable’ terms (such as angina, angina pectoris, anginal chest pain, exertional angina, unstable angina etc) appeared in their medical records. Patients were excluded if they were recorded only as having ‘chest pain’, or if there was any medical doubt/disagreement concerning a diagnosis of angina.
Using a previously piloted proforma our ‘primary care data managers’ determined if the patient’s smoking habit, body mass index (BMI) or serum cholesterol had ever been recorded; and if the patients blood pressure (BP) had been recorded within the previous 12 months.
Information was also extracted concerning the use of once daily aspirin and the presence of medical problems that might caution against aspirin use (peptic ulceration; upper gastrointestinal bleed; indigestion; allergy to aspirin or related drugs; anti-coagulant treatment; liver or kidney impairment). The prescription of beta-blockers and calcium antagonists over the previous six months was also recorded.
Since all patients were identified through nitrate prescribing, individuals prescribed both beta-blockers and calcium antagonists (limited to those indicated for angina pectoris in the British National Formulary, BNF) were categorised as receiving ‘triple therapy ’, whilst those receiving only one of these two drugs were categorised as receiving ‘dual therapy’.
The provision of medical care for angina since diagnosis (and also over the previous 12 months) was categorised as either: GP alone, non-cardiac hospital specialist, or cardiac specialist. Any previous medical history of myocardial infarction (MI) and coronary revascularisation (coronary angioplasty, coronary artery bypass grafting) was noted. The number of face-to-face GP consultations over the previous 12 months was determined from the medical records.
Statistical analysis
Information from the data collection forms was initially entered into Epi-Info (v6) record files with an associated ‘check file’ to restrict keying errors. Data checking was performed in Microsoft Excel (v5). The majority of the statistical analysis was performed in SPSS (v10). Adjusted odds ratios (AOR) were calculated in SPSS (v10) using multiple logistic regression to adjust for sex differences in age, duration of angina (in years) and previous MI.
Results
A total of 1,269 patients (656 men; 613 women) were identified as having been prescribed nitrates. Of these 936 (498 men; 438 women) were unequivocally labelled as having angina pectoris. Overall 74% (936/1,269) of patients prescribed nitrates were labelled as having angina, although the diagnosis was more likely to be applied to men than women (unadjusted odds ratio, OR= 1.26, 95%CI 0.97-1.63). The overall prevalence of labelled angina for adults (aged 16 years or more) was 2.4%(95%CI 2.3-2.6). Complete medical records were available for 925 (99%) patients labelled as having angina pectoris; five of these patients lacked a date of diagnosis for their angina (and consequently duration of angina could not be determined).
Patient features (Table I)
The characteristics of these 925 individuals with angina pectoris are shown in Table I. Women with angina pectoris were on average 5.5 years older than men (95%CI 4.1- 7.0). Women were also 4.7 years older at diagnosis (95%CI 3.3-6.2), with a median duration of angina that was significantly longer (Mann-Whitney U test p=0.04). A previous history of MI was an absolute 15% (95%CI 9- 21%) higher for men.
Women had a higher annual GP consultation rate (median 7; interquartile range, IQR 4-10) than men (median 5; IQR 3-9); a difference that was statistically significant (Mann-Whitney U test p=0.0001). A higher proportion of women (281, 64%) than men (258, 53%) had received their entire medical care for angina over the previous 12 months solely from their GP (absolute difference of 11%, 95%CI 5-18%). A third of women (34%, 95%CI 30-37%) had only ever received GP care for their angina.
Clinical management of angina (Table II; Figs 1& 2)
The sex differences found in the clinical management of angina pectoris in primary care are shown in Table II. The overall patterns of these sex differences are shown graphically as forest plots in Figs 1 & 2.
Provision of care since diagnosis
In unadjusted analysis women were significantly more likely to have their angina diagnosed and managed entirely by their GP (OR=0.43, 95%CI 0.32-0.59), whilst men were significantly more likely to have been assessed by a cardiac specialist (OR=2.07, 95%CI 1.55-2.76). Such differences persisted, although they were reduced, after adjustment for current age, duration of angina and previous MI.
Adjusted odds ratios (AOR) (Table II; Fig 1)
Age at diagnosis was not available for five patients, so that adjusted odds ratios (AOR) are based on complete data for 920 individuals. These adjusted odds ratios were consistently closer to unity than unadjusted ratios. Since an odds ration of one indicates no gender difference, adjustment reduced the size of the observed gender gap. Age was an important influence on clinical management. Adjustment for patient age had a greater influence on reducing these odds ratios than either duration of angina or previous MI. All of the following results refer to fully adjusted odds ratios (AOR). On adjusted analysis women were still significantly more likely to have received GP care alone since diagnosis (AOR=0.64, 95%CI 0.46-0.89), whilst men were significantly more likely to have received care from a cardiac specialist (AOR=1.47, 95%CI 1.09-2.00).
Anti-anginal therapy (Table II; Fig 1)
Women were more likely to be prescribed nitrates alone for their angina (AOR=0.83, 95%CI 0.63-1.10), whilst men were significantly more likely to be prescribed triple (nitrate, calcium antagonist and beta-blocker) anti-anginal therapy (AOR=1.58, 95%CI 1.03-2.42).
Risk factor assessment (Table II; Fig 2)
Men were significantly more likely to have their BMI recorded (AOR=1.35, 95%CI 1.02-1.78), but the higher recording of smoking and cholesterol (AOR=1.23; 1.11 respectively) was not statistically significant. Women were more likely to have a blood pressure recorded over the previous 12 months (AOR=0.77), although this was not statistically significant.
Secondary prevention, investigation & intervention (Table II; Fig 2)
Men were significantly more likely than women to have been prescribed/advised once daily aspirin (AOR=2.07, 95%CI 1.56-2.74). This under-utilisation of aspirin was not accounted for by sex differences in contra-indications to aspirin (peptic ulceration; upper gastrointestinal bleed; indigestion; allergy to aspirin or related drugs; anticoagulant treatment; liver or kidney impairment). The presence of potential contra-indications was similar for both sexes (men 31%; women 29%).
Beta-blockers were more commonly prescribed to men with angina, although this difference was not statistically significant (AOR=1.23, 95%CI 0.90-1.68). In patients with a previous MI there was no sex difference in the use of beta-blockers (AOR=0.99, 95%CI 0.59-1.69). Men with angina were significantly more likely to have undergone both exercise ECG testing (AOR=1.56, 95%CI 1.14-2.15) and coronary revascularisation (AOR=1.71, 95%CI 1.03-2.85) compared to women. Whilst the level of exercise ECG testing was considerably higher for men than women, the overall level was low at only 35%.
Specialist care and GP consultation rate
Including the provision of specialist care in the multiple logistic regression model made little difference to the adjusted odds ratios (AOR) shown in Table II. For example, adjusting aspirin use for ‘any specialist care since diagnosis’ produced an odds ratio of 2.08 (95%CI 1.56 - 2.79). Adjusting for sex differences in annual GP consultation rates also made no important differences to the reported odds ratios.
Discussion
This study demonstrates a less favourable approach in primary care to the clinical management of women with angina pectoris compared to men. The pattern of inequality between the sexes remained (although it was somewhat reduced) after adjusting for the lower prevalence of MI in women, their older age and longer duration of angina. The findings were statistically significant across a broad range of measures, including the provision of specialist cardiac care, triple anti-anginal therapy, secondary prevention with aspirin, and the performance of exercise ECG and coronary revascularisation.
Interpretation of our findings needs to be carefully considered in relation to both the study design and the inherent difficulties and uncertainties of assessing chest pain/angina in clinical practice. Chest pain is notoriously difficult to assess in women and the lack of a diagnostic gold-standard for angina introduces a considerable degree of clinical heterogeneity. For example, on arteriography a greater proportion of women than men with angina will be found to have apparently normal coronary arteries.
The presence of trained primary care data managers in each of the six ‘sentinel practices’ ensured a rigorous and systematic approach to data extraction. We extracted data on a wide range of clinical measures for which there is a strong evidence-base (Table III).24,25 It is likely that almost all of the relevant clinical information contained within the medical records was identified and extracted by our data managers. The prevalence of angina in our study is comparable with other surveys, suggesting that we achieved a high ascertainment of angina cases.23
Labelled angina
An advantage of our study is that unlike many other studies it does not relate to a highly selected group of patients with CHD recruited from a specialist care setting. We intentionally restricted our study to patients ‘explicitly labelled’ as having angina pectoris for three reasons. Firstly, the diagnosis of angina is essentially a clinical one as there is no diagnostic ‘gold standard’.
Secondly, nitrates are commonly prescribed as a ‘diagnostic trial of therapy’, on the assumption that chest pain relieved by nitrates is more likely to be cardiac. We did not wish to include patients given nitrates in the past, but whose physician’s suspected a non-cardiac cause for their chest pain.
Thirdly, observed clinical practice could be compared against evidence-based guidelines concerning the appropriate management of patients with “clinically certain angina” in primary care (Table III).24,25 It seemed reasonable to assume that patients unequivocally labelled as having angina pectoris by their physicians should receive appropriate assessment and intervention for their angina.
Retrospective record review
The use of medical records (and the retrospective nature of the study) imposes some important limitations on our findings. In particular we did not attempt to assess whether a patient’s symptoms were typical of ‘classic angina’ nor measure their severity. Both of these factors are likely to influence the clinical management of angina, but are often unrecorded in GP medical records. For example, if men’s anginal symptoms are more severe than women’s, then men may consequently receive more assertive medical management. Although a plausible proposition the available evidence suggests that women’s anginal symptoms are at least as severe (and possibly more disabling) than men’s.9,12 Furthermore, whilst previous MI is not an ideal proxy for CHD severity, the sex differences we found persisted despite adjustment for a previous MI.
The study is also constrained by what was recorded in the medical records. We limited our data extraction to items that we felt would be reliably recorded as part of routine healthcare in general practice. For example, we did not attempt to distinguish between whether the use of betablockers was primarily for symptomatic relief or prevention. In relation to the use of aspirin, we found no evidence that co-morbidity accounted for the sex differences observed in the provision of clinical care. Although, other than assessing potential contra-indications to aspirin use, we did not assess the presence of other co-morbidities that might influence the clinical management of angina (such as emphysema and beta-blockade).
Provision of care
Some 64% of women in this study received medical care for their angina solely in primary care over the previous 12 months. Primary care is a key area for ensuring that women with angina receive effective clinical care. The unequal care of women that we observed existed despite their higher annual GP consultation rate. Whilst many of these consultations are undoubtedly initiated in relation to other health problems, the opportunity exists in primary care to address gender inequalities in the management of CHD.
Conclusions
Ensuring that all patients have the opportunity to benefit from effective healthcare, irrespective of gender, is an important challenge for all healthcare systems. We have demonstrated that important sex differences in the clinical management of CHD were present in UK general practice. Women with angina pectoris were significantly less likely to be prescribed aspirin, see a heart specialist, undertake exercise ECG testing or undergo cardiac revascularisation when compared to men.
Considering the profile that secondary intervention for the prevention of adverse cardiac events in patients with CHD has received over the last decade, it is surprising how little attention has focused on CHD gender differences in the UK. There is limited understanding as to why women (even when explicitly labelled as having CHD by their physicians) appear to receive less favourable medical care than men. Furthermore, we don’t know what impact national healthcare initiatives are having on such a gender gap in relation to coronary heart disease.
ACKNOWLEDGEMENTS: We thank the data collection managers and general practitioners of the six practices involved for their assistance and co-operation.
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