Abstract
Background Despite the fact that peripheral arterial disease (PAD) significantly increases the risk of cardiovascular mortality, it is significantly underdiagnosed and undertreated. The purpose of this study was to evaluate the practice at a northeast Tennessee university primary care clinic regarding the diagnosis and treatment of PAD.
Methods A retrospective medical record survey was conducted to evaluate practice patterns in diagnosing and treating PAD in a university primary care clinic. A clinic population of 711 patients was selected using International Classification of Diseases-9 codes for coronary artery disease (CAD), cerebovascular disease (CVD), and/or PAD. A sample of 180 patients (25.3%) was randomly selected using a systematic statistical method. Of these, 125 patients met the diagnostic criteria for CAD, CVD, and/or PAD. The study covered a 3-year period, from July 2001 until June 2004. Demographic and other data, including the use of antiplatelet therapy, were collected.
Results One hundred ten patients met all of the inclusion and exclusion criteria. Thirty-nine percent were males, and 61% were females. Overall, 79% had CAD, 53% had CVD, and 25% had PAD. Almost half of the patients had some combination of these. Only about 2% had PAD only compared with 36% with CAD only and 17% with CVD only. Although the prevalence of CAD and CVD (among other atherosclerotic vascular diseases) in our clinic was comparable to national figures, the prevalence of PAD was significantly lower (p = .004). The overall use of any antiplatelet agent was 84.2% for patients with only CAD and 80% for only CVD. There was not an adequate number of patients with only PAD to evaluate the use of antiplatelet therapy in this group.
Conclusion The low prevalence of PAD only (most PAD patients had coexisting CAD and CVD) indicates that PAD is underdiagnosed at our clinic. There was suboptimal use of aspirin and other antiplatelet drugs among patients with atherosclerotic vascular disease.
By convention, peripheral arterial disease (PAD) is a disease of the distal aorta and the lower extremities, although some general definitions consider any extracranial and extracoronary arterial involvement to be PAD.1-4In this article, we refer to PAD as a disease of the distal aorta and the lower extremities, as it is commonly known. PAD is a critical public health problem because it is extremely common and is associated with a significantly increased risk of coronary artery disease (CAD), cerebrovascular disease (CVD), and mortality. About 11 million people in the United States have PAD compared with 4 million with CVD and 7 million with a history of myocardial infarction.4-7The prevalence of PAD increases with age. It also increases among high-risk populations, such as smokers and patients with abdominal aortic aneurysm, to a higher rate than that observed for other atherosclerotic vascular diseases.8,9The San Diego Artery Study revealed that PAD significantly increases the risk of cardiovascular mortality. Furthermore, severe PAD was associated with a higher mortality than that of mild disease.10Although the morbidity from PAD is significant, only 5% and 1% of PAD patients require specific treatment or amputation for lower extremity disease, respectively. On the other hand, the 5-year mortality rate from atherosclerotic vascular disease in PAD patients reaches 23%. The natural history of PAD in regard to morbidity and mortality is compounded by the fact that it is an underdiagnosed and untreated disease.4-7,11-13Physicians' awareness of PAD is very low, although its prevalence in primary care settings is very high. The PAD Awareness, Risk, and Treatment: New Resources for Survival (PARTNERS) study, the largest of its kind, was designed to evaluate the frequency of detecting PAD in primary care clinics.5It was a cross-sectional, multicenter study that was conducted at 350 primary care clinics in 25 cities throughout the United States, and it included 6,979 patients aged 70 years or older or between 50 and 70 years with a high risk of PAD. The study revealed that only 49% of physicians were aware that their patients had PAD. The prevalence of PAD was 29%, of which 13% had only PAD (without CAD, CVD, or abdominal aortic aneurysm) (Table 1). Two other large studies have looked at the prevalence of coexistence of PAD, CAD, and CVD. A prospective study of Aronow and Ahn, which included 1,886 patients in a long-term health care facility aged 62 years or older, revealed that 62.6% of patients had atherosclerotic vascular disease.6,14Of these, 39% had PAD and 11.9% had only PAD. (see Table 1). A randomized, blinded trial of clopidogrel versus aspirin in patients at risk of ischemic events (CAPRIE) looked at the prevalence of PAD in relation to other atherosclerotic vascular diseases in 20,000 patients.15It was revealed that the prevalence of PAD in this patient population was 38.2%. The prevalence of PAD only in this population was 19.2% (see Table 1).
Large epidemiologic studies have revealed the efficacious role of the ankle-brachial index (ABI) in diagnosing and screening for PAD.16-18Aspirin and other antiplatelet drugs have been shown to reduce the risk of nonfatal MI, nonfatal stroke, and vascular death in patients with PAD and other atherosclerotic vascular diseases; hence, antiplatelet therapy plays an essential role in the management of these atherosclerotic vascular disorders.13,19-24
Literature about actual physician and patient compliance with aspirin and other antiplatelet therapy for atherosclerotic vascular diseases is scarce. One reason for this is the lack of a universal system for tracking the use of over-the-counter drug therapy other than direct patient information from interviews and questionnaires. A better estimation of compliance with antiplatelet drug or aspirin use could be obtained from the Canadian health system or the US Veteran Affairs (VA) system.
US studies are mostly based on questionnaires and self-reporting. According to these studies, overall doctor and/or patient compliance with antiplatelet therapy ranged from 89 to 96%. Among PAD patients, compliance ranged from 88 to 94%, although most of these studies on PAD did not exclude PAD patients who had other atherosclerotic vascular diseases.25,26
Our study was performed at a university community-based clinic to assess the frequency of diagnosing PAD compared with national figures and the degree of physician and patient use of antiplatelet therapy once PAD or any other atherosclerotic vascular disease is identified.
PRACTICE AT EAST TENNESSEE STATE UNIVERSITY CLINICS
ETSU Physicians and Associates is the main community-based clinic at East Tennessee State University (ETSU). It provides care for over 5,000 active patients, with over 38,400 patient visits annually. Approximately 90% of the patients at ETSU clinics are white, less than 5% are black, and approximately 5% belong to other minority groups. A little less than half of the patient population lives outside the city limits, with some patients coming from neighboring states (Virginia and North Carolina). Approximately 50% of the patients are Medicare beneficiaries, approximately 20% are on Medicaid, approximately 30% are on private health insurance plans, with BlueCrossBlueShield being the biggest provider, and approximately 10% are indigent patients. Approximately 70% of the patient population is attended solely by university attending physicians, and only approximately 30% are attended primarily by medical residents.
METHODS
A retrospective medical record survey was conducted at the main university internal medicine clinic (ETSU Physicians and Associates), which included an average of seven attending physicians during the study period. The study covered a 3-year period, from July 2001 until June 2004. A clinic population of 794 patients was selected using International Classification of Diseases-9 (ICD-9) codes for CAD, CVD, and/or PAD and ICD-9 codes27for suggestive symptoms, including chest pain, limb weakness or paralysis, hemiparesis, hemiplegia, intermittent claudication, and leg pain. All of these patients met the age criterion and were not primarily seen by resident physicians. After excluding patients who had no health insurance, 711 patients remained. A sample of 180 patients (25.3%) was randomly selected using a systematic statistical method. Inclusion criteria were (1) age 35 to 90 years; (2) a diagnosis of PAD, CAD, or CVD; and (3) availability of health insurance. Exclusion criteria were (1) PAD, CAD, or CVD related to a disease process other than atherosclerosis; (2) patient noncompliance as evidenced by unexcused missing of more than one appointment, not taking medicines according to directions, or refusing diagnostic tests or treatments; and (3) seen primarily by resident physicians. Patients were considered as having CAD if they had a clinical diagnosis of angina pectoris, acute coronary syndrome, a documented history of MI, coronary bypass grafting, an abnormal stress test, or electrocardiographic signs of a previous MI. Patients were considered to have PAD if they had a documented history of intermittent claudication, ulceration or gangrene, critical limb ischemia, an ABI < 0.9, arterial duplex and Doppler waveforms confirming PAD, or surgery for PAD to include bypass grafting or amputation. Patients were considered to have CVD if they had this diagnosis documented in medical records based on a neurologic deficit lasting over 24 hours or computed tomographic or magnetic resonance imaging findings. Fifty-five patients were excluded because they did not meet the diagnostic criteria for CAD, CVD, or PAD despite having an ICD-9 code for one or more of the three diagnoses or related symptoms. One hundred twenty-five patients remained. Of these, seven patients were deemed noncompliant owing to missing more than one appointment without an excuse. Five patients were excluded owing to refusal of a diagnostic test. Three patients were excluded owing to refusal of therapy, including drug therapy. One hundred ten patients met all of the inclusion and exclusion criteria. To test compliance with antiplatelet therapy, patients who had no prescription drug coverage and patients who had documented intolerance or contraindications to all antiplatelet drugs mandating discontinuation of these drugs were excluded. Ninety-one patients were studied for compliance with antiplatelet therapy.
Information about the following variables was collected from medical records: patient's age, gender, diagnosis, symptoms of PAD, PAD diagnostic tests, total number of visits, type of physician (attending, resident, multiple physicians, or consultant), type of insurance and prescription drug coverage, and drug treatment used.
Medical records were reviewed by two trained reviewers: one medical student and the principal investigator. All patient visits to the clinic were reviewed to assess patient suitability considering all inclusion and exclusion criteria. To test the overall compliance with aspirin or any antiplatelet therapy, charts were reviewed looking for any indication that antiplatelet therapy was prescribed by doctors and/or taken by patients by reviewing the whole chart, including drug lists (by patients, nurses, or doctors), copies of hospital records, and all outpatient progress notes.
Statistical analysis using Epi Info (Centers for Disease Control and Preventon [CDC], Atlanta, Georgia) software was performed to analyze the characteristics of the patient population, such as age, gender, diagnosis, coexistence of the three atherosclerotic vascular diseases, health insurance and prescription drug coverage, number of doctor's visits, and drugs used. Analysis of variance and chi-square, and Fisher exact tests were applied to assess the effects of the frequency of doctor visits on the level of compliance with antiplatelet therapy.
RESULTS
The clinic population of 794 patients was selected using ICD-9 codes for CAD, CVD, and PAD and/or related symptoms. This group had a mean age of 64 years and was not primarily seen by resident physicians. After excluding patients without health insurance, a sampled population of 711 patients of active continuity clinic patients who met the inclusion criteria in regard to the availability of health insurance, age, diagnosis (based on ICD-9 code), and seeing primarily only attending physicians remained. The mean age for the sampled population increased to 68.8 years. A sample of 180 patients (25.3%) was randomly selected using a systematic statistical method. The sample matched with the sampled population in regard to age, gender, and health insurance distribution (p = .95, .88, .94, respectively) (Table 2). Fifty-five patients were excluded because they did not meet the diagnosis criteria for CAD, CVD, or PAD despite having ICD-9 codes for one or more of the three diagnoses or related symptoms. One hundred twenty-five patients remained. Of these, seven patients were deemed noncompliant owing to not showing up for more than one appointment without an excuse. Five patients were excluded owing to refusal of a diagnostic test. Three patients were excluded owing to refusal of therapy, including drug therapy (Table 3). One hundred ten patients met all of the inclusion and exclusion criteria; 39.1% were males, and 60.9% were females. Ages ranged from 36 to 90 years, with a mean age of 74 years and a standard deviation of 12.4 years; 51.8% of the patients were on Medicare, 23.6% were on a Tennessee managed care program (TennCare), and 24.5% were on commercial plans. Most patients (70%) were seen by more than one attending physician, but all were seen more often by their primary physician; 79.1% of patients had CAD, 52.7% had CVD, and 24.5% had PAD. Ten percent of patients had CAD, CVD, and PAD; 21.8% had CAD and CVD but no PAD; 10% had CAD and PAD but no CVD; and 2.7% had CVD and PAD but no CAD. Only 1.8% of patients had only PAD (without CAD or CVD) compared with 35.5% with only CAD and 17.3% with only CVD. Although the rate of diagnosing CAD and CVD (among other atherosclerotic vascular diseases) in our clinic was comparable to national figures, the rate of diagnosing PAD was significantly lower (p = .004) (Table 4).
To test compliance with antiplatelet therapy, patients who had no prescription drug coverage and patients who had documented intolerance or contraindications to all antiplatelet drugs mandating discontinuation of these drugs were excluded (see Table 3). Ninety-one patients were studied for compliance with antiplatelet therapy. Of these, 84.2% who had only CAD and 60% who had only CVD were on aspirin. However, 10.5% with only CAD and 60% with only CVD were on antiplatelet treatment other than aspirin. The overall use of any antiplatelet agent was 84.2% for patients with only CAD and 80% for patients with only CVD. There was not an adequate number of patients with only PAD to evaluate the use of antiplatelet therapy among this group. Among all patients with atherosclerotic vascular disease, the overall use of antiplatelet therapy was 82.9%.
Doctor visits for each patient ranged from 4 to 29 visits over 3 years, with a mean of 12.11 visits and a standard deviation of 2.33 visits. ANOVA and chi-square tests revealed that the number of doctor visits had no effects on the rate of use of antiplatelet therapy as documented in medical records. Patients who used antiplatelet therapy as documented in medical records did not see their doctors significantly more often than patients who did not use antiplatelet therapy over 3 years (mean = 12.2 vs 11.5, F = 1.16, p = .28) (Table 5).
Ninety percent of the study patients and 92% of patients evaluated for compliance with antiplatelet therapy were seen at least once during the study period by a cardiologist, a vascular surgeon, or a neurologist. The fact that patients were always suspected to have or were diagnosed with an atherosclerotic vascular disease prior to referral to cardiologists, vascular surgeons, or neurologists indicated that seeing consultants had no significant effects on the rate of diagnosing any of the atherosclerotic vascular diseases. On the other hand, since 92% of patients were seen at least once during the study period by a cardiologist, a vascular surgeon, or a neurologist, seeing a consultant at least once during the study period did not have a significant effect on the overall use of antiplatelet therapy.
LIMITATIONS
Our study has limitations. First, we reviewed only 25.3% of the study population. The sample characteristics in regard to age, gender, and type of health insurance matched with the characteristics of the sampled population. Thus, the sample reviewed seems to represent the study population.
This was a retrospective study, and not all clinic patients were systematically evaluated for atherosclerotic vascular disease. Some patients might have been missed owing to inappropriate or inaccurate use of diagnosis codes.
Finally, since this was a chart review, compliance with antiplatelet therapy might have been underestimated owing to suboptimal documentation of over-the-counter medications or incomplete drug lists.
DISCUSSION AND CONCLUSION
In reviewing the literature, the prospective study of Aronow and Ahn seemed to be one of the best studies of the true prevalence of the coexistence of PAD, CAD, and CVD.6,14Although the CAPRIE study included a larger population of 20,000, it was a retrospective study that was not primarily designed to evaluate the prevalence of the coexistence of atherosclerosis vascular diseases; hence, by design, it included artificially equal numbers of patients with PAD, CVD, and MI.15Also, diagnosing PAD was based only on patient self-reporting of symptoms, which might have led to under- or overdiagnosing PAD.14,15The PARTNERS study, which included a large and very diverse population across the United States, would have been a better predictor of the true prevalence of PAD (and other atherosclerotic diseases) compared with the study of Aronow and Ahn,6,14which looked at one long-term care facility in Bronx, New York. The PARTNERS study, however, was also based on self-reporting of symptoms.5Also, it did not evaluate individual diseases other than PAD.
Accordingly, although our study differed by design from the study of Aronow and Ahn and had some limitations, we opted to compare our data with the data from Aronow and Ahn (Table 6).6,14There was a significant difference between our data and the data about the true prevalence of the coexistence of PAD, CAD, and CVD as represented by Aronow and Ahn (p = .004).6,14The prevalence of PAD only in our clinic population was much lower than that in Aronow and Ahn's study (1.8% vs 11.9%) and that of other nationally reported data (19.2-24.5%). Although the rate of diagnosing CAD only and CVD only was not significantly different between our study and that of Aronow and Ahn, the rate of diagnosing PAD only represented the most significant difference between the two study groups. It is concluded that PAD is underdiagnosed in our clinic. This seems to be related to the fact that there is a suboptimal level of compliance in our clinic with the national consensus for screening high-risk populations for PAD by performing ABI. This includes patients over 70 years of age or over 50 years with risk factors, smokers, diabetics, and patients with intermittent claudication, resting leg pain, or nonhealing leg ulcers.5,14
As mentioned previously, the literature on compliance with aspirin and antiplatelet therapy in the United States is scarce owing to the lack of a universal health care system for tracking drug therapy. Available data from Canada revealed an overall compliance with aspirin therapy among patients with atherosclerotic vascular diseases, including PAD, of 89 to 92%.28-30A study of a veteran population of 8,925 coronary artery bypass grafting patients revealed a compliance rate of 88.5% with filling prescriptions for aspirin and other antiplatelet drugs, although the patients were slightly more compliant with filling prescriptions for aspirin than for other antiplatelet drugs.31Another study from a VA outpatient clinic in Orlando, Florida, revealed a compliance rate of 92% with prescribing and filling antiplatelet therapy.32
From an international perspective, a large study from the German Stroke Data Bank, Ludwig Maximilian University, Munich, Germany, revealed an overall level of compliance with antiplatelet therapy for CVD ranging from 92 to 96%, depending on the length of follow-up.33Another study from Hebrew University, Jerusalem, Israel, revealed an overall compliance with antiplatelet therapy of 89%.34Finally, a Japanese study revealed an overall rate of compliance with antiplatelet therapy of 90% among ischemic CVD patients.35
According to several US studies, the rate of prescribing aspirin and other antiplatelet drugs among older patients was lower than that for other age groups, but it did not seem to differ based on gender or type of health insurance.36,37
Most US studies that evaluated physician and patient compliance with aspirin and other antiplatelet therapies in the treatment of atherosclerotic vascular diseases are based on questionnaires and self-reporting. A study from the University of Michigan revealed that the degree of adherence to daily aspirin intake based on self-reporting was significantly different from the degree of compliance obtained when a medication event monitoring system was used.38Compliance varied from 89 to 96% depending on the population, setting, and the type of atherosclerotic disease process of the studied population.28,30,39In one study, however, compliance with the use of aspirin was as low as 53%.28Despite the flaws of these methods of questionnaires and self-reporting, the overall level of compliance with antiplatelet therapy in the United States is similar to that of Canada and other developed countries. Also, it was similar to that of the VA system. Data from our clinic regarding the overall compliance with antiplatelet therapy for atherosclerotic vascular diseases, based on review of medical records, revealed a significant difference in compliance among CAD and CVD patients when the standard level of compliance was set at 96%. However, if the standard level of compliance is considered to be 89% (the lower limits of the available national data), only CAD-only patients have a level of compliance with antiplatelet therapy, similar to the national data. CVD-only patients seem to have a slightly lower level of compliance with antiplatelet therapy than the lower limits of the national data (p = .038).
Since our data regarding compliance with antiplatelet therapy were based on medical record review only, it is possible that the level of compliance with antiplatelet therapy was underestimated owing to inadequate documentation of the use of over-the-counter drugs, incomplete patient drug lists, or, generally, a suboptimal level of documenting current drugs.
It is presumed that the low level of compliance (or documentation) with antiplatelet therapy in our clinic is related to physician factors; however, other studies that relied on patient self-reporting revealed that compliance might be related to patient and physician factors. National data reveal that once aspirin is prescribed, patient self-reported compliance is high35; however, there is a suboptimal level of physician compliance with prescribing antiplatelet therapy for eligible patients. Several reasons have been proposed, among which are difficulties in applying universal guidelines to individual patients, patient reluctance in taking aspirin, inadequate review of medications during doctor visits, and time-constrained doctor visits leading to prioritization of other issues.40
According to our data, patients being seen by their doctors more often did not improve the level of compliance in documenting or prescribing antiplatelet therapy. This indicates the need for implementing a standard drug review method, protocol, or program that is applied each time a patient with PAD, CAD, or CVD presents to a clinic or a hospital.41One example of this is the Cardiac Hospitalization Atherosclerosis Management Program (CHAMP).41A physician reminder system or a drug flow sheet in the chart that is updated every visit by nurses and audited by physicians may improve documentation and compliance with medications, including over-the-counter and antiplatelet medications.42An Italian study on 15,343 patients revealed that automated electronic reminders improved antiplatelet-prescribing behavior among general practitioners.43
The recent success of many combination drugs for hypertension has accelerated the interest in combination drugs for lipids and atherosclerosis, such as the combination of pravastatin with aspirin. Drug combination could be a positive step in improving compliance with prescribing and taking routine drugs for atherosclerosis.44
Finally, physicians and pharmacists should be aware of recent evidence from randomized, controlled trials that led to changes in the national guidelines for indications of antiplatelet therapy for atherosclerotic diseases and counsel their patients about appropriate antiplatelet therapy.45