Susan MacDonald

Pragmatic controlled clinical trials in primary care: the struggle between external and internal validity

BackgroundControlled clinical trials of health care interventions are either explanatory or pragmatic. Explanatory trials test whether an intervention is efficacious; that is, whether it can have a beneficial effect in an ideal situation. Pragmatic trials measure effectiveness; they measure the degree of beneficial effect in real clinical practice. In pragmatic trials, a balance between external validity (generalizability of the results) and internal validity (reliability or accuracy of the results) needs to be achieved. The explanatory trial seeks to maximize the internal validity by assuring rigorous control of all variables other than the intervention. The pragmatic trial seeks to maximize external validity to ensure that the results can be generalized. However the danger of pragmatic trials is that internal validity may be overly compromised in the effort to ensure generalizability. We are conducting two pragmatic randomized controlled trials on interventions in the management of hypertension in primary care. We describe the design of the trials and the steps taken to deal with the competing demands of external and internal validity.DiscussionExternal validity is maximized by having few exclusion criteria and by allowing flexibility in the interpretation of the intervention and in management decisions. Internal validity is maximized by decreasing contamination bias through cluster randomization, and decreasing observer and assessment bias, in these non-blinded trials, through baseline data collection prior to randomization, automating the outcomes assessment with 24 hour ambulatory blood pressure monitors, and blinding the data analysis.SummaryClinical trials conducted in community practices present investigators with difficult methodological choices related to maintaining a balance between internal validity (reliability of the results) and external validity (generalizability). The attempt to achieve methodological purity can result in clinically meaningless results, while attempting to achieve full generalizability can result in invalid and unreliable results. Achieving a creative tension between the two is crucial.

Trial of Prevention and Reduction of Obesity Through Active Living in Clinical Settings: A Randomized Controlled Trial

BACKGROUND The efficacy of physical activity with a healthful diet to reduce obesity is established; however, little is known about the translation of effective lifestyle strategies for obesity reduction in primary care settings. METHODS We assessed the effectiveness of a 2-year behaviorally based physical activity and diet program implemented entirely within clinical practices to reduce obesity. A total of 490 sedentary, obese adults were randomized to usual care (n = 241) or to the behavioral intervention (n = 249). The usual care group received advice from their physicians about lifestyle as a strategy for obesity reduction. The behavioral intervention included individual counseling from health educators to promote physical activity with a healthful diet. The primary outcome was change in waist circumference (WC). RESULTS A total of 396 participants completed the trial (80.8%). A significant main effect was observed for WC change within the intervention compared with usual care (P < .001) that was sustained at 24 months (mean [SE], -0.9 [0.4] vs 0.2 [0.4] cm; P = .05). Secondary analyses revealed significant main effects for change in WC in men (P = .009) and women (P = .02). In men, the mean (SE) reduction in WC at 24 months was greater with behavioral intervention compared with usual care (-1.6 [0.6] vs 0.1 [0.6] cm; P = .049). In women, the behavioral intervention was associated with differences in WC compared with usual care at 6 and 12 months (P ≤ .01) but not at 24 months (P = .10). CONCLUSIONS Behavioral intervention in clinical settings is associated with modest reductions in WC during a 2-year study in obese patients. However, the effectiveness of the intervention is restricted to men. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00665158.

Manual and automated office measurements in relation to awake ambulatory blood pressure monitoring

BACKGROUND Automated blood pressure (BP) devices are commonly used in doctors offices. How BP measured on these devices relates to ambulatory BP monitoring is not clear. OBJECTIVE To assess how well office-based manual and automated BP predicts ambulatory BP. METHODS Using data on 654 patients, we assessed how well sphygmomanometer measurements and measurements taken with an automated device (BpTRU) predicted results on ambulatory BP monitoring. We assess positive and negative predictive values and overall accuracy. We look at different cut-points for systolic (130, 135 and 140 mmHg) and diastolic (80, 85 and 90 mmHg) BP. RESULTS A single automated office BP (AOBP) assessment provides superior predictive values and overall accuracy compared to three manual office BP assessments. For systolic BP, the predictive values are ≤69% for any of the cut-points while the positive predictive values for the single automated measurement is between 80.0% and 86.9% and the overall accuracy gets as high as 74% for the 130 mmHg cut-point. For diastolic BP, the automated readings are also more predictive but in this case, it is the negative predictive values that are better, as well as the overall accuracy. CONCLUSIONS Based on the results, we suggest that 135/85 mmHg continue to be used as the cut-point defining high BP with the BpTRU device. However, future research might suggests that values in a grey zone between 130-139 mmHg systolic and 80-89 mmHg diastolic be confirmed using ambulatory BP monitoring. As well, three AOBP assessments might produce much greater accuracy than the single AOBP assessment used in the study.

Hypertensive Disorders of Pregnancy and Long-Term Risk of Hypertension: What Do Ontario Prenatal Care Providers Know and What Do They Communicate?

OBJECTIVES The objective of this study was to ascertain the knowledge base of Ontario maternity care providers (family physicians, obstetrician-gynaecologists, and midwives) regarding the future health risks of gestational hypertension and preeclampsia and the practices with respect to communication of these risks. METHODS In 2004, all obstetricians (639) and midwives (249) in Ontario and a random sample of 600 Ontario family physicians were mailed a survey and a reminder. Non-responders were also sent a second, and in some cases, a third copy of the survey. The survey addressed areas of knowledge, reported practices, and both patient and interprofessional communication. Descriptive analysis was used for the responses. RESULTS The overall response rate was 42%. The majority of respondents were familiar with the long-term risks of gestational hypertension and preeclampsia. Although maternity care providers stated that they inform women with these conditions about their subsequent risks and recommend follow-up, only 36% usually inform the womens primary care providers about that subsequent risk. Only 58% of family physicians reported that they are usually informed by the maternity care providers about their patients who developed hypertension in pregnancy, compared with the 83% of maternity care providers who reported that they usually communicate this information to family physicians. CONCLUSION We have identified weaknesses in knowledge base and communication amongst Ontario maternity care providers that suggest that the identification and follow-up of women with hypertensive disorders of pregnancy is not occurring. These deficiencies would be amenable to directed educational activities, including reviews, presentations, and the development and implementation of guidelines.

A primary care pragmatic cluster randomized trial of the use of home blood pressure monitoring on blood pressure levels in hypertensive patients with above target blood pressure

BACKGROUND The measurement of blood pressure (BP) at home by patients with hypertension is increasingly used to assess and monitor BP. Evidence for its effectiveness in improving BP control is mixed. METHODS To determine if home BP monitoring improves BP a pragmatic cluster randomized contolled trial was carried out in family practices in southeastern Ontario, Canada. Family practice patients with uncontrolled hypertension were recruited to the trail. Patients were divided into two groups: one with at least weekly measurements of BP at home, recording those measurements and showing those to the family physician during office visits for hypertension and the control group were given usual care. The primary outcome was mean awake BP on ambulatory monitoring at 6- and 12-month follow-up and the secondary outcomes were mean BP on full 24-hour ambulatory blood pressure monitoring (ABPM), mean sleep BP on ABPM and BP on the BpTRU device, all at 6- and 12-month follow-up. RESULTS Home BP monitoring did not improve BP compared to usual care at 12-month follow-up: mean awake systolic BP on ABPM [141.1 versus 142.8 mmHg, mean difference 1.7 mmHg; 95% confidence interval (CI) -0.6 to 4.0, P = 0.314] and mean awake diastolic BP on ABPM (78.7 versus 79.4 mmHg, mean difference 0.7 mmHg; 95% CI -7.7 to 9.1, P = 0.398). Similar negative results were obtained for men and women separately. However, outcomes using the full 24-hour ABPM and the BpTRU device showed a significantly lower diastolic BP at 12 months. When analysis was done by sex, this effect was shown to be only in men. CONCLUSION Home BP monitoring may improve BP control in men with hypertension.

Prevention and Reduction of Obesity through Active Living (PROACTIVE): rationale, design and methods

The Prevention and Reduction of Obesity through Active Living (PROACTIVE) is a randomised controlled trial to evaluate the effectiveness of a behaviourally based physical activity and diet composition programme to prevent and reduce obesity and related comorbidities in a primary healthcare setting. 491 abdominally obese men and women 25–75 years of age who were patients of primary care physicians were randomly assigned to either a usual care group (N  =  242) or a behavioural intervention group (N  =  249). Those in usual care received general advice from the physician regarding the merits of physical activity and a healthy diet as a strategy for obesity reduction. Those in the behavioural intervention group received an individually designed counselling programme from a specially trained health educator, with respect to physical activity, diet and obesity reduction. The study was designed to provide 95% power in both men and women to detect a 2% (2 cm) difference in waist circumference and 80% power to identify a 15% reduction in the prevalence of the metabolic syndrome, the two primary outcomes. PROACTIVE is the first behavioural intervention study to assess the effects of physical activity and diet on abdominal obesity and associated metabolic risk factors in a primary healthcare setting, include a generalised sample of men and women and examine long-term (24 months) effects. PROACTIVE has the potential to provide the basis for changing clinical practice (primary care) with respect to the prevention and reduction of obesity and related health risks. The purpose of this report is to present and discuss the rationale, design and methods of PROACTIVE.

Effectiveness of a protocol-based strategy for achieving better blood pressure control in general practice.

BACKGROUND There continues be a problem with the proportion of treated hypertension patients who are actually at recommended blood pressure targets. OBJECTIVE Is an intensive protocol-based strategy for achieving blood pressure control effective in family practice and will family physicians and their hypertensive patients adhere to such a protocol. METHODS Design of the study is a cluster randomized controlled trial at the Centre for Studies in Primary Care, Queens University, Kingston, Ontario. Participants were 19 family physicians and 156 (98 intervention group and 58 control group) of their patients in and around the Kingston area. Patients were eligible if they had a diagnosis of hypertension and had not yet achieved their target blood pressure. Patients in the intervention group were managed according to a protocol that involved seeing their family doctor every 2 weeks over a 16-week period and having their antihypertensive medication regimen adjusted at each visit if target was not achieved. This was compared to usual care. Main outcomes were primary effectiveness outcome measured at 12 months was the differences in blood pressure between baseline and 12 months in the two groups. Secondary effectiveness outcomes included rates of achieving BP target and compliance with protocol by physicians and patients. Adherence outcomes were assessed by determining the number of visits made during the 16-week intervention period and the increase in the number of drugs being used. RESULTS Of the patients enrolled, 72 (74%) from the intervention group and 41 (71%) in the control group were available for analysis. Improvement between baseline and 12-month follow-up was significantly better for the intervention group than the control for diastolic mean daytime BP on 24 hours ambulatory blood pressure monitoring (4.5 mmHg reduction versus 0.5 mmHg reduction) and for both systolic (14.7 mmHg reduction versus 2.7 mmHg reduction) and diastolic (7.4 mmHg reduction versus 0.6 mmHg increase) blood pressure on BpTRU. Of the 98 patients in the intervention, 80% attended four or more of the eight visits and 25% attended all eight visits; physicians increased the number or dosage of drugs the patient was taking in 52% of the visits. Conclusions. An intensive, protocol-based, management approach to achieving blood pressure control in hypertensive patients in family practice is effective and works even when there is flexibility built into the algorithm to allow family physicians to use their judgement in individual patients.

Spouse Abuse in Pregnancy: A Survey of Physicians’ Attitudes and Interventions

Abstract Spouse abuse is a pervasive social and medical issue. Pregnant women are noted to be a population at especially high risk or such violence. The objective of this prospective, cross-sectional investigation was to survey physicians involved in the care of pregnant women on issues of spouse abuse during pregnancy. An anonymous self-reporting questionnaire was mailed to 128 family physicians and obstetricians known to provide antepartum and/or intrapartum care to the greater Kingston area. A response rate of 53.9 percent was achieved. While most physicians were knowledgeable about domestic violence and provided appropriate interventions or abused women they rated their competency in this area as low. Continuing medical education was rated to be helpful and used by most physicians. Fewer than 10 percent of physicians always screen pregnant patients for spouse abuse.