Rachelle Seguin

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.

Faculty's and residents' perceptions of teaching and evaluating the role of health advocate: a study at one Canadian university.

Purpose To examine the views of faculty and residents about teaching and evaluating health advocacy, one of the more difficult CanMEDS roles to integrate into postgraduate medical education. Method In 2002, two focus groups of faculty and two of residents at Queens University, Kingston, Ontario, Canada, were asked standardized questions to elicit their answers to what was a health care advocate as understood and reported by teachers and residents, and what were the reported barriers and enhancers to teaching and evaluating the role of residents as health care advocates. Results The study found that faculty and residents knew little about how to teach and evaluate the role of the health advocate. There was consensus between the two types of groups with congruity between residents and faculty about the key issues. The one exception to this was the disconnect between the faculty members’ belief that advocacy was an aspect of their daily work and the residents’ apparent lack of awareness of this. The majority of participants were not familiar with the Royal Colleges description of the role of health advocate and were very keen to receive further guidance on teaching tools and methods of evaluation. Conclusion The authors’ hypothesis was that little is known about how to teach and evaluate the role of the health advocate. The results confirmed this and identified important areas upon which to build an educational framework. The definition of the health advocate and the expectations require clarity and direction. Academic programs would benefit from clear objectives.

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.

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.

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.