Dianne Delva

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.

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.

A new model for collaborative continuing professional development

For collaborative patient-centered practice models to develop, improved collaboration in the workplace is needed. In this project we aimed to create a model of continuing professional development (CPD) using a case based approach that would allow the exchange of information between primary health care providers in the community. Over 60 participants from community care sectors including physicians, nurses and administrators participated in a planning group and two consultation workshops. Using participatory action research methods, themes contributing to and inhibiting communication, collaboration and coordination of care in the community were identified. Recommendations for solutions were prioritized and implemented. Evaluations suggest that the case scenario and consultation approach successfully focused participants to address relevant local issues to improve collaboration among community providers.