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Issues in planning a placebo-controlled trial of manual methods: results of a pilot study
Cheryl Hawk1, Cynthia R Long, Robert Reiter
1Palmer Center for Chiropractic Research, Davenport, IA 52803, USA. hawkcheryl@aol.com
Objective:
There are fundamental differences between the administration of medications and the application of manual procedures, such as those used by chiropractors. The objective of this study was to gather preliminary information on how to address these differences in the design of a multisite, randomized placebo-controlled trial of chiropractic care for women with chronic pelvic pain (CPP).
Design:
Pilot study for a multisite, randomized, placebo-controlled clinical trial.
Setting:
Three chiropractic research clinics in the midwest United States.
Subjects:
Thirty-nine (39) women with CPP of at least 6 months' duration, diagnosed by board-certified gynecologists.
Interventions:
The active intervention consisted of the chiropractic technique, lumbar spine flexion-distraction, combined with manual Trigger Point Therapy. The placebo intervention consisted of a sham chiropractic procedure performed with an instrument combined with effleurage (light massage).
Outcome Measures:
The primary outcome measure was the change in the Pain Disability Index (PDI) from baseline to the end of treatment (6 weeks), assessed by group and site. If the change score was in the same direction at all sites, the results were to be combined to estimate treatment effect size.
Results:
Patient characteristics were similar to those of patients with CPP in other studies. Recruitment methods, particularly in respect to the eligibility criteria and screening protocols, would require modification in order to recruit an adequate sample for the planned randomized controlled trial. Clinicians followed standardized procedures with apparently minimal deviation, patients in both groups were satisfied with their care and blinding appeared to be successful. PDI change scores were not consistent across sites and so results were not combined and overall treatment effect sizes were not estimated.
Conclusions:
The technical and personnel resources required to achieve adequate standardization of procedures at multiple sites may make a placebo-controlled trial unfeasible, given our current lack of knowledge about the active agent in manual chiropractic procedures.