Clinical research in obstetrics and gynecology: a Baedeker for busy clinicians

Magic Mirror, on the Wall-Which Is the Right Study Design of Them All?-Part I

The assessment of a new or existing treatment or intervention typically answers 1 of 3 research-related questions: (1) "Can it work?" (efficacy); (2) "Does it work?" (effectiveness); and (3) "Is it worth it?" (efficiency or cost-effectiveness). There are a number of study designs that on a situational basis are appropriate to apply in conducting research. These study designs are classified as experimental, quasi-experimental, or observational, with observational studies being further divided into descriptive and analytic categories. This first of a 2-part statistical tutorial reviews these 3 salient research questions and describes a subset of the most common types of experimental and quasi-experimental study design. Attention is focused on the strengths and weaknesses of each study design to assist in choosing which is appropriate for a given study objective and hypothesis as well as the particular study setting and available resources and data. Specific studies and papers are highlighted as examples of a well-chosen, clearly stated, and properly executed study design type.

Outcome assessment with blinded versus unblinded POP-Q exams

OBJECTIVE

To determine whether blinded and unblinded Pelvic Organ Prolapse Quantification (POP-Q) examinations differ in a randomized trial.

STUDY DESIGN

Blinded POP-Q examinations performed at 3 months and 1 year were compared with unblinded examinations performed by the surgeon in a randomized trial of vaginal mesh for pelvic organ prolapse.

RESULTS

Sixty-five patients were included in the study. Correlations between the blinded and unblinded POP-Q points and stages varied from low to moderate (rho = 0.29-0.78). At 3 months, the blinded overall prolapse recurrence rate was 45.3% compared with 39.1% based on unblinded staging (P = .34). At 1 year, the blinded overall recurrence rate was significantly higher than the unblinded recurrence rate: 68.3% vs 53.3% (P = .004). The 1-year blinded anterior wall recurrence rate was also higher than the recurrence based on unblinded staging: 56.7% vs 43.3% (P = .021).

CONCLUSION

Use of unblinded POP-Q staging resulted in underestimation of 1-year overall recurrence after prolapse repair.

Statistical analysis and interpretation of prenatal diagnostic imaging studies, part 3: approach to study design

A critical step in planning a successful study is choosing the appropriate design to feasibly answer the clinical question at hand. We provide an overview of common study designs, discuss their advantages and disadvantages, and provide practical examples from the prenatal diagnosis and ultrasound literature. In addition, we highlight specific design considerations that need to be built into the analysis of study results.