OVER 96% PASS RATE FOR THE NCS, OCS, AND PCS EXAMS › forums › PCS Advantage › number 20 stats question
The explanation of this question seems to differ from the “level of Evidence” table in the handout. Can you explain a bit more on the multiple baseline studies.
0. When a randomized controlled clinical trial is unavailable to provide evidence to support a physical therapy intervention, which would provide the next best level of evidence?
a. Comprehensive literature review
b. Series of case studies using 5 children
c. Single subject multiple baseline design
d. Cohort nonrandomized design
Cohort nonrandomized designs are level III research. Comprehensive literature reviews and series of case studies are level V research. Single subject multiple baseline studies are level IV research.
In a multiple baseline study, the “baseline” state of a patient is recorded before the experimental treatment is completed. Changes between the baseline and then the response to treatment are then evaluated. The baseline for the patient is then recorded again before another experimental treatment is completed. This allows the experimenter to account for change over time and change due to the first experimental treatment without it affecting the second treatment they are implementing.
Level of Evidence Study Design/Methodology of articles
I Systematic reviews, meta-analysis, randomized controlled trials
II Two groups, non-randomized studies (ex. cohort, case-control)
III One group, non-randomized (ex. before and after, pretest and post-test)
IV Descriptive studies that include analysis of outcomes (ex. single subject design, case series)
V Case reports and expert opinion, which include narrative literature reviews and consensus statements.
Sorry for the confusion. We used a different resource when writing this question, however, this is a good example of some differences in interpretation for levels of evidence. A non-randomized cohort design is sometimes considered a lower quality level II, however, for the purposes of this question, it is a higher level than the others (so is the correct answer). There is a cohort (not single subjects) and at least 2 groups, since the design is non-randomized (group assignment is not randomized). This makes for a stronger design than a case series as there is a comparison group.
Literature reviews are merely summaries of what is published on the topic; a systematic review or a meta-analysis, however, are stronger designs if they analyze and interpret data from multiple studies.
Case studies are usually level V, unless they have been grouped and analyzed as a series.
A multiple baseline design is a single subject research design where the subject serves as it’s own control. The researcher measures the baseline status of a trait of interest (such as walking speed), then applies a treatment before measuring that trait again. A stronger design will repeat this process and have multiple measurements along a continuum of intervention and no intervention periods. The term “multiple baselines” refers to the multiple measurements of the trait taken along the course of the study. If the exact design is used across 3 or more subjects and the data is analyzed collectively, the strength of the study increases.
Hope this helps!