Measurement Errors of a Test to Determine the Scapular Position Using a Tape Measure

[Purpose] Investigation of intra- and inter- measurer errors employing a scapular position measurement method using a tape measure designed by us. [Methods] Two measurers, a physical therapist (RPT) and a student on a physical therapist training course (PTS), measured the scapular position relative to the spine twice using a tape measure, and intra- and inter- measurer measurement errors were investigated. For statistical analysis, Bland-Altman analysis was employed. The limits of agreement (LOA) were determined when a systematic error was present, and the 95% confidence interval of the minimal detectable change (MDC95) was calculated when no systematic error was detected. The significance level was chosen as 5%. [Results] Regarding intra- measurer measurement error, the mean value of the second measurement was greater than that of the first. Regarding inter- measurer error, the mean value measured by PTS was lower than that measured by RPT. [Conclusion] The mean of the first measurement was greater than that of the second measurement as the intra- measurer measurement error of this measurement method, and the mean measured by PTS was lower than that measured by RPT, showing a fixed error. By sufficiently practicing the measurement and applying markers to the bone index points, the measurement error may become small enough to be clinically acceptable.