To determine the intratester reliability of the 18-site 10-g monofilament test, the average intratester reliability value from model 3 of the ICC was computed using SPSS, version 17.0 (SPSS Inc, Chicago, Illinois).29 To determine intertester reliability for the 3 testers, model 2 of the ICC was used.29 Interpretation of the ICC values for this study follows commonly used grouping, where an ICC value of less than 0.40 indicates poor reproducibility, ICC values in the range 0.40 to 0.75 indicate fair to good reproducibility, and an ICC value of greater than 0.75 shows excellent reproducibility.30 Using the reliability value from the intertester ICC, the Standard Error of Measurement (SEM) was calculated with the following formula:29
Results from the present study support other studies indicating that the 10-g monofilament is a reliable tool. Also, responsiveness of the tool using MDC95 in an 18-site examination was assessed. A 3-site change in protective sensation was determined to be the MDC at a 95% confidence interval on an individual level. Therefore, when performing an 18-site examination of protective sensation using the 10-g monofilament, a change in 3 or more sites would allow the clinician to be 95% confident an actual change in protective sensation had occurred. This allows for more accurate and confident referral, client education, and disease progression or regression measurement.
A limitation of this study may be that only 1 touch of the monofilament per test site was performed during testing. While this was according to the manufacturers' instructions, other researchers have used up to 10 touches per test site before a determination was made on the sensation of that site.9,13–16,19,25,32,33 The authors recommend that each site be tested 3 times and the best 2 of the 3 responses be used to score the site as described by other researchers.19 The participants in this study demonstrated experimenter expectancy33 by occasionally saying “yes,” when the monofilament was not in contact with the skin. In future studies, the authors recommend that participants be asked to point to the foot location on a diagram where they felt the monofilament.
Also, it may have been difficult for multiple testers to consistently place the monofilament in exactly the same test location. In future studies, drawing circles or dots around or on site locations on the participants' feet before testing may help to reduce or eliminate intertester inaccuracy when placing the monofilament.
An 18-site 10-g monofilament examination demonstrated good reliability and had an individual MDC95 of 3 sites for the participant pool in this study. By repeating the examination over time and comparing the results, clinicians can be confident that a change in protective sensation at 3 or more sites on the 18-site examination represents actual improvement or decline in the protective sensation of their individual clients.
The authors thank Merrill Landers, PT, DPT, for his assistance with the statistical analysis of this manuscript.
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monofilament; reliability; reproducibility; responsiveness; sensory