The aim of this study was to assess the inter-rater and test-retest reliability of the FPI-6 and NDT in a healthy adult population. Reliability was evaluated for both physiotherapy students and experienced physiotherapists.
Twenty participants (7 women), aged 25 to 63 and without any foot pain or issues, were recruited through a convenience sample. Participants were assessed in two separate sessions, 6–7 days apart. The FPI-6 and NDT assessments were conducted by three different raters, none of whom had prior experience using these clinical tests. Intraclass correlation coefficients (ICCs), along with 95% confidence intervals (95% CI) and the standard error of measurement (SEM), were calculated to determine reliability.
For the FPI-6, inter-rater reliability ranged from poor to good, with higher ICC values between the two experienced physiotherapists (ICC 0.839) and lower ICCs between the student and experienced physiotherapists (ICC 0.425–0.517). Test-retest reliability for the FPI-6 ranged from moderate to excellent, with higher ICCs for the physiotherapists (ICC 0.915–0.920) and lower for the student (ICC 0.683). In contrast, for the NDT, inter-rater reliability ranged from poor to moderate (ICC 0.141–0.573), and test-retest reliability also ranged from poor to moderate (ICC 0.378–0.565).
The results indicate that FPI-6 is a reliable test, also among inexperienced evaluators whereas the NDT demonstrated poor reliability. Regarding NDT, the test needs to be better standardized. Overall, the experienced physiotherapists showed higher reliability. Future research should focus on examining reliability in different populations with foot and ankle problems and involving raters with varying levels of clinical experience.
The FPI-6 can be a valuable tool for systematically assessing foot posture in physiotherapy practice. It may also be useful in the education and training of physiotherapy students.
psychometric properties
clinical tests
