Reliability and validity of Foot Posture Index (FPI-6) for evaluating foot posture in participants with low back pain

Authors：Yang, Jiaman; Ou, Zhiwen; Mao, Zhitao; Wang, Yi; Zhong, Yiheng; Dong, Wei; Shen, Zhen^*; Chen, Zehua^*

Source：Scientific Reports, 2022, 12(1): 21168.

DOI：10.1038/s41598-022-22220-1

• INTRACLASS CORRELATION-COEFFICIENTS
• MINIMAL DETECTABLE CHANGE
• INTERRATER RELIABILITY
• VALIDATION
• DISABILITY

Previous studies have demonstrated that Foot Posture Index (FPI-6) is a valid and moderately reliable tool to evaluate foot posture. However, data about reliability and validity of FPI-6 in the assessment of foot posture in people with low back pain (LBP) is lacking. To investigate reliability and validity of FPI-6 in the assessment of foot posture in people with LBP. Thirty volunteers with LBP, aged 20-64 years, were recruited for the research and assessed by two raters. The data measured by different raters on the same day were used to calculate the inter-rater reliability. The data measured by the same rater on different dates were used to calculate the test-retest reliability. The reliability of FPI-6 was tested with intraclass correlation coefficient (ICC), and absolute reliability with standard error of measurement (SEM), minimal detectable change (MDC) and Bland-Altman analysis. The validity of FPI-6 was tested with Exploratory Factor Analysis (EFA) and Spearman's correlation coefficients. The FPI-6 indicated excellent inter-rater and test-retest reliability in the evaluation of foot posture in people with LBP (ICC=0.97 and 0.95). The agreement for inter-rater and test-retest was excellent based on the SEM (SEM=0.12) and MDC value (MDC=0.33). Bland-Altman plots showed that there was no significant systematic bias for the agreement on the ground of low mean difference (<1). The EFA suggested that the fit indices were considered acceptable according to the Kaiser-Meyer-Olkin (KMO) value (KMO=0.620) and Bartlett's sphericity test (P<0.01). There was a statistically significant positive correlation between each item and total score of FPI-6 because the Spearman's correlation coefficient of six items were all>0.3 (P<0.01). The inter-rater and test-retest reliability and validity of FPI-6 on people with LBP were proved reliable. It might be considered a reliable and valid adjunctive tool to detect possible changes of foot posture after interventions in patients with LBP.

• Institution
  5; 云南大学