Inexperienced examiners and the Foot Posture Index: A reliability study

Highlights

• The FPI-6 is reliable when used by novice examiners.

• Experience, even limited, in musculoskeletal assessment is of benefit.

• The reliable use of the FPI-6 is not restricted to podiatrists.

Abstract

The Foot Posture Index (FPI-6) is a reliable (experienced examiners) assessment tool used in clinical practice to classify foot posture. No work has been completed to determine the reliability of the FPI-6 between novice examiners. Therefore, the aim was to determine the inter-examiner reliability of the FPI-6 using two novice examiners (graduate level osteopathy students). The FPI-6 was used to classify the feet of 83 students recruited as part of a larger study. Data were collected simultaneously by both examiners, but there was no communication between them. The scoring system provided by the FPI-6 manual was used to assess all feet. Collated data were assessed between examiners for reliability based on raw, transformed and foot type scores. The inter-examiner reliability was high for both left (intra-class correlation coefficient ICC_2,1 = 0.86) and right (ICC_2,1 = 0.85) feet for the novice examiners. When data were assessed based on foot type classification the examiners agreed on 76% of the left feet and 82% of the right feet with Kappa values of 0.73 and 0.72 respectively. The FPI-6 is a robust clinical tool that can be reliably utilised by inexperienced clinicians.

Introduction

The Foot Posture Index (FPI-6) is a clinical assessment tool used to classify foot posture. Developed by Redmond et al. (2006), the FPI-6 is predominantly used in podiatry, but has applications across manual therapy. The tool requires the subjective assessment of six parameters of the foot/ankle complex whilst the patient stands bilaterally in a static position. Redmond et al. (2008) have reported descriptive norms pooled from various data collection centres. These normative values indicate a value of +4 (slightly pronated foot) is the most common foot type classification.

The FPI-6 has been shown to possess good inter-examiner reliability between experienced clinicians (Morrison and Ferrari, 2009; weighted kappa (Kw) = 0.86), with lower reliability between clinicians of different levels of experience (Cornwall et al., 2008; intra-class correlation coefficient ICC = 0.52–0.62, Evans et al., 2012; ICC = 0.71–0.86). The subjectivity of the examiner influences the final score and therefore classification of foot type. When two or more examiners assess the same patient, this subjectivity has an influence on the perceived reliability of the FPI-6. Inter-examiner reliability of the FPI-6 is the focus of the current paper as previous studies have demonstrated high intra-examiner reliability (>0.90) regardless of experience level (Cornwall et al., 2008, Evans et al., 2012). Evans et al. (2012) demonstrated substantial to almost perfect agreement between an experienced and novice clinician for analysis of children's feet using FPI-6. As yet, no previous work has assessed inter-examiner reliability using novice clinicians only.