Background/Aims: Diabetic foot ulcers (DFU) negatively affect the quality of life (QoL) of people with diabetes. The Lower Extremity Functional Scale (LEFS) is a patient-reported outcome measure (PROM) for measuring physical functioning in patients with lower extremity disorders. It consists of 20 items and can distinguish between pain and function. To date, the LEFS is not yet validated for assessing functional impairment of foot and ankle in diabetic foot conditions. This study aimed to validate the LEFS questionnaire for Flemish Dutch-speaking patients with DFU in Belgium.

Methods: This observational cohort study included 100 patients with DFU from the multidisciplinary diabetic foot clinic of Onze-Lieve-Vrouw Hospital Aalst, Belgium. Reliability was assessed through the test-retest reliability (intraclass correlation coefficient (ICC)), internal consistency (Cronbach’s alpha) and measurement error (agreement). Spearman’s correlations and known-group comparisons were conducted to examine construct validity. Correlation with EQ-5D-5L was used to test criterion validity. The full study protocol has been published earlier (Rezaie et al. 2019. doi:10.1136/bmjopen-2019-034491).

Results: The majority of the patients were men (71.1%), with a mean age of 67.7±10.3 years and mean diabetes duration of 20.1±12.5 years. 81 patients (83.5%) had type 2 diabetes. Ischemia was present in 31.7% of the patients, neuropathy in 88.5%. Most DFU were deep (93.2%) and showed signs of infection (60,6%). ICC of the LEFS questionnaire was 0.85 (95% CI 0.75-0.91). Cronbach’s alpha equaled 0.95. Agreement was 4.55. No floor or ceiling effect was observed. Only 1 of the 6 predefined hypotheses to determine the construct validity of LEFS was confirmed (17%). The LEFS score showed a strong correlation with the EQ-5D-5L index value (p<0.0001) and a moderate correlation with the EQ-5D-5L visual analytical scale (p<0.0001). The LEFS score was not sensitive to ulcer changes over time.

Conclusions: The Flemish-Dutch version of the LEFS questionnaire has good reliability properties and criterion validity could be confirmed. However, the construct validity was not optimal and the scale was not sensitive to ulcer change during follow-up in our patient population. The LEFS provided only minor relevant additional information on quality of life beyond the general EQ-5D-5L.