Diabetic Foot Scale-Short Form

Authors

Purpose

Generic quality-of-life instruments, such as the widely used SF-36, often lack the sensitivity needed to isolate the specific effects of diabetic foot ulcers from other diabetes-related complications. When a patient reports decreased physical functioning or emotional distress on a general survey, it can be difficult to determine whether these issues stem from their foot ulcer, neuropathy, retinopathy, or general metabolic decline. The DFS-SF addresses this critical measurement gap by providing a targeted, disease-specific assessment tool.

For clinicians and researchers, having a specialized instrument is essential for accurately tracking disease progression, evaluating the efficacy of wound care interventions, and understanding the patient's lived experience. The short-form version specifically minimizes respondent burden—a crucial consideration for patients who may already be experiencing significant fatigue and distress due to their medical condition.

Construct

The psychological and physical construct measured by the DFS-SF is the disease-specific Health-Related Quality of Life in individuals suffering from diabetic foot ulcers. This construct encompasses a multidimensional framework that goes beyond mere physical symptoms to include the emotional, social, and functional disruptions caused by chronic wounds. The scale operates on the theoretical premise that chronic, non-healing ulcers fundamentally alter a patient's daily life, self-care routines, and psychological stability.

The instrument is structured around six distinct factors that collectively map the patient's experience. While the overarching construct recognizes that Quality of life in this population is heavily influenced by factors such as ulcer size, infection status, and the psychological trauma associated with the fear of amputation, measuring these dimensions provides a holistic view of the patient's health status and functional impairment.

Validity

The validation of the Turkish DFS-SF involved a comprehensive, multi-faceted approach to ensure the tool accurately measures what it intends to measure. Content validity was initially established through expert review, yielding an excellent Content Validity Index of 0.93, which indicates that the translated items are highly relevant and culturally appropriate. To establish construct validity, the researchers utilized known-group comparisons, demonstrating that the scale could successfully differentiate between patients with varying severities of foot ulcers based on the Wagner classification system. Specifically, patients with more severe wounds reported significantly lower Quality of life, confirming the scale's clinical sensitivity.

Furthermore, concurrent validity was evaluated by comparing the DFS-SF scores with those from the SF-36, a gold-standard general health survey. The results showed moderate to strong positive correlations ranging from 0.43 to 0.76, indicating that while the DFS-SF aligns with general health constructs, it retains its unique disease-specific variance. This robust validity evidence confirms that the instrument is a highly capable tool for clinical assessment.

Convergent & Discriminant Validation Correlations

Reliability

Reliability testing focused primarily on the internal consistency of the scale, ensuring that the items within each subscale reliably measure the same underlying concept. The psychometric analysis revealed exceptionally strong internal consistency, with Cronbach's alpha coefficients ranging from 0.93 to 0.97 across the subscales. In psychometric terms, values above 0.80 are generally considered highly reliable, and the values observed here suggest excellent cohesion among the scale items.

Additionally, item-total correlations were examined to verify that each individual question meaningfully contributed to the overall measurement. These correlations ranged from 0.73 to 0.86, well above the standard acceptable threshold of 0.30. This indicates that no items needed to be removed or revised, and the translated instrument functions consistently and reliably when administered to Turkish-speaking patients.

Factor Analysis

To verify the structural integrity of the translated scale, the researchers employed both exploratory and confirmatory factor analyses (EFA and CFA). Relying solely on EFA is often insufficient for adapting established scales, so the inclusion of CFA provides a more rigorous test of the instrument's theoretical framework. The analysis successfully replicated the original six-factor structure of the DFS-SF, confirming that the conceptual dimensions of the scale remain stable across different cultural contexts.

The confirmatory factor analysis yielded strong fit indices, which are crucial metrics for evaluating how well the data fits the proposed model. The Comparative Fit Index (CFI) and Normed Fit Index (NFI) both fell within the acceptable range of 0.90 to 0.95. Additionally, the Root Mean Square Error of Approximation (RMSEA) was below the 0.08 threshold, and the chi-square to degrees of freedom ratio was under 3, indicating an excellent fit. These robust statistical markers demonstrate that the items map accurately onto their respective factors, validating the multidimensional architecture of the scale.

Instrument

Diabetic Foot Scale-Short Form Items

Sample

174 Turkish patients with diabetic foot ulcers (mean age 59.35 ± 8.55 years; 63.2% male; 97.1% type 2 diabetes), recruited from an inpatient hospital setting between March and December 2020.