This feasibility and pilot study has two aims. The primary aim is to assess the feasibility of collecting clinical, nutritional, and functional data among adults with diabetic foot ulcers (DFUs) who are treated at an outpatient wound clinic. Specifically, the study will evaluate recruitment and inclusion rates, the relevance and clinical utility of selected variables, and assess the completeness and reliability of data collection.

The secondary aim is to provide a preliminary characterisation of nutritional status, dietary intake, body composition, muscle strength, mobility, and wound-related quality of life, to inform the design and methodology of a future full-scale national study.

DFUs are associated with delayed healing, recurrent infections, reduced quality of life, and increased risk of hospitalization and amputation. These conditions are frequently accompanied by systemic inflammation, impaired circulation, and metabolic disturbances, which may increase nutritional requirements and negatively affect wound healing.

Despite nutrition being recognized as a modifiable factor of ulcer healing, the nutritional status of individuals with DFUs remains insufficiently characterised, and evidence regarding clinically relevant nutritional deficiencies in this population is limited.

Participants will undergo assessment of height, weight, body composition, handgrip strength, and a 24-hour dietary recall interview during an outpatient clinic visit. Nutritional screening questionnaires and patient-reported measures of appetite, nutritional impact symptoms, mobility, and quality of life will be collected through telephone interviews within one week of the clinical visit.

Eligible participants are adults (>18 years) who are referred to the outpatient wound clinic with a hard-to-heal foot ulcer. Participants must be able to communicate in Danish or English.

Background Diabetic Foot Ulcers (DFUs) affect up to one third of individuals with diabetes and are associated with systemic inflammation, impaired circulation, and metabolic disturbances that may increase nutritional requirements and may impair collagen synthesis, immune function, and tissue repair in the foot ulcer. Despite nutrition being recognized as a modifiable factor in the ulcer healing process, the nutritional status of individuals with DFUs remains insufficiently characterized, and evidence regarding clinically relevant nutritional deficiencies in this population is limited. This feasibility and pilot study is designed to test the data collection procedure and generate preliminary descriptive data on nutritional status in a Danish outpatient population, in preparation for a future full-scale multicentre study.

Study Setting and Design Prospective observational feasibility and pilot study conducted at the Wound Outpatient Clinic, Department of Orthopaedic Surgery, Hvidovre Hospital, Denmark. Data are collected at two time points: a scheduled outpatient visit (Baseline) and a telephone interview within one week.

Recruitment Eligible patients are identified through the scheduled appointment list on designated inclusion days (Monday and Wednesdays). Wound care nurses review referrals in the electronic health record system prior to each clinic day and identify potentially eligible patients in collaboration with the research team. Upon arrival, patients are informed about the opportunity to participate in a research study and if patients express interest the researcher will provide oral and written information. Written informed consent is obtained prior to any data collection.

Data collected during the outpatient visit - Baseline:

• Anthropometry: (height, weight, BMI). If the participant is unable to stand upright, height is estimated from knee-to-heel length or fingertip-to-sternum distance (estimated 5 minutes)
• Body composition: bioelectrical impedance analysis (BIA) using the InBody S10, measuring muscle mass, fat percentage, and fluid balance. Performed between wound dressing removal and re-application. Omitted in participants with implanted electronic devices; mid-upper arm muscle circumference (MAMC) used as surrogate where BIA is not feasible (estimated 10 minutes)
• Muscle strength: Handgrip dynamometry, three maximal attempts with dominant hand, highest value recorded (estimated 10 minutes)
• Dietary intake: 24-hour dietary recall interview assessing all foods and beverages consumed in the preceding 24 hours. Portion sizes estimated using standardised photographic aids (Technical University of Denmark (DTU): National Dietary Survey) (estimated duration: 40 minutes). Macro- and micronutrient intake are calculated using www.Vitakost.dk

Data collected during telephone follow-up (Within One Week)

• Malnutrition is diagnosed according to the Global Leadership Initiative on Malnutrition (GLIM), requiring at least one phenotypic criterion (low muscle mass by BIA or MAMC, low BMI, or unintentional weight loss) and one etiologic criterion. In this pilot study, the etiologic criterion will be based solely on reduced food intake or assimilation, assessed by 24-hour dietary recall and the presence of nutritional impact symptoms (NIS). Inflammatory markers are not available as routine clinical data in this outpatient setting and will not be included in GLIM classification. The availability and accessibility of routine biochemical data will be assessed as part of the feasibility evaluation to inform data collection procedures for the future full-scale study.
• NIS factors: The Patient-Generated Subjective Global Assessment Short Form (PG-SGA SF, Box 3) will be used to identify symptoms impairing food intake, including nausea, vomiting, diarrhoea, constipation, mouth sores, dry mouth, pain, taste changes, and reduced appetite. NIS data will contribute to the etiologic criterion of reduced food intake or assimilation within the GLIM malnutrition assessment
• Physical activity and mobility: (Life-Space Assessment- Denmark, LSA-DK) assessing mobility range inside and outside the home over the preceding four weeks
• Wound-related quality of life: Wound-QoL questionnaire, covering physical, psychological, and everyday life domains. Scored according to the Wound-QoL scoring manual; higher scores indicate greater impairment
• Demographic data: age, sex, ethnic background, marital status, living situation, educational level, work status, and need for community care or nursing.
• Clinical data include comorbidity burden assessed using the Charlson Comorbidity Index, diabetes type and duration, latest glycated haemoglobin (HbA1c) value, smoking status, foot deformities, previous foot ulceration, number of active ulcers, previous ulcer healing and recurrence, antibiotic treatment related to the foot ulcer, and symptoms of infections (fever).

Data management All data are recorded in REDCap, supported by the Centre for IT, Medico and Telematic Services (CIMT), Capital Region of Denmark, in accordance with approval from the Danish Data Protection Agency.

Statistical analysis Feasibility outcomes will be reported as proportions with 95% confidence intervals, evaluated against an a priori success threshold of ≥70% protocol completion. Continuous variables will be summarised as means ± Standard Deviation (SD) or medians with Interquartile Range (IQR). Nutritional status will be classified according to the GLIM criteria. Associations between nutritional variables are exploratory and hypothesis-generating.

Sample Size A formal sample size calculation is not applicable. A sample of 30 participants is sufficient to assess recruitment feasibility and generate preliminary descriptive data, consistent with recommendations for pilot studies

Inclusion Criteria:

• Age ≥ 18 years
• Diagnosed with diabetes type 1 or type 2
• Presence of one or more DFUs
• Receiving treatment in a participating outpatient wound clinic
• Able to provide written informed consent

Exclusion Criteria:

• Above ankle amputation of the contralateral leg
• Current treatment with intravenous antibiotics for acute infection.
• Current hospitalisation for acute surgical management of the foot ulcer
• Declining or unable to participate in a telephone follow-up interview.
• Current long-term enteral (tube feeding) or parenteral nutritional support.

Exclusion criteria for bioelectrical impedance analysis (BIA)

- Presence of a cardiac pacemaker or other implanted electronic device

Adult patients with non-healing diabetic foot ulcers (DFUs) receiving treatment at the outpatient clinic at Hvidovre Hospital.

Anonymised study data may be shared with Danish researchers working within the same field, subject to the establishment of a formal data sharing agreement in accordance with the Danish Act on Processing of Personal Data (Databeskyttelsesloven) and the General Data Protection Regulation (GDPR). Data sharing will not be initiated prior to the completion of such an agreement.