The Personalised Antibiotic Duration for Cellulitis (PAD-C) Study (PAD-C)

The Personalised Antibiotic Duration for Cellulitis (PAD-C) Cohort Study

Cellulitis is an increasingly common and unpleasant bacterial infection of the skin, usually affecting the legs. Patients experience pain and swelling, loss of mobility, fever, and chills. Patients may be left with chronic skin damage and 1 in 5 experience recurrences.

Cellulitis is treated with antibiotics, but it is unclear as to how long treatment should be for. As a result, many patients get much longer antibiotic treatment than needed. This exposes patients to the risks of taking unnecessary antibiotics.

This study aims to find out what features of individual patients predict a good, sustained recovery from cellulitis. These may include medical conditions and clinical response to the first few days of antibiotic treatment, such as changes in skin temperature.

Patients who are being treated in hospital for cellulitis will be invited to take part. Information will be collected about patients who will be followed up for 3-6 months. Devices for measuring skin temperature will also be compared to see which one works best. This information will be used to help develop a set of rules that doctors can use to guide the length of antibiotic treatment. This should ensure that future patients receive the amount of antibiotics needed and no more.

Study Overview

• Status: Completed
• Conditions: Cellulitis; Cellulitis of Leg; Antibiotic Duration

Detailed Description

This study is a single centre prospective cohort study of patients with cellulitis of the lower limb. The primary objective of this study is to understand what features of individual patients predict a sustained recovery from cellulitis. This information will be used to test and refine a previously developed risk score that predicts clinical outcomes of patients with cellulitis.

Secondary objectives include investigating whether early response to antibiotic treatment (e.g. reduction in skin temperature and patient-reported symptoms) improves the predictive ability of the risk score. The study design also includes a nested technology comparison of temperature measurement devices to identify the best device for measuring affected skin temperature change in patients with cellulitis.

Clinical response will be measured for up to four days from starting antibiotic treatment. This includes the change in temperature and area of affected skin, physiological observations, blood test results (e.g. C-reactive protein) and patient-reported pain and swelling scores. Patients will be followed up at 28 and 90 days (+/- 180 days for those recruited in the first year) to assess recovery, recurrence, cellulitis-related mortality, quality of life, and return to normal activities.

• Study Type: Observational
• Enrollment (Actual): 230

Contacts and Locations

Study Locations

• United Kingdom
  • Brighton, United Kingdom
    • University Hospitals Sussex NHS Foundation Trust

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

Hospital-based or services delivering antibiotic treatment and ongoing follow-up regardless of location.

Description

Inclusion Criteria:

• Adults (age ≥18 years) identified by their treating clinician as having lower limb cellulitis that requires IV or oral antibiotic treatment either from the hospital or another service based outside of the hospital, which will conduct ongoing follow-up regardless of location.

Exclusion Criteria:

Patients:

• who have already received 3 or more calendar days of antibiotics from the hospital for cellulitis.
• receiving antibiotic therapy for another indication that is anticipated to continue for longer than the antibiotic treatment for cellulitis and that, in the judgement of the investigator, would impact the study assessments.
• for whom a surgical procedure to treat their cellulitis is planned (i.e. debridement of suspected necrotising skin / soft tissue infection).
• who, in the judgement of the investigator, do not have a clear diagnosis of cellulitis (to enable the exclusion of infections, such as severe/deep diabetic foot infection, which may be loosely labelled as cellulitis, but treated with different guideline antibiotic agents and durations).
• lack capacity to give informed consent to participate.
• are receiving end-of-life care.
• are already involved in a CTIMP of relevance to the treatment of their cellulitis.
• are unlikely, in the opinion of the investigator, to comply with study procedures.

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort
Population; Adults (age ≥18 years) identified by their treating clinician as having lower limb cellulitis that requires intravenous or oral antibiotic treatment either from the hospital or another service based outside of the hospital, which will conduct ongoing follow-up regardless of location.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Sustained Recovery	Number of Participants with Sustained Recovery	90 days

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Cellulitis-related Readmission	Number of participants with new hospital admission/reattendance containing a cellulitis diagnostic code	90 days
Recovery at 28 Days	Number of participants who recovered within 28 days (investigator assessed)	28 days
Patient-reported Recovery by 28 Days	Number of patients recovered within 28 days (patient-reported)	28 days
Time to Return to Work / Normal Activities	Number of patients who reported they had returned to work / normal activities within 90 days	Baseline to 90 days
Change in Physical Component Score Assessed Using the Medical Outcomes Study Short Form 12-Item Health Survey (SF-12)	The Medical Outcomes Study Short Form 12-Item Health Survey (SF-12) comprises a Physical Component Summary and a Mental Component Summary, each reported as norm-based scores (mean 50, SD 10; range 0-100), where higher values indicate better physical or mental health.	Baseline to 90 days
Change in Mental Component Score Assessed Using the Medical Outcomes Study Short Form 12-Item Health Survey (SF-12)	The Medical Outcomes Study Short Form 12-Item Health Survey (SF-12) comprises a Physical Component Summary and a Mental Component Summary, each reported as norm-based scores (mean 50, SD 10; range 0-100), where higher values indicate better physical or mental health.	Baseline to 90 days

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Repeatability Coefficient	Repeatability, defined as the consistency of measurements when taken repeatedly at short intervals by the same device under the same conditions, was assessed by calculating the repeatability coefficient. The repeatability coefficient and estimated 95% Confidence Interval were calculated from one temperature measurement and an instant repeated temperature measurement of the limb of interest on each participant on days 0, 1, 2, 3, all combined. The repeatability coefficient can be interpreted as the range (between the negative and positive values of the coefficient) within which the difference between any two repeated measurements on the same subject is expected to lie for 95% of subjects.	Measurements taken at 0 to 3 days
Limits of Agreement	The mean represents the estimated mean difference in affected-limb temperature between measurement methods; the reported 95% interval corresponds to the limits of agreement.	Measurements taken at 0 to 3 days

Collaborators and Investigators

• Sponsor: University of Sussex
• Investigators: Principal Investigator: Elizabeth LA Cross, University of Sussex

Study record dates

Study Major Dates

• Study Start (Actual): June 9, 2021
• Primary Completion (Actual): June 6, 2023
• Study Completion (Actual): September 2, 2023

Study Registration Dates

• First Submitted: August 12, 2021
• First Submitted That Met QC Criteria: August 20, 2021
• First Posted (Actual): August 26, 2021

Study Record Updates

• Last Update Posted (Actual): March 27, 2026
• Last Update Submitted That Met QC Criteria: March 25, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Keywords: Antibiotics; Cellulitis; Treatment duration; Treatment length
• Additional Relevant MeSH Terms: Pathologic Processes; Connective Tissue Diseases; Infections; Inflammation; Skin Diseases, Infectious; Suppuration; Pathological Conditions, Signs and Symptoms; Skin and Connective Tissue Diseases; Cellulitis
• Other Study ID Numbers: 081 CRO / 295690; NIHR300952 (Other Identifier: NIHR Doctoral Fellowship); 295690 (Other Grant/Funding Number: IRAS)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Anonymised study data is intended to be made available via an open access research database.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No