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

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.

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.

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.