Can diagnostic criteria be developed for cellulitis of the lower limb, that are valid and suitable for use in a primary care setting?

Problem

Cellulitis is an acute bacterial inflammation of the dermis and associated subcutaneous tissue, occurring when organisms enter through a break in the skin and present as a tender, swollen, erythematous area of skin. 60% of cases of cellulitis affect the lower limb, recurrence is 40% and healthcare costs estimated at £96.6 million per year. However, the diagnosis of cellulitis can be challenging, with over 25% of presentations diagnosed as lower limb cellulitis incorrectly. Traditional biochemical tests are not specific for cellulitis and cultures are often not positive, or colonized with agents not causing the cellulitis. A recent cellulitis research priority setting partnership, which included patients, carers and health care professionals, ranked questions on ‘diagnosis' and 'diagnostic criteria' as the top ranked questions overall for future research on cellulitis. The Eron, Dundee and CREST classifications help to guide treatment choice and admission. However, currently, no diagnostic criteria for cellulitis are available in the UK. Improving diagnostic precision could help prevent unnecessary inpatient hospital admissions and ensure patients get the most appropriate treatment for their condition, reducing unnecessary antibiotic use. In addition, definitive diagnostic criteria would provide a key role in improving clinical research on cellulitis. This was highlighted by a systematic review showing that overall antibiotic treatment failure occurred in 12% of clinically evaluable patients recruited with cellulitis. The aim is to develop diagnostic criteria for cellulitis of the lower limb, suitable for use in primary care.

Approach

A series of linked projects will be conducted. Initially a scoping review establishing barriers and facilitators for implementation of a diagnostic criteria for lower limb cellulitis (currently being undertaken). This leads onto a systematic review identifying diagnostic criteria and tools developed or validated to aid the diagnosis of lower limb cellulitis (currently being undertaken). Following this, a mixed methods qualitative study with patients and healthcare professionals to inform development of a diagnostic criteria will be completed. Subsequently, an international e-Delphi consensus study to define the provisional diagnostic set will be undertaken before preliminary testing of the diagnostic criteria / tool using a case-controlled diagnostic accuracy study.

Findings

The scoping review identified 3926 records from database searching, with 533 eligible for full text data extraction. Key themes of misdiagnosis and training/services to aid diagnosis of lower limb cellulitis which will be further explored. The systematic review identified 13955 records from database searching, with 35 papers currently being full text screened.

Consequences

Improving diagnostic precision for lower limb cellulitis is important as it would help reduce the rate of misdiagnosis and prevent unnecessary inpatient hospital admissions. Furthermore, a defined criteria would attenuate unnecessary antibiotic use, which is a key driver in the development of antimicrobial resistance and provide a key role in improving clinical research on cellulitis.