Red Leg Dilemma: Development and Validation of Clinical Decision Tools for Non-Necrotizing Bacterial Dermohypodermitis, Necrotizing Fasciitis, and Eczematous Dermatitis

BackgroundDiagnosing red legs on first presentation is challenging. There exists a lack of robustly developed and validated diagnostic red leg tools in clinical practice. Physicians fear missing cases of infectious red legs and treat many patients unnecessarily with antibiotics.ObjectiveDevelop and validate easy-to-use diagnostic tools applicable at bedside of patients to orient diagnosis of the commonest and most serious causes of infectious red legs (non-necrotizing bacterial dermohypodermitis (NNBDH), and necrotizing fasciitis (NF)) versus the commonest inflammatory cause (eczema).MethodsWe collected data of patients presenting to our dermatology department from January first 2012 until May 17th 2017 with a diagnosis of red leg. Three models were developed using fast frugal trees. Validation was performed in a second cohort of patients.ResultsA total of 187 patients (mean age 56, SD = 21 years, 48.1% women) were included in the development phase and 62 patients (mean age 64, SD = 19, 52% women) in the validation phase. In the validation data set, sensitivity and specificity were respectively 67% and 91% for NNBDH, 83% and 66%, for NF and 88% and 93%, for eczema.ConclusionPresentations of suspected lower-limb infections are commonly misdiagnosed, resulting in avoidable antibiotic prescription and hospitalization. We developed an easy-to-use clinical diagnostic tool applicable at the bedside of patients to help orient physicians in certain situations and avoid unnecessary initiation of antibiotics. Future work should focus on validating this tool in primary care to minimize misdiagnosis of red legs and overprescription of antibiotics.