Objectives: Differentiating cellulitis from pseudocellulitis is challenging and misdiagnosis leads to unnecessary antimicrobial use and increased healthcare expenditures. Clinical diagnosis remains the criterion standard and may involve expert consultation. Our objective was to evaluate the utility of a handheld infrared thermometer to improve diagnostic certainty in cases of suspected cellulitis.
Methods: We conducted a cross-sectional study from August 2018 to January 2020 at a tertiary care hospital in Montreal, Canada, and enrolled adult patients with suspected limb cellulitis. Using the infrared thermometer, we compared the average temperature of the affected area with the contralateral limb and used Youden's method to determine the optimal temperature difference which best differentiated cellulitis from pseudocellulitis as determined by an independent and blinded infectious diseases specialist. We used bootstrapping to estimate 95% confidence intervals for the sensitivity, specificity and the area under the receiver operating curve.
Results: Of 65 patients screened for enrolment, a total of 52 patients were recruited (median age: 64 years, IQR 52-76). 39 were diagnosed with cellulitis and 13 were not. The mean temperature difference between affected and unaffected limbs was 2.6oC (95% CI 2.1 oC - 3.1oC) for patients with cellulitis and 0.4oC (95% CI -1.2ºC - 2.1ºC) for patients without (p<0.001). An average temperature difference between limbs of 0.8oC or more was 95% sensitive (95% CI 74%-100%) and 69% specific (95% CI 44%-95%) for the diagnosis of cellulitis (c-statistic 0.82).
Conclusions: In this proof of concept single-centre study, a handheld infrared thermometer was a useful adjunct to differentiate cellulitis from pseudocellulitis.
Study registration: NCT03846635.
Keywords: Cellulitis; Infrared thermometer; Pseudocellulitis.
Copyright © 2021 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.