Dermatologic Involvement Improves the Diagnosis and Treatment of Patients With Presumed Cellulitis: A Randomized Clinical Trial

Abstract

Background: Each year, cellulitis leads to 650,000 hospital admissions and is estimated to cost $3.7 billion in the United States. Previous literature has demonstrated a high misdiagnosis rate for cellulitis, leading to unnecessary antibiotic use and health care cost. Purpose: In this study, we had three objectives – to determine whether dermatologic consultation decreases duration of hospital stay or intravenous antibiotic treatment duration in patients with cellulitis (Part I), to evaluate the cost and clinical utility of diagnostic imaging and blood cultures for cellulitis (Part II), and to assess whether thermal imaging is a viable way to streamline cellulitis diagnosis moving forward (Part III). Methods: This randomized clinical trial was conducted in a large urban tertiary care hospital between October 2012 and January 2017. Adult patients hospitalized with presumed diagnosis of cellulitis were eligible. Enrolled patients were randomized to the control group, which received the standard of care (i.e. treatment by primary medicine team), or the intervention group, which received dermatology consultation. Thermal images of affected and unaffected skin were obtained for each patient. Following hospitalization, patient demographics, hospital course information, and results of all laboratory, microbiological, and imaging studies were recorded via medical chart review in a retrospective fashion. Statistical analysis was employed to identify significant outcome differences between the groups and the main outcomes studied were length of hospital stay and duration of intravenous antibiotic treatment (Part I). Upon retrospective analysis, we quantified the total number and types of imaging modalities obtained for all patients, as well as the rate at which each test changed management. Using HeathCare Bluebook, we estimated the overall cost of diagnostic imaging and blood cultures in cellulitis diagnosis (Part II). Lastly, statistical analysis was performed on the thermal images of patients in the intervention group to establish a predictive model for the probability of cellulitis. This model was subsequently validated in the standard of care cohort (Part III). Results: We enrolled 175 patients, 70 (40%) were women and 105 (60%) were men. The mean age was 58.8 years. Length of hospital stay was not statistically different between the 2 groups. The duration of intravenous antibiotic treatment (<4 days: 86.4% vs 72.5%; absolute difference, 13.9%; 95% CI, 1.9%-25.9%; P = .04) and duration of total antibiotic treatment was significantly lower in patients who had early dermatology consultation (<10 days: 50.6% vs 32.5%, P = .01). Clinical improvement at 2 weeks was significantly higher for those in the intervention group (89.3% vs 68.3%; P < .001). Upon retrospective analysis, the rate of cellulitis misdiagnosis was 30.7% in the intervention group. 68% of the study population underwent ≥1 form of imaging, with imaging changing the management and/or diagnosis in 6.4% of patients who underwent scans. 33% of patients had blood cultures drawn, of which 1.7% were positive for microbial growth. The estimated national annual cost of imaging and blood cultures for cellulitis patients is $226.9 million dollars. Among those who were thermally imaged, cellulitis patients had an average affected skin temperature of 34.1°C, 3.7°C higher than the corresponding unaffected skin area (95%CI:2.7-4.8°C, p<0.00001). Pseudocellulitis patients had an average affected temperature of 31.5°C, 0.2°C higher than the corresponding unaffected area (95%CI:-1.1-1.5°C, p=0.44). Temperature differences between sites were higher in cellulitis patients than in pseudocellulitis patients (3.7 vs. 0.2°C, p=0.002). Using a logistic regression model, a skin temperature difference of ≥0.47°C conferred a sensitivity of 96.6%, specificity of 45.5%, PPV of 82.4%, and NPV of 83.3% for cellulitis diagnosis. This model was validated in the control cohort and correctly diagnosed 100% of cellulitis patients and 50% of pseudocellulitis patients. Conclusions: Early dermatologic consultation can improve outcomes in patients with suspected cellulitis by identifying alternate diagnoses, treating modifiable risk factors, and decreasing length of antibiotic treatment. As has been posited in previous literature, diagnostic imaging and blood cultures are currently overused in patients presenting with presumed cellulitis despite their lack of clinical utility. Moving forward, measuring skin surface temperatures via thermal imaging may be a more cost-effective and accurate modality to improve cellulitis diagnosis.