The following is a summary of “Validation of Thermal Imaging and the ALT-70 Prediction Model to Differentiate Cellulitis From Pseudocellulitis,” published in the March 2024 issue of Dermatology by Pulia, et al.
Cellulitis misdiagnosis is common, often attributed to conditions mimicking its symptoms, leading to antibiotic misuse. Thermal imaging and the ALT-70 (asymmetry, leukocytosis, tachycardia, and age ≥70 years) model aim to differentiate cellulitis from pseudocellulitis. For a study, researchers sought to validate skin temperature differences between cellulitis and pseudo cellulitis, determine optimal temperature measures and cut points, and compare the performance of skin temperature and the ALT-70 model in distinguishing between the two conditions.
A prospective diagnostic validation study was conducted among patients presenting to the emergency department with acute dermatologic lower extremity symptoms. Skin surface temperatures were obtained, and cellulitis vs. pseudocellulitis was assessed through consensus review. Logistic regression identified optimal temperature measures and cut points. The diagnostic performance of the ALT-70 model, skin temperature, and combined measures were assessed.
The study included 204 participants (mean [SD] age, 56.6 [16.5] years; 121 men [59.3%]), with 92 (45.1%) having cellulitis. Significant differences in all skin surface temperature measures were observed between cellulitis and pseudocellulitis. The maximum temperature of the affected limb was 33.2°C for patients with cellulitis and 31.2°C for patients with pseudo cellulitis (difference of 2.0°C [95% CI, 1.3-2.7°C]; P < .001). The maximum temperature was identified as the optimal measure, with a cut point of 31.2°C, yielding a mean (SD) negative predictive value of 93.5% (4.7%) and a sensitivity of 96.8% (2.3%). Sensitivity for all three measures exceeded 90%, while specificity varied: ALT-70 (22.0% [95% CI, 15.8%-28.1%]), maximum temperature (38.4% [95% CI, 31.7%-45.1%]), and combination measure (53.9% [95% CI, 46.5%-61.2%]).
Significant differences in skin surface temperatures between cellulitis and pseudocellulitis were observed, supporting thermal imaging’s potential as a diagnostic tool. Combining thermal imaging with the ALT-70 model enhances specificity and could help reduce cellulitis misdiagnosis and antibiotic overuse.
Reference: jamanetwork.com/journals/jamadermatology/article-abstract/2816455
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