Study Validates Thermal Imaging, ALT-70 Model for Distinguishing Cellulitis from Pseudocellulitis

The findings suggests a way to reduce overdiagnosis for cellulitis.

A new diagnostic validation study in JAMA Dermatology has shed light on the potential of surface thermal imaging and the ALT-70 (asymmetry, leukocytosis, tachycardia, and age ≥70 years) prediction model in differentiating cellulitis from pseudocellulitis.

"Cellulitis is misdiagnosed in up to 30% of cases due to mimic conditions termed pseudocellulitis," the authors wrote. "The resulting overuse of antibiotics is a threat to patient safety and public health. Surface thermal imaging and the ALT-70 (asymmetry, leukocytosis, tachycardia, and age ≥70 years) prediction model have been proposed as tools to help differentiate cellulitis from pseudocellulitis."

The authors conducted the study in patients presenting with acute dermatologic lower extremity symptoms in the ED, aiming to validate differences in skin surface temperatures between cellulitis and pseudocellulitis cases. They assessed various temperature measures and optimal cut points for differentiation, comparing their performance with the ALT-70 prediction model. The study population included 204 patients.

According to the results, there were significant differences in skin surface temperature measures between cellulitis and pseudocellulitis cases. The maximum temperature of the affected limb emerged as the optimal measure, with a cut point of 31.2 °C, demonstrating high sensitivity (96.8%) and a notable negative predictive value (93.5%). Both thermal imaging and the ALT-70 model demonstrated high sensitivity in distinguishing between the two conditions. When combined, the two measures improved specificity.

"This study suggests that thermal imaging, alone or in combination with the ALT-70 prediction model, could be used as a diagnostic adjunct to help decrease overdiagnosis of cellulitis," they concluded.

Source: Pulia MS, Schwei RJ, Alexandridis R, et al. Validation of Thermal Imaging and the ALT-70 Prediction Model to Differentiate Cellulitis From Pseudocellulitis. JAMA Dermatology. Published online March 27, 2024. Doi:https://doi.org/10.1001/jamadermatol.2024.0091