Does dermal thermometry predict clinical outcome in diabetic foot infection? Analysis of data from the SIDESTEP* trial

The purpose of the study was to assess in patients with a diabetic foot infection (DFI), whether differences in skin temperature of the affected foot as compared to the corresponding site on the contralateral foot using dermal thermometry (DT) correlates with infection severity and clinical outcome. As part of the SIDESTEP DFI study, investigators took DT measurements at baseline and the discontinuation of intravenous therapy (DCIV) and performed a systematic evaluation of the infected limb to calculate a wound score. We compared the skin temperature differential between the limbs at the two assessments and determined the correlation between this value and surrogate markers of inflammation and the clinical response to treatment. Among patients enrolled in SIDESTEP, 332 were fully evaluable. The mean temperature differential between the limbs was 2.81 ± 5.75°F at baseline and 2.43 ± 4.84°F at DCIV (mean change: -0.37; 95% confidence interval (CI): -0.98, 0.23; P = 0.225). Skin temperature differential at baseline did not correlate with white blood cell count, level of C-reactive protein or erythrocyte sedimentation rate or the infection severity score (r = 0.058, 0.148, -0.002, 0.067, respectively). We observed no overall trend between surface temperature differential at baseline and clinical outcome at DCIV, but patients with a skin temperature differential of ≥10°F at baseline had a significantly lower clinical response than those whose differential was <10°F (81.4% versus 94.3%; difference 12.9%; 95% CI: 3.5, 27.3%, P = 0.007). While there was no overall relationship between skin temperature and poor clinical outcome, there may be a threshold effect in DT (<10°F versus >10°F) between the limbs at baseline that predicts outcome of therapy.