Supplementary Material for: C-Reactive Protein and Procalcitonin in Case Reports of Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) Syndrome

<b><i>Background:</i></b> The spectrum of inflammatory marker response in DRESS (drug reaction with eosinophilia and systemic symptoms) syndrome has not been systematically characterized. <b><i>Methods:</i></b> An epidemiological biomarker study of C-reactive protein (CRP) and procalcitonin (PCT) values in patients with DRESS syndrome reported at 2 regional pharmacovigilance centers in Switzerland or published in the medical literature 2008–2016 was performed. <b><i>Results:</i></b> Ninety-four DRESS cases were studied. All cases showed a CRP value > 10 mg/L (the upper limit of normal). The mean CRP value was 109.2 ± 79.4 mg/L. CRP values were significantly higher in 22 cases where a cause of inflammation besides DRESS could not be excluded (mean 162.1 vs. 92.9 mg/L; <i>p</i> = 0.003). Receiver operator characteristics curve analysis showed a moderate performance with a CRP cut-off value of 99.4 mg/L (AUC 0.717) to distinguish between patients with and without a possible additional cause of inflammation. The mean and median PCT values were 2.44 ± 5.94 and 0.69 ng/mL, respectively (<i>n</i> = 25 patients). Patients in whom an additional cause of inflammation besides DRESS could not be excluded showed a median PCT of 1.37 ng/mL (<i>n</i> = 9) versus 0.67 ng/mL (<i>n</i> = 16) in patients with DRESS only. PCT values were above the normal cut-off of 0.1 ng/mL, suggestive of bacterial infection in all but 1 case. Furthermore, there was a correlation between PCT values and hepatic enzyme measurements. <b><i>Conclusions:</i></b> Evaluating CRP and PCT values might be of use in helping physicians to distinguish between cases of DRESS syndrome with and without concurrent infection or other causes of inflammation. Further prospective investigation is required to define the use of these inflammatory markers in the management of DRESS.