Diagnostic value of three complete blood count abnormalities, hypereosinophilia, hyperlymphocytosis and basophilic lymphocytes, in DRESS

The prevalence and kinetics of hypereosinophilia (HE), hyperlymphocytosis (HL), basophilic lymphocyte (BL), are misdescribed. We aimed to assess their diagnostic value in the acute phase of DRESS in a monocentric retrospective study. Among 60 patients, 47% had probable DRESS, and 53% definite DRESS. HE and HL were present in 62% and 27% of patients, respectively, with no link to DRESS severity. BL, found in 85% of blood smears, were associated with definite DRESS. BL detection, although not specific nor sufficient alone, appears to be the most sensitive hematological factor for diagnosing DRESS, especially when HE or HL is absent. Clinicians should ensure that a blood smear review is performed whenever a DRESS is suspected. A prospective study is needed to confirm these findings.