Diagnostic value of three complete blood count abnormalities, hypereosinophilia, hyperlymphocytosis and basophilic lymphocytes, in Drug Reaction with Eosinophilia and Systemic Symptoms

The prevalence and kinetics of hypereosinophilia (HE), hyperlymphocytosis (HL) and basophilic lymphocytes (BL) are not well understood. This monocentric retrospective study aimed to assess the diagnostic value of these blood count abnormalities in the acute phase of Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS). Of 60 patients included in the study, 47% had probable DRESS and 53% had 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. The detection of BL, although not specific to DRESS nor sufficient to diagnose DRESS alone, appears to be the most sensitive haematological factor for diagnosing DRESS, especially when HE or HL are 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.