Background Several classification criteria for Adult-onset Still’s disease (AOSD) have been suggested, but there have been no objective laboratory tests established for its diagnosis. Especially in the early phase, it is more difficult to discriminate AOSD from infection due to their indistinguishable symptoms and laboratory findings. Delta neutrophil index (DNI) is an automatically calculated parameter that reflects the ratio of immature granulocytes (IGs) over total neutrophil count in the peripheral circulation. DNI has been reported to be more specific for sepsis severity and prognosis than the traditional markers. With these reasons, it can be speculated that DNI may be helpful to discriminate AOSD from sepsis in the confusing early phase before the report of microbial culture studies, but its clinical application has not been reported to date.
Objectives To investigate the clinical usefulness of DNI to discriminate AOSD from sepsis in the early phase.
Methods We investigated the medical records of 13 patients with AOSD and 33 sex- and age- matched patients with sepsis. DNI and other laboratory values were assessed two or three times during the first 3 days and represented by their mean levels. In all subjects, microbial tests were performed to exclude or confirm sepsis.
DNI was calculated by the automatic cell analyzer (ADVIA 2120 Hematology System, Siemens Healthcare Diagnostics, Forchheim, Germany). DNI was calculated using the following formula: DNI = [the neutrophil sub fraction and the eosinophil sub fraction measured in the MPO channel by the cytochemical MPO reaction] - [the PMN sub fraction measured in the nuclear lobularity channel by the reflected light beam].
Results Mean age of AOSD patients (male 3, female 10) was 43.9 ± 13.4 years old and that of sepsis patients (male 8, female 25) was 48.8 ± 11.0 years old. There were no significant differences in white blood cell counts, neutrophil proportion, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) between two groups. AOSD patients had notably lower DNI than sepsis patients regardless of the presence of bacteremia or not (1.8 ±1.0% vs. 9.9 ± 8.9% and 1.8 ±1.0% vs. 7.9 ± 3.7%, respectively)(Figure 1). Although the usefulness of DNI did not surpass that of ferritin for the differential diagnosis of the two diseases, the area under the receiver operating characteristic curve of DNI was slightly higher than that of ferritin. When we set DNI of 2.75% as the cut-off value for differential diagnosis of the two diseases, eleven (84.6%) of AOSD patients had a DNI value below 2.75% and 2 (15.4%) of them had a DNI over 2.75%. In contrast, in sepsis patients only 1 (3.0%) had a DNI below 2.75%. And the relative risk for predicting sepsis was 176 (p < 0.001, 95% confidential interval 14.501–2136.176).
Conclusions AOSD patients had significantly lower DNI than sepsis patients regardless of the presence of bacteremia. Also DNI over 2.75 showed a high risk for sepsis in patients suspected of both AOSD and sepsis (RR=176.0). Thus, we suggest that DNI may help physicians to discriminate AOSD from sepsis in the confusing early phase before the report of microbial culture studies.
Disclosure of Interest None Declared