Blood monocyte fraction and computed tomography attenuation value of bone marrow in fever of unknown origin: A retrospective analysis for differentiating adult-onset Still's disease and intravascular large B-cell lymphoma.

OBJECTIVES

To investigate the factors affecting laboratory data and computed tomography (CT) attenuation values of L1 trabecular and femoral bone marrow, potential markers for differentiating between adult-onset Still's disease (AOSD) and intravascular large B-cell lymphoma (IVLBL).

METHODS

We conducted a retrospective observational study on patients diagnosed with AOSD or IVLBCL. Clinical and laboratory data, and CT attenuation values of the bone marrow were compared. An exploratory analysis was conducted to identify factors useful for discriminating between the two groups.

RESULTS

Thirty patients with AOSD and 14 with IVLBCL were included; among them, 17 and 14 patients, respectively, underwent plain CT. No significant differences in CT attenuation values were noted; however, significant differences in various clinical and laboratory data, including neutrophil counts and soluble interleukin 2 receptor levels, were observed. Exploratory analysis of the monocyte fraction, guided by previous reports, suggested a cutoff of ≥ 9.65% for IVLBCL, with a sensitivity of 64.3% and specificity of 96.7%.

CONCLUSION

This study suggests that, besides neutrophil counts and soluble interleukin 2 receptor levels, monocyte fractionation is a useful differentiation criterion between AOSD and IVLBCL.