Validation of the neutrophil-to-lymphocyte ratio as a new simple biomarker of adult onset Still’s disease: A STROBE-Compliant prospective observational study

This study was performed to investigate the role of neutrophil-to-lymphocyte ratio (NLR) in the diagnosis of adult onset Still disease (AOSD) and its performance to improve the sensitivity of the classifications criteria (Yamaguchi and Fautrel Classifications). We conducted a multicenter prospective nationwide case-control study in Internal medicine, Rheumatology and Infectious disease departments, to include successively patients with suspected AOSD (2 or more major criteria of Yamaguchi or Fautrel classifications). All clinical and biological features were collected in a consensual and standardized clinical assessment at baseline and during follow-up. A receiving operating characteristic (ROC) curve was used to reassess the cutoff value of NLR. After determination of the cutoff value for NLR by ROC curve, 2 composite sets (Yamaguchi classification + NLR as a major criterion and Fautrel classification + NLR as a major criterion) were performed and evaluated. One hundred sixty patients were included, 80 patients with AOSD and 60 controls with different diagnoses. Twenty patients with incomplete data were excluded. The cutoff value for NLR equals 4 (area under the curve, AUC: 0.82). The NLR was ≥ 4 in 93.7% (75/80) of AOSD patients with a sensitivity of 93.8% and specificity of 61.7%. The association of NLR as a major criterion with the classification of Yamaguchi or Fautrel improved their sensitivity, respectively for Fautrel (76.3% to 92.5%, P = .004) and Yamaguchi (78.8% to 90%, P = .05). This study validates the NLR as a good simple biomarker of AOSD with a cutoff value of 4 and high sensitivity (93.8%). The addition of NLR (NLR ≥ 4) as a major criterion to the classifications (Yamaguchi and Fautrel) improved significantly their sensitivity and accuracy.