Supplementary Material for: Leukocyte Profile in Peripheral Blood and Neutrophil-Lymphocyte Ratio in Hidradenitis Suppurativa: A Comparative Cross-Sectional Study of 462 Cases

<b><i>Background:</i></b> Hidradenitis suppurativa (HS) is a chronic, inflammatory skin disease. Increasing evidence suggests that HS involves dysfunctional immune responses in both the adaptive and the innate immune system. The recently proposed association of HS with metabolic syndrome may further add to the inflammatory state in HS. <b><i>Objective:</i></b> To investigate the status of inflammation and leukocyte profile in the peripheral blood of HS patients. <b><i>Materials and Methods:</i></b> Using a comparative cross-sectional study design, we investigated blood samples of high-sensitivity C-reactive protein (hs-CRP) and leukocyte profile in hospital-treated HS patients (HS-HOSP), self-reported population-based HS patients (HS-POP) and population controls. <b><i>Results:</i></b> Our study comprised 32 individuals in the HS-HOSP group, 430 in the HS-POP group, and 20,780 controls. The median hs-CRP for the HS-HOSP group was 5.1 mg/l (quartile range 2.6-8.2), 2.2 mg/l (1.0-4.3) for the HS-POP group and 1.3 mg/l (0.7-2.9) for the controls. An age-sex-adjusted analysis revealed a significantly higher hs-CRP for both HS groups compared to controls (p < 0.0001). When performing age-sex-adjusted analysis, both HS groups had significantly higher odds of leukocytosis when compared to controls with an odds ratio for the HS-HOSP group of 4.38 (95% CI = 2.18-8.80; p < 0.0001) and 1.95 (95% CI = 1.58-2.42; p < 0.0001) for the HS-POP group. The age-sex-adjusted leukocyte differential count yielded significantly higher neutrophil (p < 0.0001) and monocyte (p = 0.0014, p = 0.0004) levels in the HS groups compared with controls. <b><i>Conclusion:</i></b> The hs-CRP levels associated with HS appear to be intermediate (2.2-5.1 mg/l), implying systemic inflammation rather than infection. The peripheral blood leukocytosis in HS was dominated by neutrophils and monocytes.