Myeloid marker S100A8/A9 and lymphocyte marker, soluble interleukin 2 receptor: biomarkers of hidradenitis suppurativa disease activity?

BACKGROUND

Hidradenitis suppurativa (HS) is a chronic inflammatory and debilitating disease of the skin. No biomarkers for this disease exist.

OBJECTIVES

We set out to test whether angiotensin-converting enzyme (ACE), lysozyme, soluble interleukin 2 receptor (sIL-2R) and S100A8/A9 (calprotectin) are elevated in patients with HS.

METHODS

Serum was collected from 29 patients with HS at different stages of the disease, and from 51 controls. ACE, lysozyme, sIL-2R and S100A8/A9 levels were measured. Clinical observation of disease activity was scored according to the Hurley grading system and by a physician global score (PGS) of disease severity.

RESULTS

Serum levels of lysozyme and ACE were not increased above the normal reference values in controls or patients with HS. Levels of sIL-2R and S100A8/A9 were significantly higher in patients with HS than in controls (P<0·001 for both sIL-2R and S100A8/A9). Based on the receiver operating characteristic curves, the optimum sIL-2R and S100A8/A9 cut-off values were 375 U mL(-1) and 680 ng mL(-1), respectively, with a sensitivity of 0·79 and specificity of 0·78 for sIL-2R, and 0·86 and 0·88, respectively, for S100A8/A9. No correlations with Hurley classification scores were found. However, when using PGS of disease activity to categorize patients, levels of S100A8/A9, but not sIL-2R, tended to be higher in patients with more active disease.

CONCLUSIONS

Levels of S100A8/A9 and sIL-2R, but not ACE or lysozyme, are elevated in the serum of patients with HS. However, there is no correlation between S100A8/A9 or sIL-2R levels and disease stage according to the Hurley classification system. Further research is needed to study the potential of S100A8/A9 to score disease activity in larger cohorts of patients and to predict disease flares.