Asmar MH, et al. - Authors assessed whether secreted protein acidic and rich in cysteine (SPARC) could represent a serum biomarker for chronic rhinosinusitis (CRS) by verifying if SPARC could be detected in serum, whether levels were sensitive to disease burden reduction following surgery, and if it could predict response to therapy. Study participants included 26 patients undergoing endoscopic sinus surgery (ESS) for CRS. The investigators collected serum samples at the time of surgery and 4 months following ESS; SPARC levels were measured using enzyme-linked immunosorbent assay. They detected and measured in serum samples for all study participants. The authors suggested that SPARC may be an interesting serum biomarker of disease activity in CRS because of its reliable measurement and decreases after successful reduction of disease burden post-surgery. Nonetheless, it does not predict post- ESS evolution, suggesting that the link between epithelial-to-mesenchymal transition and outcome is not linear.