Supplementary Material for: Serum Squamous Cell Carcinoma Antigen in Psoriasis: A Potential Quantitative Biomarker for Disease Severity

<b><i>Background:</i></b> An objective and quantitative method to evaluate psoriasis severity is important for practice and research in the precision care of psoriasis. <b><i>Objectives:</i></b> We aimed to explore serum biomarkers quantitatively in association with disease severity and treatment response in psoriasis patients, with serum squamous cell carcinoma antigen (SCCA) evaluated in this pilot study. <b><i>Methods:</i></b> 15 psoriasis patients were treated with adalimumab. At different visits before and after treatment, quantitative body surface area (qBSA) was obtained from standardized digital body images of the patients, and the psoriasis area severity index (PASI) was also monitored. SCCA were detected by using microparticle enzyme immunoassay. The serum biomarkers were also tested in healthy volunteers as normal controls. Receiver-operating characteristic (ROC) curve analysis was used to explore the optimal cutoff point of SCCA to differentiate mild and moderate-to-severe psoriasis. <b><i>Results:</i></b> The serum SCCA level in the psoriasis group was significantly higher (<i>p</i> &lt; 0.05) than in the normal control group. After treatment, the serum SCCA levels were significantly decreased (<i>p</i> &lt; 0.05). The SCCA level was well correlated with PASI and qBSA. In ROC analysis, when taking PASI = 10 or qBSA = 10% as the threshold, an optimal cutoff point of SCCA was found at 2.0 ng/mL with the highest Youden index. <b><i>Conclusion:</i></b> Serum SCCA might be a useful quantitative biomarker for psoriasis disease severity.

**背景**：客观且量化的银屑病病情严重程度评估方法，对于银屑病精准诊疗的临床实践与研究均具有重要意义。
**目的**：本研究旨在量化探索与银屑病患者病情严重程度及治疗应答相关的血清生物标志物，并在本预实验中对血清鳞状细胞癌抗原（squamous cell carcinoma antigen, SCCA）进行评估。
**方法**：本研究纳入15例银屑病患者并给予阿达木单抗治疗。于治疗前后的不同随访节点，通过患者的标准化数字化躯体图像获取量化体表面积（quantitative body surface area, qBSA），同时监测银屑病面积与严重性指数（psoriasis area severity index, PASI）。采用微粒酶免疫测定法检测血清SCCA水平，并以健康志愿者作为正常对照，检测其血清生物标志物水平。采用受试者工作特征曲线（Receiver-operating characteristic curve, ROC）分析，探索用于区分轻度与中重度银屑病的SCCA最佳截断值。
**结果**：银屑病组血清SCCA水平显著高于正常对照组（P<0.05）。治疗后，患者血清SCCA水平显著降低（P<0.05）。SCCA水平与PASI及qBSA均具有良好的相关性。在ROC曲线分析中，以PASI=10或qBSA=10%作为划分阈值时，SCCA的最佳截断值为2.0 ng/mL，此时约登指数最高。
**结论**：血清SCCA有望成为评估银屑病病情严重程度的有效量化生物标志物。