Supplementary Material for: Reliability of Histopathology for the Early Recognition of Fibrosis in Traction Alopecia: Correlation with Clinical Severity

Traction alopecia (TA) is hair loss caused by prolonged pulling or repetitive tension on scalp hair; it belongs to the biphasic group of primary alopecia. It is non-scarring, typically with preservation of follicular stem cells and the potential for regrowth of early lesions especially if traction hairstyles are stopped. However, the alopecia may become permanent (scarring) and fail to respond to treatment if the traction is excessive and prolonged. Hence, the ability to detect fibrosis early in these lesions could predict patients who respond to treatment. Histopathological diagnosis based on scalp biopsies has been used as a gold standard to delineate various forms of non-scarring alopecia and to differentiate them from scarring ones. However, due to potential discrepant reporting as a result of the type of biopsy, method of sectioning, and site of biopsy, histopathology often tends to be unreliable for the early recognition of fibrosis in TA. In this study, 45 patients were assessed using the marginal TA severity scoring system, and their biopsies (both longitudinal and transverse sections) were systematically assessed by three dermatopathologists, the aim being to correlate histopathological findings with clinical staging. Intraclass correlation coefficients were used to determine the level of agreement between the assessors. We found poor agreement of the identification and grading of perifollicular and interfollicular fibrosis (0.55 [0.23–0.75] and 0.01 [2.20–0.41], respectively), and no correlation could be drawn with the clinical severity score. Better methods of diagnosis are needed for grading and for recognition of early fibrosis in TA.

牵拉性脱发（Traction alopecia, TA）是因头皮毛发长期受牵拉或反复张力作用引发的脱发，属于原发性脱发的双相型组别。该疾病属于非瘢痕性脱发，通常可保留毛囊干细胞（follicular stem cells），早期病变存在毛发再生的潜力，尤其是在停止牵拉发型的情况下。但若牵拉过度且持续时间过长，脱发可能进展为永久性（瘢痕性）脱发，且对治疗无应答。因此，早期识别此类病变中的纤维化情况，可预测患者对治疗的响应性。
基于头皮活检的组织病理学诊断（histopathological diagnosis）曾被视为区分各类非瘢痕性脱发与瘢痕性脱发的金标准（gold standard）。然而，由于活检类型、切片方法及活检部位的差异可能导致报告结果不一致，组织病理学在早期识别TA纤维化方面往往可靠性不足。
本研究纳入45例患者，采用边缘性TA严重程度评分系统进行评估，并由3名皮肤病理学家（dermatopathologists）对其活检样本（包括纵切面与横切面）进行系统病理学分析，旨在将组织病理学发现与临床分期相关联。研究采用组内相关系数（intraclass correlation coefficients）评估评估者间的一致性水平。
结果显示，毛囊周纤维化与毛囊间纤维化的识别及分级一致性较差（分别为0.55 [0.23–0.75]和0.01 [2.20–0.41]），且与临床严重程度评分无相关性。因此，亟需更优质的诊断方法，用于TA的纤维化分级与早期纤维化识别。