The Distribution of Cervical Transformation Zone and Its Impact on Colposcopic Diagnosis: A Multicenter Study in China.

Objective: The value of the transformation zone (TZ) is often overlooked in clinical settings. This study aims to assess TZ distribution, associated factors, and its impact on colposcopic diagnosis.

Methods: χ2 tests were used to analyze demographics, clinical history, and tissue samples to examine the differences in TZ distribution. Factors affecting the TZ were explored using logistic regression, and diagnostic indicators were calculated.

Results: A total of 5,302 individual datasets were finally included. TZ1, TZ2, and TZ3 accounted for 31.6%, 38.5%, and 30.0%, respectively. Age is the most important factor that influences the location of the TZ. The proportion of TZ3 steadily increased with age, comprising over 55% in women over 50. The colposcopic diagnostic performance shows that high-grade squamous intraepithelial lesion or worse (HSIL+) sensitivity of TZ3 (58.1%, 95% confidence interval [CI] = 52.9-63.4) is significantly lower than that of TZ1 (69.8%, 95% CI = 65.5-74.1) and TZ2 (73.2%, 95% CI = 69.7-76.8). The HSIL+ specificity of TZ3 (96.3, 95% CI = 95.3-97.4) was higher than that of TZ1 (96.3, 95% CI = 95.2-97.3) and TZ2 (92.5, 95% CI = 91.1-93.9). The HSIL+ positive predictive value (81.3%, 95% CI = 76.4-86.2) and negative predictive value (89.3%, 95% CI = 87.6-90.9) for TZ3 are high, with no significant differences when compared with TZ1 and TZ2.

Conclusions: Age predominantly influences TZ location, with TZ3 being most frequently found in women over 50. While TZ3 poses a higher risk of missed diagnosis during colposcopy, it remains clinically valuable in identifying diseased and nondiseased status. Increasing colposcopists' awareness of TZ importance is needed in clinical practice.