Validation of noninvasive focal depth measurements to determine epithelial thickness of the vaginal wall

Objective: This study investigates whether noninvasive focal depth (FD) measurements correlate with vaginal wall epithelial thickness (ET). If FD accurately reflects ET of the vaginal wall, this would allow noninvasive longitudinal assessment of (newly developed) treatment modalities aiming to increase ET, without the need for invasive biopsies. Methods: Fourteen women, median age 62 years (inter quartile ranges: 57-65), undergoing vaginal prolapse surgery because of anterior and/or posterior compartment pelvic organ prolapse were included. We used the CytoCam, a handheld video microscope based on incident dark field imaging, and performed FD measurements of the vaginal wall before surgery. Histology was performed on tissue that was removed during the surgical procedure, and ET was measured in stained sections. We compared ET with FD interindividually, and determined the expected linear correlation and agreement between the two measurements. Results: Seventeen ET measurements (mean 125 mu m +/- 38.7, range 48-181 mu m) were compared with 17 FD measurements (mean 128 mu m +/- 34.3, range 68-182 mu m). The lineair correlation between the two measurements was strong (r = 0.902, P < 0.01). Bland-Altman analysis demonstrated a mean difference of 13.5 mu m when comparing ET to FD. Conclusions: The results demonstrate good agreement between ET and FD measurements. We consider the mean difference demonstrated with Bland-Altman analysis acceptable for these measurements. This suggests that FD accurately reflects ET, which further supports the use of FD to measure ET of the vaginal wall. For a complete assessment of the vaginal wall, FD measurements are preferably combined with the assessment of vaginal angioarchitecture.