Intra and Inter-Observer Variability of Transformation Zone Assessment in Colposcopy: A Qualitative and Quantitative...

Colposcopy is an important tool in the diagnosis of cervical precancer and early cancer. The assessment of women with abnormal cytology and selection of those who require further therapy or follow up depends on the colposcopic assessment of the Transformation Zone (TZ). Identification of the TZ is thus an important part of this examination. Intra and inter-observer variability is known to be relatively high in the colposcopic interpretation of abnormal features. However, there are hardly any studies on the observer variability in the assessment of the type of TZ.

The present study was conducted with the aim to compare the intra and inter-observer variability of the TZ type classification and the Squamo-Columnar Junction (SCJ) visibility and to quantitatively measure the intra and inter-observer correlations of tracing of the TZ contours.

Colposcopy images were obtained for a total of 170 cases. They were reviewed by three colposcopists independently. The colposcopists classified the TZ type and also marked the SCJ contours on the images. Each observer independently reviewed the cases on two different instances (few weeks apart) and the result was compiled for intra-observer variation. The intra and inter observer variability on the TZ type was compared using Cohen's Kappa. This was followed by a quantitative measurement of TZ observation variability using Hausdorff distance.

The inter-observer agreement for the TZ type classification was moderate (Kappa= 0.53 to 0.66). The Intra-observer agreement was moderate to strong (0.60 to 0.86).

Colposcopic in vivo examination increases the variability in the identification of the TZ when compared to the analysis of recorded images. The disagreement in the TZ type was mostly in categories Type 2 vs Type 3 followed by Type 1 vs Type 2. A computerized quantification method can be used for quality control and training purpose in colposcopy.