Development and validation of a predictive model for endocervical curettage in patients referred for colposcopy: A multicenter retrospective diagnostic study in China

Abstract

Objective: This study aimed to develop a nomogram that can predict occult high-grade squamous intraepithelial lesions or worse (HSIL+) and determine the need for endocervical curettage (ECC) in patients referred for colposcopy.

Methods: This retrospective multicenter study included 4,149 patients who were referred to any one of six tertiary hospitals in China for colposcopy between January 2020 and November 2021 because of abnormal screening results. ECC data were extracted from the medical records. Univariate and multivariate logistic regression analyses were performed to identify factors that could predict HSIL+ on ECC. Patients were randomly assigned to a training set or to an internal validation set for performance and comparability testing. The model was externally validated and tested in patients from two additional hospitals. The nomogram was assessed in terms of discrimination and calibration and subjected to decision curve analysis.

Results: HSIL+ was found on ECC in 38.8% (n=388) of cases. Our predictive nomogram included age group, cytology, human papillomavirus (HPV) status, visibility of the cervix and colposcopic impression. The nomogram had good overall discrimination, which was internally validated [area under the receiver-operator characteristic (AUC), 0.839; 95% confidence interval (95% CI), 0.773-0.904]. In terms of external validation, the AUC was 0.843 (95% CI, 0.773-0.912) for the consecutive sample and 0.843 (95% CI, 0.783-0.902) for the comparative sample. Calibration analysis suggested good consistency between predicted and observed probabilities. Decision curve analysis suggested this nomogram would be clinically useful with almost the entire range of threshold probabilities.

Conclusions: This internally and externally validated nomogram can be easily applied and incorporates multiple clinically relevant variables that can be used to identify patients with occult HSIL+ who need ECC.

Keywords: Cervical cancer; colposcopy; endocervical curettage; nomogram.

Figure 1

Flow chart showing the process used to develop and validate the predictive model. ECC, endocervical curettage; HSIL+, high-grade squamous intraepithelial lesion or worse.

Figure 2

Discrimination performance of predictive model in training, internal and external validation sets. Traning set: AUC 0.885 (95% CI, 0.863−0.906); Internal validation set: AUC 0.839 (95% CI, 0.773−0.904); External validation set 1: AUC 0.843 (95% CI, 0.773−0.912); External validation set 2: AUC 0.843 (95% CI, 0.783−0.902). AUC, area under the receiver-operator characteristic; 95% CI, 95% confidence interval.

Figure 3

Calibration plots showing the observed frequency and predicted probability for the predictive model in training set (N=2,806, E:O=1.000, CITL=−0.000, slope=1.000, AUC=0.885) (A), internal validation set (N=702, E:O=0.979, CITL=0.033, slope=0.826, AUC=0.839) (B), external validation set 1 (N=341, E:O=0.706, CITL=0.640, slope=0.667, AUC=0.843) (C) and external validation set 2 (N=300, E:O=0.873, CITL=0.217, slope=0.679, AUC=0.843) (D). E:O, the observed divided by expected number, with a number close to 1 showing good model fit; CITL, calibration-in-the-large; AUC, area under the receiver-operator characteristic.

Figure 4

Decision curve analysis showing the net benefit derived from training set (A), internal validation set (B), external validation set 1 (C) and external validation set 2 (D). The horizontal and ordinate axis of this figure represents the threshold probability, and the net benefit after the advantages was subtracted by the disadvantage, respectively. When a patient’s risk of HSIL+ reached a certain threshold, it was defined as high-risk and ECC was performed to confirm the final diagnosis. Decision curve analysis showed higher net benefit than ECC for all patients, which suggests that the model developed in this study is clinical useful. ECC, endocervical curettage; HSIL+, high-grade squamous intraepithelial lesions or worse.