Development and External Validation of a Prediction Model for Patients with Varicose Veins Suitable for Isolated Ambulatory Phlebectomy

Abstract

Isolated ambulatory phlebectomy is a potential treatment option for patients with an incompetent great saphenous vein (GSV) or anterior accessory saphenous vein and one or more incompetent tributaries. Being able to determine which patients will most likely benefit from isolated phlebectomy is important. This study aimed to identify predictors for avoidance of secondary axial ablation after isolated phlebectomy and to develop and externally validate a multivariable model for predicting this outcome. For model development, data from patients included in the SAPTAP trial were used. The investigated outcome was avoidance of ablation of the saphenous trunk one year after isolated ambulatory phlebectomy. Pre-defined candidate predictors were analysed with multivariable logistic regression. Predictors were selected using Akaike information criterion backward selection. Discriminative ability was assessed by the concordance index. Bootstrapping was used to correct regression coefficients, and the C index for overfitting. The model was externally validated using a population of 94 patients, with an incompetent GSV and one or more incompetent tributaries, who underwent isolated phlebectomy. For model development, 225 patients were used, of whom 167 (74.2%) did not undergo additional ablation of the saphenous trunk one year after isolated phlebectomy. The final model consisted of three predictors for avoidance of axial ablation: tributary length (< 15 cm vs. > 30 cm: odds ratio [OR] 0.09, 95% confidence interval [CI] 0.02 - 0.40; 15 - 30 cm vs. > 30 cm: OR 0.18, 95% CI 0.09 - 0.38); saphenofemoral junction (SFJ) reflux (absent vs. present: OR 2.53, 95% CI 0.81 - 7.87); and diameter of the saphenous trunk (per millimetre change: OR 0.63, 95% CI 0.41 - 0.96). The discriminative ability of the model was moderate (0.72 at internal validation; 0.73 at external validation). A model was developed for predicting avoidance of secondary ablation of the saphenous trunk one year after isolated ambulatory phlebectomy, which can be helpful in daily practice to determine the suitable treatment strategy in patients with an incompetent saphenous trunk and one or more incompetent tributaries. Patients having a longer tributary, smaller diameter saphenous trunk, and absence of terminal valve reflux in the SFJ are more likely to benefit from isolated phlebectomy.