Evaluation and validation of a new risk score (CLEOPATRA score) to predict the probability of premature delivery for patients with threatened preterm labor

Abstract

To develop a clinically useful tool to predict the probability of preterm delivery in patients with threatened preterm labor. One hundred and seventy patients with preterm labor between 24 and 34 weeks of gestation were included. Preterm delivery < 37 weeks of gestation was the main endpoint of the study. The data were randomized and split into an evaluation set (n = 85) and a validation set (n = 85). The evaluation set was subjected to stepwise backward logistic regression analysis to quantify the relative impact of four potential risk factors, including individual patient factors, results of a rapid fetal fibronectin assay, and sonographic measurement of cervical length. Using the constant of the logistic regression analysis and the beta-coefficients for the identified risk factors the individual probability of preterm delivery for each woman of the validation dataset was calculated. The area under a receiver-operating characteristics curve (AUC) was used to evaluate the discriminating power of the score. The overall rate of preterm delivery was 27.1%. The logistic regression analysis was performed for the potential predictors of spontaneous preterm delivery, identified by univariate analysis. These were positive fetal fibronectin, cervical length, previous preterm delivery and maternal age. Two risk factors were independent predictors of preterm delivery and were included in the CLEOPATRA I (clinical evaluation of preterm delivery and theoretical risk assessment) score: cervical length measurement and previous preterm delivery were associated with a higher risk of preterm delivery (odds ratio, 7.65 and 6.74, respectively). Since fetal fibronectin assay is not available at all institutions worldwide, it was excluded from the initial model. In the CLEOPATRA II model the risk factors fetal fibronectin and previous preterm delivery were associated with higher risk of preterm delivery, with odds ratios of 17.9 and 4.56, respectively. The discrimination power (AUC) obtained from the models were: CLEOPATRA I, 0.69 (95% CI, 0.56-0.82); CLEOPATRA II, 0.81 (95% CI, 0.69-0.93). In symptomatic women the risk for preterm delivery can be predicted best with the CLEOPATRA II score based on fetal fibronectin and previous preterm delivery.