Abstract
Objective This study aimed to create a statistical model using clinical and laboratory parameters
to predict which patients presenting with pruritus in pregnancy will have elevated
total bile acids (TBA) and thus, have a high risk of intrahepatic cholestasis of pregnancy
(ICP).
Study Design Retrospective cohort study of patients presenting with pruritus in pregnancy and
had TBA sent from a single public hospital from January 1, 2017, to December 31, 2017.
Primary outcome is TBA ≥ 10 µmol/L. Multivariate logistic regression with stepwise
and backward variable selection were used to create predictive models. Four models
were compared using Akaike information criterion (AIC), C-statistic, and the DeLong
nonparametric approach to test for differences between area under the curve (AUC)
of receiver operating characteristic (ROC) curves. Internal validation was performed
via fivefold cross-validation technique on the best-fitting, most parsimonious model.
Results Of the 320 patients with pruritus, 153 (47.8%) had elevated bile acid levels ≥10
µmol/L. Sixty-nine variables were assessed for association with the primary outcome.
Five variables were significantly associated with elevated TBA: pruritus of palms
and soles (adjusted odds ratio [aOR]: 2.35 [95% confidence interval, CI: 1.22, 4.54]),
gestational hypertension (aOR: 0.10 [95% CI: 0.02, 0.60]), log of total bilirubin
(aOR: 4.71 [95% CI: 2.28, 9.75]), systolic blood pressure (aOR: 0.97 [95% CI: 0.94,
0.99]), and alanine aminotransferase (aOR: 1.05 [95% CI: 1.02, 1.07]). The final model
was chosen for being parsimonious while having the lowest AIC with highest AUC (0.85;
95% CI: 0.81, 0.89). Internal validation using a probability threshold of 50% demonstrated
a sensitivity of 65.5%, specificity of 83.5%, and accuracy of 75.1%.
Conclusion We provide a predictive model using five simple variables to determine the probability
that a patient presenting with pruritus in pregnancy carries the diagnosis of ICP.
This tool, available via a web app, is designed to aid providers and enhance clinical
judgment in difficult triage situations.
Key Points
Currently, no standard method to triage pruritus in pregnancy exists.
We present a predictive statistical model using five readily available clinical variables.
Final calculator yields probability of having intrahepatic cholestasis of pregnancy.
Keywords calculator - cholestasis - pruritus - pregnancy - transaminitis
