Machine Learning for Hypertension Classification After Blood Pressure Measurement: An Interpretable and Calibrated Approach

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Abstract
Hypertension is a leading contributor to cardiovascular morbidity worldwide. When blood pressure and routine clinical variables are available during clinic visits or health checks, guideline thresholds support binary classification but do not necessarily provide reliable calibrated probabilities for decision support. Machine learning studies in hypertension have concentrated on predicting future disease incidence rather than binary classification at the time of measurement, and calibration and validation design are reported inconsistently across this literature. This study examines whether machine learning, trained under a stratified protocol with held‐out calibration and test subsets, can improve probabilistic reliability in post‐measurement classification while remaining comparable to a clinical blood pressure rule. We analysed a public hypertension dataset of 4240 records with a positive‐class prevalence of 31.1% using a scikit‐learn pipeline that integrates preprocessing, recursive feature elimination, Optuna‐based hyperparameter tuning, and isotonic calibration on a held‐out calibration set. A tuned decision tree was compared against a clinical rule based on systolic blood pressure of at least 140 mmHg or diastolic blood pressure of at least 90 mmHg across 30 stratified random splits. Accuracy and recall were comparable to the clinical rule, with no statistically significant Wilcoxon differences, whereas Brier score and expected calibration error were significantly lower for the machine learning model, with mean values of 0.081 versus 0.090 and 0.027 versus 0.084. Interpretability analysis was consistent with blood‐pressure‐related predictors dominating model attributions. These findings suggest that machine learning classification after blood pressure measurement aligns with guideline‐based decisions while offering better calibrated probabilities for clinical decision support.

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