A Machine Learning–Based Prediction Model for Acute Kidney Injury in Patients With Community-Acquired Pneumonia: Multicenter Validation Study - Mengqing Ma; Caimei Chen; Dawei Chen; Hao Zhang; Xia Du; Qing Sun; Li Fan; Huiping Kong; Xueting Chen; Changchun Cao; Xin Wan (Journal of Medical Internet Research)