External Multicenter Validation of the APTTO Model for Prolonged APTT Using Clot Waveform Analysis

Prolonged activated partial thromboplastin time (APTT) is a frequent laboratory finding that may reflect a broad spectrum of underlying conditions, ranging from benign laboratory abnormalities to clinically relevant hemostatic disorders. Clot waveform analysis (CWA), automatically generated during routine APTT testing by optical coagulation analyzers, provides additional quantitative and qualitative information on clot formation dynamics. The APTTO model is a previously developed two-step predictive algorithm based on CWA features designed to estimate the probability of a pathological cause of prolonged APTT and to differentiate lupus anticoagulant from intrinsic pathway factor deficiency or von Willebrand disease. Internal validation has demonstrated good discrimination and calibration. This multicenter observational study aims to perform an external validation of the APTTO model in independent patient cohorts, assessing its discrimination, calibration, and decision-analytic performance without model updating.

NCT Number	NCT07418099
Lead Sponsor	Instituto de Investigación Sanitaria de la Fundación Jiménez Díaz
Conditions	Coagulation Disorder, Blood, Prolonged APTT
Enrollment	1,500 participants
Start Date	2026-01-13
Primary Completion	2027-03 (estimated)
Study Completion	2027-03 (estimated)
Updated on ClinicalTrials.gov	2026-08-13