External Multicenter Validation of the APTTO Model for Prolonged APTT Using Clot Waveform Analysis (APTTO-EXT)

Multicenter External Validation of the APTTO Predictive Model Based on Clot Waveform Analysis for the Assessment of Prolonged Activated Partial Thromboplastin Time

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.

Study Overview

• Status: Recruiting
• Conditions: Coagulation Disorder, Blood; Prolonged APTT
• Intervention / Treatment: Other: Clot waveform analysis-based risk stratification (APTTO models)

Detailed Description

This multicenter observational cohort study is designed to externally validate the APTTO predictive model in patients with prolonged APTT and normal prothrombin time evaluated in routine clinical practice across multiple hospitals.

All laboratory data, including CWA parameters and waveform morphology, are generated as part of standard diagnostic workflows. No additional blood sampling, laboratory testing, or modifications to clinical management are introduced for research purposes.

The study focuses on evaluating model performance in independent cohorts by applying the original APTTO model coefficients and predefined cut-offs without recalibration or re-estimation. Model discrimination, calibration, and decision-analytic measures will be assessed. Secondary analyses will explore model performance across predefined subgroups and analytical robustness.

This study adheres to the TRIPOD statement for validation of prediction models.

• Study Type: Observational
• Enrollment (Estimated): 1500

Contacts and Locations

• Study Contact: Name: Diego Velasco Rodríguez, MD, PhD; Phone Number: +34 669 98 04 32; Email: diego.velascor@quironsalud.es

Study Locations

• Spain
  • Barcelona, Spain
    • Recruiting
    • Hospital De La Santa Creu I Sant Pau
    • Contact: Noèlia Vilalta Seto, MD, PhD; Phone Number: +34 932 91 90 00; Email: nvilalta@santpau.cat
  • Lleida, Spain
    • Recruiting
    • Hospital Universitario Arnau de Vilanova
    • Contact: Albert Tugués Peiró, MD; Phone Number: +34 973 24 81 00; Email: atugues.lleida.ics@gencat.cat
  • Madrid, Spain
    • Recruiting
    • Hospital Universitario 12 de Octubre
    • Contact: Nerea Castro Quismondo, MD; Phone Number: +34 913 90 80 00; Email: nerecq@hotmail.com
  • Madrid, Spain
    • Recruiting
    • Hospital Universitario Ramon y Cajal
    • Contact: Pilar Massó Asensio, MD; Phone Number: +34 91 336 80 00; Email: pmasso@salud.madrid.org
  • Madrid, Spain
    • Not yet recruiting
    • Hospital Universitario Clínico San Carlos
    • Contact: Cristina García Sánchez, MD; Phone Number: +34 913 30 30 00; Email: cgarciasanchez@salud.madrid.org
  • Madrid, Spain
    • Recruiting
    • Hospital Universitario Fundacion Jimenez Diaz
    • Contact: Diego Velasco Rodríguez, MD, PhD; Email: diegovelascorodriguez@gmail.com
    • Contact: Nuria Revilla, MD, PhD; Email: nuria.revilla@quironsalud.es
  • Madrid, Spain
    • Not yet recruiting
    • Hospital Universitario Gregorio Maranon
    • Contact: Cristina Pascual Izquierdo, MD, PhD; Phone Number: +34 91 586 80 00; Email: crisizquierdo3@yahoo.es
  • Madrid, Spain
    • Not yet recruiting
    • Hospital Universitario Puerta de Hierro
    • Contact: Cristina Fernández Maqueda, MD; Phone Number: +34 91 191 60 00; Email: Cristinat.maqueda@gmail.com
  • Murcia, Spain
    • Not yet recruiting
    • Hospital Clínico Universitario Virgen de la Arrixaca
    • Contact: Vanessa Roldán Schilling, MD, PhD; Phone Number: +34 968 369 500; Email: vroldans@um.es
  • Pamplona, Spain
    • Not yet recruiting
    • Clinica Universidad de Navarra
    • Contact: María Marcos Jubilar, MD, PhD; Phone Number: +34 948 25 54 00; Email: mmarcos.3@unav.es
  • Salamanca, Spain
    • Not yet recruiting
    • Hospital Clínico Universitario de Salamanca
    • Contact: José Ramón González Porras, MD, PhD; Phone Number: +34 923 29 11 00; Email: jrgp@usal.es
  • Santiago de Compostela, Spain
    • Not yet recruiting
    • Complexo Hospitalario Universitario De Santiago
    • Contact: Matilde Rodríguez Ruiz, MD; Phone Number: +34 981 95 10 00; Email: matilde.rodriguez.ruiz@sergas.es
  • Valladolid, Spain
    • Recruiting
    • Hospital Clinico Universitario de Valladolid
    • Contact: Carolina Bombín Canal, MD; Phone Number: +34 983 42 00 00; Email: cbombin@saludcastillayleon.es
  • Vigo, Spain
    • Not yet recruiting
    • Complexo Hospitalario Universitario de Vigo
    • Contact: María Elsa López Ansoar, MD; Phone Number: +34 986 51 47 51; Email: elsa.lopez.ansoar@sergas.es
  • Zaragoza, Spain
    • Not yet recruiting
    • Hospital Clinico Universitario Lozano Blesa
    • Contact: Olga Gavín Sebastián, MD, PhD; Phone Number: +34 976 76 57 00; Email: ogavin@salud.aragon.es
  • Madrid
    • Leganés, Madrid, Spain
      • Recruiting
      • Hospital Universitario Severo Ochoa
      • Contact: Ramón Rodríguez Rodríguez, MD; Phone Number: +34 91 481 80 00; Email: ramon.rodriguez@salud.madrid.org

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child; Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

The study population includes pediatric and adult patients undergoing routine coagulation testing in clinical practice who present with isolated prolongation of activated partial thromboplastin time (APTT) and normal prothrombin time (PT). Patients may be evaluated in the preoperative setting or during routine clinical care for other indications.

All laboratory data, including clot waveform analysis (CWA), are generated as part of standard diagnostic procedures, without additional blood sampling or modification of clinical management. Patients receiving anticoagulant therapy that may prolong APTT are included, provided that PT remains within the normal range.

The study uses pseudonymized data obtained from electronic medical records and laboratory systems, with no direct patient contact and no anticipated risks beyond routine care.

Description

Inclusion Criteria:

1. Patients of any age (pediatric and adult populations) undergoing coagulation testing with:

   - Prolonged activated partial thromboplastin time (APTT), defined as an APTT ratio ≥ 1.25.

   - Normal prothrombin time (PT), according to local laboratory reference ranges.

2. Availability of clot waveform analysis (CWA) data obtained during routine APTT testing using:

   • Optical coagulation analyzers (ACL TOP platform).
   • Silica-based APTT reagent (SynthASil®).
3. Completion of the standard laboratory evaluation for prolonged APTT as part of routine clinical care, when clinically indicated.
4. Samples collected and processed in accordance with the standardized preanalytical protocol defined in the study SOP.

5. Patients evaluated in either:

   • Preoperative assessment, or
   • Routine clinical practice (non-preoperative setting).

Exclusion Criteria:

1. Prolonged prothrombin time (PT) or combined prolongation of PT and APTT.

2- Inadequate preanalytical conditions, defined as non-compliance with the study SOP, including but not limited to:

• Incorrect blood-to-anticoagulant ratio.
• Delayed plasma processing beyond protocol-defined time limits.

• Inadequate centrifugation or plasma quality.

  3. Absence of required CWA data or unavailable clot waveform images.

  4. Samples in which APTT values are outside the measurable range of the analyzer, preventing extraction of CWA-derived parameters.

  5- Patients with missing essential clinical or laboratory data required for application of the APTTO models.

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort

Intervention / Treatment

Patients with prolonged activated partial thromboplastin time (APTT); Patients with prolonged activated partial thromboplastin time (APTT) and normal prothrombin time undergoing routine laboratory evaluation. Clot waveform analysis (CWA) data and clinical information are collected prospectively as part of standard care and analyzed using the APTTO predictive models. No additional diagnostic or therapeutic procedures are performed.

Other: Clot waveform analysis-based risk stratification (APTTO models); Application of the APTTO predictive models (APTTO1 and APTTO2) to clot waveform analysis parameters generated during routine activated partial thromboplastin time testing, for research purposes only. The model output does not influence clinical management or surgical decision-making during the study.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Discriminatory performance of the APTTO model	Discrimination of the APTTO1 and APTTO2 models for identifying the cause of prolonged activated partial thromboplastin time (APTT), assessed by the area under the receiver operating characteristic curve (AUC) in an independent multicenter cohort.	Baseline (at the time of prolonged APTT laboratory assessment)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Calibration-in-the-large of the APTTO model	Calibration-in-the-large of the APTTO1 and APTTO2 models assessing agreement between predicted and observed probabilities in an independent multicenter cohort.	Baseline (at the time of prolonged APTT laboratory assessment)
Calibration slope of the APTTO model	Calibration slope of the APTTO1 and APTTO2 models, evaluating the relationship between predicted and observed risk across the probability spectrum.	Baseline (at the time of prolonged APTT laboratory assessment)
Overall prediction error of the APTTO model	Overall prediction error of the APTTO1 and APTTO2 models, assessed using the Brier score.	Baseline (at the time of prolonged APTT laboratory assessment)
Clinical utility of the APTTO model assessed by decision curve analysis	Net clinical benefit of the APTTO models compared with investigate-all and investigate-none strategies, assessed by decision curve analysis across clinically plausible threshold probabilities.	Baseline (at the time of prolonged APTT laboratory assessment)
Diagnostic accuracy of predefined APTTO cut-offs	Sensitivity, specificity, positive predictive value, and negative predictive value of predefined APTTO cut-offs for identifying pathological causes of prolonged APTT.	Baseline (at the time of prolonged APTT laboratory assessment)
Interobserver agreement in clot waveform morphology classification	Agreement between local investigators and central reader (blinded to clinical data) for qualitative clot waveform morphology classification, assessed using Cohen´s kappa or Fleiss´kappa statistics, as appropriate.	Baseline (at the time of prolonged APTT laboratory assessment)
Estimated impact of the APTTO algorithm on preoperative workflow	Estimated potential reduction in time to surgical cleareance and avoidance of additional etiologic testing based on application of the APTTO algorithm.	Baseline (model-based estimation using timing data from index APTT laboratory assessment through surgical clearance)
Association between clot waveform morphology and severity of factor deficiency	Assessment of the association between clot waveform morphology, particularly strictly normal waveform patterns, and the severity of intrinsic pathway factor deficiencies in patients with prolonged activated partial thromboplastin time (APTT). This analysis aims to determine whether a normal waveform is associated with higher residual factor levels and a lower likelihood of clinically relevant deficiency. During the course of the study, additional exploratory objectives were incorporated to further investigate the clinical and physiological implications of clot waveform analysis. In particular, the relationship between strictly normal waveform morphology and the severity of factor deficiency will be evaluated prospectively in the remaining study cohort.	During the preoperative evaluation period
Clinical impact of APTTO implementation in preoperative management	Evaluation of the clinical impact of implementing a clot waveform analysis-based diagnostic strategy (APTTO) in the preoperative management of prolonged activated partial thromboplastin time (APTT). This analysis will compare patients managed before and after implementation of APTTO at the development center, time to surgical clearance, and perioperative outcomes. This objective was incorporated during the course of the study to further assess the clinical implications of APTTO in routine practice and will be evaluated prospectively in the remaining study cohort.	During the preoperative evaluation period and up to 30 days after surgery.

Collaborators and Investigators

• Sponsor: Instituto de Investigación Sanitaria de la Fundación Jiménez Díaz
• Investigators: Principal Investigator: Diego Velasco Rodríguez, MD, PhD, Hospital Universitario Fundación Jiménez Díaz / IIS-FJD

Publications and helpful links

General Publications

• Velasco-Rodríguez D, et al. Development and internal validation of the APTTO model: a clot waveform analysis-based tool to identify preoperative patients with prolonged APTT who do not require etiologic investigation.
• Shimomura D, Matsumoto T, Sugimoto K, Takata T, Kouno A, Shimada M, Matsuo S, Kamioka M. The First-Derivative Curve of the Coagulation Waveform Reveals the Cause of aPTT Prolongation. Clin Appl Thromb Hemost. 2020 Jan-Dec;26:1076029620978810. doi: 10.1177/1076029620978810.
• Tokunaga N, Inoue C, Sakata T, Kagawa K, Abe M, Takamatsu N, Nakao T, Doi T. Usefulness of the second-derivative curve of activated partial thromboplastin time on the ACL-TOP coagulation analyzer for detecting factor deficiencies. Blood Coagul Fibrinolysis. 2016 Jun;27(4):474-6. doi: 10.1097/MBC.0000000000000436. No abstract available.

Study record dates

Study Major Dates

• Study Start (Actual): January 13, 2026
• Primary Completion (Estimated): March 1, 2027
• Study Completion (Estimated): March 1, 2027

Study Registration Dates

• First Submitted: January 26, 2026
• First Submitted That Met QC Criteria: February 10, 2026
• First Posted (Actual): February 18, 2026

Study Record Updates

• Last Update Posted (Actual): May 1, 2026
• Last Update Submitted That Met QC Criteria: April 27, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Hemostasis; Risk Stratification; Coagulation Disorders; von Willebrand Disease; Clinical Decision-Making; Resource Utilization; CWA; Lupus Anticoagulant; Diagnostic Algorithm; Preoperative Assessment; Decision Support Systems; Predictive Model; Activated Partial Thromboplastin Time; Prolonged APTT; Clot Waveform Analysis; Coagulation Factor Deficiency; Laboratory Automation; Surgical Delay
• Additional Relevant MeSH Terms: Vascular Diseases; Cardiovascular Diseases; Genetic Diseases, Inborn; Hematologic Diseases; Hemorrhagic Disorders; Blood Platelet Disorders; Blood Coagulation Disorders, Inherited; Coagulation Protein Disorders; Congenital, Hereditary, and Neonatal Diseases and Abnormalities; Hemic and Lymphatic Diseases; Hemostatic Disorders; Blood Coagulation Disorders; von Willebrand Diseases
• Other Study ID Numbers: APTTO-EXT-IISFJD-2026; Pending ethics committee aprov (Other Identifier: Ethics Committee of Fundacion Jimenez Diaz)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Individual participant data will not be shared publicly. Data will be analyzed in aggregated and pseudonymized form exclusively for the objectives of the study, in accordance with applicable data protection regulations and ethics committee approval.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No