Blood ClotNCT06329921
Inpatient Monitoring of Unfractionated Heparin
A study testing PTT protocol and anti-Xa protocol in people with Blood Clot and Thrombosis, run by Vanderbilt University Medical Center at 1 site in United States.
Trial summary
Unfractionated heparin (UFH) is the most widely used intravenous (IV) anticoagulant for treating and preventing thromboembolic disease (e.g., blood clots ). UFH must be closely monitored and adjusted in the hospital. Read more about this study
- Who is it for?
- Ages 18 years and older
- Conditions the study is for
- Blood Clot, Thrombosis
- What is being tested?
- PTT protocol and anti-Xa protocol
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 700 participants
- Where
- 1 siteUnited States
- Study dates
- 26 Jun 2024to 8 Sep 2026
- Phase
- Interventional
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Patients at Vanderbilt University Hospital age 18 years and older who are admitted as observation or inpatients for whom intravenous unfractionated heparin (monitored via the PTT nurse-managed protocol) is ordered.
- Baseline PTT value is ≥0 and ≤ 36.0 seconds
- Baseline heparin level anti-Xa assay value is ≥0 and ≤0.3
Who cannot join
- Indication for anticoagulation is extracorporeal membrane oxygenation or cerebrovascular ischemic event.
- Provider determines patient is not appropriate for the study.
Trial locations and contacts
1 site in 1 country.
United States1 site
Vanderbilt University Medical Center
Nashville, Tennessee, 37232
About this study
Unfractionated heparin (UFH) is the most widely used intravenous (IV) anticoagulant for treating and preventing thromboembolic disease (e.g., blood clots ). UFH must be closely monitored and adjusted in the hospital. There are two assays used to monitor UFH: 1) the activated partial thromboplastin time (PTT) and 2) the chromogenic anti-factor Xa assay (anti-Xa). This study aims to compare PTT and anti-Xa methods for monitoring UFH in a pragmatic, randomized controlled trial to determine which helps patients reach a therapeutic anticoagulation range faster.
Read the detailed description
Unfractionated heparin (UFH) is the most widely used intravenous (IV) anticoagulant for the treatment and prevention of thromboembolic disease (e.g., blood clots ). When administered by intravenous injection, the onset of action is immediate. Indications for use of UFH include venous thromboembolism, acute coronary syndrome, and acute ischemic stroke. UFH is used to prevent thrombosis in the setting of arrhythmias, extracorporeal membrane oxygenation (ECMO), cardiopulmonary bypass (CPB), and endovascular procedures. The unpredictable pharmacokinetics of UFH and interpatient variability result in a narrow therapeutic index restricting its use to the hospital setting with close monitoring and adjustments.
Two validated assays exist and are in use at the VUMC adult hospital for the monitoring of unfractionated heparin: 1) the activated partial thromboplastin time (PTT) and 2) the chromogenic anti-factor Xa assay (anti-Xa). At VUMC, the PTT protocol is managed by nursing; the anti-Xa protocol is managed by clinical pharmacy. Both are clinically acceptable methods for titration and adjustment of unfractionated heparin. Assessing the therapeutic effect of unfractionated heparin is most often performed with the PTT, which requires institutional calibration to a specific heparin level to account for the variable PTT responses with different commercial reagents and laboratory instruments. The PTT can be influenced by various elements during sample processing, laboratory analysis, and patient biological factors that may cause it to be an inaccurate indication of the degree of anticoagulation. This can lead to patients not getting the correct heparin dosing for their clinical needs.
The anti-Xa assay is another method of measuring the degree of therapeutic effect of heparin. In routine clinical practice the anti-Xa is not as widely available and less familiar among many providers. This assay can be impacted by variability in sample collection and processing and laboratory analysis. Compared to the PTT assay, however, it is much less influenced by patient-specific biological factors. This may help improve heparin monitoring and titration to ensure patients receive therapeutic levels of anticoagulation and do not get too much or too little heparin. However, large studies using anti-Xa for management of heparin in the treatment of venous thromboembolism have not been performed.
PTT and anti-Xa heparin monitoring protocols have not been compared in a prospective, randomized setting. The study team will conduct a pragmatic, randomized clinical trial comparing the effectiveness of both methods for optimal monitoring of intravenous unfractionated heparin for systemic anticoagulation in hospitalized adult patients.
- Conditions
- Blood Clot, Thrombosis
- Being tested
- PTT protocol, anti-Xa protocol
- Keywords
- heparin, anticoagulation, anti-Xa, PTT
- Medical subject headings
- Thrombosis
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
PTT protocolOther
Patients will be monitored using the nurse-managed PTT protocol.
anti-Xa protocolOther
Patients will be monitored using the pharmacy-managed anti-Xa protocol.
| Study group | Role | What they receive |
|---|---|---|
| Active Comparator: PTT protocol | Active comparator | Patients randomized to this arm will be monitored using the nurse-managed PTT guided protocol. This includes patients on both high- and low-dose heparin protocols. Receives: Other: PTT protocol |
| Active Comparator: anti-Xa protocol | Active comparator | Patients randomized to this arm will be monitored using the pharmacy-managed anti-Xa protocol. This includes patients on both high- and low-dose heparin protocols. Receives: Other: anti-Xa protocol |
What is being measured
The primary outcome is the main question the study is designed to answer.
Time to therapeutic anticoagulation range
Time to reach therapeutic anticoagulation range by coagulation assay
Measured: Randomization to hospital discharge at approximately 5-7 days post-randomization
Secondary outcomes (6)
Measurements in therapeutic anticoagulation range
Percent of measurements in therapeutic range per coagulation assay, as defined by assay protocol
Measured: Randomization to hospital discharge at approximately 5-7 days post-randomization
Coagulation laboratory measurements
The number of coagulation laboratory measurements for overall in-hospital coagulation time.
Measured: Randomization to hospital discharge at approximately 5-7 days post-randomization
Heparin rate changes
Total number of heparin rate changes for overall in-hospital coagulation time
Measured: Randomization to hospital discharge at approximately 5-7 days post-randomization
New thrombotic events
Incidence of new thrombotic events on anticoagulation or within 24 hours of anticoagulation cessation
Measured: Randomization to hospital discharge at approximately 5-7 days post-randomization and for 24 hours after anticoagulation cessation.
New clinically relevant bleeding events
Incidence of clinically relevant bleeding adverse events on anticoagulation or within 48 hours of anticoagulation cessation, defined as: fatal bleeding, or overt events causing a decline in hemoglobin >2 g/dL over a 24-hour period, or bleeding leading to transfusion of two or more units of whole blood or red blood cells, or intracranial bleeding events.
Measured: Randomization to 48 hours after anticoagulation cessation, approximately 5-7 days post-randomization
New coagulation events
Incidence of new coagulation events on anticoagulation, including thrombotic events and clinically relevant bleeding adverse events as defined in Outcomes 5 and 6.
Measured: Randomization to 48 hours after anticoagulation cessation, approximately 5-7 days post-randomization
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted26 Mar 2024
- Study start26 Jun 2024
- Primary completion8 Sep 2026
- Study completion8 Sep 2026
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (7)Papers the sponsor has linked to this study.
- Other trials for Blood ClotStudies of the same condition, open and under way.
- More trials run by Vanderbilt University Medical CenterThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Health services research
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Model description
- This study will be performed as a pragmatic, randomized controlled clinical trial with parallel group assignment.
- Masking
- None (open label)
- Enrolment
- 700 participants (actual)
Sponsor and investigators
- Lead sponsor
- Vanderbilt University Medical Center
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Benjamin Tillman, Vanderbilt University Medical Center
- Investigators
- Benjamin Tillman, MD, Principal investigator, Vanderbilt University Medical Center
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06329921
- Sponsor's protocol ID
- 232192
- Status last verified
- Sep 2026
- First submitted
- 19 Mar 2024
- Last updated
- 21 Sep 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Yes: Individual participant data that underlie the results reported will be made available (including data dictionaries) after de-identification.
Publications
Hirsh J, Warkentin TE, Raschke R, Granger C, Ohman EM, Dalen JE. Heparin and low-molecular-weight heparin: mechanisms of action, pharmacokinetics, dosing considerations, monitoring, efficacy, and safety. Chest. 1998 Nov;114(5 Suppl):489S-510S. doi: 10.1378/chest.114.5_supplement.489s. No abstract available.
PubMed 9822059Smythe MA, Priziola J, Dobesh PP, Wirth D, Cuker A, Wittkowsky AK. Guidance for the practical management of the heparin anticoagulants in the treatment of venous thromboembolism. J Thromb Thrombolysis. 2016 Jan;41(1):165-86. doi: 10.1007/s11239-015-1315-2.
PubMed 26780745Eikelboom JW, Hirsh J. Monitoring unfractionated heparin with the aPTT: time for a fresh look. Thromb Haemost. 2006 Nov;96(5):547-52.
PubMed 17080209Olson JD, Arkin CF, Brandt JT, Cunningham MT, Giles A, Koepke JA, Witte DL. College of American Pathologists Conference XXXI on laboratory monitoring of anticoagulant therapy: laboratory monitoring of unfractionated heparin therapy. Arch Pathol Lab Med. 1998 Sep;122(9):782-98.
PubMed 9740136Wool GD, Lu CM; Education Committee of the Academy of Clinical Laboratory Physicians and Scientists. Pathology consultation on anticoagulation monitoring: factor X-related assays. Am J Clin Pathol. 2013 Nov;140(5):623-34. doi: 10.1309/AJCPR3JTOK7NKDBJ.
PubMed 24124140Marlar RA, Clement B, Gausman J. Activated Partial Thromboplastin Time Monitoring of Unfractionated Heparin Therapy: Issues and Recommendations. Semin Thromb Hemost. 2017 Apr;43(3):253-260. doi: 10.1055/s-0036-1581128. Epub 2016 Jun 6.
PubMed 27272964Van Winkle G, Tillman B, Choi L, Berardi S, Dear ML, Lewis A, Rice TW; Vanderbilt Center for Learning Healthcare. Comparison of heparin assay monitoring protocols (CHAMP): study protocol for a pragmatic randomised trial. BMJ Open. 2026 Jul 29;16(7):e114634. doi: 10.1136/bmjopen-2025-114634.
PubMed 42526926
Study at a glance
From the registry record, last updated by the sponsor on 21 Sep 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Inpatient Monitoring of Unfractionated Heparin
- ClinicalTrials.gov ID
- NCT06329921
- Acronym / sponsor ID
- 232192
- Conditions
- Blood Clot, Thrombosis
- Keywords
- heparin, anticoagulation, anti-Xa, PTT
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 700 participants (actual)
- Lead sponsor
- Vanderbilt University Medical CenterUniversity, hospital or other
- Study start
- 26 Jun 2024 (actual)
- Primary completion
- 8 Sep 2026 (actual)
- Study completion
- 8 Sep 2026 (actual)
- First posted
- 26 Mar 2024 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Unfractionated heparin (UFH) is the most widely used intravenous (IV) anticoagulant for treating and preventing thromboembolic disease (e.g., blood clots ). UFH must be closely monitored and adjusted in the hospital. There are two assays used to monitor UFH: 1) the activated partial thromboplastin time (PTT) and 2) the chromogenic anti-factor Xa assay (anti-Xa). This study aims to compare PTT and anti-Xa methods for monitoring UFH in a pragmatic, randomized controlled trial to determine which helps patients reach a therapeutic anticoagulation range faster.
Detailed description
Unfractionated heparin (UFH) is the most widely used intravenous (IV) anticoagulant for the treatment and prevention of thromboembolic disease (e.g., blood clots ). When administered by intravenous injection, the onset of action is immediate. Indications for use of UFH include venous thromboembolism, acute coronary syndrome, and acute ischemic stroke. UFH is used to prevent thrombosis in the setting of arrhythmias, extracorporeal membrane oxygenation (ECMO), cardiopulmonary bypass (CPB), and endovascular procedures. The unpredictable pharmacokinetics of UFH and interpatient variability result in a narrow therapeutic index restricting its use to the hospital setting with close monitoring and adjustments.
Two validated assays exist and are in use at the VUMC adult hospital for the monitoring of unfractionated heparin: 1) the activated partial thromboplastin time (PTT) and 2) the chromogenic anti-factor Xa assay (anti-Xa). At VUMC, the PTT protocol is managed by nursing; the anti-Xa protocol is managed by clinical pharmacy. Both are clinically acceptable methods for titration and adjustment of unfractionated heparin. Assessing the therapeutic effect of unfractionated heparin is most often performed with the PTT, which requires institutional calibration to a specific heparin level to account for the variable PTT responses with different commercial reagents and laboratory instruments. The PTT can be influenced by various elements during sample processing, laboratory analysis, and patient biological factors that may cause it to be an inaccurate indication of the degree of anticoagulation. This can lead to patients not getting the correct heparin dosing for their clinical needs.
The anti-Xa assay is another method of measuring the degree of therapeutic effect of heparin. In routine clinical practice the anti-Xa is not as widely available and less familiar among many providers. This assay can be impacted by variability in sample collection and processing and laboratory analysis. Compared to the PTT assay, however, it is much less influenced by patient-specific biological factors. This may help improve heparin monitoring and titration to ensure patients receive therapeutic levels of anticoagulation and do not get too much or too little heparin. However, large studies using anti-Xa for management of heparin in the treatment of venous thromboembolism have not been performed.
PTT and anti-Xa heparin monitoring protocols have not been compared in a prospective, randomized setting. The study team will conduct a pragmatic, randomized clinical trial comparing the effectiveness of both methods for optimal monitoring of intravenous unfractionated heparin for systemic anticoagulation in hospitalized adult patients.
Study design
- Primary purpose
- Health services research
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Number of arms
- 2
- Model description
- This study will be performed as a pragmatic, randomized controlled clinical trial with parallel group assignment.
| Arm | Type | Receives |
|---|---|---|
| Active Comparator: PTT protocol | Active comparator | Other: PTT protocolPatients randomized to this arm will be monitored using the nurse-managed PTT guided protocol. This includes patients on both high- and low-dose heparin protocols. |
| Active Comparator: anti-Xa protocol | Active comparator | Other: anti-Xa protocolPatients randomized to this arm will be monitored using the pharmacy-managed anti-Xa protocol. This includes patients on both high- and low-dose heparin protocols. |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (3 listed)
- Patients at Vanderbilt University Hospital age 18 years and older who are admitted as observation or inpatients for whom intravenous unfractionated heparin (monitored via the PTT nurse-managed protocol) is ordered.
- Baseline PTT value is ≥0 and ≤ 36.0 seconds
- Baseline heparin level anti-Xa assay value is ≥0 and ≤0.3
Key exclusion criteria (2 listed)
- Indication for anticoagulation is extracorporeal membrane oxygenation or cerebrovascular ischemic event.
- Provider determines patient is not appropriate for the study.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| PTT protocolPatients will be monitored using the nurse-managed PTT protocol. | Other | Active Comparator: PTT protocol |
| anti-Xa protocolPatients will be monitored using the pharmacy-managed anti-Xa protocol. | Other | Active Comparator: anti-Xa protocol |
Primary outcome
Time to therapeutic anticoagulation range
Time frame: Randomization to hospital discharge at approximately 5-7 days post-randomization
Time to reach therapeutic anticoagulation range by coagulation assay
6 secondary outcomes
Measurements in therapeutic anticoagulation range
Time frame: Randomization to hospital discharge at approximately 5-7 days post-randomization
Coagulation laboratory measurements
Time frame: Randomization to hospital discharge at approximately 5-7 days post-randomization
Heparin rate changes
Time frame: Randomization to hospital discharge at approximately 5-7 days post-randomization
New thrombotic events
Time frame: Randomization to hospital discharge at approximately 5-7 days post-randomization and for 24 hours after anticoagulation cessation.
New clinically relevant bleeding events
Time frame: Randomization to 48 hours after anticoagulation cessation, approximately 5-7 days post-randomization
New coagulation events
Time frame: Randomization to 48 hours after anticoagulation cessation, approximately 5-7 days post-randomization
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 21 Sep 2026.
- Background: PubMed 9822059Hirsh J, Warkentin TE, Raschke R, Granger C, Ohman EM, Dalen JE. Heparin and low-molecular-weight heparin: mechanisms of action, pharmacokinetics, dosing considerations, monitoring, efficacy, and safety. Chest. 1998 Nov;114(5 Suppl):489S-510S. doi: 10.1378/chest.114.5_supplement.489s. No abstract available.
- Background: PubMed 26780745Smythe MA, Priziola J, Dobesh PP, Wirth D, Cuker A, Wittkowsky AK. Guidance for the practical management of the heparin anticoagulants in the treatment of venous thromboembolism. J Thromb Thrombolysis. 2016 Jan;41(1):165-86. doi: 10.1007/s11239-015-1315-2.
- Background: PubMed 17080209Eikelboom JW, Hirsh J. Monitoring unfractionated heparin with the aPTT: time for a fresh look. Thromb Haemost. 2006 Nov;96(5):547-52.
- Background: PubMed 9740136Olson JD, Arkin CF, Brandt JT, Cunningham MT, Giles A, Koepke JA, Witte DL. College of American Pathologists Conference XXXI on laboratory monitoring of anticoagulant therapy: laboratory monitoring of unfractionated heparin therapy. Arch Pathol Lab Med. 1998 Sep;122(9):782-98.
- Background: PubMed 24124140Wool GD, Lu CM; Education Committee of the Academy of Clinical Laboratory Physicians and Scientists. Pathology consultation on anticoagulation monitoring: factor X-related assays. Am J Clin Pathol. 2013 Nov;140(5):623-34. doi: 10.1309/AJCPR3JTOK7NKDBJ.
- Background: PubMed 27272964Marlar RA, Clement B, Gausman J. Activated Partial Thromboplastin Time Monitoring of Unfractionated Heparin Therapy: Issues and Recommendations. Semin Thromb Hemost. 2017 Apr;43(3):253-260. doi: 10.1055/s-0036-1581128. Epub 2016 Jun 6.
- Derived from this study: PubMed 42526926Van Winkle G, Tillman B, Choi L, Berardi S, Dear ML, Lewis A, Rice TW; Vanderbilt Center for Learning Healthcare. Comparison of heparin assay monitoring protocols (CHAMP): study protocol for a pragmatic randomised trial. BMJ Open. 2026 Jul 29;16(7):e114634. doi: 10.1136/bmjopen-2025-114634.
- Individual participant dataSharing planned: Yes. Individual participant data that underlie the results reported will be made available (including data dictionaries) after de-identification.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Benjamin Tillman, MD principal investigator
Vanderbilt University Medical Center
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing PTT protocol and anti-Xa protocol in people with Blood Clot and Thrombosis, run by Vanderbilt University Medical Center at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 3 inclusion and 2 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 21 Sep 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Time to therapeutic anticoagulation range (time frame: Randomization to hospital discharge at approximately 5-7 days post-randomization). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT06329921, which also lists 7 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 21 Sep 2026.