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Blood LossNCT06855472

The MAR Method Versus the Visual Estimation Method in Predicting External Blood Loss

A study testing The MAR method in people with Blood Loss, run by Betül Akbuğa Özel at 2 sites in Turkey (Türkiye).

Completed

Finished. The study has ended and is not enrolling. Results may be posted on the official record.

Official record
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Trial summary

The goal of this educational clinical trial is to determine whether the MAR method is more effective than the Visual Estimation method for estimating blood loss. It also aims to assess whether factors such as gender, weight, and height influence blood loss estimates when using the MAR method. Read more about this study

Who is it for?
Any ageHealthy volunteers can take part
Conditions the study is for
Blood Loss
What is being tested?
The MAR method
Could I receive a placebo?
No, everyone receives an active treatment
How many people
237 participants
Where
2 sitesTurkey (Türkiye)
Study dates
7 May 2017to 10 May 2017
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 Any age
  • All sexes
  • Healthy volunteers accepted
  • Child, Adult, Older adult

Who may be able to join

  • Being a second-year paramedic or medical student
  • No prior theoretical or practical training in estimating external blood loss
  • Willingness to participate in the study

Who cannot join

  • Not being a second-year paramedic or medical student
  • Having received theoretical or practical training in estimating external blood loss
  • Declining to participate in the study

Trial locations and contacts

2 sites in 1 country.

Turkey (Türkiye)2 sites
  • Baskent University

    Ankara, Ankara, 06790

  • Ankara Yıldırım Beyazıt University, Faculty of Medicine, Ankara Bilkent City Hospital, Department of Emergency Medicine

    Ankara, Ankara, 06800

Other trials in Turkey (Türkiye)

About this study

Official title: Comparison of the MAR Method and the Visual Estimation Method in Predicting External Blood Loss in Health Students

The goal of this educational clinical trial is to determine whether the MAR method is more effective than the Visual Estimation method for estimating blood loss. It also aims to assess whether factors such as gender, weight, and height influence blood loss estimates when using the MAR method.

The main research questions it aims to answer are:

Read more
  • Does the MAR method provide more accurate blood loss estimates than the Visual Estimation method on flat, non-absorbent surfaces?
  • Does the MAR method take longer to estimate blood loss compared to the Visual Estimation method?
  • Do demographic factors such as gender, height, and weight affect blood loss estimates using the MAR method?
  • Do these demographic factors also influence the time required for estimation using the MAR method? Researchers will compare the MAR method with the Visual Estimation method to determine whether the MAR method is a useful tool for accurately estimating external blood loss in clinical skill training.

Participants will:

  • Sign an Informed Consent Form at the start of the study
  • Receive a 10-minute orientation session
  • Receive a 2-minute MAR method training (for the intervention group-)
  • Use either the MAR method or the Visual Estimation method for up to 60 seconds at each of the three stations
  • Receive a 2-minute MAR method training (for the control group)
  • Use the MAR method for up to 60 seconds at each of the three stations (for the control group)
Read the detailed description

Preliminary Preparation:

For this study, the Professional Skills Laboratories were used as the physical setting. The scenarios were set up at three different stations, each positioned in a separate corner of a large room. Room dividers separated the stations, and each had a designated entrance and exit to prevent participants who had completed their estimations from encountering those who had not yet participated.

Two researchers designed three distinct simulated environments and scenarios for the study. A synthetic blood product was used to enhance the realism of the simulated blood loss cases. In line with the MAR method's design principles, all three stations featured flat, non-absorbent surfaces.

  • Station 1: An acrylic (plexiglass) surface with 75 ml of blood.
  • Station 2: A flat, varnished wood surface with 150 ml of blood.
  • Station 3: A vinyl surface with 750 ml of blood.

Research Staff:

Three faculty researchers were present in the simulation area, overseeing orientation training for investigators and participants and coordinating activities at each station. Additionally, three medical student investigators were assigned to record blood volume estimates and estimation times.

Randomization:

Out of 237 eligible participants, 140 met the inclusion criteria and consented to participate. Since students from both departments had similar academic levels, ages, educational backgrounds, and no prior formal training in external blood loss estimation, the researchers used a non-stratified selection method. Participants were randomly assigned into two equal groups of 70 using a block randomization method (1:1 ratio) via the online service https://researchrandomizer.com/.

To assign participants, group names were written on paper, placed in a bag, and selected blindly.

  • Group 1: Control group (Visual Estimation method), (n1:70).
  • Group 2: Experimental group (MAR method), (n2:70). Group assignments were revealed to participants only when they arrived at the simulation room. To ensure allocation concealment, an independent researcher conducted both the randomization and group assignment before the trial began. While faculty researchers who prepared the stations knew the actual blood volumes, participants and study investigators who recorded the data were blinded to this information.

Study Description:

Student investigators at the stations received a 20-minute orientation before the study, covering its purpose, workflow, data form usage, and chronometer operation. Investigators recorded data in real-time as estimations were made. Neither participants nor investigators knew the actual blood volumes at the stations (double-blind design). At the start of the study, both groups received a 10-minute briefing, including:

  • Signing the consent form
  • Explaining the study's purpose
  • Introducing the simulation lab and research team

To clearly describe the procedures, the study is presented in two distinct periods. Period I was conducted to obtain the primary outcomes based on the primary objectives of the study. During this period::

  • Group 1 (Control): Estimated blood loss using the Visual Estimation (VE) method.
  • Group 2 (Experimental): Received 1-2 minutes of MAR method training separately, then estimated blood loss using the MAR method at all three stations.

Investigators at each station recorded blood volume estimates and estimation times for both groups. Researcher analysed data providing intergroup records (Visual estimation method [n1] vs MAR method [n2]) and intragroup records (Visual method [n1] vs MAR method [n1])

Period II process was conducted to obtain the secondary outcomes based on the secondary objectives of the study. In this period::

•Group 1 (Previously Control): Received 1-2 minutes of MAR method training separately, then estimated blood loss using the MAR method at all three stations.

Investigators recorded blood volume estimates and estimation times. For secondary outcomes, data from 140 participants (MAR method [n2] plus MAR method [n1]) were analyzed to determine whether gender, height, and weight influenced blood loss estimates and estimation durations using the MAR method.

Conditions
Blood Loss
Being tested
The MAR method
Keywords
blood loss, clinical skills, emergency medicine, medical students, paramedics, randomized controlled trial, simulation training
Medical subject headings
Hemorrhage

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • The MAR methodOther

    The study was conducted in three isolated stations. Two faculty researchers designed the scenarios, while three others supervised training. Medical student investigators recorded blood loss estimates and estimation times.

    Before the study, investigators received 20-minute training. Participants and investigators were blinded to actual blood volumes. Group 1 and Group 2 attended a 10-minute briefing, including consent and study introduction.

    The study had two phases. In Phase 1, Group 1 used the Visual Estimation (VE) method, while Group 2 received a 2-minute MAR method training before making estimations. In Phase 2, Group 1 was trained in the MAR method and repeated estimations.A data form recorded demographics, blood loss estimates, and estimation times.

    Group 1's VE data and Group 2's MAR data were compared between groups, while Group 1's VE and MAR data were analyzed within the group. Combined MAR data from both groups were used to assess the impact of gender, height, and weight.

Study groups in NCT06855472
Study groupRoleWhat they receive
Group 1: Visual Estimation Method (Control), (n1:70)No interventionThe Visual Estimation Method is the most commonly used technique for estimating external blood loss. It relies on quick visual assessment rather than precise measurement, providing an estimate within seconds.
Group 2: The MAR Method (Intervention), (n2:70)ExperimentalThe MAR (Merlin, Alter, Raffel) method, which was first described by Merlin et al. in 2009, is an alternative clinical skill recommended for estimating the amount of external blood loss on flat surfaces and does not depend on visualization. The method can learn within 1-2 minutes. In this method, the participants are given 60 sec to complete their estimations.
Receives: Other: The MAR method

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Blood loss volume estimate

    Blood loss volume estimates using the MAR and Visual Estimation (VE) methods were recorded in milliliters (ml). The participants had 60 seconds to complete their estimations at each station. Participants' verbal estimates were documented by researchers at each station on the study record form. Blood loss volume estimates obtained using Group 1's VE method (n1:70) Group 2's MAR method (n2:70) were compared between the groups. Blood loss volume estimates obtained using Group 1's VE method and MAR method (n1:70) were then compared within the group.

    Measured: From enrollment to the completion of method application in 20 minutes.

  2. Blood loss estimation time

    The blood loss estimation times for the MAR and VE methods were recorded in seconds. The participants had 60 seconds to complete their estimations at each station. A chronometer was used for each measurement. Blood loss estimation times obtained using Group 1's VE method (n1:70) and Group 2's MAR method (n2:70) were compared between the groups. Blood loss estimation times obtained using Group 1's VE method and MAR method (n1:70) were then compared within the group.

    Measured: From enrollment to the completion of method application in 20 minutes.

Secondary outcomes (2)
  1. Blood loss volume estimate of each participant using the MAR method

    In Phase 1, data from Group 2's MAR application (n2:70) and in Phase 2, data from Group 1's MAR application (n1:70) were combined, resulting in a total of 140 data points (n1:70 + n2:70). The analysis examined the relationship between blood loss estimates and participants' gender, height, and weight.

    Measured: From enrollment to the completion of method application in 25 minutes.

  2. Blood loss estimation time of each participant using the MAR method

    In Phase 1, data from Group 2's MAR application (n2:70) and in Phase 2, data from Group 1's MAR application (n1:70) were combined, resulting in a total of 140 data points (n1:70 + n2:70).The analysis examined the relationship between blood loss estimation times and participants' gender, height, and weight.

    Measured: From enrollment to the completion of method application in 25 minutes.

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted3 Mar 2025
  2. Study start7 May 2017
  3. Primary completion7 May 2017
  4. Study completion10 May 2017

Resources

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
Other
Allocation
Randomised
Intervention model
Parallel groups
Model description
Our study does not involve treatment, prevention, diagnosis, supportive care, screening, or medical devices. Instead, it is a randomized controlled trial that focuses on clinical skills training for estimating external blood loss in emergency medicine. The study designed a monocenter, double-blind, randomized, parallel-group, and controlled clinical educational study.
Masking
Double blind
Who is masked
Participant, Investigator
Enrolment
237 participants (actual)
IDs, dates and publications
ClinicalTrials.gov ID
NCT06855472
Sponsor's protocol ID
KA17/92
Status last verified
Feb 2025
First submitted
18 Feb 2025
Last updated
6 Mar 2025
Results posted
No
Data monitoring committee
No
FDA-regulated drug
No
FDA-regulated device
No
Individual data sharing
No: There is no plan to make IPD available. The IPD belongs to Baskent University; therefore, this decision must be made at the institutional level.

Publications

  • Merlin MA, Alter SM, Raffel B, Pryor PW 2nd. External blood loss estimation using the MAR Method. Am J Emerg Med. 2009 Nov;27(9):1085-90. doi: 10.1016/j.ajem.2008.07.039.

    PubMed 19931755
  • Yeung CY, Yim WW, Chan SY, Lo RSL, Leung LY, Hung KKC, Graham CA. Improvement of blood loss volume estimation by paramedics using a pictorial nomogram: A developmental study. Injury. 2017 Dec;48(12):2693-2698. doi: 10.1016/j.injury.2017.10.045. Epub 2017 Oct 31.

    PubMed 29108791
  • Ashburn JC, Harrison T, Ham JJ, Strote J. Emergency physician estimation of blood loss. West J Emerg Med. 2012 Sep;13(4):376-9. doi: 10.5811/westjem.2011.9.6669.

    PubMed 22942938
  • Williams B, Boyle M. Estimation of external blood loss by paramedics: is there any point? Prehosp Disaster Med. 2007 Nov-Dec;22(6):502-6. doi: 10.1017/s1049023x0000532x.

    PubMed 18709938
  • Shafi S, Kauder DR. Fluid resuscitation and blood replacement in patients with polytrauma. Clin Orthop Relat Res. 2004 May;(422):37-42. doi: 10.1097/01.blo.0000129149.15141.0c.

    PubMed 15187831
  • Akbuga Ozel B, Ozel G, Mamak Ekinci EB, Demirtola AE, Sahin G, Aksoy G, Yanikyurek I, Karaaslan MU. The MAR method versus the visual estimation method in predicting external blood loss: a randomized controlled study. Sci Rep. 2025 Aug 24;15(1):31091. doi: 10.1038/s41598-025-16169-0.

    PubMed 40851079

Questions about this trial

What is this clinical trial studying?

A study testing The MAR method in people with Blood Loss, run by Betül Akbuğa Özel at 2 sites in Turkey (Türkiye).

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 3 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 6 Mar 2025. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 2 sites in Turkey (Türkiye). 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?

Blood loss volume estimate (time frame: From enrollment to the completion of method application in 20 minutes.). The study lists 2 primary outcomes in all. 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 NCT06855472, which also lists 6 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 6 Mar 2025.

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