Abstract
Background: Ultrasonography is an essential clinical tool, offering rapid, bedside, imaging that supports timely clinical decision-making. Its effectiveness, however, depends heavily on examiner skill, requiring structured, practice-oriented training. Traditional tutor-led ultrasound teaching is limited by personnel and resource shortages. Blended learning, combining self-directed digital preparation with targeted hands-on teaching, may help overcome these constraints while maintaining educational quality. This randomized controlled non-inferiority trial evaluated whether a blended-learning abdomen ultrasound curriculum with reduced face-to-face teaching is as effective as a conventional full-day peer-teaching course. Methods: Clinical-phase medical students at Philipps University Marburg were eligible to participate. After enrollment and written informed consent, students were randomized to either a conventional one-day (8-hour) face-to-face curriculum or a blended-learning curriculum consisting of online preparatory modules, followed by a shortened, 4-hour hands-on session. Both formats were delivered by trained student peer tutors. The primary outcome was performance in an Objective Structured Clinical Examination (OSCE; 0–20 points). Secondary outcomes included theoretical knowledge assessed through a written test (0–20 points) and student perceptions measured via a Likert-scale questionnaire. Results: A total of 118 students were randomized (60 blended learning; 58 conventional). Blended learning was non-inferior to the conventional curriculum in OSCE performance (14.68 ± 2.72 vs 14.86 ± 2.67; mean difference 0.18; 95% CI −0.80 to 1.16), with the confidence interval fully within the non-inferiority margin of Δ = 4. Mean theoretical knowledge scores did not differ significantly (16.35 ± 2.74 vs 16.59 ± 2.69; p = 0.35). Student evaluations indicated high perceived knowledge and skills gain in both groups, with comparable acceptance and course organization ratings. Conclusions: A blended-learning curriculum that shifts theoretical instruction from face-to-face teaching to structured self-directed online preparation, was non-inferior to a conventional full-day ultrasound course in teaching practical abdominal ultrasound skills. This approach provides an effective and resource-efficient strategy to broaden access to ultrasound education while preserving instructional quality. Trial registration: Not applicable.
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Article
ERCT Criteria Breakdown
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Level 1 Criteria
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C
Class-level RCT
- Participants were randomized individually (not by class/school), and the intervention was not one-to-one tutoring.
- After course registration and provision of written informed consent, participants were randomized to either the blended-learning curriculum or the conventional face-to-face curriculum.
Relevant Quotes:
1) "After course registration and provision of written informed consent, participants were randomized to either the blended-learning curriculum or the conventional face-to-face curriculum." (p. 6)
2) "All medical students at Marburg University who had passed the first German state examination and were therefore in the clinical phase of training were eligible to participate." (p. 6)
Detailed Analysis:
Criterion C requires randomization at the class level (or stronger), unless the intervention is clearly one-to-one tutoring/personal teaching.
The paper explicitly states that "participants" were randomized, which indicates individual student-level randomization into two curricula. The intervention is delivered as a course format (peer-taught ultrasound course) rather than an individualized tutoring program.
Because randomization was not at the class (or school/site) level and the tutoring exception does not apply, the study does not meet Criterion C.
Final sentence: Criterion C is not met because randomization occurred at the individual student level rather than by class/school and the study is not a one-to-one tutoring intervention.
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E
Exam-based Assessment
- Outcomes were assessed with an OSCE developed for this study and a short written test, not a widely recognized standardized external exam.
- The OSCE was specifically developed for this study in collaboration with the clinical head of the university hospital ultrasound unit in internal medicine and was aligned with the predefined learning objectives of the course.
Relevant Quotes:
1) "The primary outcome was performance in an Objective Structured Clinical Examination (OSCE) [21] administered at the end of the curricula (maximum score: 20 points)." (p. 9)
2) "The OSCE was specifically developed for this study in collaboration with the clinical head of the university hospital ultrasound unit in internal medicine and was aligned with the predefined learning objectives of the course." (p. 9)
3) "Theoretical knowledge was measured using a short written test." (p. 9)
Detailed Analysis:
Criterion E requires a standardized exam-based assessment that is widely recognized and not custom-built for the study.
The primary outcome (OSCE) is explicitly stated to be "specifically developed for this study" and aligned to the course learning objectives, which indicates a bespoke assessment. The secondary theoretical measure is described as a "short written test" with no indication that it is an externally standardized, widely recognized examination.
Therefore, the study does not meet the ERCT requirement for standardized exam-based assessment.
Final sentence: Criterion E is not met because the primary OSCE and the written test were study-specific assessments rather than a recognized standardized exam.
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T
Term Duration
- Outcomes were measured immediately at the end of a short course (one day, plus one week of preparatory access), not at least one academic term after the intervention began.
- The primary outcome was performance in an Objective Structured Clinical Examination (OSCE) administered at the end of the curricula.
Relevant Quotes:
1) "The extracurricular course was delivered as a one-day (8-hour) peer-to-peer program, alternating between focused theoretical teaching and supervised hands-on practice." (p. 7)
2) "Students were given access to the online materials one week before the on-site course and were asked to complete all modules by then." (p. 8)
3) "The primary outcome was performance in an Objective Structured Clinical Examination (OSCE) [21] administered at the end of the curricula (maximum score: 20 points)." (p. 9)
Detailed Analysis:
Criterion T requires outcomes to be measured at least one academic term (roughly 3 to 4 months) after the intervention begins.
The conventional curriculum is explicitly "one-day (8-hour)". The blended curriculum adds online access "one week before the on-site course" and then a shorter in-person session. The OSCE (primary outcome) is administered "at the end of the curricula", indicating immediate post-curriculum measurement rather than term-long follow-up.
Thus, the required minimum follow-up duration is not satisfied.
Final sentence: Criterion T is not met because the primary outcome was assessed at the end of a short course rather than after at least one academic term from intervention start.
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D
Documented Control Group
- The study explicitly states key baseline demographics and prior ultrasound experience were not collected, and it does not report baseline performance measures for the control group.
- Basic demographic variables such as age, gender, or prior clinical exposure were also not collected, which limits the ability to explore subgroup effects or identify potential confounders.
Relevant Quotes:
1) "Students' prior ultrasound experience was not formally assessed, although randomization likely minimized group differences." (p. 20)
2) "Basic demographic variables such as age, gender, or prior clinical exposure were also not collected, which limits the ability to explore subgroup effects or identify potential confounders." (p. 20)
Detailed Analysis:
Criterion D requires a well-documented control group, including baseline demographics and baseline performance (or equivalent) to support comparability.
While the paper describes the control condition as the conventional face-to-face curriculum, it explicitly reports that prior ultrasound experience was not formally assessed and that basic demographic variables were not collected. The paper also does not present a baseline pre-test (e.g., pre-course OSCE/knowledge test) for either group that could serve as baseline performance documentation.
Therefore, control group documentation is insufficient for ERCT Criterion D.
Final sentence: Criterion D is not met because the paper lacks baseline demographics and baseline performance documentation for the control group.
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Level 2 Criteria
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S
School-level RCT
- The trial was conducted at a single university site and randomized individual students, not schools (or equivalent institutional sites).
- After course registration and provision of written informed consent, participants were randomized to either the blended-learning curriculum or the conventional face-to-face curriculum.
Relevant Quotes:
1) "On-site teaching took place at the Dr. Reinfried Pohl Center for Medical Education, Philipps University Marburg." (p. 5)
2) "After course registration and provision of written informed consent, participants were randomized to either the blended-learning curriculum or the conventional face-to-face curriculum." (p. 6)
Detailed Analysis:
Criterion S requires school-level (or equivalent site-level) randomization among multiple schools/sites.
The study was implemented at one institution (Philipps University Marburg) and randomizes individual participants to two curricula. There is no indication that multiple schools (or comparable sites) were randomized.
Final sentence: Criterion S is not met because randomization was at the participant level within a single site rather than among schools/sites.
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I
Independent Conduct
- The authors created the blended modules and were involved in course implementation and assessments, with no stated independent external evaluation team.
- T.S., L.B., and H.S were involved in the implementation of the ultrasound course and assessments.
Relevant Quotes:
1) "Building on the selected structures (Table 1) and the teaching materials used in the conventional course, we created self-directed preparatory modules specifically for this study." (p. 8)
2) "L.B., T.S. and H.S. developed the trial. T.S., L.B., and H.S were involved in the implementation of the ultrasound course and assessments." (p. 22)
3) "L.B., A.M., J.K. F.M. and H.S. analyzed the data and interpreted the findings." (p. 22)
Detailed Analysis:
Criterion I requires evidence that the study was conducted independently from the intervention designers (e.g., external evaluators or a clear separation of roles).
The paper states the authors created the blended-learning modules and the author contributions explicitly report that the same author group developed the trial and was involved in implementation and assessments, and also analyzed the data. No statement indicates an independent third-party evaluation team conducted the outcome assessment or analysis.
Final sentence: Criterion I is not met because the intervention designers were also involved in implementation, assessment, and analysis without documented independent evaluation.
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Y
Year Duration
- Outcomes were assessed at the end of the curriculum and the study duration is far shorter than 75% of an academic year; also, T is not met.
- The primary outcome was performance in an Objective Structured Clinical Examination (OSCE) administered at the end of the curricula.
Relevant Quotes:
1) "The extracurricular course was delivered as a one-day (8-hour) peer-to-peer program, alternating between focused theoretical teaching and supervised hands-on practice." (p. 7)
2) "The primary outcome was performance in an Objective Structured Clinical Examination (OSCE) [21] administered at the end of the curricula (maximum score: 20 points)." (p. 9)
Detailed Analysis:
Criterion Y requires outcome measurement at least 75% of an academic year after intervention start. Per ERCT rules, if Criterion T is not met then Criterion Y is not met either.
The quoted timeline shows a one-day course (plus short pre-access to online materials for the blended condition) with assessment at the end of the curriculum, which is far below the year-duration threshold.
Final sentence: Criterion Y is not met because outcomes were measured immediately after a short course and Criterion T is not met.
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B
Balanced Control Group
- The blended and conventional conditions provide comparable supervised hands-on resources and intentionally substitute online preparation for face-to-face theory; there is no evidence of a non-integral resource advantage for the intervention group.
- Students were randomized to either a conventional one-day (8-hour) face-to-face curriculum or a blended-learning curriculum consisting of online preparatory modules, followed by a shortened, 4-hour hands-on session.
Relevant Quotes:
1) "After enrollment and written informed consent, students were randomized to either a conventional one-day (8-hour) face-to-face curriculum or a blended-learning curriculum consisting of online preparatory modules, followed by a shortened, 4-hour hands-on session." (p. 2)
2) "Students were given access to the online materials one week before the on-site course and were asked to complete all modules by then." (p. 8)
3) "Face-to-face teaching time was reduced to a total of four hours and focused exclusively on hands-on scanning." (p. 8)
4) "In both curricula each instructor supervised a maximum of four students, with a maximum course size of seven participants." (p. 9)
5) "The extracurricular course was delivered as a one-day (8-hour) peer-to-peer program, alternating between focused theoretical teaching and supervised hands-on practice." (p. 7)
Detailed Analysis:
Criterion B asks whether the nature, quantity, and quality of educational resources (time, supervision, materials) are balanced between conditions, unless the difference is explicitly integral to what is being tested.
Here, the intervention is explicitly a blended-learning format that reduces face-to-face teaching and shifts theoretical instruction into structured online preparation. The control condition provides the theoretical component face-to-face within an 8-hour day.
Critically, supervised hands-on scanning (the in-person practical component) is documented as being delivered under comparable supervision structure, including a maximum of four students per instructor in both curricula. The intervention does not appear to add a separate, optional extra resource unrelated to the blended-format definition; rather, it substitutes online modules for face-to-face theory and reduces on-site time by design.
The paper does not quantify total time spent in the online modules, but the intervention is framed as a structured replacement of face-to-face theory, not an additional non-integral add-on that would confound causal attribution.
Final sentence: Criterion B is met because the groups have comparable supervised hands-on resources and the online preparation versus in-person theory difference is integral to the intervention being tested rather than an unbalanced, non-integral resource advantage.
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Level 3 Criteria
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R
Reproduced
- No independent replication of this specific trial by a different research team was found or documented at the time of this ERCT check.
Relevant Quotes:
1) "A prospective, randomized controlled parallel group non-inferiority trial was conducted during the winter term 2022/2023." (p. 5)
Detailed Analysis:
Criterion R requires that the specific study (or its core experimental claim, using substantially the same intervention comparison and design) be independently replicated by other authors in a peer-reviewed outlet.
The paper itself does not claim replication. An internet search conducted on 2026-03-13 did not identify a peer-reviewed independent replication of this specific 2022/2023 Marburg non-inferiority trial comparing an AMBOSS-based blended curriculum with a conventional full-day peer-taught course.
Given the paper’s very recent publication date (2026-02-28), the absence of identified replications is expected, but still means the criterion is not met.
Final sentence: Criterion R is not met because no independent replication of this specific trial was found at the time of checking.
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A
All-subject Exams
- E is not met (no standardized external exams), so A cannot be met; the outcomes are limited to ultrasound OSCE and a short written test rather than all-subject standardized exams.
- The primary outcome was performance in an Objective Structured Clinical Examination (OSCE) administered at the end of the curricula.
Relevant Quotes:
1) "The primary outcome was performance in an Objective Structured Clinical Examination (OSCE) [21] administered at the end of the curricula (maximum score: 20 points)." (p. 9)
2) "Theoretical knowledge was measured using a short written test." (p. 9)
Detailed Analysis:
Criterion A requires standardized exam-based assessment across all main subjects, and per ERCT rules, if Criterion E is not met then Criterion A is not met.
The study assesses abdominal ultrasound competence via an OSCE and a short written test. These are not standardized external exams, and they do not represent assessment across all main subjects (they are focused on the specific ultrasound training outcomes).
Final sentence: Criterion A is not met because Criterion E is not met and outcomes are limited to ultrasound-specific assessments rather than standardized all-subject exams.
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G
Graduation Tracking
- The paper reports no long-term follow-up, and no follow-up publications by the same authors tracking participants to graduation were found; also, Y is not met so G cannot be met.
- No long-term follow-up was conducted, leaving the durability of acquired skills uncertain.
Relevant Quotes:
1) "No long-term follow-up was conducted, leaving the durability of acquired skills uncertain." (p. 20)
Detailed Analysis:
Criterion G requires tracking participants until graduation. Per ERCT rules, if Criterion Y is not met then Criterion G is not met.
Independently of that dependency, the paper explicitly states that no long-term follow-up was conducted. An internet search on 2026-03-13 did not identify subsequent follow-up publications by the same author team that track this cohort to graduation (or an equivalent completion endpoint for the participants).
Final sentence: Criterion G is not met because the study conducted no long-term follow-up to graduation and no graduation-tracking follow-up paper was found, and Criterion Y is not met.
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P
Pre-Registered
- The study states trial registration was not applicable and explicitly reports it was not pre-registered in a trial registry.
- The study was not pre-registered in a trial registry.
Relevant Quotes:
1) "Trial registration: Not applicable." (p. 3)
2) "The study was not pre-registered in a trial registry." (p. 21)
Detailed Analysis:
Criterion P requires that the study protocol be pre-registered before data collection begins, with evidence (registry and dates) supporting that timing.
The paper explicitly states trial registration is "Not applicable" and further clarifies that the study was not pre-registered in a trial registry. This directly indicates the ERCT pre-registration requirement is not satisfied.
Final sentence: Criterion P is not met because the study was not pre-registered in any trial registry.
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