This prospective, randomised controlled trial aims to compare the safety and adequacy of the FH and NG methods for teaching PRB on a synthetic model to novice operators.
This study involved junior medical staff at Liverpool Hospital, Sydney, Australia. The trial protocol was approved by the South Western Sydney Local Health District Human Research Ethics Committee and registered with the Australia and New Zealand Clinical Trial Registry on 11/02/2020 (Registration number ACTRN12620000132943p).
We recruited participants in May-June 2020. Medical students, junior medical officers and basic physician trainees at Liverpool Hospital, who had no previous experience performing renal biopsies, were eligible to participate. Participants were approached either in person at an education session or via email. They were provided with the Participant Information Sheet. Participants provided written informed consent to participate.
Participants provided written information about their self-reported gender (male or female), medical seniority (medical student or doctor), previous experience with ultrasound (yes or no) and dominant hand (left or right). Randomisation was performed using a computer-generated allocation (MinimPy). A minimisation protocol was used to randomise participants by the variables described above. Participants watched an educational video created by the investigators detailing how to perform a renal biopsy that was specific to their allocation. This video showed the equipment used, and then demonstrated a safe and adequate renal biopsy on the model the participants were using. Elements emphasised in the educational video included the importance of performing an inferior pole biopsy, as well as being able to see the needle tip at the time of biopsy. Participants then had 5 minutes to familiarise themselves with an automatic spring-loaded biopsy needle (Max-Core™ Disposable Core Biopsy Instrument 16G x 16cm) and ask any questions of a nephrologist. They then directly entered the simulation room where an assessor, an ultrasound machine (GE Logiq S7, GE Healthcare, Wisconsin, USA) with all imaging settings pre-optimised, a synthetic human model (Blue Phantom Renal Biopsy Ultrasound Training Model, USA) and a curvilinear probe (C1-5D,1.8 – 5 MHz) with or without a needle guide attached (Ultra-Pro II™ In-Plane Ultrasound Needle Guides-Multi-Angle, GE Healthcare, Wisconsin, USA) were setup for the procedure. The assessor was one of six local interventional nephrologists who have each performed an extensive number of biopsies and have experience supervising and teaching trainees to perform renal biopsies. Blinding of participants and assessors to randomisation was unable to be performed secondary to the nature of the trial. Each participant was asked to perform three passes.
The NG was pre-fitted to the ultrasound probe by the assessor. It was set to the most vertical setting and was not altered throughout the trial. Corresponding predictive throwlines were set on the ultrasound screen for the NG group (Figure 1). The FH group used the same ultrasound machine and probe with the same optimised settings.
Each participant wore gloves. The timing began when they picked up the US probe. The time taken to complete 3 passes was recorded with timing ending when the participant put the ultrasound probe down. Whilst performing each of the 3 passes, the assessor judged whether each pass would have biopsied the inferior pole, whether they could visualise the needle tip at the time of biopsy, and whether the pass would have biopsied renal cortical tissue. Once the participant had completed 3 passes, they exited the assessment room. Both participant and assessor then completed a questionnaire about the experience. Answers were provided using a visual analogue scale (VAS). This involved participants and assessors answering a range of questions by making a single vertical mark that intersected a 10cm long horizontal line. The distance along the horizontal line was measured and entered as a value in millimeters.
The primary outcome of the trial was a combination of adequacy and safety. To meet the primary outcome, participants had to fulfill the criteria of both an adequate biopsy and a safe biopsy. This was defined by:
- Adequate biopsy: adequacy was achieved if 2 of the 3 passes performed by one individual participant were judged to have biopsied cortical tissue based on ultrasound visualisation by the assessor.
- Safe biopsy: safety was achieved if both the inferior pole biopsy was performed in 100% of attempts, and the needle tip was visualised at the time of biopsy in 100% of attempts.
Secondary outcomes assessed were the proportion of participants in each group who performed an adequate biopsy (2 of 3 passes would have obtained cortical renal tissue), the proportion of participants in each group who performed an inferior pole biopsy in 100% of attempts, the proportion of participants in each group who adequately visualised the needle at the time of biopsy in 100% of attempts, the average total procedural time between the two groups, and the participant and the assessor’s assessment of the participant’s difficulty undertaking various components of the renal biopsy between the two groups.
Power calculations were difficult given the paucity of evidence in this field. The outcome rates were agreed upon based on the local experience of the interventional nephrologists. We predicted a safe and adequate biopsy would occur in 70% of participants in the NG group and 30% in the FH group. Based on these assumptions and Type 1 error two-sided probability of 0.05, we calculated 84 participants would be required to be able to reject the null hypothesis with 80% power. We planned to recruit an extra 15% (98 participants) to allow for dropout due to the unpredictable workload of junior medical staff that might preclude their participation as planned.
Participants were randomised as they arrived to partake in the study. All outcomes were analysed in an intention to treat analysis which included all randomised participants. Analysis of continuous variables was performed using the relevant parametric or non-parametric test. The primary outcome was analysed using a hierarchical conditional backward binary logistic regression and expressed as a relative risk with 95% confidence intervals. Time taken to perform biopsies (a continuous variable) was analysed using a hierarchical conditional backward stepwise generalised linear regression model. Statistical models controlled for gender, experience and seniority and where relevant interactions terms if p<0.20. Data was analysed using SPSS v.27 (California, United States of America).