Adoption of high-sensitivity cardiac troponin for early rule out of NSTEMI at Belfast Health and Social Care Trust

The aim of the project was to review and update the Trust’s chest pain pathway and safely implement a 1 hour early rule out protocol using the Elecsys® high sensitivity troponin assay.

The objectives were to:

• Maintain patient safety throughout.
• Reduce length of stay in the Emergency Department for patients presenting with chest pain – earlier AMI rule-out and discharge for appropriate patients and more rapid diagnosis for high-risk patients.
• Improve patient experience.
• Improve clinician confidence.

Belfast has two Emergency Departments providing 24-hour access to people aged 14 years and older; the Royal Victoria Hospital (RVH) and the Mater Hospital (MH). The RVH has the larger Emergency Department with 245 nurses, 38 healthcare workers and 78 medical staff. It has, on average, 1817 attendances each week, including 210-230 people with chest pain indicating a possible AMI. There is a biochemistry laboratory in each of these hospitals as well as a third laboratory at the trust’s Belfast City Hospital (no ED at this hospital).

In 2014, NICE recommended the high sensitivity troponin assays (Elecsys Troponin T high‑sensitive assay and ARCHITECT STAT High Sensitive Troponin‑I assay) use with early rule out protocols (which is typically a 3 hour protocol) for the early rule-out of non-ST-segment-elevation myocardial infarction (NSTEMI) in people presenting with chest pain. The 2015 ESC Guidelines recommended an accelerated 1-hour protocol when high-sensitivity cardiac troponin assays with a validated algorithm are available and NICE CG95 recommended a single high sensitivity troponin test to rule out NSTEMI in certain low risk patients.

Belfast were already using a 3 hour early rule out protocol using a high sensitivity troponin assay. Following publication of these Guidelines and presentation of the TRAPID study (Mueller, C. et al, 2016), a team in the BHSCT decided to review and update the Trust’s chest pain pathway and at the same time incorporate the 1-hour protocol using high sensitivity troponin.

Belfast use the Roche Elecsys® Troponin T high sensitive (TnT-hs) assay. High sensitivity TnT assays enable an earlier rule-out of acute myocardial infarction compared to traditional troponin assays (Reichlin, T. et al, 2009). This means that patients in whom NTSEMI can be ruled out can be discharged more quickly or an alternative diagnosis sought.

The Belfast pathway for patients presenting with chest pain symptoms includes a full clinical assessment, 12-lead ECG and blood sample taken at presentation (T⁰) for high sensitivity troponin testing. Unless they were ruled out at that point, they then had a blood sample tested at 1 hour after the first sample (T¹). As a cautionary measure, a lower threshold of <3 ng/L was initially used to rule-out AMI at T0 and this was later replaced by the <5 ng/L level presented in the ESC Guidelines.

Following the T1 test result, patients were categorised into three groups referred to as ‘go home’ (assigned the colour green), ‘stay in’ and treat for AMI (red) and ‘observe’ (amber) equivalent to ‘rule-out’, ‘rule-in’ and ‘observe’. Patients categorised as ‘go home’ were discharged.

Implementing the change:

In 2015, the 1-hour pathway was piloted alongside the existing 3-hour pathway to assess its feasibility, safety and validate whether the thresholds were appropriate for the local population. Cardiac specialist nurses recorded data for 125 patients including final diagnosis and 30-day follow-up. Results of the pilot showed that the 1-hour protocol was appropriate and safe for use in this setting. In the rule-out group there were no mortalities or major adverse cardiac events (MACE) within 30 days. There were no cases where the results from the 3-hour pathway contradicted results from the 1-hour pathway.

Following the pilot, the Belfast chest pain pathway was finalised. A 'chest pain education week' was organised in the Emergency Department to inform staff of the changes to the chest pain pathway. Managed by the cardiac specialist nurses, the new pathway was officially launched on 1st July 2016 with a plan to audit all patients for the first 3 months with the remit of assessing patient safety and identifying opportunities for further improvement and streamlining.

A multidisciplinary team was established at the outset with staff involvement from the Emergency Department, Cardiology and Clinical Biochemistry. With a large clinical team split across two sites, communication between staff within the Emergency Department and with the laboratory was crucial to the successful implementation of the new pathway (see below).

Promoting the Belfast Chest Pain Pathway

• 'Chest pain education week', spearheaded by the cardiac specialist nurses, was advertised with posters, on notice boards and on the staff intranet.
• The new pathway was displayed throughout the department and on the staff intranet.
• Rolling staff education sessions throughout the week within the Emergency Department.
• Cardiac specialist nurses used ward rounds to talk with staff about the new pathway.

Supporting the change

• The triage nurses were key to the adoption of the new pathway.
• Triage and support nurses were encouraged to record in electronic notes the time when the first sample was taken to ensure the T1 sample was taken on time.
• Patients were informed that they would need a repeat blood test 1-hour after the first. They were asked to return to the nurses’ station if, after 1-hour, the repeat blood sample had not been taken.
• Staff were reminded of the new pathway at handovers.

The successful change to a 1-hour protocol shows that it is possible to use an accelerated protocol, even in a large Emergency Department. The new pathway is now well accepted within the Belfast Emergency Departments and used in 99% of eligible cases.

Of patients assessed during the 3-month audit, 70% of patients were categorised as ‘rule-out’, 6% as ‘rule-in’ and 23% to the observation group. Mortality was high in the rule-in group at 11%. There were no cardiac deaths in the rule-out group.

An internal audit of the laboratory performed in January 2017, found that the median turnaround time of samples was 1 hour 14 minutes, including the transport time. The RVH was able to return 90% of hsTnT-hs results within 90 minutes, and the MH was able to return 77% of hsTnT results within this time, since the laboratory closes at night and samples are then subsequently transferred to the RVH.

Initial results after 1 year showed an average decrease for hsTnT requests per month compared to before the pathway was implemented.

Collaboration between the lab and emergency department and cardiology was seen as key to the successful implementation.

Understanding: Some staff found the 1-hour pathway complicated and did not initially see its value. The audit revealed a small number of patients who should have been in the observation group were discharged early and re-attended. High sensitivity troponin tests were performed on individuals who did not fit the criteria for the chest pain pathway including very young people and unwell patients with no chest pain. Cardiac specialist nurses worked with staff who were reluctant to implement the new pathway or who found it complicated. Additional training was given to eliminate the incorrect or inappropriate use of the pathway. Once everyone started to use the pathway on a daily basis they started to see the value of it.

Emergency Department: For efficiency, blood forms are sometimes printed before a blood sample is taken. As the time of the sample can be printed on the form, this could mean that the wrong time is recorded for Tº and/or T1. To prevent this, staff were instructed to print out forms at the time the blood sample was taken.

Laboratory: Within the hospital laboratory, three quality control (QC) samples are analysed daily using each hsTnT assay, which contain specified levels of TnT. However, there was some variation in quality between the control batches. If QC results varied, it was not clear whether this was due to variations with the individual hsTnT assay or variations between control batches. Rather than rely solely on manufactured IQC analysis, the laboratory put in place measures to guarantee performance. A number of serum sample pools were generated and used to assess performance between analysers across the 3 lab sites. In addition, there was regular review of cross-site TnT-hs assay performance using laboratory IT software.

The new pathway requires a short turnaround for processing blood tests. Occasionally, a blood test would have to be taken at T1, prior to receiving the T0 results, but the patient could be discharged based on the results of T0 alone, meaning the T1 result was not required. To improve turnaround times, the biochemistry team decided to implement a dashboard system to allow better ED sample and result tracking and to alert staff to any delays in receiving samples or reporting hsTnT results.

References

Mueller, C. et al. Multicenter Evaluation of a 0-Hour/1-Hour Algorithm in the Diagnosis of Myocardial Infarction With High-Sensitivity Cardiac Troponin T. Ann Emerg Med. 68, 76–87.e4 (2016).

Reichlin, T. et al. Early diagnosis of myocardial infarction with sensitive cardiac troponin assays. N Engl J Med. 361, 858–867 (2009).