1. RESEARCH POSTER PRESENTATION DESIGN © 2012 www.PosterPresentations.com Cardiac Troponin Assay Cardiac troponin I is the diagnostic marker used for myocardial injury in Queensland Health. It plays a crucial role in the Cardiac Chest Pain Risk Stratification Pathway used by Emergency Departments state-wide. There are two Cardiac Troponin I assays utilised by Queensland Health: Laboratory Cardiac troponin I - Beckman Coulter AccuTnI Point of Care Cardiac troponin I - Abbott iStat cTnI Introduction Objective We performed a retrospective audit comparing concurrent iStat-cTnI (Abbott iStat cTnI) and laboratory-cTnI (Beckman Coulter AccuTnI) results from chest pain patients presenting to a rural ED. Concurrent samples of 481 patients were investigated between September 2013 and August 2014. All iStat-cTnI assays were performed at bedside by clinicians using the Abbott iStat cTnI, while the laboratory-cTnI samples were analysed at a Queensland Health Laboratory using an Beckman Coulter AccuTnI assay. The patient lists were generated by Pathology Queensland Rockhampton Laboratory and the cTnI results were sourced from AUSCARE Clinical and Scientific Information System. The 99 th percentile cut-off of 0.04μg/L was used for both cTnI tests to determine a negative or positive result. 2x2 Contingency tables were used to evaluate the iStat-cTnI results using the Laboratory cTnI as the gold standard. Methods Results Conclusions In a rural ED setting, the iStat-cTnI underperforms compared to the laboratory-cTnI assay. The iStat showed poor sensitivity and cannot be relied on to confidently rule out disease when using the 99 th percentile cut off. This is of particular concern in rural facilities where iStat-cTnI is the only assay available. This has implications for ongoing patient care as well as the cost of providing clinical care. We suggest further evaluation and research of the assay and how we use it in clinical practice. This includes a closer analysis of whether test failure has impacted clinical outcomes Acknowledgements Images: http://www.exclusivasmedicas.com/productos/materialmedico/analizadorsangre/istat1.jpg https:///maps.google.com.au La 1, Phillip, Peter Thompson 1, 3, Darren Moisey 2, 3, Sarah Robertson 1 and Gwenda Chapman 1 Retrospective audit comparing the iStat cardiac troponin I (cTnI) with Laboratory cTnI Assay in a rural emergency setting The Rural Context Capricorn Coast Hospital and Health Service (CCH&HS), a 22 inpatient bed public hospital 42 kilometres outside of Rockhampton, providing services for the 25 000 residents of Yeppoon and the surrounding Capricorn Coast. The CCH&HS has no pathology laboratory and specimens are only sent to the Rockhampton Base Hospital laboratory twice a day. Thus the iStat-cTnI is the primary cardiac marker used. Does the iStat cTnI perform accurately enough, compared with the gold standard Laboratory cTnI, to warrant a place in the rural emergency department setting? Two Assays Laboratory Cardiac troponin I (Lab-cTnI) is the preferred assay and is available at the 33 Pathology Queensland Laboratory sites. Lab-cTnI is collected in an SST tube so only the serum is tested by qualified laboratory scientists in a well controlled environment. However at least 28 out of Queensland Health’s 61 reporting hospitals do not have immediate access to onsite laboratories. Instead the iStat point-of-care cTnI is the only assay available with a practical turnaround time. The iStat-cTnI uses whole blood, collected into a heparinised tube and is performed bedside by clinical staff. A total of 481 comparisons were made between the iStat and Laboratory cTnI assays. Using the Laboratory cTnI as the gold standard, the iStat produced 22 false negatives, 37 false positives, resulting in a sensitivity of 74.7% (95% CI: 64.25% to 83.42%), a specificity of 90.6% (95% CI: 87.29% to 93.30%), false positive rate of 9.4% and a false negative rate of 25.3%. Of the 22 false negative recordings, 7 of these cases were diagnosed with an acute coronary syndrome, 5 of these as nonSTEMI. Laboratory-cTnI (Gold Standard) PositiveNegative iStat-cTnI Positive 6537 Negative 22357 iStat-cTnI Performance Sensitivity74.71% Specificity90.61% Positive predictive value63.73% Negative predictive value94.20% There is a difference in the diagnostic capabilities of the iStat-cTnI compared with formal laboratory cTnI assay. This discrepancy between the iStat-cTnI and the laboratory-cTnI has the potential to cause patient harm through delayed or false diagnosis, especially in rural facilities where iStat-cTnI is the only assay available. The possibility of test errors in the iStat-cTnI may contribute to either a delayed or false diagnosis of an acute coronary syndrome. This could then lead to a delay in appropriate management, or in the case of a false diagnosis, unnecessary transfer and treatment. We identified the need to evaluate the accuracy of the iStat-cTnI assay with Laboratory-cTnI. Table 1. 2 x 2 Table comparing the iStat-cTnI and Lab-cTnI from the 481 concurrent samples. A value equal to or greater than the 99 th percentile cut-off of 0.04μg/L was considered positive. Table 2. Diagnostic test evaluation of the iStat-cTnI against the gold standard Lab-cTnI References Figure 2. Map of surrounding area, showing the distance between the Capricorn Coast Hospital in Yeppoon and the nearest Pathology Queensland Laboratory in Rockhampton Figure 1. Capricorn Coast Hospital and Health Service 1.Queensland, P., Guidelines for cardiac Troponin I Testing and Interpretation, in chemlite, H.S.S. Agency, Editor. 2013. 2.Palamalai, V., M.M. Murakami, and F.S. Apple, Diagnostic performance of four point of care cardiac troponin I assays to rule in and rule out acute myocardial infarction. Clin Biochem, 2013. 46(16-17): p. 1631-5. 3.Loten, C., et al., Validation of a point of care troponin assay in real life Emergency Department conditions. Emerg Med Australas, 2009. 21(4): p. 286-92. Special thanks to Dr Peter Thompson, Dr Darren Moisey and Gwenda Chapman for their supervision and advice. I would also like to thank Sarah Robertson and Paul Slater for the help with data collection. 1 The University of Queensland Rural Clinical School – Rockhampton 2 Capricorn Coast Hospital and Health Service 3 Rockhampton Base Hospital Contact phillip.la@uqconnect.edu.au 0404106562