Outliers affecting cardiac troponin I measurement: comparison of a new high sensitivity assay with a contemporary assay on the Abbott ARCHITECT analyser.

BACKGROUND: False-positive cardiac troponin (Tn) results caused by outliers have been reported on various analytical platforms. We have compared the precision profile and outlier rate of the Abbott Diagnostics contemporary troponin I (TnI) assay with their high sensitivity (hs) TnI assay. METHODS: Three studies were conducted over a 10-month period using routine patients' samples. TnI was measured in duplicate using the contemporary TnI assay in Study 1 and Study 2 (n = 7011 and 7089) and the hs-TnI assay in Study 3 (n = 1522). Critical outliers were defined as duplicate results whose absolute difference exceeded a critical difference (CD = z x √2 x SDAnalytical) at a probability level of 0.0005, with one of the results on the opposite side of the decision limit to its partner. RESULTS: The TnI concentration at 10% imprecision (coefficient of variation) for the contemporary TnI assay was 0.034 µg/L (Study 1) and 0.042 µg/L (Study 2), and 0.006 µg/L (6 ng/L) for the hs-TnI assay. The critical outlier rates for the contemporary TnI assay were 0.51% (Study 1) and 0.37% (Study 2) using a cut-off of 0.04 µg/L, and 0% for the hs-TnI assay using gender-specific cut-offs. CONCLUSION: The significant number of critical outliers detected using the contemporary TnI assay may pose a risk for misclassification of patients. By contrast, no critical outliers were detected using the hs-TnI assay. However, the total outlier rates for both assays were significantly higher than the expected variability of either assay. The cause of these outliers remains unclear.

Development of the surgical science examination of the Royal Australasian College of Surgeons surgical education and training programme: putting the chicken before the egg.

Basic science knowledge is a foundational element of surgical practice. Increasing surgical specialization may merit a reconsideration of the 'whole-body' approach to basic science curriculum in favour of specialty specific depth. The conundrum of depth or breadth of basic science curriculum is currently being addressed by the Royal Australasian College of Surgeons, which introduced a new surgical education and training programme for nine surgical specialties in 2008. This paper describes an innovative solution to the design of a basic science curriculum in the nine different surgical specialty streams of this programme. The task was to develop a curriculum and rigorous assessment in basic sciences to meet the needs of the training programme, for implementation within the first year. A number of political/cultural and technical issues were identified as critical to success. To achieve a robust assessment within the required time frame attention was paid to engagement, governance, curriculum definition, assessment development, and implementation. The pragmatic solution to curriculum and assessment was to use the existing assessment items and blueprint to determine a new curriculum definition and assessment. The resulting curriculum comprises a generic component, undertaken by all trainees, and specialty specific components. In a time critical environment, a pragmatic solution to curriculum, applied with predetermined, structured and meticulous methodology, allowed explicit definition of breadth for the generic basic science curriculum for surgical training in Australia and New Zealand. Implicit definition of specialty specific-basic science curricula was through the creation of a blueprinted assessment.

Spontaneous acroangiodermatitis in a young woman.

We present a case of acroangiodermatitis that for nearly 15 years was unrecognized and treated with skin grafting and radiotherapy. This case is also unusual in that neither venous insufficiency nor an underlying arteriovenous malformation could be demonstrated. Acroangiodermatitis is infrequently reported; a review of the literature emphasizes the similarities to Kaposi sarcoma both clinically and histologically. Because treatment for Kapsoi's sarcoma and hemangioendothelioma involves skin grafting and radiotherapy, awareness of this entity by dermatologists, surgeons, and pathologists is important.

Decision limit for troponin I and assay performance.

BACKGROUND: The redefinition of acute myocardial infarction by the Joint European Society of Cardiology and American College of Cardiology places troponin at the centre of the diagnostic strategy, in addition to lowering the diagnostic cut-off to the 99th centile of a healthy reference population. The required percentage coefficient of variation (%CV) for the assay at this level is 10. Recent publications have examined the utility of the Bayer ACS:180 troponin I assay at a cut-off of 0.1 microg/L to risk-stratify patients with non-ST-elevation myocardial infarction. METHODS: This study examines the appropriateness of using this assay at this cut-off in individual patients. It also examines the functional sensitivity of the assay and assesses the impact of sample quality on assay performance. RESULTS: At the decision limit of 0.1 microg/L, 8% of patients would be assigned to a different risk group on repeat analysis of the same sample on the ACS:180 due to assay imprecision. The functional sensitivity (at inter-assay %CV = 10) of the ACS:180 troponin I assay was determined to be 0.27 microg/L. Nineteen of 4850 routine samples (0.39%) failed duplicate precision checks as a result of poor sample quality; this was usually due to the presence of small fibrin particles. CONCLUSIONS: Careful attention to sample quality is vital in troponin I measurement. The use of the Bayer assay for risk stratification at a cut-off of 0.1 microg/L can lead to inconsistency of risk assessment in a small but significant proportion of cases.