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This weeks Lancet article on Troponin (Vol 354; 1757-62) showed that the AxSYM troponin I assay appeared to have a useful clinical utility in the PRISM study. The AxSYM cut-off of 1ug/L appeared to distinguish the patients with acute coronary syndromes who were likely to benefit from glycoprotein-IIb/IIIa-receptor antagonists from those who were not. Perhaps this is the best evidence-based level to use. Dr. Eric S. Kilpatrick Consultant in Chemical Pathology Department of Clinical Biochemistry Hull Royal Infirmary Anlaby Road Hull HU3 2JZ Tel 01482-674312 Fax 01482-674310 >Regarding cuttoffs, we are guided very heavily by the literature, and there >has been remarkably little peer-reviewed data using the AxSYM so far. >Abbott are getting there and the best source of information is the package >insert. >So: we use their disease-free reference interval of </= 0.5 ug/L (most >walking-well are well below this) and a diagnostic cuttoff for AMI of 2.0 >ug/L. The unanswered question to me at present is what level is significant >with regard to Minor Mycardial Damage (MMD) with associated poor prognosis >in the UAP patient group? None of the Abbott data addresses this problem. >Causes of elevated troponin (>0.5 ug/L) on the AxSYM then can be due to: >AMI (usually above 2.0 ug/L, can reach several hundred ug/L); MMD - >indicating the need for inpatient management (obviously moving the cuttoff >up from 0.5 ug/L will improve specificity for coronary disease / cardiac >event prediction but at a loss of sensitivity - I have seen little data eg >ROC curve on the Abbott assay for this - Hans, please publish soon!); renal >failure (5% above 1.2 ug/L - Abbott); Skeletal muscle damage (5% above 1.0 >ug/L - Abbott); cardiac bypass surgery (gross elevations peak 3-6 hours >post-op - in-house data); peri/myocarditis; cardiac trauma; other cardiac >procedures (eg stenting). > >Experience at at least one Hospital in Sydney was to discontinue the use of >the assay due to too many "false-positives" leading to overcrowding of >coronary care beds. Abbott have raised the cuttoff from 0.4 to 0.5 since >then and the hospitals troubles were probably exacerbated by the well-known >episode of quality problems with the assay. I think (unsubstantiated >opinion) that a cuttoff of about 0.6-0.8 ug/L would give a suitable >balance. > >As an aside I hope to see vast improvements in TnI assays in the near >future. The Dade Stratus method shows an order of magnitude improvement in >precision and this looks like it will allow much better patient >stratification in the troublesome range (Clin Chem 1999;10:1789-96). > >These are my opinions and should be treated as such. I would be interested >in any other thoughts on cuttoffs for different troponin assays. > >Best wishes, > > > > >Graham Jones > >Staff Specialist in Chemical Pathology >St Vincent's Hospital, Sydney ______________________________________________________ Get Your Private, Free Email at http://www.hotmail.com %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%