The measurement of the degradation product of the C-telopeptide of type I collagen in serum (s-betaCTX) has been evaluated in the form of an automated chemiluminometric assay. The between-day coefficients of variation ranged between 2.6 and 6.0% over the concentration range 0.12 to 3.25 microg/l. The s-betaCTX value correlated well with alternative serum C-telopeptide (r = 0.983) and urine deoxypyridinoline (r = 0.729) measurements. A significant inverse correlation was found between the s-betaCTX measurement and creatinine clearance in patients with renal disease.

Few studies have evaluated cardiac troponin I (cTnI) as a marker for infarct size and left ventricular (LV) dysfunction. Here we investigated the ability of a single-point cTnI, measured with a second-generation assay (Access AccuTnI), to estimate infarct size and assess LV function in patients with a first myocardial infarction (AMI). cTnI measurements were performed 12 and 48 h after admission in 63 consecutive AMI patients. LV function was evaluated by gated single-photon emission computed tomography (SPECT) and infarct size was estimated by CK-MB peak and SPECT myocardial perfusion. LV function and infarct size were evaluated by SPECT before hospital discharge. SPECT was also repeated 3 months later. Significant correlations (p<0.001) were found between cTnI at 12 and 48 h and both the peak CK-MB (r=0.61 and r=0.82, respectively) and the perfusion defect size at SPECT (r=0.55 and r=0.61, respectively). cTnI at 12 and 48 h were inversely related (p<0.001) to LV ejection fraction (LVEF) assessed both early (r=-0.45 and r=-0.57, respectively) and 3 months after AMI (r=-0.51 and r=-0.69, respectively). cTnI >14.8 microg/L at 48 h predicted an LVEF <40% at 3 months with a sensitivity of 100% [95% confidence interval (CI) 73.5-100%], specificity of 65% (CI 49-79%), and a negative predictive value of 100%. Our findings demonstrate that a single cTnI measurement 48 h after admission is useful for ruling out impaired LV function in a routine clinical setting.

Objectives: This study evaluated the analytical characteristics of the LiaisonR immunoassay for cardiac troponin I (cTnI). Design and methods: The protocol consisted of eight sections: evaluation of antibody specificity, linearity, detection limit and imprecision, method comparison, evaluation of endogenous interferents, anticoagulant interference, sample stability, and reference values.Results: The assay equally measured free and complexed cTnI. The minimum detectable cTnI concentration was 0.021 Ag/l. The cTnI concentration corresponding to a total CV of 10% was 0.056 Ag/l. Linearity of response was demonstrated along the entire dynamic range of the assay. Assay interferences were minimal. cTnI concentrations in serum and heparinized plasma were significantly different. Values in EDTA plasma were on average approximately 5% higher than in matched serum, but this difference was not significant. The 99th percentile cTnI value in healthy subjects was 0.036 Ag/l.Conclusions: Being sensitive, specific, and precise, the LiaisonR cTnI assay meets current requirements to aid in the diagnosis of myocardial necrosis.

Cardiac troponin has been designated as the preferred biomarker for diagnosis of myocardial infarction (MI) (1 ). Previously published data, however, confirm the large diversity among cardiac troponin assays with respect to important analytical characteristics, including assay standardization, antibody specificity, interferences, and assay imprecision, and underscore the need for improved cardiac troponin assays (2, 3 ). Results obtained with more recently released next-generation assays show that the newer assays indeed have substantially improved analytical performance (4,5 ). The aim of this study was to evaluate one of these next-generation cardiac troponin I (cTnI) assays, performed on the Aio! TM immunoanalyzer (Innotrac Diagnostics Oy), by defining key performance characteristics, including detection limit, linearity on dilution, imprecision, reference interval, and cutoff for MI diagnosis.The assay is based on "all-in-one" dry chemistry technology, in which all of the reagents are precoated in assay cups, and time-resolved fluorometric detection, with a total analysis time of Ͻ20 min (6 ). An eight-point factory-constructed calibration curve is provided on a bar code with each reagent lot, and the instrument-specific calibration adjustment is performed by running the cups of the appropriate calibration pen. A purified preparation of human cardiac ternary troponin I-troponin T-troponin C complex (HyTest Ltd.) is used as calibration antigen. The antibody configuration of the assay, adding a monoclonal antibody with an epitope in the Nterminal region of cTnI (amino acid residues 20 -35) and one with an epitope in the C-terminal region (amino acid residues 185-200) to the mid-fragment cTnI antibodies (epitopes in the region of amino acid residues 35-55 and 80 -95), has recently been described, and the potential ramifications of this have been discussed (7,8 ).The Aio! analyzer was handled strictly according to the manufacturer's instructions. Unless otherwise stated, fresh serum was used as sample. The minimum detectable cTnI concentration was assessed by 20 replicate measurements of the cTnIfree diluent in a single run and defined as the cTnI value corresponding to a signal 3 SD greater than the mean found for this sample (9 ). In the linearity study, five cTnI-rich serum specimens (native cTnI concentrations of 4.3, 9.2, 27.6, 46.9, and 79.5 g/L) were serially diluted with serum pools having undetectable cTnI concentrations, i.e., lower than the detection limit of the Aio! assay, or with the instrument buffer solution. The undiluted sample and four separate dilutions (3:4, 1:2, 1:4, and 1:8) were assayed in duplicate in the same analytical run. The curve obtained was tested for linearity as suggested by Burnett (10 ). After demonstration of linearity, linear regression analysis of the data was performed, and correlation coefficients (r) were calculated. A recovery study was also performed. For the imprecision study, seven serum pools were prepared and stored at Ϫ80°C until used. Two replicates/specimens we...

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