Clinical evaluation of the CARDIAC STATus, a rapid immunochromatographic assay for simultaneous detection of elevated concentrations of CK-MB and myoglobin in whole blood

Upconverting phosphor reporters in immunochromatographic assays

Immunochromatographic assays have become popular diagnostic tools in a variety of settings because they are sensitive, fast, and easy to use. Here, we describe the use of a novel reporter, upconverting phosphors (UCP), in this assay format. UCP are submicron-sized, inorganic crystals that are excited with infrared light and that emit photons in the visible range depending on the ion composition of the crystal. Using human chorionic gonadotropin (hCG) as a model analyte to describe the properties of phosphors in immunochromatographic assays, a detection limit of 10 pg hCG in a 100-microl sample has been achieved on a regular basis, with occasional detection of 1 pg hCG. This represents at least a 10-fold improvement over conventional reporter systems such as colloidal gold or colored latex beads. Quantitation of analytes is possible over at least 3 orders of magnitude. Furthermore, an example is given of how UCP can be used for analyte multiplexing using a two-plexed wick for the detection of mouse IgG and ovalbumin. Thus, UCP lateral flow assays can be used for applications that are currently limited by assay sensitivity, and they can increase the probability of a diagnosis by verifying the presence of several analytes in the same sample.

Evaluation of a point-of-care system for quantitative determination of troponin T and myoglobin

We present the results of a multicenter evaluation of a new point-of-care system (Cardiac Reader) for the quantitative determination of cardiac troponin T (CARDIAC T Quantitative test) and myoglobin (CARDIAC M test) in whole blood samples. The Cardiac Reader is a CCD camera that optically reads the immunochemical test strips. The measuring range is 0.1 to 3 microg/l for CARDIAC T Quantitative and 30 to 700 microg/l for CARDIAC M. Both tests are calibrated by the manufacturer. The reaction times of the tests are 12 or 8 minutes, respectively. Method comparisons were performed with 281 heparinized blood samples from patients with suspected acute coronary syndromes. The results obtained with CARDIAC T Quantitative showed a good agreement compared with cardiac troponin T ELISA (r = 0.89; y = 0.93x + 0.02). The method comparison between CARDIAC M and Tina-quant Myoglobin also showed a good agreement between both assays (r = 0.98; y = 0.92x + 1.6). Test lot-to-lot comparisons yielded differences of 2% and 6% for CARDIAC T Quantitative and of 0 to 11% for CARDIAC M. The within-run imprecision with blood samples and control materials was acceptable for CARDIAC T Quantitative (CV 10 to 15%) and good for CARDIAC M (CV 5 to 10%). The between-instrument CV was below 7% for CARDIACT Quantitative and below 5% for CARDIAC M. The cross-reactivity of CARDIAC T Quantitative with skeletal troponin T was approximately 0.003%. No significant analytical interference was detected for any of the assays in investigations with biotin (up to 100 microg/l), hemoglobin (up to 0.125 mmol/l), hematocrit (26 to 52%), bilirubin (up to 340 micromol/l), triglycerides (up to 5.0 mmol/l), and 18 standard drugs. With the Cardiac Reader reliable quantitative results can be easily obtained for both cardiac markers. The system is, therefore, particularly suitable for use in emergency rooms, coronary care units and small hospitals.

Laboratory diagnosis of patients with acute chest pain

The enzyme activities of creatine kinase (CK), its isoenzyme MB (CK-MB) and of lactate dehydrogenase isoenzyme 1 (LD-1) have been used for years in diagnosing patients with chest pain in order to differentiate patients with acute myocardial infarction (AMI) from non-AMI patients. These methods are easy to perform as automated analyses, but they are not specific for cardiac muscle damage. During the early 90's the situation changed. First creatine kinase MB mass (CK-MB mass) replaced the measurement of CK-MB activity. Subsequently cardiac-specific proteins troponin T (cTnT) and troponin I (cTnI) appeared on the scene, displacing LD-1 analysis. However, troponin concentrations in blood increase only from four to six hours after onset of chest pain. Therefore a rapid marker such as myoglobin, fatty acid binding protein or glycogen phosphorylase BB could be used in early diagnosis of AMI. On the other hand, CK-MB isoforms alone may also be useful in rapid diagnosis of cardiac muscle damage. Myoglobin, CK-MB mass, cTnT and cTnI are nowadays widely used in diagnosing patients with acute chest pain. Myoglobin is not cardiac-specific and therefore requires supplementation with some other analyses such as troponins to support the myoglobin value. Troponins are very highly cardiac-specific. Only the sera of some patients with severe renal failure, which requires hemodialysis, have elevated cTnT and/or cTnI without there being any evidence of cardiac damage. On the other hand, the latest studies have shown that elevated troponin levels in sera of hemodialysis patients point to an increased risk of future cardiac events in a similar manner to the elevated troponin values in sera of patients with unstable angina pectoris. In addition, the bedside tests for cTnT and cTnI alone or together with myoglobin and CK-MB mass can be used instead of quantitative analyses in the diagnosis of patients with chest pain. These rapid tests are easy to perform and they do not require expensive instrumentation. For routine clinical laboratory practice we suggest that in diagnosis of patients with chest pain, myoglobin and CK-MB mass measurements should be performed whenever they are requested (24 h/day) and cTnT or cTnI on admission to the hospital and then 4-6 and 12 hours later.

Myoglobin, creatine kinase MB, troponin T, and troponin I - rapid bedside assays in patients with acute chest pain

Three new rapid, qualitative bedside immunoassays were evaluated in the diagnosis of patients with acute chest pain. The subjects, 122 patients in group 1 (bedside tests for myoglobin, creatine kinase MB) and 233 patients in group 2 (bedside tests for troponin I and sensitive troponin T) were admitted to hospital with acute chest pain for less than 12 h. The bedside tests were performed on admission, and 2, 4, and 6 h later. The correlation between the two parts of the rapid creatine kinase MB/myoglobin test during the first 12 h after the onset of chest pain was moderate in all patients (kappa=0.401, 95% confidence interval 0.321-0.483). The highest correlation was seen with the patients with definite and probable myocardial infarction. The correlations were smaller but significant also in other diagnostic groups (unstable angina pectoris, prolonged chest pain, and non-cardiac chest pain). The correlation between the rapid sensitive test for troponin T and rapid test for troponin I was significant in all groups (kappa=0.776, 95% confidence interval 0.711-0.841). The myoglobin part of the rapid creatine kinase MB/myoglobin test may be too non-specific for clinical diagnostic purposes [in non-infarct patients the myoglobin part was significantly more often positive than creatine kinase MB or troponin tests (P<0.001)].