Common scenarios to clarify the interpretation of cardiac markers.

The authors present a practical approach for physicians in clinical practice to use cardiac troponins in the interpretation of heart disease and myocardial damage. Laboratory results that fall within the intermediate area of facility-specific cutoff reference values for elevated troponin levels confer lower risks to patients than do higher levels of cardiac troponin. Perhaps not surprisingly, the actual anatomy of the vessels at cardiac catheterization does not correlate well with the troponin level. In the six cases presented here, the patients' low levels of troponin release are discussed using the new term minimal myocardial infarction, which is synonymous with conditions that would previously have been diagnosed as unstable angina. Elevated levels of cardiac troponin provide a very sensitive measure for clinicians diagnosing patients with myocardial necrosis, but such measures are also useful in defining a broad spectrum of disease. Whenever the troponin levels are elevated (barring laboratory error), the patient has a poorer prognosis. The greatest challenge for physicians is in determining which patients with cardiac troponin elevation will best benefit from heart catheterization and percutaneous intervention.

Decreased laboratory testing for lecithin-to-sphingomyelin ratio and phosphatidylglycerol after fetal lung maturity assessment from lamellar body count in amniotic fluid.

The objectives of this study were to do inexpensive lamellar body count (LBC) in amniotic fluid, to do statistical analysis to evaluate cutoff values for fetal lung maturity (FLM) and fetal lung immaturity (FLI), to derive a threshold for obtaining a lecithin-to-sphingomyelin (L/S) ratio and phosphatidylglycerol percentage (%PG), and to determine the potential cost savings to the hospital if they use this new method. Testing (LBC, L/S ratio, and %PG) was done on 123 specimens of amniotic fluid. Receiver operating characteristic (ROC) curve, discriminant, linear regression, chi2, and cost analyses were used to evaluate the laboratory and financial parameters. Lamellar body counts of greater than 41,500 (Coulter MAXM: sensitivity, 90.5%; specificity, 87.7%; positive predictive value, 79.2%; negative predictive value, 94.7%) and greater than 32,000 (Coulter Gen.S: sensitivity, 90.5%; specificity, 85.2%; positive predictive value, 76.0%; negative predictive value, 94.5%) were the best threshold for biochemical FLM. Similarly, LBC of less than 24,000 (MAXM: sensitivity, 78.6%; specificity, 100%; positive predictive value, 100%; negative predictive value, 90.0%) and less than 21,000 (Gen.S: sensitivity, 71.4%; specificity, 100%; positive predictive value, 100%; negative predictive value, 87.1%) provided the best statistical cutoff for biochemical FLI from discriminant analysis. The authors concluded that FLM and FLI can be predicted with reasonable accuracy from LBC in amniotic fluid specimens. The expensive and not easily accessible L/S ratio and %PG can then be done only in cases in which LBC indicates transitional FLM. A cascade approach results in 86% savings to the hospital if the L/S ratio and %PG are not sent to a reference laboratory.