Analytical evaluation of a newly developed ELISA mass assay for pancreatic amylase.

OBJECTIVE: To evaluate a newly developed ELISA mass assay for Pancreatic Amylase. METHODS: The serum levels of pancreatic amylase were measured by an in-house developed ELISA assay on microtitre plate and compared with two activity assays: immunoinhibition and electrophoresis. RESULTS: The proposed method was accurate and precise, as indicated by a recovery of 102% and coefficient of variation of less than 5% for within-run and less than 10% for between-run assay. The proposed assay showed good correlation with the activity assays (r = 0.98). The mass concentrations were three times higher than the activities. The relative values (mass or activity units/upper reference limits), however, were concordant in controls and in pancreatic and non-pancreatic conditions. CONCLUSION: Our results indicate that the activity measurements and mass concentrations of pancreatic amylase in serum are comparable and interchangeable after adjusting for the reference range.

Discordance between results for serum troponin T and troponin I in renal disease.

Two patients were investigated for unexplained increases in troponin T. In the first patient, who had rhabdomyolysis and acute renal failure, troponin T reached a peak value of 13.50 micrograms/L (67.5-fold the upper reference limit). The second patient had chronic renal failure and the troponin T peak value was 2.85 micrograms/L (14.3-fold the upper reference limit). Clinical investigations indicated no evidence of myocardial damage. Serum or plasma specimens were analyzed for total creatine kinase (CK), CK-2 mass, CK-2 isoform ratio, myoglobin, troponin T, troponin I, and myosin light chains; all except troponin I were at above-normal concentrations. We also investigated six additional renal patients with above-normal troponin T; troponin I was slightly increased in only one of these six patients. Our findings demonstrate discordance between results for troponin T and troponin I in renal patients.

Combination (multiple) testing for myocardial infarction using myoglobin, creatine kinase-2 (mass), and troponin T.

We retrospectively determined the mass concentrations of myoglobin, creatine kinase-2 (CK-2), and troponin T in serial samples from 80 patients with confirmed myocardial infarction (MI) and 60 non-MI patients. Results from receiver operating characteristic curve analyses show that all three tests are comparable in their diagnostic utility within the first 12 h of infarction. Decision thresholds were selected at a constant rule-in specificity of 95% and rule-out sensitivities of 95% at, respectively, 3-6, 6-9, and 9-12 h intervals after the onset of symptoms. Test sensitivities and specificities were compared for each, used as: a single test; two-test parallel combination; three-test parallel combination; two-test series combination; and three-test series combination. Our results from combination testing indicate what for the early diagnosis of MI, a single serum myoglobin measurement has diagnostic utility at 3 h after the onset of symptoms, and myoglobin and CK-2 (mass) in combination later than 3 h following the onset of symptoms. Serum troponin T is diagnostically similar to CK-2 (mass), although it has superior cardiac-tissue specificity, but it is not as yet commercially available as a "stat" test. Therefore, we recommend using troponin T as a confirmatory test 9 h after the onset of MI. Based on our findings, we suggest a testing algorithm for the early biochemical diagnosis of MI.

Diagnostic evaluation of creatine kinase-2 mass and creatine kinase-3 and -2 isoform ratios in early diagnosis of acute myocardial infarction.

The diagnostic efficacy of creatine kinase (CK) isoforms (CK-3 and CK-2) was compared with measurement of CK-2 mass concentrations for the early diagnosis of myocardial infarction (MI). Serial serum samples drawn from 76 patients with confirmed MI and 55 non-MI patients were used for determining CK-2 mass concentrations and the MM3/MM1 (CK-3 isoforms) and MB2/MB1 (CK-2 isoforms) ratios. We compared the diagnostic utility of each by receiver-operating-characteristic (ROC) curve and likelihood ratio analyses. Our results indicate that all three tests were ineffective within the first 4 h after the onset of chest pain. All three were most effective at 4-18 h after onset, but both CK-3 and CK-2 isoform ratios were less effective than CK-2 mass concentrations in the next 6-h period (18-24 h). In the critical time between 3 and 6 h, the diagnostic performance of all three was comparable.