Tiopental y falsa hipernatremia: compruebe su analizador / Thiopental and false hypernatremia: Check your analyzer

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Cross-reactivity of insulin analogues with three insulin assays.

BACKGROUND: Immunometric assays have recently shown higher specificity in the detection of human insulin than radioimmunoassays with almost no cross-reaction with proinsulin or C peptide. The introduction of the new insulin analogues on the market, however, has raised the need to define their cross-reactivity in these assays. Several studies have been published in this regard with different results. METHODS: The analogues studied were insulins lispro, aspart, glargine, detemir, and glulisine. Insulin concentrations were measured in Immulite(®) 2000 and Advia Centaur(®) XP (Siemens Healthcare Diagnostics), and Elecsys(®) Modular Analytics E170 (Roche). All samples were processed 15 times in the same analytical run following a random sequence. Those samples which showed statistically and clinically significant changes in insulin concentration were reprocessed using increasing concentrations of analogue, and this was done twice, using two different serum pools, one with a low concentration of insulin and one with a high concentration of insulin. RESULTS: In the Elecsys(®) E170 analyser, glargine showed statistical changes (comparison of mean concentrations with p < 0.05) and clinically significant changes in measured insulin (percentage difference 986.2% > reference change value: 59.8%), and the interference increased with increasing concentrations of analogue; the differences were not significant in the case of the other analogues. In the Advia Centaur(®) and Immulite(®) 2000 only the results for glulisine did not present significance (percentage difference 44.7% < reference change value 103.5%). Increasing concentrations of aspart, glargine, and lispro showed increased interference in Immulite(®) 2000. CONCLUSIONS: In the Elecsys(®) E170 assay, relevant cross-reactivity was only detected with insulin glargine, whereas in the other analysers all analogues except glulisine showed significant interference.

Analytical performance of a sensitive assay for cardiac troponin I with loci technology.

OBJECTIVES: To confirm the analytical performance of the Dimension Vista LOCI troponin I assay (cTnI). DESIGN AND METHOD: Limit of blank (LoB), limit of detection (LoD), limit of quantitation (LoQ) with a 10% coefficient of variation (CV), linearity, precision, method comparison, and 99th percentile upper reference limits (URL) were analyzed. Endogenous analytes and rheumatoid factor (RF) were tested for assay interference. RESULTS: The 99th percentile was 0.022 microg/L (CV=14%) and the LoQ was 0.036 microg/L. The ratio of 10% CV concentration to 99th percentile was 1.63. Linearity extended from 0 to 44.36 microg/L. The method comparison equation was Dimension(R) Vista=0.94 (Dimension RxL)+0.00 microg/L with bias at low levels. No interference was detected. CONCLUSIONS: This study shows acceptable performance characteristics of the LOCI cTnI assay on Dimension Vista to diagnosis and risk stratification of patients with acute coronary syndrome symptoms.