Analytical Interference by Contrast Agents in Biochemical Assays

Objective. To provide a clinically relevant overview of the analytical interference by contrast agents (CA) in laboratory blood test measurements. Materials and Methods. The effects of five CAs, gadobutrol, gadoterate meglumine, gadoxetate disodium, iodixanol, and iomeprol, were studied on the 29 most frequently performed biochemical assays. One-day-old plasma, serum, and whole blood were spiked with doses of each agent such that the gadolinium agents and the iodine agents reached concentrations of 0.5 mM and 12 mg iodine/mL, respectively. Subsequently, 12 assays were reexamined using 1/2 and 1/4 of these CA concentrations. The results were assessed statistically by a paired Student’s t-test. Results. Iodixanol produced a negative interference on the bicarbonate (p=0.011), lactate dehydrogenase (p<0.0001), and zinc (p=0.0034) assays and a positive interference on the albumin (p=0.0062), calcium (p<0.0001), ionized calcium (p=0.0086), iron (p<0.0001), and potassium (p=0.0003) assays. Iomeprol produced a negative interference on the bicarbonate (p=0.0057) and magnesium (p=0.0001) assays and a positive interference on the calcium (p<0.0001) and potassium (p=0.0012) assays. Gadoxetate disodium produced a negative interference on the iron (p<0.0001) and zinc (p<0.0001) assays and a positive interference on the sodium (p=0.032) assay. Conclusion. CAs cause analytical interference. Attention should be given to the above-mentioned analyte-CA combinations when assessing laboratory blood test results obtained after CA administration

NT-proBNP and Circulating Inflammation Markers in Prediction of a Normal Myocardial Scintigraphy in Patients with Symptoms of Coronary Artery Disease

Myocardial perfusion imaging (MPI) can detect myocardial perfusion abnormalities but many examinations are without pathological findings. This study examines whether circulating biomarkers can be used as screening modality prior to MPI.243 patients with an intermediate risk of CAD or with known CAD with renewed suspicion of ischemia were referred to MPI. Blood samples were analyzed for N-terminal fragment of the prohormone brain natriuretic peptide (NT-proBNP), YKL-40, IL-6, matrix metalloproteinase 9 (MMP-9) and high sensitive C-reactive protein (hsCRP). Patients with myocardial perfusion defects had elevated levels of NT-proBNP (p<0.0001), YKL-40 (p = 0.03) and IL-6 (p = 0.03) but not of hsCRP (p = 0.58) nor of MMP-9 (p = 0.14). The NT-proBNP increase was observed in both genders (p<0.0001), whereas YKL-40 (p = 0.005) and IL-6 (p = 0.02) were elevated only in men. A NT-proBNP cut off-concentration at 25 ng/l predicted a normal MPI with a negative predictive value >95% regardless of existing CAD.20-25% of patients suspected of CAD could have been spared a MPI by using a NT-proBNP cut-off concentration at 25 ng/l with a negative predictive value >95%. NT-proBNP has the potential use of being a screening marker of CAD before referral of the patient to MPI