Suitability of Becton Dickinson Vacutainer rapid serum tube for collecting and storing blood samples for antibiotic and anticonvulsant drug monitoring.

AIMS: To investigate the suitability of newly developed Becton Dickinson Vacutainer rapid serum tube (RST) for therapeutic drug monitoring of antibiotics and anticonvulsants. METHODS: Two pools of citrated whole blood were created by spiking high and low concentrations of gentamicin, vancomycin, phenytoin, lamotrigine and carbamazepine. After recalcification with 15 mmol/L calcium chloride, spiked whole blood was added into four different Becton Dickinson blood collection tubes: RST, serum separator tube, red top tube and polyethylene plain tube. Serum aliquots were collected at baseline (0 h), 2 h, 24 h, day 3 and day 7. Drug concentrations were measured in batch by HPLC and the Architect c8000. RESULTS: Gentamicin and vancomycin concentrations were stable up to 7 days in all 4 blood collection tubes. Anticonvulsants results for the RST were stable and did not deviate substantially from those of the red top and plain tubes, and demonstrated better performance than the serum separator tubes that showed significant (≥10% bias, p<0.05) decrease in phenytoin and carbamazepine levels after 3 days of storage. CONCLUSIONS: The RST provides acceptable drug stability over the course of 7 days for gentamicin, vancomycin, phenytoin and lamotrigine and over 3 days for carbamazepine.

Comparison of Becton Dickinson Vacutainer rapid serum tube with the serum separator tube for routine chemistry and immunoassay tests.

AIMS: To shorten the clotting time and resolve the delayed clotting or no clotting on specimens from patients on anticoagulant therapy, Becton Dickinson (BD) recently developed the Vacutainer rapid serum tube (RST). The aim of this study was to systematically compare the new RST tube with the widely used serum separator tube (SST) for routine chemistry and immunoassay tests on 3 common analyser platforms. METHODS: Blood from 45 people (24 women and 21 men, age 21-77 years) was collected using the SST and RST tubes in sequence. Sera from both tubes were separated and analysed simultaneously for 54, 50, and 10 chemistry and/or immunoassay tests on the Roche Modular, Abbott Architect, and Siemens Centaur analysers, respectively. RESULTS: The results from the RST tube were comparable with those from the SST tube on most analytes. Although the results for a few analytes showed statistically significant differences between the two tubes (p<0.05), the differences had no clinical significance for most assays. Only for parathyroid hormone on the Abbott Architect, the RST tube demonstrated clinical significant bias versus the SST tube (-15.3%, p<0.01). CONCLUSIONS: The RST tube provides acceptable performance for routine chemistry and immunoassay tests.

Interference of gadolinium-based contrast agents on colorimetric calcium assays.

OBJECTIVE: The aim of this study was to evaluate the potential interference of five gadolinium-based contrast agents (GBCAs), gadodiamide (Omniscan®), gadobenate dimeglumine (Multihance®), gadoxetate disodium (Primovist®), gadobutrol (Gadovist®), and gadoteridol (Prohance®), on three clinical laboratory widely used colorimetric calcium assays including the newly developed 5-nitro-5'methyl-l,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (NM-BAPTA) method. METHODS: Plasma was collected from healthy volunteers aged 23-52, and spiked with varying concentrations of the five GBCAs. Calcium determinations were performed in duplicates using the o-cresolphthalein complexone (OCP), arsenazo-III dye, and NM-BAPTA methods on the Roche Integra 400, Abbott Architect 16000, and Roche Modular P automated analyzers respectively. RESULTS: Gadobenate dimeglumine, gadobutrol, and gadoteridol did not interfere with any of the assays. There was a small positive bias (8%, p<0.01) at a very high concentration (25mmol/L) of gadoxetate disodium when calcium was assayed using the arsenazo-III method. Gadodiamide at a very high concentration (50mmol/L) induced a significant positive bias (16%, p<0.01) on calcium when measured using the NM-BAPTA method; however a much larger bias (90%, p≪0.01) was observed when calcium was measured using the arsenazo-III method. Significant interferences in calcium measurements using the OCP method began at gadodiamide concentrations as low as 0.5mmol/L (-9%, p<0.01). This negative bias was more pronounced at higher gadodiamide concentrations. CONCLUSIONS: Of all 5 GBCAs tested, only gadodiamide showed significant interference on the OCP calcium assay at clinically relevant concentrations. The NM-BAPTA assay showed minimum interference with the five GBCAs and demonstrated equal or better performance than the OCP and the arsenazo-III methods in terms of interference with GBCAs.

Na+/H+ exchanger regulatory factor-1 is involved in chemokine receptor homodimer CCR5 internalization and signal transduction but does not affect CXCR4 homodimer or CXCR4-CCR5 heterodimer.

Chemokine receptors are members of the G protein-coupled receptor (GPCR) family. CCR5 is also the principal co-receptor for macrophage-tropic strains of human immunodeficiency virus, type 1 (HIV-1), and efforts have been made to develop ligands to inhibit HIV-1 infection by promoting CCR5 receptor endocytosis. Given the nature of GPCRs and their propensity to form oligomers, one can consider ligand-based therapies as unselective in terms of the oligomeric composition of complexes. For example, a ligand targeting a CCR5 homomer could likely induce signal transduction on a heteromeric CCR5-CXCR4. Other avenues could therefore be explored. We identified a receptor adaptor interacting specifically with one receptor complex but not others. NHERF1, an adaptor known for its role in desensitization, internalization, and regulation of the ERK signaling cascade for several GPCRs, interacts via its PDZ2 domain with the CCR5 homodimer but not with the CXCR4-CCR5 heterodimer or CXCR4 homodimer. To further characterize this interaction, we also show that NHERF1 increases the CCR5 recruitment of arrestin2 following stimulation. NHERF1 is also involved in CCR5 internalization, as we demonstrate that co-expression of constructs bearing the PDZ2 domain can block CCR5 internalization. We also show that NHERF1 potentiates RANTES (regulated on activation normal T cell expressed and secreted)-induced ERK1/2 phosphorylation via CCR5 activation and that this activation requires NHERF1 but not arrestin2. Taken together, our results suggest that oligomeric receptor complexes can associate specifically with partners and that in this case NHERF1 could represent an interesting new target for the regulation of CCR5 internalization and potentially HIV infection.