Potassium-based algorithm allows correction for the hematocrit bias in quantitative analysis of caffeine and its major metabolite in dried blood spots

Although dried blood spot (DBS) sampling is increasingly receiving interest as a potential alternative to traditional blood sampling, the impact of hematocrit (Hct) on DBS results is limiting its final breakthrough in routine bioanalysis. To predict the Hct of a given DBS, potassium (K+) proved to be a reliable marker. The aim of this study was to evaluate whether application of an algorithm, based upon predicted Hct or K+ concentrations as such, allowed correction for the Hct bias. Using validated LC-MS/MS methods, caffeine, chosen as a model compound, was determined in whole blood and corresponding DBS samples with a broad Hct range (0.18-0.47). A reference subset (n = 50) was used to generate an algorithm based on K+ concentrations in DBS. Application of the developed algorithm on an independent test set (n = 50) alleviated the assay bias, especially at lower Hct values. Before correction, differences between DBS and whole blood concentrations ranged from -29.1 to 21.1 %. The mean difference, as obtained by Bland-Altman comparison, was -6.6 % (95 % confidence interval (CI), -9.7 to -3.4 %). After application of the algorithm, differences between corrected and whole blood concentrations lay between -19.9 and 13.9 % with a mean difference of -2.1 % (95 % CI, -4.5 to 0.3 %). The same algorithm was applied to a separate compound, paraxanthine, which was determined in 103 samples (Hct range, 0.17-0.47), yielding similar results. In conclusion, a K+-based algorithm allows correction for the Hct bias in the quantitative analysis of caffeine and its metabolite paraxanthine

Volumetric absorptive microsampling at home as an alternative tool for the monitoring of HbA1c in diabetes patients

Background: Microsampling techniques have several advantages over traditional blood collection. Dried blood spot (DBS) sampling and blood collection with heparinized capillaries are the standard techniques. Volumetric absorptive microsampling (VAMS) is a novel technique that collects a fixed volume of blood by applying an absorbent tip to a blood drop. In the present study we explored the feasibility of HbA(1c) monitoring with VAMS sampling at home and analysis in the laboratory. Methods: Diabetic patients were enrolled in this study during consultation with the endocrinologist. A venous (adults) or capillary (children) sample was taken for immediate HbA(1c) analysis. DBS (n=1)and dried VAMS (n=2) were collected at home and sent to the laboratory. For 25 pediatric patients one VAMS was collected during consultation for immediate analysis (without drying), referred to as "wet VAMS". HbA(1c) analyses were performed on a Tosoh HLC-723 G8 high-performance liquid chromatography (HPLC) analyzer. Results: The median time between sampling at home and analysis was 3 days. Results of HbA(1c) in dried VAMS showed a poor agreement with venous/capillary blood collected in hospital (concordance correlation coefficient CCC=0.72). Similar observations were found with standard DBS. An excellent agreement was obtained between HbA(1c) results on wet VAMS (CCC=0.996) and standard blood samples. Patients experienced VAMS and DBS as easy and convenient to use. Conclusions: Utilizing equipment standard available in the clinical laboratory, the use of home-sampled dried VAMS and DBS is not a reliable tool for the monitoring of HbA(1c). However, perfect agreement between HbA(1c) measured on wet VAMS and capillary microsamples was obtained

The Heregulin/Human Epidermal Growth Factor Receptor as a New Growth Factor System in Melanoma with Multiple Ways of Deregulation

In a screening for new growth factors released by melanoma cells, we found that the p185-phosphorylating capacity of a medium conditioned by a melanoma cell line was due to the secretion of heregulin, a ligand for the human epidermal growth factor receptor (HER) family of receptor tyrosine kinases. Expression of heregulin, including a new isoform, and secretion of functionally active protein was found in several cell lines. Receptor activation by heregulin, either autocrine or paracrine, resulted in a potent growth stimulation of both melanocytes and melanoma cells. Heregulin receptor HER3 and coreceptor HER2 were the main receptors expressed by these cells. Nevertheless, none of the cell lines in our panel overexpressed HER2 or HER3. In contrast, loss of HER3 was found in two cell lines, whereas one cell line showed loss of functional HER2, both types of deregulations resulting in unresponsiveness to heregulin. This implies the heregulin/HER system as a possible important physiologic growth regulatory system in melanocytes in which multiple deregulations may occur during progression toward melanoma, all resulting in, or indicating, growth factor independence

Quantitative urine test strip reading for leukocyte esterase and hemoglobin peroxidase

Background: Recently, urine test strip readers have become available for automated test strip analysis. We explored the possibilities of the Sysmex UC-3500 automated urine chemistry analyzer based on complementary metal oxide semiconductor (CMOS) sensor technology with regard to accuracy of leukocyte esterase and hemoglobin peroxidase results. We studied the influence of possible confounders on these measurements. Methods: Reflectance data of leukocyte esterase and hemoglobin peroxidase were measured using CMOS technology on the Sysmex UC-3500 automated urine chemistry analyzer. Analytical performance (imprecision, LOQ) as well as the correlation with white blood cell (WBC) and red blood cell (RBC) counts (Sysmex UF-5000) were studied. Furthermore, the influence of urinary dilution, haptoglobin, pH and ascorbic acid as confounders was determined. Results: Within- and between-run imprecision (reflectance signal) ranged from 1.1% to 3.6% and 0.9% to 4.2% for peroxidase and 0.4% to 2.5% and 0.4% to 3.3% for leukocyte esterase. Good agreement was obtained between the UF-5000 for RBCs and peroxidase reflectance (r = 0.843) and for WBCs and leukocyte esterase (r = 0.821). Specific esterase activity decreased for WBC counts exceeding 100 cells/mu L. Haptoglobin influenced the peroxidase activity, whereas leukocyte esterase and peroxidase activities showed a pH optimum between 5.0 and 6.5. A sigmoidal correlation was observed between urinary osmolality and peroxidase activity. Conclusions: CMOS technology allows to obtain high quality test strip results for assessing WBC and RBC in urine. Quantitative peroxidase and leukocyte esterase are complementary with flow cytometry and have an added value in urinalysis, which may form a basis for expert system development

Synthetic cannabinoids : general considerations

Around 2008 synthetic cannabinoids were found to be present in and responsible for the psychoactive effects of herbal mixtures with names like ‘Spice’ or ‘K2’. In response to the increased popularity of these products, (inter)national organizations and governments started banning these cannabimimetics gradually. However, the lack of an uniform and international regulation makes it hard to control this issue. For the different types of synthetic cannabinoids the scientific knowledge in terms of pharmacokinetics and pharmacodynamics is limited. This also means that little is known on the health of users, both on short and long term. In the last years effort has been made to make detection of these products possible in different biological matrices. However, since the number of cannabimimetic compounds on the market appears to grow every month, both scientist and legislators run after a moving target