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  • Author: A. J. Bakker x
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Abstract

Background: Detection and quantification of monoclonal proteins is hampered when the monoclonal peak coincides with one of the regular bands in serum proteinelectrophoresis. The objective of this study was to evaluate four procedures for serum proteinelectrophoresis with respect to detection and quantification of monoclonal proteins.

Methods: For 466 patient samples with a monoclonal protein, three variants of agarose gel electrophoresis (5-band, split-β and high resolution) and one variant of capillary electrophoresis were compared with the results of the routinely used agarose gel electrophoresis followed by immunofixation analysis using specific or pentavalent antisera.

Results: In total, 310 patient samples were analyzed by the four methods, consisting of 295 samples with a monoclonal protein, seven with oligoclonal bands and eight without any bands. Suspicion of a monoclonal protein was raised in 295/256/256/232/265 of the samples using the reference/5-band/split-β/high resolution/capillary procedure. In 152/147/135/142/126 of the samples the concentration of monoclonal protein was >1.0 g/L and in 51/33/53/33/67 of the cases, the monoclonal protein was not separated from one of the normal protein zones.

Conclusions: In high resolution agarose gel electrophoresis, monoclonal bands of low concentration often remain undetected. In split-β agarose gel electrophoresis as well as capillary electrophoresis monoclonal bands more often were not separated from the regular protein bands.

Abstract

Myotonic dystrophy is a multi-organ disease inherited in a complicated way. Congenital myotonic dystrophy is a distinct entity with severe symptoms leading to a high rate of perinatal morbidity and mortality. The occurrence of congenital myotonic dystrophy often allows a subsequent diagnosis in the mother with important implications for her life, her further pregnancies and offspring. Genetic principles of anticipation and somatic mosaicism are involved and hamper the prenatal diagnostic possibilities.

A family is presented in which maternal myotonic dystrophy and congenital myotonic dystrophy were diagnosed after the third pregnancy. The key features leading to the diagnosis were obstetric history, neonatal hypotonia and asphyxia, facial abnormalities in the mother together with the inability to bury eyelashes and delayed release of grip after shaking hands. The disorder is reviewed with respect to clinical symptoms, pathogenesis and genetics.

Abstract

Background: Determination of the length of sedimentation reaction in blood (LSRB) is frequently used in daily practice to assess disease intensity. Recently, a micro-sedimentation method was introduced (TEST 1™) that uses EDTA anti-coagulated blood samples. The aim of this study was to characterize this method by comparing it to a conventional Westergren method (Sedimatic 100). Furthermore, correlation between fibrinogen and the LSRB and the influence of M-proteins on the LSRB was investigated.

Methods: Unselected paired samples were used for comparison between the TEST 1 and Sedimatic 100 methods (n=733); fibrinogen was measured in EDTA samples (n=765) using a turbidimetric method. Furthermore, LSRB was measured in 29 EDTA samples in paired serum tubes from patients in whom an M-protein was detected.

Results: TEST 1 showed excellent correlation with the Sedimatic 100 method (y=1.00x; n=733; r=0.92, 95% CI 0.90–0.93; p<0.0001), and had no significant bias (0.15mm/h, 95% CI –0.48 to 0.75mm/h). Furthermore, TEST 1 LSRB showed satisfactory correlation with the fibrinogen content (y=3.13+0.06x; n=765; r=0.78, 95% CI 0.75–0.80; p<0.0001). In samples containing M-proteins, satisfactory correlation between the M-protein content and TEST 1 LSRB was found (y=0.69+0.22x; n=29; r=0.71, 95% CI 0.45–0.85; p<0.0001), while excellent correlation was found when only M-proteins of the IgM type were taken into account (y=–0.95+0.23x; n=9; r=0.93, 95% CI 0.71–0.99; p<0.0002).

Conclusions: The results confirm previous reports that TEST 1 is a reliable method to measure the LSRB, and shows for the first time the quantitative relationship between TEST 1 LSRB and M-proteins, particularly those of the IgM type.

Clin Chem Lab Med 2006;44:904–6.

Abstract

Objectives

Monitoring tacrolimus blood concentrations is important for preventing allograft rejection in transplant patients. Our hospital offers dried blood spot (DBS) sampling, giving patients the opportunity to sample a drop of blood from a fingerprick at home, which can be sent to the laboratory by mail. In this study, both a volumetric absorptive microsampling (VAMS) device and DBS sampling were compared to venous whole blood (WB) sampling.

Methods

A total of 130 matched fingerprick VAMS, fingerprick DBS and venous WB samples were obtained from 107 different kidney transplant patients by trained phlebotomists for method comparison using Passing-Bablok regression. Bias was assessed using Bland-Altman. A multidisciplinary team pre-defined an acceptance limit requiring >80% of all matched samples within 15% of the mean of both samples. Sampling quality was evaluated for both VAMS and DBS samples.

Results

32.3% of the VAMS samples and 6.2% of the DBS samples were of insufficient quality, leading to 88 matched samples fit for analysis. Passing-Bablok regression showed a significant difference between VAMS and WB, with a slope of 0.88 (95% CI 0.81–0.97) but not for DBS (slope 1.00; 95% CI 0.95–1.04). Both VAMS (after correction for the slope) and DBS showed no significant bias in Bland-Altman analysis. For VAMS and DBS, the acceptance limit was met for 83.0% and 96.6% of the samples, respectively.

Conclusions

VAMS sampling can replace WB sampling for tacrolimus trough concentration monitoring, but VAMS sampling is currently inferior to DBS sampling, both regarding sample quality and agreement with WB tacrolimus concentrations.