Influence of apixaban on commonly used coagulation assays: results from the Belgian national External Quality Assessment Scheme.

INTRODUCTION: The Belgian national External Quality Assessment Scheme performed a survey to assess the effect of the direct oral anticoagulant apixaban on the coagulation assays prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen and antithrombin as performed with a large number of reagent/instrument combinations. METHODS: Four lyophilized plasma samples spiked with apixaban (0, 41, 94 and 225 ng/mL) were sent to the 195 Belgian and Luxembourg clinical laboratories performing coagulation testing. RESULTS: PT and aPTT were barely influenced at the concentrations tested. At 225 ng/mL apixaban, PT and aPTT clotting times were only 1.15 times longer than at 0 ng/mL. Among PT reagents, RecombiPlasTin 2G® showed a slightly higher sensitivity with 225 ng/mL apixaban prolonging the PT clotting time 1.3-fold. Among aPTT reagents, there was no appreciable difference in sensitivity. Fibrinogen results were unaffected by the presence of apixaban, but antithrombin activity was considerably overestimated when measured with a FXa-based assay. At 225 ng/mL apixaban, the median percentage increase in antithrombin level was 31% when measured with the Liquid Antithrombin® reagent and 44% with the Innovance Antithrombin® reagent. CONCLUSION: Our data provide clinical laboratories with useful information on the impact of apixaban on their routine coagulation assays.

Belgian recommendations on ANA, anti-dsDNA and anti-ENA antibody testing.

Autoantibodies to nuclear antigens, i.e. antinuclear antibodies (ANA), antibodies to double-stranded DNA (dsDNA) and extractable nuclear antigens (ENA), are useful as diagnostic markers for a variety of autoimmune diseases. In March 2010, the Belgian national External Quality Assessment Scheme sent a questionnaire on ANA, anti-dsDNA and anti-ENA antibody testing designed by the Dutch EASI (European Autoimmunity Standardization Initiative) team, to all clinical laboratories performing ANA testing. Virtually all laboratories completed the questionnaire (97·7%, 127/130). This paper discusses the results of this questionnaire and provides valuable information on the state-of-the-art of ANA, anti-dsDNA and anti-ENA antibody testing as practiced in the Belgian laboratories. In addition, this work presents practical recommendations developed by the members of the advisory board of the scheme as a result of the outcome of this study.

External quality assessment in the measurement of haemoglobin by blood gas analysers in Belgium.

OBJECTIVE: The Belgian national External Quality Assessment Scheme (EQAS) for haematology organized a survey to assess the reliability of haemoglobin (Hb) measurements with the blood gas analysers (BGAs) currently available in Belgian hospitals. MATERIAL AND METHODS: All hospital laboratories received two specimens of fresh EDTA anticoagulated whole blood and were asked to determine the Hb concentration using both the conventional haematology analyser (HA) and all BGAs in the hospital. Ninety-seven hospital laboratories participated in the study and a total of 166 results were reported. The BGAs used (grouped according to technology) were Rapidlab 845, 855, 865 (Bayer 1, n = 41), Rapidlab 1245, 1265, Rapidpoint 405 (Bayer 2, n = 19), GEM Premier 3000 (Instrumentation Laboratory, IL, n = 13), ABL 500 and 600 series (Radiometer 1, n = 13), ABL 700 and 800 series (Radiometer 2, n = 35), Omni C, S5 (Roche 1, n = 7), Omni 3, 6, 9, S2, S4, S6 (Roche 2, n = 21). RESULTS: For the BGAs from Bayer, Radiometer and Roche, interlaboratory variation ranged from 0.6 % to 4.1 %, indicating good precision and close agreement between centres. A significant negative bias observed on the GEM Premier 3000 using the EDTA anticoagulated blood samples did not appear to be present in fresh heparinized whole blood samples. There was no significant difference in imprecision and bias between Hb measurements on BGA situated in and outside the central laboratory.

Four radioisotopic immunoassays of free thyroxine compared.

The analytical and clinical performance of three radioisotopic methods for the measurement of free thyroxine-Gamma Coat (125I) Free T4, RIA-gnost FT4 and Amerlex-MAB* FT4-were assessed in comparison with the Scalvo two-step chromatographic method. The analytical evaluation indicated excellent performance of Amerlex-MAB FT4. For the other methods, precision and sensitivity were comparable and acceptable for routine use. Only Gamma Coat FT4 showed a significant positive intra-assay drift. None of the methods showed a significant correlation with thyroxine-binding globulin. Amerlex-MAB FT4 results were weakly positively correlated with albumin. Sclavo, RIA-gnost and particularly GammaCoat FT4 results were affected by the presence of increased concentrations of free fatty acids. All methods classified hyperthyroid patients correctly. Slight overlaps existed between the hypothyroid and euthyroid populations. Significant decreases in free thyroxine (FT4) during the third trimester of pregnancy were detected by all assays. In patients with chronic renal failure, serum FT4 was within reference limits more often when measured by Sclavo or Amerlex-MAB methods than by RIA-gnost or GammaCoat techniques. In conclusion, all assays performed well from both technical and diagnostic points of view.

Ektachem slides overestimate serum albumin in patients with nephrotic syndrome.

In a non-selected patient population (n = 140), serum albumin concentrations obtained with Ektachem slides were very significantly correlated with results determined with serum protein electrophoresis on Olympus Hite 200. In 7 patients with nephrotic syndrome, however, no such correlation existed, concentrations on Ektachem being 20 to 200% higher (up to 16 g/l difference). In other samples, albumin concentrations on Ektachem were 10 g/l lower. Between-method differences appeared most closely correlated with the sum of alpha 1- and alpha 2-globulins as determined by serum protein electrophoresis. Immunonephelometric determination of various serum proteins demonstrated that haptoglobin concentrations most closely paralleled the observed between-method differences.

Second-trimester cancer antigen 125 and Down's syndrome.

This study explores if assay of cancer antigen 125 (CA 125) in maternal serum might aid the detection of Down's syndrome in the second trimester of pregnancy. CA 125 levels were determined retrospectively in stored maternal serum samples from ten Down's syndrome pregnancies and 78 controls matched for gestational and maternal age. In addition, second-trimester amniotic fluid samples from nine Down's syndrome and 109 unaffected pregnancies were analysed for CA 125. Maternal serum CA 125 values for Down's syndrome pregnancies were lower, with the median being 0.72 multiples of the unaffected population median. The medians for affected and unaffected pregnancies did not differ significantly and there was a considerable overlap in the range of values of cases and controls. The distribution of amniotic fluid CA 125 levels for Down's syndrome pregnancies resembled that for controls. From our present results, we could not find an association between Down's syndrome and second-trimester maternal serum or amniotic fluid CA 125 levels.

Analytical and clinical evaluation of creatine kinase MB mass assay by IMx: comparison with MB isoenzyme activity and serum myoglobin for early diagnosis of myocardial infarction.

We analytically and clinically evaluated Abbott's IMx assay for creatine kinase (CK) isoenzyme MB (CK-MB) in serum. Over a 1-year period, the method was more specific but less precise than catalytic isoenzyme measurements by electrophoresis or immunoinhibition. Sera from different individuals without electrophoretic evidence of CK-MB but containing macro CK type 1 (n = 20), mitochondrial CK (n = 5), or CK-BB (n = 5) were scored as CK-MB negative by the IMx. Likewise, CK-MB-negative by the sera remained so after addition of purified human CK-MM (< or = 7600 U/L) or CK-BB (< or = 8100 U/L). For 39 patients admitted for suspicion of uncomplicated acute myocardial infarction (precordial pain for < or = 4 h), the diagnostic performance of the IMx CK-MB assay on admission and 4 h later was superior to that of total CK activity and compared well with that of CK-MB activity measured by electrophoresis or immunoinhibition. An admission, myoglobin showed a higher diagnostic sensitivity, specificity, and predictive value than did CK-MB and was the most informative test. Diagnostic performance on admission and 4 h later was further improved by considering positivity for myoglobin and for CK-MB by IMx and for the change in each over the first 4 h of hospitalization as criteria. Twelve hours after admission, diagnostic performance was further improved for all CK and CK-MB methods but began to decline for myoglobin.

Activation of mouse oocytes, fertilization and development of mouse embryos in vitro after staining with trypan blue or fluorescein diacetate.

The influence of vital staining with trypan blue or fluorescein diacetate on the fertilization of mouse oocytes and the developmental potential of mouse embryos was assessed. Neither stain induced spontaneous activation in mouse oocytes, nor did they impair the in vitro development and implantation of mouse zygotes, two-cell embryos, stressed morulae or blastocysts. However, fertilization and subsequent development of mouse oocytes have been shown to be reduced by vital staining.

Plasma insulin-like growth factor-I determinations in patients with cystic fibrosis: Influence of the nutritional and liver status.

Insulin-like growth factor-1 (Igf1), a useful and early marker of undernutrition in inflammatory diseases, is dependent on the calorie and protein content of the diet. In 31 children and adolescents with cystic fibrosis (CF), a chronic inflammatory disease, the influence of the degree of liver dysfunction and the protein and calorie content of the diet on the circulating Igf1 was evaluated. No significant difference in the median plasma Igf1 concentration, measured by RIA, between the CF children (0.80 U/ml) and a for age and puberty matched control group (0.61 U/ml) was found. Expressing the Igf1 concentration as a percentage of normal for age, gave for the CF patients with liver involvement a lower level (median: 76%) than in those without (median: 101%). No correlation existed between the circulating Igf1 levels and the body height SDS, the body weight index and the calorie or protein intake of the patients.

Further characterization of iodide-induced hyperthyroidism based on the direct measurement of intrathyroidal iodine stores.

Clinical, scintigraphic and laboratory findings in a group of 23 hyperthyroid patients with inappropriate total intrathyroidal iodine pool (ITI), measured by X-ray fluorescence, were compared to those of 25 hyperthyroid patients with low ITI. Differences are discussed which may be useful in the diagnosis of this clinical entity.

Treatment of high-output gastric fistulas with omeprazole.

Two patients with high-output gastrocutaneous fistulas were treated with total parenteral nutrition and gastric antisecretory drugs. IV administration of omeprazole decreased acid output in one patient in a rapid and significant way, resulting in the spontaneous healing of the fistula after eight days of treatment. In the second patient, omeprazole caused a marked reduction in the acidity of the fluid in the fistula, which also closed without surgical operation. The long-standing decrease in acid output induced by intravenous omeprazole may be very useful for promoting spontaneous closure of high-output gastrocutaneous fistula.

Decompaction and biopsy of late mouse morulae: assessment of in-vitro and in-vivo developmental potential.

The present study reports a biopsy technique on decompacted late mouse morulae. Zygotes were collected from hyperstimulated F1 hybrids (C57BL6j females x CBAca males) and cultured in modified Earle's balanced salt solution supplemented with 0.5% bovine serum albumin until the late morula stage (92 h post administration of human chorionic gonadotrophin). Decompaction was obtained by exposure of the embryos to Ca(2+)-Mg(2+)-free phosphate-buffered saline (PBS) or an aqueous solution of ethylene-diaminetetraacetic acid (EDTA) and glycine. Using micromanipulation, a single blastomere was aspirated without removal or softening of the zona. The impact of the different decompaction procedures and the biopsy technique was studied by vital staining, by in-vitro culture up to the early egg-cylinder staged and by the recovery of living mice after transfer to pseudopregnant foster mothers. Our investigations revealed no impact of decompaction and biopsy on immediate viability, as assessed by fluorescein diacetate staining. A significant reduction (P less than 0.05) in the number of mouse morulae that reached the early egg-cylinder stage in vitro was observed after the biopsy procedure. We observed that after this microbiopsy technique, successful pregnancies can be obtained but at a lower percentage compared to controls (P less than 0.01).

Beta-glucuronidase activity in mouse oocytes, mouse preimplantation embryos, and human gametes.

A microfluorimetric assay was designed to monitor beta-glucuronidase (beta-gluc) activity during the early development of mouse embryos and was also applied to measure beta-gluc activity in human sperm cells and single human oocytes. Mouse oocytes and preimplantation embryos at different stages of development, failed fertilized human oocytes, and human sperm cells were collected, and beta-gluc activity was analysed. In the mouse, beta-gluc activity could be measured starting from the morula stage on in a pooled sample of 15 embryos and at blastocyst formation in one single embryo. beta-Gluc activity was low in human sperm cells. The enzyme could be readily demonstrated in 87 per cent of non-fertilized human oocytes. Considerable variation in beta-gluc activity was noticed between individual oocytes.

Oligoclonal bands in cerebrospinal fluid detected by PhastSystem isoelectric focusing.

Pharmacia's "PhastSystem" for semi-automated isoelectric focusing (IEF) in thin precast polyacrylamide gels (PAGE) was found to be as sensitive as high-resolution protein electrophoresis (HRPE) in agarose gels and conventional PAGE-IEF for detection of oligoclonal banding (OB) in concentrated cerebrospinal fluid (CSF) samples. Both PhastSystem IEF and HRPE revealed OB in CSF from eight of nine multiple sclerosis patients and four of 10 patients with various types of infection of the central nervous system as opposed to only two of 70 patients with miscellaneous neuropsychiatric disorders. The PhastSystem also frequently detected OB in silver-stained, unconcentrated CSF from patients with multiple sclerosis.