Thrombin generation as marker to estimate thrombosis risk in patients with abnormal test results in lupus anticoagulant routine diagnostics.

BACKGROUND: Lupus anticoagulant (LA) is known to inhibit thrombin generation although patients have an increased risk to develop thrombosis. We tried to determine whether thrombin generation is altered in plasma samples of patients with abnormal test results in LA routine diagnostics and whether its measurement may improve the risk assessment of thrombosis. METHODS: Samples from 63 patients (39 with abnormal test results; 24 controls) were included in the study. Measurement of diluted Russel's viper venom time (dRVVT) was part of the initial guideline conform diagnostic procedure for detection of LA. In addition, measurement of anticardiolipin-IgM, -IgG and ß2-glycoprotein-I-IgM, -IgG were performed. Thrombin generation was measured using two different phospholipid concentrations in the starting reagent. RESULTS: Analyzing all samples by logistic regression, thrombin generation after induction with high phospholipid concentrations was the best predictor of thrombosis. After preselection of samples with alterations in dRVVT, specificity of selected thrombin generation derived parameters for the detection of previous thrombosis increased in this subgroup. CONCLUSIONS: In patients with phospholipid-dependent prolongation of dRVVT, thrombin generation is variably inhibited and the degree of inhibition corresponds to the occurrence of previous thrombosis. Measuring thrombin generation in patients with phospholipid-dependent dRVVT prolongation may improve risk assessment of thrombosis.

Evaluation of a straightforward and rapid method for the therapeutic drug monitoring of digitoxin by LC-MS/MS.

OBJECTIVES: Therapeutic drug monitoring of digitoxin is strongly recommended but metabolites of digitoxin and digitoxin-like immunoreactive substances may interfere with widely used immunoassays. Recently evaluated assays on LC-MS/MS have the drawback of long turnaround time. We sought to evaluate a specific method on LC-MS/MS optimizing sample preparation thereby significantly reducing turnaround time. DESIGN AND METHODS: Linearity, functional sensitivity, and precision of the method were established. External quality control samples were used for the evaluation of accuracy of the LS-MS/MS method. In addition, digitoxin concentrations in 221 samples were measured by LC-MS/MS and immunoassay. RESULTS: Linearity was validated between 0.15 and 80 ng/mL. Limit of quantification was established at 0.14 ng/mL. Between-day imprecision lay between 1.4 and 4.9% and meets the conditions required for routine analysis. Comparison to results obtained by immunoassay revealed a mean difference of -1.2 ng/mL. CONCLUSIONS: By optimizing preparation steps turnaround time was shorter for LC-MS/MS than for immunoassay. This did not result in increased susceptibility to matrix effects. Analytical performance was sufficient for routine analysis. Therefore, the method is suitable for routine therapeutic drug monitoring of digitoxin.

Immature platelet fraction as marker for platelet recovery after stem cell transplantation in children.

OBJECTIVES: Thrombocytopenia occurs in pediatric patients after SCT and has to be treated with platelet transfusions which bear certain risks and represent a significant cost factor. Monitoring immature platelet (IPF) fraction has been proposed to predict platelet recovery thereby reducing the need for transfusions. DESIGN AND METHODS: Hematological parameters including IPF were systematically studied in 17 pediatric patients after either peripheral blood or bone marrow stem cell transplantation. RESULTS: Time to platelet recovery depended on the source of stem cells while no differences were detected between percentaged IPF peak concentration and time between IPF peak concentration and platelet recovery between the groups. Correlation between the timepoints of percentaged IPF peak and platelet recovery was high but large interindividual differences were observed concerning the duration of this period. In addition, in some patients high IPF concentrations were not followed by platelet recovery. CONCLUSIONS: Although in general high IPF concentrations are followed by platelet recovery wide interindividual variations exist and even no recovery was recorded in four patients. As the latter children are not readily identifiable beforehand IPF should not be used to omit platelet transfusions.

Immediate diagnosis of ventriculits: evaluation of parameters independent of microbiological culture.

BACKGROUND: Generally accepted reference values in CSF diagnostics are not valid in cerebrospinal fluid (CSF) containing large amounts of blood. Residual blood may obscure ventriculitis as diagnostics largely depend on parameters such as cell count, lactic acid and total protein measurement. We sought to improve the diagnostics by evaluating a cytokine panel and soluble CD62L as markers of ventriculitis. In addition, we tested an algorithm of established parameters to predict ventriculitis in a specific patient collective. METHODS: Analysis was performed on ventricular CSF samples from 50 consecutive patients. Gram staining, microbiological culture, total cell count, total protein and CD62L expression on neutrophil granulocytes were analysed immediately. Cytokines and soluble CD62L were measured by flow cytometry. FINDINGS: Positive culture was detected in ten patients. Of all parameters tested only IL1-beta, IL8 and CD62L on neutrophils were significantly different between culture-positive and -negative patients. The highest predictive value was obtained when analysing IL1-beta. The predictive value of a parameter combination (IL6 in CSF, C-reactive protein and leukocytes in periphereal blood) was comparable to IL1-beta. Half of the patients in this analysis were identified as culture positive because of the lack of inflammatory response. CONCLUSIONS: IL1-beta and perhaps also IL8 provide very good analytical performance when looking for ventriculitis in patients with residual blood in CSF. Turn-around time is short, and results could be reported within 1 h for 24 h a day. In some patients application of glucocorticoids may result in restricted inflammatory response. Even in these patients IL1-beta provides a reliable parameter for the immediate diagnosis of ventriculitis.

Comparison of six D-dimer assays for the detection of clinically suspected deep venous thrombosis of the lower extremities.

Deep venous thrombosis is a common disease that may lead to life-threatening embolism of the lung as a common complication. Therefore, early diagnosis followed by sufficient treatment is necessary to decrease mortality of this disease. D-dimer testing is established as a standard to rule out deep venous thrombosis in selected patient groups. However, there is no standardization among D-dimer assays, and a periodical comparison of assay performance in a select patient group is indispensable. We evaluated six commonly used D-dimer assays for their assay performance in an outpatient cohort with clinically suspected deep venous thrombosis. Although area under the curve for these assays did not differ significantly (0.83-0.88), differences in sensitivity (90-100%) and specificity (10-40%) of the assays were detected. Alternative cut-offs were established, and these cut-offs could enhance assay performance in some cases. This points to the fact that the manufacturers should more regularly review studies on the performance of their respective assays to widen the data basis for their recommended cut-offs and increase assay performance.

Correction of ventricular cerebrospinal fluid (CSF) samples for blood content does not increase sensitivity and specificity for the detection of CSF infection.

BACKGROUND: Blood contamination is commonly observed in ventricular cerebrospinal fluid (CSF) samples from patients with extraventricular drainage systems. Because the introduction of blood may interfere with the white blood cell count as a useful marker for the diagnosis of an infection, correction for blood content would be desirable. METHODS: In a retrospective study, we analysed the use of correction formulas in 724 blood-contaminated ventricular CSF samples. RESULTS: Using a standard correction method the white blood cell count was not normalised in most CSF samples, with pleocytosis indicating an inflammatory stimulus set by the blood itself or by the foreign body. When correcting white blood cell counts in the CSF of culture-positive patients, some samples were normalised or overcorrected. In addition, correction of the CSF white blood cell count did not increase sensitivity and specificity for the detection of culture-positive CSF samples. CONCLUSIONS: Correction is not necessary when using the white blood cell count as a parameter to predict CSF infection in ventricular CSF samples.