Relationship between pharmacokinetics and pharmacodynamics of clopidogrel in patients undergoing percutaneous coronary intervention: comparison between vasodilator-stimulated phosphoprotein phosphorylation assay and multiple electrode aggregometry.

UNLABELLED: ESSENTIALS: The reliability of platelet tests as markers of the variable bioavailability of clopidogrel is not yet defined. Kinetics of clopidogrel active metabolite (CAM) and platelet response were studied in ischemic heart disease. CAM plasma maximum concentration (Cmax ) predicted vasodilator-stimulated phosphoprotein (VASP-P). Timely performed VASP-P, not an aggregation-based test, may be a surrogate for clopidogrel bioavailability. BACKGROUND: The high inter-individual variability in the inhibition of platelet function by clopidogrel is mostly explained by high variability in its transformation to an active metabolite (CAM). Objective We investigated the relations between pharmacokinetics and pharmacodynamics of CAM by comparing two methods of platelet function. METHODS: We enrolled 14 patients undergoing percutaneous coronary interventions for non-ST-segment elevation acute coronary syndrome or inducible myocardial ischemia. Plasma concentrations of clopidogrel and CAM, phosphorylation of vasodilator-stimulated phosphoprotein (VASP-P), expressed as a platelet reactivity index (PRI) and whole-blood platelet aggregation (multiple electrode aggregometer, MEA) were measured before and after a 600-mg clopidogrel loading dose (nine time-points) and before and after 75-mg maintenance doses on days 2, 7 and 30. RESULTS: Plasma concentrations of clopidogrel and CAM were highly variable. CAM reached maximal concentration (Cmax ) (median, 110.8 nm; range, 41.9-484.8) 0.5-2 h after the loading dose. A sigmoid dose-response curve defined the relations between CAMCmax and PRI after 3 to 24 h (IC50 , 459.6 nm; 95% confidence interval, 453.4-465.7; R(2) = 0.82). PRI was unchanged from baseline in patients with the lowest CAMCmax (< 83 nm, n = 7), indicating low sensitivity of VASP-P. PRI values were also predicted by CAMCmax at days 2, 7 and 30. Platelet aggregation measured by MEA did not show significant relations with either PRI or with CAM pharmacokinetics at any time-point. CONCLUSIONS: After 600 mg clopidogrel, VASP-P, but not whole-blood platelet aggregation measured by MEA, is almost entirely predicted by CAMCmax . VASP-P could be useful in studies aimed at investigating relations between CAM bioavailability and clinical events.

Sodium citrate blood contamination by K2 -ethylenediaminetetraacetic acid (EDTA): impact on routine coagulation testing.

INTRODUCTION: The potential cross-contamination of additives between primary blood tubes is a well-known problem during sample collection. The aim of this study was to assess the impact of citrated blood contamination with different amounts of dipotassium ethylenediaminetetraacetic (K2 EDTA blood) on activated partial thromboplastin time (APTT), prothrombin time (PT), and fibrinogen. METHODS: Blood was collected from 15 ostensibly healthy volunteers into four 0.109 m citrate blood tubes followed by one K2 EDTA blood tube. The citrate tubes of each subject were pooled and divided in five aliquots. The whole blood of the K2 EDTA tube was then added in scalar amounts to autologous citrated blood aliquots, to obtain K2 EDTA contamination ranging from 0% to 43%, and thus mimic potential pre-analytical contamination. RESULTS: A statistically and clinically significant prolongation was observed for both APTT and PT between 29% and 43% K2 EDTA contamination, whereas the decrease of fibrinogen values became statistically and clinically significant at 43% K2 EDTA contamination. CONCLUSION: The results of this investigation show that contamination of citrated blood with as much as 29% of K2 EDTA blood generates a significant bias in results of routine clotting assays. This has serious implications for patient safety and management.

Epigenetic alteration: new insights moving from tissue to plasma - the example of PCDH10 promoter methylation in colorectal cancer.

BACKGROUND: Tumour-released DNA in blood represents a promising biomarker for cancer detection. Although epigenetic alterations such as aberrant promoter methylation represent an appealing perspective, the discordance existing between frequencies of alterations found in DNA extracted from tumour tissue and cell-free DNA (cfDNA) has challenged their practical clinical application. With the aim to explain this bias of agreement, we investigated whether protocadherin 10 (PCDH10) promoter methylation in tissue was associated with methylation pattern in matched cfDNA isolated from plasma of patients with colorectal cancer (CRC), and whether the strength of concordance may depend on levels of cfDNA, integrity index, as well as on different clinical-pathological features. METHODS: A quantitative methylation-specific PCR was used to analyse a selected CpG site in the PCDH10 promoter of 67 tumour tissues, paired normal mucosae, and matched plasma samples. The cfDNA integrity index and cfDNA concentration were assessed using a real-time PCR assay. RESULTS: The PCDH10 promoter methylation was detected in 63 out of 67 (94.0%) surgically resected colorectal tumours and in 42 out of 67 (62.7%) plasma samples. The median methylation rate in tumour tissues and plasma samples was 43.5% (6.3-97.8%) and 5.9% (0-80.9%), respectively. There was a significant correlation between PCDH10 methylation in cfDNA and tumour tissue in patients with early CRC (P<0.0001). The ratio between plasma and tissue methylation rate increases with increasing cfDNA integrity index in early-stage cancers (P=0.0299) and with absolute cfDNA concentration in advanced cancers (P=0.0234). CONCLUSION: Our findings provide new insight into biological aspects modulating the concordance between tissues and plasma methylation profiles.

Brand of dipotassium EDTA vacuum tube as a new source of pre-analytical variability in routine haematology testing.

This study assesses the use of different dry K2 (dipotassium) EDTA vacuum tubes and whether or not they might represent a bias in haematological testing. Blood was collected in three dipotassium EDTA vacuum tubes from different manufacturers: Venosafe, Vacuette and Vacutainer. Samples were analysed on an Advia 2120i analyser. Significant differences among results and biases were compared with current quality specifications. Significant differences were found for haematocrit (HCT), mean corpuscular volume (MCV), white blood cell count (WBC) and platelet distribution width (PDW) when comparing Venosafe vs. Vacuette; for MCV, WBC and PDW when comparing Venosafe vs. Vacutainer; and for HCT and MCV when comparing Vacuette vs. Vacutainer. Clinically significant variations were observed for HCT and PDW in Venosafe vs. Vacuette; PDW in Venosafe vs. Vacutainer; and HCT and MCV in Vacuette vs. Vacutainer. The use of dipotassium EDTA vacuum tubes from different manufacturers represent a clinically relevant source of variation for HCT, MCV and PDW.

Vanin-1 T26I polymorphism, hypertension and cardiovascular events in two large urban-based prospective studies in Swedes.

BACKGROUND AND AIMS: Vanin-1 (gene name VNN1) is an enzyme with pantetheinase activity generating the amino-thiol cysteamine which is implicated in the regulation of red-ox status through its effect on glutathione. We tested the hypothesis that the rs2294757 VNN1 T26I polymorphism could affect blood pressure (BP) levels, hypertension prevalence, and risk of incident cardiovascular events. METHODS AND RESULTS: The VNN1 T26I polymorphism was genotyped in 5664 participants of the cardiovascular cohort of the "Malmö Diet and Cancer" (MDC-CVA) study and successively in 17874 participants of the "Malmö Preventive project"(MPP). The incidence of cardiovascular events was monitored for an average of nearly 12 years of follow-up in the MDC-CVA and for 25 years in the MPP. Both before and after adjustment for sex, age and BMI in the MDC-CVA the polymorphism had a mild lowering effect on diastolic BP and hypertension, especially in females. However in MPP no effect on BP phenotypes was detectable. Before and after adjustment for major cardiovascular risk factors, the hazard ratio for incident ischemic stroke and coronary events in the MDC-CVA was not significantly different in carriers of different genotypes. CONCLUSIONS: Our data do not support a major role for the VNN1 T26I variant in determining BP level and incident ischemic events.

Impact of the CYP4F2 p.V433M polymorphism on coumarin dose requirement: systematic review and meta-analysis.

A systematic review and a meta-analysis were performed to quantify the accumulated information from genetic association studies investigating the impact of the CYP4F2 rs2108622 (p.V433M) polymorphism on coumarin dose requirement. An additional aim was to explore the contribution of the CYP4F2 variant in comparison with, as well as after stratification for, the VKORC1 and CYP2C9 variants. Thirty studies involving 9,470 participants met prespecified inclusion criteria. As compared with CC-homozygotes, T-allele carriers required an 8.3% (95% confidence interval (CI): 5.6-11.1%; P < 0.0001) higher mean daily coumarin dose than CC homozygotes to reach a stable international normalized ratio (INR). There was no evidence of publication bias. Heterogeneity among studies was present (I(2) = 43%). Our results show that the CYP4F2 p.V433M polymorphism is associated with interindividual variability in response to coumarin drugs, but with a low effect size that is confirmed to be lower than those contributed by VKORC1 and CYP2C9 polymorphisms.

HE4 in ovarian cancer: from discovery to clinical application.

Despite the relatively low prevalence, ovarian cancer is the fifth leading cause of death from cancer among women. As such, an early diagnosis for establishing a timely surgical and/or chemotherapeutic treatment is essential for improving the outcome. The most reliable, but not always straightforward, approach to diagnose ovarian cancer relies on multiple, time-consuming and expensive investigative tools. These typically include clinical presentation (i.e., pelvic or abdominal pain, urinary frequency or urgency, increased abdominal size or bloating) with pelvic examination, transvaginal ultrasonography (US), and measurement of carbohydrate antigen 125 (CA125). Although the conventional pathway to develop and market a clinically useful biomarker is challenging, recent advances in genomic and proteomic technologies have led to the identification of previously unknown candidate markers of ovarian cancer. Some of these are currently under clinical validation. The human epididymis protein 4 (HE4) has recently been approved by the Food and Drug Administration for monitoring recurrence or progression of epithelial ovarian cancer. Nevertheless, reliable clinical evidence demonstrates that HE4, used alone or in combination with CA125, substantially improves the accuracy of screening and/or disease monitoring. This chapter will review the current knowledge on biologic and clinical applications of ovarian cancer biomarkers, with particular emphasis on the newly proposed marker, HE4.

Transillumination: a new tool to eliminate the impact of venous stasis during the procedure for the collection of diagnostic blood specimens for routine haematological testing.

INTRODUCTION: The collection of diagnostic blood specimens for routine haematological testing (RHT) is traditionally performed with tourniquet. However, the transillumination devices based on cold near-infrared LEDs have been formerly proposed as a valuable tool for identifying reliable venous accesses, especially in patients with difficult or small veins, such as children. This study was aimed to evaluate whether a transillumination device can advantageously replace the use of the tourniquet during the procedure for collection of blood specimens for RHT and thereby eliminating the discomfort and risk of spurious results caused by excessive or prolonged venous stasis. METHODS: Two hundred and fifty volunteers were divided into five groups (G1, G2, G3, G4 and G5) to compare the results of RHT between blood sample collected with transilluminator device (left arm) and with tourniquet application (right arm) for 30 s(G1), 60 s(G2), 90 s(G3), 120 s(G4) and 180 s(G5). RESULTS: No significant increases were observed in any of the haematological parameters tested in G1 when compared with blood collected by the transilluminator device. From G2 to G5, significant increases were observed for the platelet count, red blood cell count, haemoglobin, haematocrit, white blood cell count, neutrophils, monocytes and eosinophils. From G3-G5, further increases were observed for lymphocytes. Clinically significant variations were, however, observed for basophils in G2; red blood cell count, haemoglobin, haematocrit and basophils in G3 and eosinophils in G3 only. CONCLUSION: As such, considering that inappropriate use of the tourniquet is commonplace, we conclude that transillumination devices can represent a suitable tool to eliminate the venous stasis and to improve the quality of phlebotomy procedures.

Right or wrong sample received for coagulation testing? Tentative algorithms for detection of an incorrect type of sample.

Inappropriate blood collection potentially comprises the major pre-analytical problem for coagulation testing. Inappropriate samples are most difficult to detect when received as secondary aliquots, common for referred tests. This study aimed to identify a simple, quick and inexpensive process to help laboratories distinguish the type of sample, should there be suspicion of inappropriate collection. Samples from 15 patients [selected on the basis that four different primary tubes were available: serum, citrated plasma, ethylene diamine tetraacetic acid (EDTA) plasma, lithium-heparin plasma], were tested for common electrolytes that might substantially differ according to the type of sample. In citrated plasma, potassium, chloride, calcium and magnesium were significantly decreased compared with serum and lithium-heparin plasma, while sodium was markedly increased. In EDTA plasma, sodium and chloride were significantly decreased compared with both serum and lithium-heparin plasma, potassium was always >14 mmol/l, whereas magnesium and calcium were virtually undetectable. These data allowed development of two algorithms for differential identification of citrated plasma vs. other samples with 100% sensitivity and specificity, the former based on the sequential measurement of potassium, calcium and sodium, the latter on potassium and sodium. These simple assays can supplement classical coagulation test methods to identify most inappropriate blood collections and validate sample rejection.

Thrombin generation assay: a useful routine check-up tool in the management of patients with haemophilia?

Severity assessment of patients with haemophilia A (HA) is traditionally based on FVIII activity (FVIII:C). Clinical phenotype of HA patients often differs between individuals with the same FVIII:C determined with clotting and chromogenic assays. The aim of this study was to assess the influence of the FVIII:C on thrombin generation (TG) assay parameters both in vitro and ex-vivo postinfusion plasma. For in-vitro approach, influence of FVIII:C was evaluated on TG parameters in several dilutions of a normal plasma pool with commercial FVIII-depleted-plasma (FVIIIDP) and in others experiments, adding increasing amounts of different commercial FVIII concentrates (Fanhdi, Haemate-P, Hemofil-M and Kogenate Bayer) to FVIIIDP. In a series of 50 postinfusion samples, from HA patients of different severity, we assayed TG and FVIII:C (chromogenic and clotting). In vitro experiments, the 50% of maximum TG peak (TGMP) was achieved using only 5% FVIII:C and the TGMP was obtained with 40% of normal VIII:C. Impaired response compared with normal plasma was found in FVIIIDP using addition of increasing amounts of different commercial FVIII concentrates. An overall good correlation between the two FVIII assays was observed (y = 0.9115x - 0.273, r = 0.975, P < 0.001); TGMP and the Lag-Phase-Time (LPT) provided some discrepant results when compared with the total range of FVIII:C measurements. In contrast, correlations for TGMP, LPT and endogenous thrombin potential were improved in samples restricted to FVIII:C <5%. We conclude that TG parameters tentatively could be a tool to tailor the global haemostatic capacity in haemophilic patients.

Evaluating endothelial function of the common carotid artery: an in vivo human model.

BACKGROUND AND AIMS: Flow mediated dilation (FMD) of peripheral conduit arteries is a well-established tool to evaluate endothelial function. The aims of this study are to apply the FMD model to cerebral circulation by using acetazolamide (ACZ)-induced intracranial vasodilation as a stimulus to increase common carotid artery (CCA) diameter in response to a local increase of blood flow velocity (BFV). METHODS AND RESULTS: In 15 healthy subjects, CCA end-diastolic diameter and BFV, middle cerebral artery (MCA) BFV and mean arterial blood pressure (MBP) were measured at basal conditions, after an intravenous bolus of 1g ACZ, and after placebo (saline) sublingual administration at the 15th and 20th minute. In a separate session, the same parameters were evaluated after placebo (saline) infusion instead of ACZ and after 10 microg/m(2) bs and 300 microg of glyceryl trinitrate (GTN), administered sublingually, at the 15th and 20th minute, respectively. After ACZ bolus, there was a 35% maximal MCA mean BFV increment (14th minute), together with a 22% increase of mean CCA end-diastolic BFV and a CCA diameter increment of 3.9% at the 3rd minute (p=0.024). There were no MBP significant variations up to the 15th minute (p=0.35). After GTN administration, there was a significant increment in CCA diameter (p<0.00001). CONCLUSIONS: ACZ causes a detectable CCA dilation in healthy individuals concomitantly with an increase in BFV. Upon demonstration that this phenomenon is endothelium dependent, this experimental model might become a valuable tool to assess endothelial function in the carotid artery.

Influence of temperature and time before centrifugation of specimens for routine coagulation testing.

The accurate standardization of the preanalytical phase is of pivotal importance for achieving reliable results of coagulation tests. Because information on the suitable storage conditions for coagulation testing is controversial, we aimed at investigating the sample stability with regard to the temperature and time before centrifugation. The activated partial thromboplastin time (aPTT), prothrombin time (PT), fibrinogen and D-dimer were assayed in specimens collected from 26 consecutive patients on antivitamin K therapy on the ACL TOP analyzer. Three primary 3.6-ml siliconized evacuated tubes containing 0.109 mol/l buffered trisodium citrate were sequentially collected from each patient. These three tubes were mixed, pooled and divided into seven identical aliquots. The first aliquot was immediately centrifuged according to the standard protocol [1500 g for 15 min at room temperature (RT)] and analyzed. The other aliquots were left for 3, 6 and 24 h, respectively, at RT or 4 degrees C, and then centrifuged and analyzed. Test results were compared with those obtained on the reference specimen. Statistically significant prolongations were observed for aPTT in all the samples. Such differences exceeded the analytical quality specifications for desirable bias in the samples stored for 24 h. A significant reduction, yet comprised within the desirable bias, was observed for PT and fibrinogen in uncentrifuged specimens stored at RT for 3 and 6 h. No significant biases could be recorded in D-dimer. In conclusion, a 6-h storage of uncentrifuged specimens at either RT or 4 degrees C may still be suitable to achieve results of routine coagulation testing comprised within the analytical quality specifications for desirable bias.