Clopidogrel Resistance in Neurovascular Stenting: Correlations between Light Transmission Aggregometry, VerifyNow, and the Multiplate.

BACKGROUND AND PURPOSE: Clopidogrel resistance is blamed for thromboembolic complications in neurovascular stent placement. Platelet-function assays are weakly standardized. The aim of this study was to correlate the results of 3 different platelet-inhibition measurements (from light transmission aggregometry, the VerifyNow P2Y12 test, and the Multiplate analyzer) and their relation to periprocedural thromboembolic complications in elective neurovascular stent placement. MATERIALS AND METHODS: Clopidogrel resistance was determined on the day of the intervention according to predefined platelet reactivity cutoff values. All 3 tests were performed in 103 consecutive neurovascular stent-placement procedures in 97 patients (extracranial, n = 77; intracranial, n = 26). RESULTS: The clopidogrel resistance rates were 47.6% (light transmission aggregometry), 50.5% (VerifyNow), and 35.9% (Multiplate). In 67% of the patients, clopidogrel resistance was present according to at least one method. The correlations of qualitative results that classified a patient as responsive or resistant to clopidogrel were 67.9% for light transmission aggregometry with VerifyNow, 77.7% for light transmission aggregometry with the Multiplate, and 66% for VerifyNow with the Multiplate. Periprocedural thromboembolic complications (n = 9) occurred more frequently in patients who were determined by all 3 methods to be clopidogrel resistant. The difference was most pronounced with light transmission aggregometry (complication rates, 14.4% [clopidogrel-resistant patients] vs 3.7% [clopidogrel-responsive patients]). Sensitivity and specificity rates of clopidogrel resistance in relation to embolic complications were, respectively, 78% and 55% for light transmission aggregometry, 67% and 51% for VerifyNow, and 44% and 67% for the Multiplate. CONCLUSIONS: Clopidogrel resistance is a frequent finding in patients who undergo neurovascular stent placement. The correlations among the different testing methods are only modest and differ considerably. Light transmission aggregometry results seem to correlate with thromboembolic complications more accurately than with VerifyNow and Multiplate point-of-care methods.

[Therapy of inherited diseases of platelet function. Interdisciplinary S2K guideline of the Permanent Paediatric Committee of the Society of Thrombosis and Haemostasis Research (GTH e. V.)]. / Therapie hereditärer Thrombozytopathien. Interdisziplinäre S2K-Leitlinie der Ständigen Kommission Pädiatrie der Gesellschaft für Thrombose- und Hämostaseforschung e. V.

Inherited disorders of platelet function are a heterogeneous group. For optimal prevention and management of bleeding, classification and diagnosis of the underlying defect are highly recommended. An interdisciplinary guideline for a diagnostic approach has been published (AWMF # 086-003 S2K; Hämostaseologie 2014; 34: 201-212). Underlying platelet disorder, platelet count, age and clinical situation modify treatment. Exclusive transfusion of platelet concentrates may be inappropriate as potentially adverse effects can outweigh its benefit. A stepwise and individually adjusted approach for restitution and maintenance of haemostasis is recommended. Administration of antifibrinolytics is generally endorsed, but is of particular use in Quebec disease. Restricted to older children, desmopressin is favourable in storage pool disease and unclassified platelet disorders. Although licensed only for patients with Glanzmann thrombasthenia and alloantibodies, in clinical practice rFVIIa is widely used in inherited platelet disorders with severe bleeding tendency. This guideline aims at presenting the best available advice for the management of patients with inherited platelet function disorders.

Risk factors associated with intraabdominal infections: a prospective multicenter study. Peritonitis Study Group.

INTRODUCTION AND METHODS: A prospective observational multicenter study with 18 hospitals was performed to assess preoperative risk, therapeutic management and outcome of patients with peritonitis. Data collection was carried out according to standardized and recommended definitions. Included in the study were 355 patients with macroscopically confirmed peritonitis. RESULTS: In the univariate analysis, the following factors influenced both the mortality and the incidence of postoperative complications: age, presence of certain concomitant disease, site of origin of peritonitis, type of admission and the ability of the surgeon to eliminate the source of infection. In addition, postoperative infective complications were related to the etiology of peritonitis and the exudate. In the multivariate analysis, APACHE II (P<0.001), successful operation (P<0.001), age (P<0.001), liver disease (P<0.03), malignant disease (P<0.04) and renal disease (P<0.05) turned out to be significant with respect to death. Escherichia coli was the predominant organism (51%), following by enterococci (30%) and bacteroides (25%). There was a significantly higher postoperative infection rate in patients with no adequate treatment of enterococci than patients with adequate treatment or no enterococci (P<0.05). CONCLUSION: The study demonstrated the important role of the physiological reserve of the patient and of the surgeon, which is not adequately reflected in existing scoring systems. Further investigations are needed to study the impact of enterococci on the outcome.

Active uptake of serotonin as viability parameter of stored platelets.

The platelet-plasma serotonin (5-HT) exchange in different apheresis products and platelet concentrates (PCs) from buffy coats was studied for quality control over a period of 7 days. In PCs with steadily decreasing pH due to inappropriate gas exchange the platelet 5-HT concentration increases significantly (> 10% positive netto uptake) during the 1st day of storage. Thereafter platelet serotonin drops rapidly with t1/2 = 1 day at pH < 6.5, but platelet counts were constant and 5-HT uptake was inhibited concomitantly. Plasma 5-HT increases as pH decreases. This can be enforced by competitive inhibition of serotonin uptake due to imipramine which also moderates the total 5-HT loss. However, in PC with stable pH the operative 5-HT pump keeps steady-state conditions. The efficacy of the transmembrane uptake mechanism can be adequately monitored by the assessment of the 5-HT platelet/plasma ratio as a new platelet viability parameter.

Detection of HLA antibodies by an enzyme-linked photometric immune phagocytosis inhibition test.

The immune phagocytosis inhibition test (IPI) has been described as a sensitive method for the detection of cytotoxic and non-cytotoxic HLA antibodies. We performed a photometric IPI and compared this technique with the conventional microscopic IPI. In further investigations we used the photometric IPI in comparison with the lymphocytotoxicity test (LCT) for the detection of HLA antibodies. The photometric IPI showed a high correlation to the microscopic IPI. In tests with different known HLA antibodies the photometric IPI reached a sensitivity of 85.1% versus 80.5% in the LCT, and a specificity of 92.3 versus 100% in the LCT. Diluted patient sera showed a higher sensitivity in the photometric IPI. We conclude that the photometric IPI can be used as a convenient and sensitive technique for the detection of HLA antibodies.

Screening for hereditary hemochromatosis in prospective blood donors.

Prospective blood donors (n = 1,265, mean age 26 years) were screened for elevated serum ferritin and serum iron. Final diagnosis for hereditary hemochromatosis was made by liver iron concentration (noninvasive biomagnetometry), transferrin saturation, and 59Fe absorption in 3 male subjects. This preliminary result confirms for the first time the current frequency estimation of homozygous hemochromatosis (0.2-0.6%) in a group of young North-Germans.

[Measurement of alloreactive anti-recipient helper T-cell precursors after allogenic bone marrow transplantation]. / Messung der alloreaktiven Anti-Rezipienten-Helfer-T-Zell-Vorstufen nach allogener Knochenmarktransplantation.

Acute graft-versus-host disease (GvHD) is a severe complication after allogenous bone marrow transplantation (BMT). The compatibility of major histocompatibility complex antigens (MHC) is the strongest stimulus for GvHD, which also occurs in patients with a genetically MHC-identical sibling donor. In such cases it would be helpful to recognize anti-recipient (interleukin-2-producing) T-lymphocyte precursors to detect a minor histocompatibility antigen (mH), which escapes from typing methods. To quantitate the alloreactive immune response initiating acute GvHD, we established the helper T-lymphocyte precursor test (HTL-p) as described by Theobald et al. in 'GvHD direction', using a limiting dilution assay. Serial dilutions of the donor peripheral blood mononuclear cells (PBMCs) were cultured for 14 days with constant numbers of stimulator PBMCs from the recipient, followed by an unspecific restimulation step with phytohemagglutinin (PHA) or specific restimulation with EBV-transformed blast cells from the recipient. The Il-2 production of specific T cells was assessed by addition of CTLL-16 cells, whose proliferation was measured by an ELISA. We suppose that the HTL-p test is a good tool for measuring the number of anti-recipient T-lymphocyte precursors as a predictive value for the intensity of GvHD.

[Enzyme immunoassay for the determination of serotonin in stored platelet concentrates]. / Enzymimmunoassay zur Bestimmung von Serotonin in gelagerten Thrombozytenkonzentraten.

A new enzyme immunoassay (EIA) was applied on measurements of serotonin (5-HT) in stored platelet concentrates (PC). PC were prepared by apheresis of two separators (Cobe, Fresenius) or from buffy coats and stored for a period of 7 days at 22 degrees C and agitating. Measurements were done in pellets and suspension medium (plasma). Detection of 5-HT was specific and sensitive within the bounds of 2 and 1,000 ng/10(9) PLT.

Monoclonal antibodies and chemiluminescence immunoassay for detection of the surface protein of human T-cell lymphotropic virus.

Monoclonal antibodies (MAbs) raised against human T-cell lymphotropic virus type I (HTLV-I) recognized five distinct antigenic domains of viral env gene-encoded proteins. By using recombinant env proteins and synthetic peptides as mapping antigens, it was determined that the most immunogenic region represented a central portion of the retroviral surface protein (domain 2; amino acids 165 to 191). However, only a single MAb was able to react strongly with native viral proteins. This antibody (clone 6C2) was directed to an epitope within domain 4 (amino acids 210 to 306) of the retroviral env gene and reacted with envelope proteins in both HTLV-I and HTLV-II, as determined by immunoprecipitation, solid-phase binding, and immunoblotting. No reactivity against envelope components of other human retroviruses, including human immunodeficiency virus types 1 and 2, was present. Flow cytometry data demonstrated that MAb 6C2 reacted with cell lines chronically infected with HTLV-I or HTLV-II and also with surface antigens expressed on fresh adult T-cell leukemia cells, following up-regulation with interleukin-2. By a chemiluminescence immunoassay procedure, picogram amounts of viral surface protein could be detected in the unconcentrated supernatants of HTLV-infected cell lines and in diagnostic cultures. Levels of env and gag proteins released by cells into culture supernatants were not directly related to percent expression of cell surface viral-coat proteins. Further, the molar ratio of p19 to gp46 in conditioned media varied from strain to strain, possibly reflecting differences in viral assembly or packaging mechanisms. MAb 6C2 will be of value in characterizing the biochemical and immunological behavior of retroviral env gene proteins and in studying the interaction of HTLV-I and HTLV-II with their receptors.

[Experiences with monoclonal antibody orthoclone OKT3 following liver transplantation]. / Erfahrungen mit dem monoklonalen Antikörper Orthoclone OKT3 nach Lebertransplantation.

In 7 patients 10 cycles (5 to 21 days, dosage: 30 to 430 mg, median 138 mg) of OKT3 therapy were performed after liver transplantation. In all patients reactivation of an EBV-infection with hepatitis was observed. Two patients treated with high dosages (430 mg respectively 195 mg) developed lymphoproliferative lesions. In one patient with persistent EBV-infection (dosage: 360 mg) a B-cell-lymphoma was diagnosed. This patient died 26 months after transplantation.

Renal transplantation using cyclosporine with and without regard to HLA matching: a randomized prospective unicenter study.

A randomized prospective unicenter study produced no significant difference in 2-year outcome between the use of well matched cadaver renal allografts shared among transplantation centers, and the use of organs of local origin matched only for blood group. Graft and patient survival rates, transplant function and incidence of rejection were compared. On the basis of 1 and 2-year outcome with well matched and shared allografts we conclude that cyclosporine therapy makes HLA matching unnecessary.