Rapid and accurate Bayesian diagnosis of heparin-induced thrombocytopenia.

Prompt diagnostic evaluation of suspected heparin-induced thrombocytopenia (HIT) is critical for guiding initial patient management. We assessed the performance of 3 immunoassays detecting anti-platelet factor 4 (PF4)/heparin antibodies, derived a diagnostic algorithm with a short analytical turnaround time (TAT), and prospectively validated the algorithm. Plasma samples were analyzed by Zymutest-HIA-IgG, HemosIL-AcuStar-HIT-IgG, and ID-H/PF4-PaGIA in retrospective (n = 221) and prospective (n = 305) derivation cohorts. We calculated likelihood ratios of result intervals and cutoff values with 100% negative (NPV) and positive (PPV) predictive values for a positive gold standard functional assay (heparin-induced platelet activation [HIPA]). A diagnostic algorithm was established based on the Bayesian combination of pretest probability and likelihood ratios of first- and second-line immunoassays. Cutoffs with 100% PPV for positive HIPA were >3.0 U/mL (HemosIL-AcuStar-HIT-IgG) and titer ≥16 (ID-H/PF4-PaGIA); cutoffs with 100% NPV were <0.13 U/mL and ≤1, respectively. During the prospective validation of the derived algorithm (n = 687), HemosIL-AcuStar-HIT-IgG was used as unique testing in 566 (82.4%) of 687 cases (analytical TAT, 30 minutes). In 121 (17.6%) of 687 unresolved cases, ID-H/PF4-PaGIA was used as second-line testing (additional TAT, 30 minutes). The algorithm accurately predicted HIT in 51 (7.4%) of 687 patients and excluded it in 604 (87.9%) of 687 patients, leaving only 20 (2.9%) cases unresolved. We also identified 12 (1.7%) of 687 positive predictions not confirmed by HIPA: 10 patients with probable HIT despite negative HIPA and 2 possible false-positive algorithm predictions. The combination of pretest probability with first- and second-line immunoassays for anti-PF4/heparin antibodies is accurate for ruling in or out HIT in ≥95% of cases within 60 minutes. This diagnostic approach improves initial management of patients with suspected HIT.

Potential and Limitations of the New P2Y12 Inhibitor, Cangrelor, in Preventing Heparin-Induced Platelet Aggregation During Cardiac Surgery: An In Vitro Study.

BACKGROUND: Heparin-induced thrombocytopenia (HIT) can put cardiac surgery patients at a high risk of lethal complications. If anti-PF4/heparin antibodies (anti-PF4/Hep Abs) are present, 2 strategies exist to prevent intraoperative aggregation during bypass surgery: first, using an alternative anticoagulant, and second, using heparin combined with an antiaggregant. The new P2Y12 inhibitor, cangrelor, could be an attractive candidate for the latter strategy; several authors have reported its successful use. The present in vitro study evaluated cangrelor's ability to inhibit heparin-induced platelet aggregation in the presence of anti-PF4/Hep Abs. METHODS: Platelet-poor plasma (PPP) from 30 patients with functional anti-PF4/Hep Abs was mixed with platelet-rich plasma (PRP) from 5 healthy donors.Light transmission aggregometry was used to measure platelet aggregation after adding 0.5 IU·mL of heparin (HIT) to the plasma, and this was compared with samples spiked with normal saline (control) and samples spiked with cangrelor 500 ng·mL and heparin 0.5 IU·mL (treatment). Friedman test with post hoc Dunn-Bonferroni test was used for between-group comparisons. RESULTS: Heparin 0.5 IU·mL triggered aggregation in 22 of 44 PPP-PRP mixtures, with a median aggregation of 86% (interquartile range [IQR], 69-91). The median aggregation of these 22 positive samples' respective control tests was 22% (IQR, 16-30) (P < .001). Median aggregation in the cangrelor-treated samples was 29% (IQR, 19-54) and significantly lower than the HIT samples (P < .001). Cangrelor inhibited heparin-induced aggregation by a median of 91% (IQR, 52-100). Cangrelor only reduced heparin-induced aggregation by >95% in 10 of the 22 positive samples (45%). Cangrelor inhibited heparin-induced aggregation by <50% in 5 of the 22 positive samples (22%) and by <10% in 3 samples (14%). CONCLUSIONS: This in vitro study found that cangrelor was an unreliable inhibitor of heparin-induced aggregation in the presence of anti-PF4/Hep Abs. We conclude that cangrelor should not be used as a standard antiaggregant for cardiac patients affected by HIT during surgery. Unless cangrelor's efficacy in a particular patient has been confirmed in a presurgery aggregation test, other strategies should be chosen.

Design and establishment of a biobank in a multicenter prospective cohort study of elderly patients with venous thromboembolism (SWITCO65+).

In the field of thrombosis and haemostasis, many preanalytical variables influence the results of coagulation assays and measures to limit potential results variations should be taken. To our knowledge, no paper describing the development and maintenance of a haemostasis biobank has been previously published. Our description of the biobank of the Swiss cohort of elderly patients with venous thromboembolism (SWITCO65+) is intended to facilitate the set-up of other biobanks in the field of thrombosis and haemostasis. SWITCO65+ is a multicentre cohort that prospectively enrolled consecutive patients aged ≥65 years with venous thromboembolism at nine Swiss hospitals from 09/2009 to 03/2012. Patients will be followed up until December 2013. The cohort includes a biobank with biological material from each participant taken at baseline and after 12 months of follow-up. Whole blood from all participants is assayed with a standard haematology panel, for which fresh samples are required. Two buffy coat vials, one PAXgene Blood RNA System tube and one EDTA-whole blood sample are also collected at baseline for RNA/DNA extraction. Blood samples are processed and vialed within 1 h of collection and transported in batches to a central laboratory where they are stored in ultra-low temperature archives. All analyses of the same type are performed in the same laboratory in batches. Using multiple core laboratories increased the speed of sample analyses and reduced storage time. After recruiting, processing and analyzing the blood of more than 1,000 patients, we determined that the adopted methods and technologies were fit-for-purpose and robust.

Are circulating endothelial-derived and platelet-derived microparticles a pathogenic factor in the cisplatin-induced stroke?

BACKGROUND AND PURPOSE: To evaluate whether cisplatin-induced stroke is mediated by vascular toxicity with release of prothrombotic endothelial and platelet-derived microparticles (MPs). METHODS: Endothelial (CD31(+)CD41(-)), platelets (CD31(+)CD41(+)) and prothrombotic (Annexin V(+)) circulating MPs were quantified by flow cytometry in 18 patients with cancer, before and 3 days after administration of cisplatin, and compared with 18 healthy controls. Thrombin-antithrombin complex and prothrombin fragments (F(1+2)) were measured as markers of the activation of the coagulation. RESULTS: In patients with cancer, baseline levels of circulating prothrombotic, endothelial and platelet-derived MPs were similar to healthy controls and decreased significantly after administration of cisplatin. High-baseline MPs levels were observed in 5 patients who received cisplatin for a second or third cycle. A high-baseline activation of the coagulation was observed in all patients without further increase after cisplatin infusion. CONCLUSIONS: Cisplatin treatment is immediately followed by a decrease in circulating levels of endothelial and platelet-derived MPs. However, a transient increase in MPs is observed at the second and third infusion, and this may contribute to the cisplatin-induced stroke.

Development of a selective peptide macrocycle inhibitor of coagulation factor XII toward the generation of a safe antithrombotic therapy.

Inhibition of coagulation factor XII (FXII) activity represents an attractive approach for the treatment and prevention of thrombotic diseases. The few existing FXII inhibitors suffer from low selectivity. Using phage display combined to rational design, we developed a potent inhibitor of FXII with more than 100-fold selectivity over related proteases. The highly selective peptide macrocycle is a promising candidate for the control of FXII activity in antithrombotic therapy and a valuable tool in hematology research.