Tissue factor activity of blood mononuclear cells is increased after total knee arthroplasty.

Tissue factor (TF) is present in small quantities in normal blood and is reported to be elevated in arterial and venous thrombosis. Patients undergoing total knee arthoplasty (TKA) are at high risk of post-operative venous thromboembolism (VTE). To evaluate the possible contribution of elevated blood TF to VTE risk, we performed serial studies of peripheral blood mononuclear cell (PBMC) functional TF procoagulant activity (PCA) in 19 patients after TKA. PBMC and platelet TF PCA were measured by a functional, clot-based assay following decryption with a calcium ionophore. Plasma TF antigen levels were measured by ELISA. All subjects received chemoprophylaxis and none had VTE. After TKA total TF PCA of PBMC was elevated in 19 of 19 subjects. The peak increase above preoperative levels was 1.1-13.6 fold (>two-fold in 58% and >three-fold in 42%). Median TF PCA of PBMC was not elevated following tourniquet removal, but it was significantly elevated on postoperative days 1 and 2. Thereafter, it decreased to near preoperative values at day 6. Neither platelet TF PCA nor plasma TF antigen levels increased significantly. Since the PBMC count did not rise, the increase in TF PCA was attributable to cell synthesis. The increase in blood TF PCA preceded the median time of diagnosis of venous thromboembolism after TKA established previously. These observations indicate a) TKA stimulates synthesis of encrypted PBMC TF PCA which is likely to contribute to the pathophysiology of VTE; b) TF antigen is not a reliable indicator of TF PCA.

Blood Biomarkers of Chronic Inflammation in Gulf War Illness.

BACKGROUND: More than twenty years following the end of the 1990-1991 Gulf War it is estimated that approximately 300,000 veterans of this conflict suffer from an unexplained chronic, multi-system disorder known as Gulf War Illness (GWI). The etiology of GWI may be exposure to chemical toxins, but it remains only partially defined, and its case definition is based only on symptoms. Objective criteria for the diagnosis of GWI are urgently needed for diagnosis and therapeutic research. OBJECTIVE: This study was designed to determine if blood biomarkers could provide objective criteria to assist diagnosis of GWI. DESIGN: A surveillance study of 85 Gulf War Veteran volunteers identified from the Department of Veterans Affairs Minnesota Gulf War registry was performed. All subjects were deployed to the Gulf War. Fifty seven subjects had GWI defined by CDC criteria, and 28 did not have symptomatic criteria for a diagnosis of GWI. Statistical analyses were performed on peripheral blood counts and assays of 61 plasma proteins using the Mann-Whitney rank sum test to compare biomarker distributions and stepwise logistic regression to formulate a diagnostic model. RESULTS: Lymphocyte, monocyte, neutrophil, and platelet counts were higher in GWI subjects. Six serum proteins associated with inflammation were significantly different in GWI subjects. A diagnostic model of three biomarkers-lymphocytes, monocytes, and C reactive protein-had a predicted probability of 90% (CI 76-90%) for diagnosing GWI when the probability of having GWI was above 70%. SIGNIFICANCE: The results of the current study indicate that inflammation is a component of the pathobiology of GWI. Analysis of the data resulted in a model utilizing three readily measurable biomarkers that appears to significantly augment the symptom-based case definition of GWI. These new observations are highly relevant to the diagnosis of GWI, and to therapeutic trials.

Elevated platelet count, C-reactive protein and thromboxane analog-induced platelet aggregation in patients with Gulf War veterans' illnesses: evidence of a chronic inflammatory state?

A previous study of Gulf War veteran's illnesses (GWVI) observed evidence of platelet activation in a majority of patients with GWVI. To further characterize platelet function, we studied 43 patients (40 men) with GWVI (GWVI+) and 21 veterans who served concurrently in the Gulf War but who lacked criteria for GWVI (GWVI-). All participants were free of infection and known inflammatory diseases. Studies performed included platelet count, immature platelet fraction (IPF), plasma thrombopoietin (TPO), C-reactive protein (CRP), platelet aggregation and ATP secretion in response to six agonists, and spontaneous aggregation. Platelet counts and CRP were significantly elevated in GWVI+ compared to GWVI- patients without elevation in IPF or TPO. Platelet aggregation did not differ between GWVI+ and GWVI- patients except for spontaneous aggregation that was significantly greater in GWVI+ patients. Platelet ATP secretion was similar in the two groups, except the response to 50 µmol/l thrombin receptor agonist peptide 6 (TRAP 6) was significantly greater in GWVI+ patients. When platelet aggregation was analyzed in relation to CRP, the response to 0.5 µmol/l U46619 was significantly greater in patients whose CRP was at least 2 µg/ml. Therefore, GWVI+ patients had elevated platelet counts, spontaneous aggregation, TRAP 6-induced secretion, and CRP, but no impairment of platelet function. The increased platelet counts and U46619-induced aggregation appear to be consequences of an underlying inflammatory state in GWVI.

Enoxaparin outcomes in patients with moderate renal impairment.

BACKGROUND: Enoxaparin sodium has predictable pharmacokinetics that allow for simplified dosing without laboratory monitoring. Reliance on renal function for excretion may lead to accumulation of enoxaparin in patients with moderate renal impairment. However, there is no dose adjustment recommended for these patients. We conducted a review to compare bleeding events in patients with moderate renal impairment compared with those with normal renal function. METHODS: Patients received enoxaparin sodium, 1 mg/kg, every 12 hours or 1.5 mg/kg once daily between June 1 and November 30, 2009. Moderate renal impairment was defined as creatinine clearance (CrCl) of 30 to 50 mL/min. Normal renal function was defined as CrCl greater than 80 mL/min. The primary outcome was major bleeding, defined as any bleeding resulting in death, hospital admission, lengthened hospital stay, or an emergency department visit. The secondary outcome was thromboembolism. RESULTS: A total of 164 patients met the inclusion criteria: 105 with normal renal function and 59 with moderate renal impairment. The primary outcome occurred in 6 of 105 patients (5.7%) with normal renal function vs 13 of 59 patients (22.0%) with moderate renal impairment, representing an unadjusted odds ratio of 4.7 (95% CI, 1.7-13.0; P = .002). The odds ratio using multivariable logistic regression adjusting for differences in risk was 3.9 (95% CI, 0.97-15.6; P = .055). There was no recurrent thromboembolism in either group. CONCLUSIONS: Our results suggest an increased risk of major bleeding in patients with moderate renal impairment who receive enoxaparin. Because enoxaparin is frequently used and outcomes can be life saving or life threatening, we encourage further study of the appropriate dose in patients with moderate renal impairment.

Measurement of shear-activated platelet aggregate formation in non-anticoagulated blood: utility in detection of clopidogrel-aspirin-induced platelet dysfunction.

We studied the ability of a new instrument, the PlaCor PRT that measures shear-induced platelet aggregation in fingerstick, non-anticoagulated blood without added agonists, to detect platelet dysfunction ex vivo. Platelet reactivity time (PRT) and whole blood aggregation (WBA) were measured in 160 healthy volunteers, before and after aspirin and in 170 participants with established vascular disease or risk factors thereof treated with aspirin ± clopidogrel. Pretreatment PRT and WBA were significantly correlated (collagen r = -.63; arachidonate r = -.65; P < .0001). Following aspirin, the mean PRT increased from 82 to 142 seconds (P < .0001), and in participants treated with clopidogrel-aspirin, the mean PRT (286 seconds, n = 65) was significantly longer than with aspirin alone (166 seconds, n = 105; P < .001). Only 13% of PRTs of participants treated with clopidogrel and aspirin were within the normal range. We conclude that the PlaCor PRT is a simple, rapid, point-of-care instrument that compares favorably with published descriptions of other platelet function instruments.