C-reactive protein, cardiovascular risk factors and the association with myocardial infarction in men

OBJECTIVES

This study had three objectives: first, to investigate the association of C-reactive protein levels and myocardial infarction amongst men; secondly, to study the associations of C-reactive protein levels with cardiovascular risk factors; and thirdly, to adjust the risk of myocardial infarction for such factors.

DESIGN AND SUBJECTS

A case-control study including 560 patients with a first myocardial infarction who had survived at least 6 months, plus 646 control subjects.

RESULTS

Patients had significantly higher levels of C-reactive protein (mean 2.2 mg L-1) than control subjects (mean 1.7 mg L-1; P < 0.001). Persons in the highest quintile of C-reactive protein had an unadjusted 1.9-fold increased risk of myocardial infarction compared with persons in the lowest quintile (odds ratio 1.9, 95% CI: 1.3-2.7). C-reactive protein was, in addition to smoking, associated with several cardiovascular risk factors: age, obesity, diabetes, blood pressure, triglycerides and inversely associated to HDL cholesterol. Adjustment for these variables, especially for total cholesterol, HDL cholesterol and triglycerides, substantially decreased the risk of myocardial infarction for persons in the highest quintile of C-reactive protein, compared to those in the lowest quintile, to 1.3 (95% CI: 0.9-1.9).

CONCLUSIONS

Our findings confirm previous reports that C-reactive protein predicts the risk of myocardial infarction. However, this association does not appear to be causal, since the increase in risk can to a large extent be explained by the presence of other cardiovascular risk factors.

Relationship between intra-uterine bacterial contamination, endotoxin levels and the development of endometritis in postpartum cows with dystocia or retained placenta

A study was conducted to investigate the relationship between intra-uterine bacterial contamination, endotoxin levels and the development of endometritis in cows that experienced a dystocia or retained their placenta. Fifteen healthy cows, 31 cows with retained placenta (RP) and 13 cows that had dystocia were clinically examined 1 or 2 days after parturition when a uterine swab for bacteriological examination was taken. In addition, plasma and uterine lochia samples were collected to determine lipopolysaccharide (LPS) and the plasma IgG anti-LPS concentrations. Subsequently, 15 RP and 6 dystocia cows were initially left untreated and another uterine swab was collected at 2 and 4 wk postpartum. Immediately after calving, RP cows had significantly higher LPS levels in uterine lochia (average of 2.24 x 10(4) Endotoxin Units (EU)/mL) as compared to dystocia and healthy postpartum cows (average of 0.10 and 0.26 EU/mL, respectively). However, plasma LPS levels were below the detection limit (<0.036 EU/mL platelet-rich plasma) in all groups of cows. IgG anti-LPS levels in plasma were not significantly different between the 3 groups immediately postpartum (average of 26, 16 and 44 Median Units (MU)/mL) for healthy, dystocia and RP cows, respectively), but they were significantly lower when compared to plasma IgG anti-LPS levels of healthy cows at more than 2 months postpartum (mean 83 MU/mL). High LPS levels in lochia at 1 or 2 days postpartum were significantly related to abnormal cervical discharge, the presence of Escherichia coli, black pigmented gram-negative anaerobes and Clostridium spp. shortly after calving, and Arcanobacterium pyogenes and gram-negative anaerobes in the uterus at 14 days postpartum. These results suggest that the presence of E. coli and LPS (endotoxins) in lochia early postpartum favor the development of uterine infections by A. pyogenes and gram-negative anaerobes later postpartum. LPS were not observed in plasma, suggesting that either they are not absorbed into the blood, or they are efficiently detoxified by IgG anti-LPS or other detoxification mechanisms.

Activated platelets in patients with severe hypertriglyceridemia: effects of triglyceride-lowering therapy

Hypertriglyceridemia, a risk factor for cardiovascular disease, has been associated with hypercoagulability, but whether platelet activation is implicated is unknown. This study was designed to compare the in vivo platelet activation status between patients with severe hypertriglyceridemia and age- and sex-matched control subjects, and to evaluate the effects of triglyceride-lowering therapy. Sixteen patients with primary hypertriglyceridemia were included in a double-blind, placebo-controlled cross-over trial with 400 mg bezafibrate once daily. Platelet activation was analysed by double label flow cytometry, using monoclonal antibodies against GP53, P-selectin, and platelet-bound fibrinogen. Surface expression of the lysosomal membrane protein GP53 was significantly higher in the hypertriglyceridemic patients at baseline as compared to the group of age- and sex-matched controls (16.3+/-4.8% vs. 8.9+/-3.4%, respectively, P<0.001). No differences in the expression of P-selectin and fibrinogen binding were observed. In response to bezafibrate therapy, the expression of GP53 in the patient group decreased from 16.3+/-4.8% to 13.1+/-4.1% (P=0.018). The expression of P-selectin and fibrinogen binding was not affected by bezafibrate therapy. In conclusion, patients with hypertriglyceridemia have an increased in vivo platelet activation status, which can be improved by bezafibrate therapy.

Innate production of interleukin-10 and tumor necrosis factor affects the risk of multiple sclerosis

Multiple sclerosis (MS) typically presents with a relapsing-remitting onset. This can be distinguished from primary progressive MS. Typical MS is characterized by a profound inflammatory reaction in which anti-inflammatory cytokine interleukin-10 (IL-10) and pro-inflammatory cytokine tumor necrosis factor (TNF) may play a pivotal role. We tested the hypothesis that patients with MS have a distinct innate cytokine production that contributes to the susceptibility for and outcome of MS. The innate cytokine production of patients was estimated as the average production of cytokines in lipopolysaccharide -stimulated whole-blood cultures of 2 to 5 first-degree healthy family members. A total of 126 family members of 50 patients with typical MS, 61 family members of 25 patients with primary progressive MS, and 129 control subjects of 54 families were enrolled in this study. We found that members of families with low IL-10 and high TNF production had a fourfold increased risk of developing typical MS compared with members of families with high IL-10 and low TNF production. Patients with MS were eightfold more likely to develop typical MS than primary progressive MS when they belonged to families with low IL-10 and high TNF production. The presence of human leukocyte antigen-DR2 was associated with MS but not with TNF production. This study shows that typical MS is associated with an innate pro-inflammatory cytokine profile in contrast to primary progressive MS.

Aprotinin administration in the pericardial cavity does not prevent platelet activation

OBJECTIVES

Aprotinin is frequently administered systemically to patients undergoing cardiopulmonary bypass to inhibit activation of platelets and plasma protein systems and thus reduce postoperative blood loss. Two reports on local aprotinin administration, that is, into the pericardial cavity, also indicated improvement in postoperative blood loss, but the underlying mechanism was not investigated. We previously reported the disappearance of glycoprotein Ib from the platelet surface and the appearance of platelet-derived microparticles in the pericardial cavity of patients undergoing cardiopulmonary bypass as signs of platelet activation. Here, we investigated whether such local aprotinin administration reduced platelet activation.

METHODS

In a double-blind study, 6 patients received aprotinin (500,000 KIU) into the pericardial cavity during the operation and 7 patients received a placebo. Platelet surface glycoprotein Ib expression, concentration of microparticles, and concentration of complexes of platelets with leukocytes, erythrocytes, or each other, were measured by flow cytometry.

RESULTS

We confirmed the reduced glycoprotein Ib expression and the increased concentration of microparticles in the pericardial cavity, as previously reported, and found no increased concentration of platelet complexes. However, no differences between aprotinin and placebo treatments were observed in these platelet activation parameters in the pericardial cavity or the systemic circulation.

CONCLUSION

We conclude that administration of aprotinin into the pericardial cavity during cardiopulmonary bypass and at concentrations similar to the systemic application does not reduce platelet activation in that compartment or the systemic circulation.

High interleukin-10 production in first-degree relatives of patients with generalized but not cutaneous lupus erythematosus

BACKGROUND

Preclinical research suggests that interleukin-10 (IL-10) is associated with susceptibility to and severity of systemic lupus erythematosus. Chronic cutaneous lupus erythematosus is thought to be immunogenetically different from systemic lupus erythematosus. We hypothesized that high innate production of IL-10 underlies systemic but not chronic cutaneous lupus erythematosus.

METHODS

IL-10 production was determined after endotoxin stimulation of whole-blood samples. In whole-blood samples, disease activity and medication influence the IL-10 production in patients. Therefore, healthy first-degree relatives of patients were evaluated. One hundred sixty-six first-degree relatives of patients with systemic lupus, 50 first-degree relatives of patients with chronic cutaneous lupus, and 133 control persons were studied. Innate IL-10 production of the patient was estimated as the mean IL-10 production of the unaffected relatives. Polymorphisms located -1082, -819, and -592 base pairs relative to the IL-10 gene were typed by allele-specific oligohybridization of polymerase chain reaction-amplified DNA fragments.

RESULTS

IL-10 production was higher in the families of patients with systemic lupus than in the control families (1517 +/- 94 vs 1180 +/- 59 pg/mL; P = 0.003). IL-10 production in the families of patients with chronic cutaneous lupus was similar to that in control families (1216 +/- 82 vs 1180 +/- 59 pg/ml; P = 0.74). IL-10 production was also similar in families of patients with severe compared with nonsevere systemic lupus (P = 1.0). The frequency of -1082/-819/-592 haplotypes GCC, ACC, and ATA was similar among patients and compared with the control persons (P = 0.29).

CONCLUSIONS

High innate IL-10 production underlies susceptibility for systemic lupus erythematosus but not the severity of the disease. It is not related to chronic cutaneous lupus erythematosus.

Diagnostic value of the mean corpuscular volume in the detection of vitamin B12 deficiency

In clinical practice, the finding of an elevated mean corpuscular volume (MCV), macrocytic anaemia or specific neurological symptoms is often the reason to test for vitamin B12 (B12) deficiency. Use of the MCV as a test for the detection or exclusion of B12 deficiency is only justified if the diagnostic accuracy is sufficiently high. However, the sensitivity and specificity are not well known. We performed a systematic review of the diagnostic value of an elevated MCV for B12 deficiency in both anaemic and non-anaemic patients. Of approximately 3500 titles and/or abstracts that were screened, 37 original papers contained usable data. The population under study proved to be the characteristic of major influence on the study outcome. Pooling of data from different studies was performed in subsets of the data corresponding to the different populations studied. The cut-off levels of both MCV and serum B12 had a significant influence on the study outcomes. The data, however, were pooled without taking these cut-off levels into account. The pooled estimates should be interpreted with this limitation in mind. The reference standards were (1) a low serum B12 concentration and (2) a B12 deficiency confirmed by low serum B12 combined with additional diagnostic investigations. In the population that was randomly screened for low serum B12, the sensitivity of the MCV for B12 deficiency was 17%, whereas the sensitivity was 30% for B12 deficiency in patients with anaemia. When measurement of serum B12 was ordered to exclude B12 deficiency as part of the patients' treatment, the sensitivity was 30% for low serum B12 concentration, 58% for B12 deficiency and 75% for B12 deficiency in patients with anaemia. In the population with pernicious anaemia, the sensitivity was far from perfect (77%). In the five studies that reported data on the positive predictive value of the MCV for B12 deficiency, this ranged from 0% (0/6) to 55% (11/20). This systematic review shows that a considerable number of B12-deficient patients will remain unnoticed when the MCV is used to rule in patients for further evaluation. Depending on the population studied, up to 84% of cases will than be missed. The MCV can be used to make the diagnosis of B12 deficiency more--or less--probable. An elevated MCV justifies the measurement of serum B12. The MCV should not be used as the only parameter ruling out the diagnosis of B12 deficiency.

Cellular origin and procoagulant properties of microparticles in meningococcal sepsis

Patients with meningococcal sepsis generally suffer from disseminated intravascular coagulation (DIC). The aim of this study was to address whether these patients have elevated numbers of circulating microparticles that contribute to the development of DIC. Plasma samples from 5 survivors, 2 nonsurvivors, and 5 healthy volunteers were analyzed for the presence of microparticles by flow cytometry. Ongoing coagulation activation in vivo was quantified by enzyme-linked immunosorbent assay of plasma prothrombin fragment F(1 + 2), and procoagulant properties of microparticles in vitro were estimated by thrombin-generation assay. On admission, all patients had increased numbers of microparticles originating from platelets or granulocytes when compared with controls (P =.004 and P =.008, respectively). Patients had elevated levels of F(1 + 2) (P =.004), and their microparticles supported thrombin generation more strongly in vitro (P =.003) than those of controls. Plasma from the patient with the most fulminant disease course and severe DIC contained microparticles that expressed both CD14 and tissue factor, and these microparticles demonstrated extreme thrombin generation in vitro. We conclude that patients with meningococcal sepsis have elevated numbers of circulating microparticles that are procoagulant. These findings may suggest a novel therapeutic approach to combat clinical conditions with excessive coagulation activation.

Hyperlipoproteinemia affects cytokine production in whole blood samples ex vivo. The influence of lipid-lowering therapy

Low-density lipoprotein (LDL)-receptor deficient mice, thus hypercholesterolemic, combine protection against infection with an ex vivo two- to threefold higher pro-inflammatory cytokine production in macrophages. A pro-inflammatory cytokine profile ex-vivo is also associated with survival of gram-negative sepsis in man. We hypothesized that high lipoprotein levels would be associated with a pro-inflammatory cytokine production and could explain the resistance to fatal infection. We treated 10 patients with familial hypercholesterolemia (FH) with HMG-CoA reductase inhibitors, and 13 patients with endogenous hypertriglyceridemia (HTG) with fibrates. Blood samples were stimulated ex vivo with lipopolysaccharide (LPS), to assess the cytokine production capacity. FH patients had significantly lower tumor necrosis factor-alpha (TNF-alpha) production, compared to normolipidemic controls (P=0. 001). Lipid lowering treatment in FH patients did not affect TNF-alpha production. HTG patients showed significantly higher TNF-alpha production at baseline than matched normolipidemic controls (P<0.001), while lowering of serum triglycerides in these patients resulted in a significant decrease in TNF-alpha production (P=0.019). The IL-10 production was not affected. These data refute our hypothesis that high LDL-cholesterol levels are associated with a pro-inflammatory cytokine production capacity. In contrast, the study suggests that very-low-density lipoprotein (VLDL) in hypertriglyceridemic patients augments TNF-alpha production.

Relationship between gastro-intestinal complaints and endotoxaemia, cytokine release and the acute-phase reaction during and after a long-distance triathlon in highly trained men

The aim of the present study was to establish whether gastro-intestinal (GI) complaints observed during and after ultra-endurance exercise are related to gut ischaemia-associated leakage of endotoxins [lipopolysaccharide (LPS)] into the circulation and associated cytokine production. Therefore we collected blood samples from 29 athletes before, immediately after, and 1, 2 and 16 h after a long-distance triathlon for measurement of LPS, tumour necrosis factor-alpha and interleukin-6 (IL-6). As the cytokine response would trigger an acute-phase response, characteristic variables of these responses were also measured, along with creatine kinase (CK) to obtain an indicator of muscle damage. There was a high incidence (93% of all participants) of GI symptoms; 45% reported severe complaints and 7% of the participants abandoned the race because of severe GI distress. Mild endotoxaemia (5-15 pg/ml) was evident in 68% of the athletes immediately after the race, as also indicated by a reduction in IgG anti-LPS levels. In addition, we observed production of IL-6 (27-fold increase immediately after the race), leading to an acute-phase response (20-fold increase in C-reactive protein and 12% decrease in pre-albumin 16 h after the race). The extent of endotoxaemia was not correlated with the GI complaints or the IL-6 response, but did show a correlation with the elevation in C-reactive protein (r(s) 0.389; P=0.037). Creatine kinase levels were increased significantly immediately post-race, and increased further in the follow-up period. Creatine kinase levels did not correlate with those of either IL-6 or C-reactive protein. It is therefore concluded that LPS does enter the circulation after ultra-endurance exercise and may, together with muscle damage, be responsible for the increased cytokine response and hence GI complaints in these athletes.

Increased levels of factor VIII and fibrinogen in patients with venous thrombosis are not caused by acute phase reactions

Factor VIII activity (factor VIII:C) levels > or =150 IU/dl are associated with a 5- to 6-fold increased risk of venous thrombosis compared to levels <100 IU/dl, and fibrinogen levels > or =5.0 g/l increase the thrombosis risk 4-fold. These high levels are present in 25% resp. 3% of the patients with a first episode of venous thrombosis. These findings were based on measurements after the thrombotic event, so the factor VIII and fibrinogen levels in thrombosis patients may have been influenced by acute phase reactions or ongoing inflammatory responses. In the present study we measured plasma C-reactive protein (CRP) as a sensitive marker of an acute phase reaction in 474 thrombosis patients and 474 age- and sex-matched healthy controls, that were part of the Leiden Thrombophilia Study (LETS). Mean and median CRP levels were higher in thrombosis patients than in the controls, suggesting inflammation in some patients. CRP affected both factor VIII and fibrinogen levels, in patients and controls alike. After adjustment for the effect of CRP, high factor VIII:C levels still increased the thrombosis risk 6-fold and high fibrinogen levels 4-fold, which is for both very similar to the risk before correction for CRP levels. These results show that although systemic inflammation may be present in some of the patients, elevated levels of factor VIII:C and fibrinogen were in general not caused by acute phase reactions. This further supports a causal relationship between both high factor VIII:C and fibrinogen levels and venous thrombosis.

[Preeclampsia not (yet) predictable from the blood platelet count]

Platelet activation plays an important role in the pathogenesis of pre-eclampsia as demonstrated by reduced platelet count, increased mean platelet volume and elevated plasma concentrations of beta-thromboglobulin and platelet factor 4 in pre-eclamptic patients. Thrombocytopenia precedes the onset of clinical symptoms of pre-eclampsia. Possibly an enhanced activation state of the platelets in the circulation is present some time before the onset of pre-eclampsia: platelet activation might then be used to predict pre-eclampsia. Flow cytometry is considered the most sensitive technique at this moment to measure the activation of platelets. Fluorescent-labelled antibodies are used to detect antigens that appear on the platelet surface or change their conformation upon activation. During the first and second trimester of pregnancy pre-eclamptic patients have an increased expression of some antigens on the surface of their platelets, such as CD63. There is no reliable platelet test yet to predict the onset of pre-eclampsia.

Proinflammatory cytokines and elastase-alpha-1-antitrypsin in Argentine hemorrhagic fever

Argentine hemorrhagic fever (AHF) is a disease caused by Junin virus. In the acute phase, patients present hematologic and neurologic involvement with high levels of interferon-alpha and tumor necrosis factor-alpha (TNF-alpha. Nineteen patients with a confirmed diagnosis of AHF were studied: six severe, four moderate and nine mild cases. Serum levels of interleukin-6 (IL-6), IL-6 soluble receptor (IL-6sR), IL-8, IL-10, and elastase-alpha1-antitrypsin complex (E-alpha 1AT) were assayed by ELISAs. Levels of IL-6, IL-8, and IL-10 were high in nine, 12, and 13 patients, respectively, while levels of IL-6sR were high in two patients and low in one patient. Seven patients had increased levels of E-alpha1AT. Significant correlations were found between levels of both IL-8 and IL-10 with those of TNF-alpha as well as between IL-8 and E-alpha 1AT. These data demonstrate activation of pro-inflammatory and anti-inflammatory cytokine pathways, and statistical analysis showed differences among the clinical forms of illness. This study shows that IL-8 plays an essential role in neutrophil activation in AHF patients as demonstrated in other infectious diseases.

Determination of tumour necrosis factor-alpha and interleukin-10 production in a whole blood stimulation system: assessment of laboratory error and individual variation

Ex vivo production of cytokines as determined by whole blood stimulation and supernatant ELISA is partly determined by heritability. To assess the ability of this system to distinguish between high and low producers the laboratory error and individual variation were investigated. Whole blood samples from healthy volunteers were collected using endotoxin-free tubes and were incubated with 0 to 1000 ng/ml lipopolysaccharide concentrations for 4 and 24 h, and subsequently centrifuged. In the supernatants, TNF-alpha and IL10 were measured by ELISA. Coefficients of variation for the day-to-day variation in the blood sampling, transport and stimulation as well as in the whole blood stimulation per se ranged from 7.5% to 12.3%. The intra-individual variation was 15% (TNF-alpha) and 19% (IL10) in contrast to the inter-individual variation of, on average, 35%. No interchanging of ranks between high and low producers was observed after repeating the whole blood stimulation on distinct days. The whole blood stimulation system is able to distinguish high and low producers of TNF-alpha and IL10.

Disappearance of glycoprotein Ib from the platelet surface in pericardial blood during cardiopulmonary bypass

OBJECTIVES

Several investigators have reported decreased expression of glycoprotein Ib on the platelet surface during coronary artery bypass grafting, but others could not confirm this finding. Because platelet glycoprotein Ib functions as an adhesion receptor for von Willebrand factor and other adhesive proteins, this decreased expression may explain excessive postoperative blood loss. In this study the expressions of glycoprotein Ib and other platelet activation markers were studied in the systemic and pericardial blood of seven patients undergoing coronary artery bypass grafting. Pericardial blood was recently shown to have high activation levels of fibrinolytic and coagulation pathways; we hypothesized that this local blood activation might be paralleled by extensive platelet activation and associated disappearance of glycoprotein Ib.

METHODS

Expression of platelet surface antigens was determined by whole-blood double-label flow cytometry.

RESULTS

Glycoprotein Ib expression in systemic blood decreased 10% (p = 0.03) from preoperative levels at the start of cardiopulmonary bypass and 30% (p = 0.04) before release of the aortic crossclamp. Expression in pericardial blood at these times decreased by 50% and 51%, respectively (p = 0.003, p = 0.009). No changes were observed in the expression of the platelet activation antigens CD62P (P-selectin, indicating platelet alpha-granular release) and CD63 (indicating lysosomal release) or in binding of monoclonal antibody PAC-1 (detecting the fibrinogen-binding receptor conformation of the glycoprotein IIb-IIIa complex).

CONCLUSION

Glycoprotein Ib disappeared from the platelet surface during bypass grafting, most notably in pericardial blood. No increased expression of CD62P, CD63, or PAC-1 was found, indicating the absence of general platelet activation.

Cell-derived microparticles generated in patients during cardiopulmonary bypass are highly procoagulant

BACKGROUND

Microparticles from platelets and other cells have been extensively studied and characterized in vitro. Although the level of platelet-derived microparticles is elevated in a variety of diseases, including cardiac surgery, virtually nothing is known about their functions in vivo. The aim of the present study was to investigate the procoagulant properties of microparticles generated in vivo.

METHODS AND RESULTS

In 6 patients at the end of cardiopulmonary bypass, 14.8 x 10(9)/L (median; range, 9.7 to 27.4 x 10(9)/L) platelet-derived microparticles were present in pericardial blood, whereas blood obtained from the systemic circulation contained 1.6 x 10(9)/L (median; range, 0.4 to 8.9 x 10(9)/L) of such microparticles, as determined by flow cytometry. Microparticles stained positively for phosphatidylserine as determined with labeled annexin V. In contrast to systemic blood, pericardial blood contained not only microparticles of platelet origin but also microparticles that originated from erythrocytes, monocytes, or granulocytes, and other hitherto unknown cellular sources. Plasma prepared from pericardial blood and to a lesser extent plasma from systemic blood obtained at the same time, stimulated formation of thrombin in vitro. This activity of pericardial plasma was lost after removal of its microparticles by high-speed centrifugation, whereas the corresponding microparticle pellet was strongly procoagulant. The generation of thrombin in vitro involved a tissue factor/factor VII-dependent and factor XII-independent pathway.

CONCLUSIONS

This study is the first to demonstrate that microparticles generated in vivo can stimulate coagulation.

Antithrombin acts as a negative acute phase protein as established with studies on HepG2 cells and in baboons

Patients with sepsis or after major surgery have decreased plasma levels of the anticoagulant protein antithrombin. In such patients elevated levels of interleukin-6 (IL-6) are present and this interleukin is known to induce positive and negative acute phase responses. To investigate the possibility that antithrombin acts as a negative acute phase response-protein we performed studies on the human hepatoma cell line HepG2 in vitro and baboons in vivo. HepG2 cells were treated with recombinant human IL-6, IL-1beta, or combinations of the latter two, and tested for production of antithrombin, fibrinogen and prealbumin (transthyretin). This treatment resulted in a dose dependent increase in fibrinogen concentration (with a maximum effect of 2.8-2.9-fold) and a dose dependent decrease in prealbumin (with a maximum effect of 0.6-0.7-fold) and antithrombin concentrations (with a maximum effect of 0.6-0.8-fold). Simultaneous treatment of the HepG2 cells with IL-6 (1,000 pg/ml or 2,500 pg/ml) and IL-1beta (25 pg/ml), provided more extensively decreased prealbumin (0.8 and 0.6-fold, respectively) and antithrombin concentration (0.7 and 0.6-fold, respectively) compared to the single interleukin treatment at these concentrations. Baboons treated with 2 microg IL-6 x kg body-weight(-1) x day(-1) showed increased plasma CRP levels (59-fold, p <0.05) and decreased prealbumin (0.9-fold, p <0.05) and antithrombin (0.8-fold, p <0.05) plasma levels, without evidence for coagulation activation. Our results indicate that antithrombin acts as a negative acute phase protein, which may contribute to the decreased antithrombin plasma levels observed after major surgery or in sepsis.

Can flow cytometric detection of platelet activation early in pregnancy predict the occurrence of preeclampsia? A prospective study

OBJECTIVES

An increased platelet activation status is present in patients with preeclampsia. Our purpose was (1) to establish by means of flow cytometry whether platelets circulate in an activated state during the first and second trimesters of pregnancy and (2) to establish whether early platelet activation predicts the onset of preeclampsia.

STUDY DESIGN

Consecutively, 244 pregnant women were included in a prospective study design. Platelets in whole blood samples from the pregnant women in the first trimester, the second trimester, and after delivery were labeled with the following antibodies associated with platelet activation: anti-CD62P (P-selectin, alpha-granule secretion), anti-CD63 (GP53, lysosomal secretion), anti-CD31 (GPIIa', platelet endothelial cell adhesion molecule-1). The surface antigen exposure was determined by double-label flow cytometry with anti-CD42b (GPIb, a platelet-specific monoclonal glycoprotein) to select platelets and platelet-derived materials. Preeclampsia was defined as a diastolic blood pressure > or = 90 mm Hg and proteinuria > or = 0.3 gm in a 24-hour urine sample (International Society for Study of Hypertension in Pregnancy criteria).

RESULTS

Seventeen of 244 patients had preeclampsia (6.9%). Only first-trimester CD63 expression had an area under the curve > 0.5 by receiver-operator characteristic curve analysis and was selected as a possible predictor of preeclampsia. We found a sensitivity of 47% and a specificity of 76% with use of a percentage of activated platelets above 2% as a positive test. Likelihood ratios were 1.94 for positive likelihood and 0.69 for negative likelihood. Univariate logistic regression analysis results were odds ratio 2.8 (95% confidence interval 1.0 to 7.6). Multivariate logistic regression analysis results were odds ratio 2.9 (95% confidence interval 0.92 to 8.9). However, the odds ratio of first antenatal diastolic blood pressure was two to four times higher than the odds ratio of first-trimester CD63 expression. The combination of first-trimester CD63 and first antenatal diastolic blood pressure increases the positive likelihood ratio from 1.94 to 9.4, with a sensitivity of 41%, a specificity of 96%, and a negative likelihood ratio of 0.62.

CONCLUSIONS

Increased first-trimester CD63 expression is an independent risk factor for development of preeclampsia. CD63 expression might be useful to identify a subgroup of patients with a high risk for development of preeclampsia, especially in combination with first-trimester antenatal diastolic blood pressure. This method of patient selection may enable more efficient intervention studies in patients at risk than do the selection methods used so far.

Heparin coating of extracorporeal circuits inhibits contact activation during cardiac operations

OBJECTIVE

Heparin coating reduces complement activation on the surface of extracorporeal circuits. In this study we investigated its effect on activation of the contact system in 30 patients undergoing coronary artery bypass grafting with the use of a heparin-coated (Duraflo II, Baxter Healthcare Corp., Edwards Division, Santa Ana, Calif.; n = 15) or an uncoated extracorporeal circuit (n = 15).

METHODS

Plasma markers that reflect activation of contact (kallikrein-C1-inhibitor complexes), coagulation (prothrombin fragments F1 + 2), or fibrinolytic (plasmin-alpha 2-antiplasmin complexes) systems were determined before and during the operation. The generation of kallikrein-C1-inhibitor complexes was reduced by 62% (p = 0.06) after the onset of cardiopulmonary bypass and by 43% (p = 0.026) after the cessation of bypass in the group in which a heparin-coated circuit was used compared with the group in which the circuit was uncoated. Generation was reduced by 58% (p = 0.06) when the ratio of kallikrein-C1-inhibitor to prekallikrein after onset of bypass was considered. We detected significant increases in F1 + 2 levels in both groups and increases in plasmin-alpha 2-antiplasmin complexes in the heparin-coated group at cessation of bypass, but no intergroup differences were observed. Thus use of heparin-coated extracorporeal circuits during cardiac operations reduces formation of kallikrein-C1-inhibitor complexes when compared with use of uncoated circuits. The heparin coating is not accompanied by similar reductions in coagulation or fibrinolysis, suggesting that thrombin and plasmin formation during cardiopulmonary bypass occurs mainly independently of the contact system activation.

Activated protein C resistance--a major risk factor for thrombosis

Resistance to activated protein C is a recently detected phenomenon that has gained a rapid acceptance as a major risk factor for venous thromboembolism. The phenotypic expression of resistance to activated protein C is characterized by a poor response to the anticoagulant activity of activated protein C, a key enzyme in the down-regulation of blood coagulation, which causes a disposition for a hypercoagulable state. At least 90% of the cases with resistance to activated protein C are explained by a point mutation in the gene for coagulation factor V, resulting in replacement of an Arg to Gln at position 506 (factor V:Q506, often denoted factor V Leiden), one of the three activated protein C cleavage sites in activated factor V. The mutation is inherited as an autosomally dominant trait and has a prevalence of 2% to more than 10% in the general Caucasian population. A number of clinical studies, using different inclusion criteria, show a prevalence of activated protein C resistance of 20-60% among patients with venous thromboembolism. The actual thrombotic risk is moderate with an odds ratio of 5-7 but its high prevalence makes it by far the most important inherited risk factor known today, even higher than the sum of contributions from inherited deficiencies of antithrombin, protein C and protein S. Recent data suggest that activated protein C resistance, which is not due to factor V:Q506 and which appears to be acquired, is also a risk factor for venous thrombosis and for cerebral ischaemic disease. A decreased response to activated protein C is common during pregnancy and during use of oral contraceptives, but the clinical relevance of these findings have yet to be determined. The activated protein C resistance phenotype is typically diagnosed with an activated partial thromboplastin time-based assay, which detects factor V:Q506-dependent as well as acquired activated protein C resistance. However, the sensitivity and specificity for the factor V mutation are usually below 90%. Coagulation instruments with a turbidimetric or photometric clot detection principle generally provide a better performance as compared to electromechanical instruments. The activated partial thromboplastin time test requires careful control of preanalytical variables and platelet contamination should be below 1% since otherwise a falsely low activated protein C response will be obtained. A sensitivity and specificity of close to 100% for factor V:Q506 is obtained in a modified activated partial thromboplastin time test using predilution of sample plasma with factor V deficient plasma. The influence of preanalytical variables in this assay is minor. A number of polymerase chain reaction-based methods, some of them allele-specific, have been published, which provide convenient and objective confirmation of the factor V mutation. Thrombotic events are often triggered through the presence of a combination of inherited and circumstantial risk factors. The high prevalence of activated protein C resistance raises the issue whether it would be cost-beneficial to screen for this trait in connection with surgery, pregnancy and oral contraceptives. Some data already support this, but prospective studies will be necessary to delineate under which circumstances this might be implicated.

[Laboratory testing virtually centralized to benefit both patients and drug research]

Laboratory analyses in multicentre safety studies of new drugs usually are performed in central laboratories outside the Netherlands. Patient care requires local (hospital) laboratory tests. In the so-called Virtually Centralized Laboratory the Dutch local laboratories report their results after data communication and data transformation in such a way that they seem to form one laboratory. The local analytical results are transformed by calibrating the local methods using standard preparations, thus reducing the inter laboratory variation. This concept may lead to one set of national reference values for all general clinical chemical and haematological laboratory tests.

Extensive platelet activation in preeclampsia compared with normal pregnancy: enhanced expression of cell adhesion molecules

OBJECTIVES

Platelets play an important role in the pathophysiologic mechanisms of preeclampsia. Our purpose was to investigate by means of flow cytometry to what extent platelets circulate in an activated state during normal pregnancy and whether this activation is more extensive in preeclampsia.

STUDY DESIGN

Platelets in whole blood from 10 preeclamptic third-trimester pregnant women (highest diastolic blood pressure range 100 to 130 mm Hg, proteinuria range 0.59 to 11.5 gm/24 hr) and from 10 normotensive third-trimester pregnant controls were analyzed with the following activation markers: anti-P-selectin (alpha-granule secretion), anti-CD63 (lysosomal secretion), PAC-1 (monoclonal antibody against fibrinogen receptor conformation of the glycoprotein IIb/IIIa complex), anti-platelet endothelial cell adhesion molecule-1, and annexin-V (a placental protein that binds to negatively charged phospholipids, present on the outside of the platelet plasma membrane after activation). The differences in surface antigen exposure between the two groups were determined by double-label flow cytometry. Flow cytometric data were analyzed in two ways: first, the percentages of activated platelets above a certain threshold compared with a nonpregnant control sample were determined, indicative for activation of a subpopulation of cells, and, second, the mean fluorescence intensities were determined, indicative of the mean surface antigen expression of the total platelet population.

RESULTS

Analysis of the percentage of activated platelets proved most informative. With this analysis an enhanced platelet activation status was present in 4 of 10 normotensive patients and a more extensive platelet activation status in all 10 preeclamptic patients, as indicated by P-selectin (p = 0.008) and CD63 (p = 0.03) expression. Increased platelet endothelial cell adhesion molecule-1 (p = 0.005) expression was also observed in preeclampsia.

CONCLUSIONS

Flow cytometric analysis clearly indicated that platelets circulate in a more extensively activated state during preeclampsia than during normal pregnancy. The increased platelet endothelial cell adhesion molecule-1 expression in preeclamptic patients demonstrates that, besides alpha-granular and lysosomal release, other hitherto unknown mechanisms are involved. Platelet endothelial cell adhesion molecule-1 appears to be the best marker to distinguish preeclamptic patients from normotensive pregnant women. Only a subpopulation of the platelets appears to be activated.

Endotoxaemia and postoperative hypermetabolism in coronary artery bypass surgery: the role of ketanserin

In a randomized, double-blind clinical study in 29 patients undergoing elective coronary artery surgery, we assessed the role of ketanserin, an inhibitor of serotonin-induced vasoconstriction and weak alpha 1 sympathetic blocker, in reducing endotoxaemia and postoperative hypermetabolism. Male patients without major organ dysfunction were allocated randomly to receive either ketanserin or placebo. Hypermetabolism was defined as an increase in oxygen consumption in the early postoperative hours (delta Vo2). Circulating endotoxin (P = 0.04) and postoperative delta Vo2 (P = 0.03) were lower in the ketanserin patients. Endotoxaemia was associated also with low vascular filling. From these preliminary results we conclude that treatment with ketanserin during cardiac surgery may reduce but not abolish endotoxaemia and postoperative hypermetabolism.