Accuracy of Doppler echocardiography in the assessment of pulmonary arterial hypertension in patients with congenital heart disease

BACKGROUND AND OBJECTIVES

Pulmonary arterial hypertension (PAH) is a major cause of morbidity and mortality among patients with congenital heart disease (CHD). Earlier diagnosis of PAH would be of great benefit for the estimation of the CHD, the grasp of the indications for surgery and prognosis.

PATIENTS AND METHODS

We assessed the diagnostic accuracy of Doppler echocardiography (D-ECHO) in detecting PAH in patients with CHD and the value of estimation about ventricular morphology and function of PAH-CHD patients. 123 CHD patients evaluated for suspected PAH were prospectively recruited. D-ECHO was performed and estimated right ventricular systolic pressure (RVSP) was measured to screen for PAH. Subsequently, pulmonary hemodynamic parameters were measured by right heart catheterization (RHC) for definitive diagnosis of PAH.

RESULTS

RHC identified 66/123 (54%) patients with PAH. The noninvasive cut-point was: estimated right ventricular systolic pressure (RVSP) > 36.5 mm Hg by D-ECHO. D-ECHO classified 107 subjects correctly (sensitivity 89.4%, specificity 84.2%). The area under receiver-operating characteristic curve (AUC) was 0.96 for D-ECHO. A positive significant correlation (r = 0.853, p < 0.01) was found between RVSP measured by D-ECHO and systolic pulmonary arterial pressure (sPAP) measured by RHC. In addition, D-ECHO showed higher RVSP, left ventricular internal diameter (LV), right atrial diameter (RA), right ventricular internal diameter (RV), left ventricular end-diastolic diameter (EDD), left ventricular diastolic end-diastolic volume (EDV) and mitral velocity A wave (AMV) values in the PAH-CHD group than in the CHD group (p < 0.05).

CONCLUSIONS

D-ECHO is not only an important noninvasive diagnostic technique for PAH-CHD patients, but also a tool which can indicate the ventricular remodeling and diastolic dysfunction induced by PAH to some extent.

Optimizing dendritic cell vaccine for immunotherapy in multiple myeloma: tumour lysates are more potent tumour antigens than idiotype protein to promote anti-tumour immunity

Dendritic cells (DCs) are the most potent antigen-presenting cells and are the mediators of T cell immunity. Many investigators have explored the potential of using DCs as a vaccine for tumour-derived antigens in immunotherapy of B cell malignancies, and the results have been disappointing. To search for better tumour antigens to improve the efficacy of DC-based immunotherapy in myeloma, we evaluated and compared the efficacy of the vaccination of DCs pulsed with idiotype (Id) or tumour lysate in the 5TGM1 myeloma mouse model. Our results showed that Id- or tumour lysate-pulsed DC vaccines protected mice efficiently against developing myeloma, retarded tumour growth, induced tumour regression against established tumour and protected surviving mice from tumour rechallenge. The therapeutic responses were associated with an induction of strong humoral immune responses, including anti-Id or anti-lysate antibodies, and cellular immune responses including myeloma-specific CD8(+) cytotoxic T lymphocytes, CD4(+) type 1 T helper cells and memory T cells in mice receiving Id- or tumour lysate-pulsed DC vaccines. In addition, our studies showed that tumour lysate-pulsed DCs were more potent vaccines than the Id-pulsed DC vaccines to promote anti-tumour immunity in the model. This information will be important for improving the strategies of DC-based immunotherapy for patients with myeloma and other B cell tumours.

Exome sequencing detection of two untranslated GFPT1 mutations in a family with limb-girdle myasthenia

The term 'limb-girdle myasthenia' (LGM) was first used to describe three siblings with proximal limb weakness without oculobulbar involvement, but with EMG decrement and responsiveness to anticholinesterase medication. We report here that exome sequencing in the proband of this family revealed several sequence variations in genes linked to proximal limb weakness. However, the only mutations that cosegregated with disease were an intronic IVS7-8A>G mutation and the previously reported 3'-UTR c.*22C>A mutation in GFPT1, a gene linked to LGM. A minigene assay showed that IVS7-8A>G activates an alternative splice acceptor that results in retention of the last seven nucleotides of intron 7 and a frameshift leading to a termination codon 13 nucleotides downstream from the new splice site. An anconeus muscle biopsy revealed mild reduction of the axon terminal size and postsynaptic fold simplification. The amplitudes of miniature endplate potentials and quantal release were also diminished. The DNA of the mildly affected father of the proband showed only the intronic mutation along with sequence variations in other genes potentially relevant to LGM. Thus, this study performed in the family originally described with LGM showed two GFPT1 untranslated mutations, which may cause disease by reducing GFPT1 expression and ultimately impairing protein glycosylation.

A potential role for D-dimer in the diagnosis of tuberculous pleural effusion

BACKGROUND AND OBJECTIVES

Tuberculous pleural effusion (TPE) is associated with enhanced local fibrinolysis; however, its role in TPE has not been studied. The present study aims to investigate whether pleural D-dimer, a fibrinolysis marker, plays a diagnostic role for TPE.

PATIENTS AND METHODS

Patients with pleural effusion were recruited prospectively. All subjects underwent a standard thoracocentesis and pleural effusion samples were collected. The diagnosis of pleural effusion was based on clinical, radiological, bacteriological, and histopathological examinations. Pleural D-dimer levels were measured by immunonephelometry assay. The capacity of pleural D-dimer to differentiate TPE from non-TPE was assessed with receiver operating characteristic curve analyses.

RESULTS

A total of 87 patients with pleural effusion were included in the study (32 TPE cases and 55 non-TPE controls). Subjects with TPE showed a marked elevation of pleural D-dimer than those with other etiologies (1082.66±453.83 vs. 319.98±266.78 mg/L FEU, p < 0.05). The area under curve when pleural D-dimer was used to differentiate TPE from non-TPE was 0.928 (95% confidence interval: 0.878-979). With a cut-off value of 622.5 mg/L FEU, the sensitivity and specificity were 84.38% and 85.45%, respectively.

CONCLUSIONS

Pleural D-dimer levels are higher in TPE than other causes of pleural effusions. D-dimer might be useful as a simple, surrogate marker for TPE. Further studies are needed to confirm our findings.

PSGL-1/selectin and ICAM-1/CD18 interactions are involved in macrophage-induced drug resistance in myeloma

Chemoresistance is the major obstacle in multiple myeloma (MM) management. We previously showed that macrophages protect myeloma cells, on a cell contact basis, from melphalan or dexamethasone-induced apoptosis in vitro. In this study, we found that macrophage-mediated myeloma drug resistance was also seen with purified macrophages from myeloma patients' bone marrow (BM) in vitro and was confirmed in vivo using the human myeloma-SCID (severe combined immunodeficient) mouse model. By profiling differentially regulated and paired plasma membrane protein genes, we showed that PSGL-1 (P-selectin glycoprotein ligand-1)/selectins and ICAM-1/CD18 played an important role in macrophage-mediated myeloma cell drug resistance, as blocking antibodies against these molecules or genetic knockdown of PSGL-1 or ICAM-1 in myeloma cells repressed macrophages' ability to protect myeloma cells. Interaction of macrophages and myeloma cells via these molecules activated Src and Erk1/2 kinases and c-myc pathways and suppressed caspase activation induced by chemotherapy drugs. Thus, our study sheds new light on the mechanism of drug resistance in MM and provides novel targets for improving the efficacy of chemotherapy in patients.

Association of gastroesophageal reflux disease with asthma control

Gastroesophageal reflux disease (GERD) may make asthma difficult to control and may be a potential risk factor for frequent asthma exacerbations, but the mechanisms of the relationship between GERD and not well-controlled asthma remain unclear. The aim of this study was to explore the association of GERD with asthma control in adults. Patients with asthma were consecutively recruited, and Asthma Control Test (ACT) and Reflux Diagnostic Questionnaire scores were determined. The patients were categorized into not well-controlled asthma and well-controlled asthma groups according to the ACT score. Univariate and multivariate logistic regression analyses were performed to evaluate the relationship between GERD and not well-controlled asthma. Seven hundred and sixty-eight patients with asthma were enrolled. The mean ACT score was 18.2 ± 3.6, and there were 161 (21.0%) patients with not well-controlled asthma. The Reflux Diagnostic Questionnaire score was 10.5 ± 4.7, and 212 (27.6%) patients were complicated by GERD. Multivariate logistic regression analyses revealed the independent association of GERD with not well-controlled asthma (odds ratio, 3.12; 95% confidence interval, 1.53-4.88) after other established contributors to asthma control were adjusted. In conclusion, there is an association of GERD with not well-controlled asthma, independent of other potential contributors to asthma control.

The radiation dose-regulated AND gate genetic circuit, a novel targeted and real-time monitoring strategy for cancer gene therapy

The AND gate functions such that when all inputs are activated the downstream gene will be transcribed and it is off otherwise. To accomplish optimal and targeted gene therapy in solid tumor patients, we have constructed an AND gate genetic circuit and investigated whether it could be activated by low-dose radiation in vitro and in vivo. The enhancement green fluorescent protein (EGFP) expression in different tumor cells transfected with control vector plxsn-EGFP confirmed that 2 Gy of radiation and 1% O(2) for 3 h could activate our AND gate. Besides, the obvious different levels of EGFP expression between 2 and 6 Gy of radiation demonstrated that the AND gate could be regulated by radiation doses. Additionally, through EGFP expression and the codistribution of p53 and HIF-1α in xenografts, we illustrated the targeted activation property of the AND gate and real-time monitoring to hypoxic districts in vivo. Moreover, significant growth inhibition and cell cycle arrest in vitro and apoptosis-inducing effects in vitro and in vivo proved that the AND gate induced ideal antitumor effects. In conclusion, the radiation dose-regulated AND gate genetic circuit could not only effectively monitor the therapeutic process in real-time but also induce ideal antitumor efficacy, and can be further exploited for personal therapy in clinical tumor patients.

Effect of chloride concentration on nitrogen removal from landfill leachate in sequencing batch reactor after MAP pretreatment

Leachate generated from landfill is becoming a great environmental challenge to China as it contains high concentration of COD, ammonium and some other substances. Nitrogen removal through the conventional nitrification-denitrification process is hampered by the low C/N ratio especially for the old age landfill sites and the high energy consumption for aeration. In this study, the combination of magnesium ammonium phosphate (MAP) precipitation and Sequencing batch reactor (SBR) was suggested as a new process for the treatment of high strength ammonium, and the effect of high concentration of Cl⁻ after MAP precipitation because of the use of MgCl₂ was investigated on SBR performance. The practical upper limit of Cl⁻ for nitrification was found to be 12,000 mg/L, above which resulted in significant accumulation of ammonium in SBR system. It is suggested that an ammonium removal of 70% was suitable for the MAP treatment to achieve a balance between increasing the C/N ratio and avoiding detrimental effect from high concentration of Cl⁻ in the succeeding SBR system. DGGE analysis indicated that high diversity of Ammonium oxidizing bacteria (AOB) could be maintained at a Cl⁻ concentration of 12,000 mg/L.

Prognosis of hepatitis C virus-infected Canadian post-transfusion compensation claimant cohort

Accurate prognostic estimates were required to ensure the sufficiency of the $1.1 billion compensation fund established in 1998 to compensate Canadians who acquired hepatitis C virus (HCV) infection through blood transfusion between 1986 and 1990. This article reports the application of Markov modelling and epidemiological methods to estimate the prognosis of individuals who have claimed compensation. Clinical characteristics of the claimant cohort (n = 5004) were used to define the starting distribution. Annual stage-specific transition probabilities (F0-->F1, . . ., F3-->F4) were derived from the claimants, using the Markov maximum likelihood estimation method. HCV treatment efficacy was derived from the literature and practice patterns were estimated from a national survey. The estimated stage-specific transition probabilities of the cohort between F0-->F1, F1-->F2, F2-->F3 and F3-->F4 were 0.032, 0.137, 0.150 and 0.097 respectively. At 20 years after the index transfusion, approximately 10% of all living claimants (n = 3773) had cirrhosis and 0.5% developed hepatocellular carcinoma (HCC). For nonhaemophilic patients, the predicted 20-year (2030) risk of HCV-related cirrhosis was 23%, and the risk of HCC and liver-related death was 7% and 11% respectively. Haemophilic patients who are younger and are frequently co-infected with human immunodeficiency virus would have higher 20-year risks of cirrhosis (37%), HCC (12%) and liver-related death (19%). Our results indicate that rates of progression to advanced liver disease in post-transfusion cohorts may be lower than previously reported. The Canadian post-transfusion cohort offers new and relevant prognostic information for post-transfusion HCV patients in Canada and is an invaluable resource to study the natural history and resource utilization of HCV-infected individuals in future studies.

Cyclin D1 as a universally expressed mantle cell lymphoma-associated tumor antigen for immunotherapy

Mantle cell lymphoma (MCL) accounts for 5-10% of all non-Hodgkin lymphomas and has the worst prognosis among all lymphomas. The hallmark of MCL is a t(11;14) translocation that results in overexpression of cyclin D1 by tumor cells of virtually all patients. In this study, we examined whether cyclin D1 could be an effective tumor-associated antigen for immunotherapy. We identified cyclin D1 peptides for HLA-A(*)0201 and generated peptide-specific CD8(+) T-cell lines from HLA-A(*)0201(+) blood donors and MCL patients. These cell lines proliferated in response to cyclin D1 peptide-pulsed stimulatory cells. Moreover, the T cells efficiently lysed peptide-pulsed but not unpulsed T2 cells and autologous dendritic cells; cyclin D1(+) and HLA-A(*)0201(+) human MCL lines MINO, SP53, Jeko-1 and Granta 519; and more importantly, HLA-A(*)0201(+) primary lymphoma cells from MCL patients. No killing was observed with HLA-A(*)0201(-) primary lymphoma cells or HLA-A(*)0201(+) normal blood cells, including B cells. These results indicate that these T cells are potent cytotoxic T cells and recognize cyclin D1 peptides naturally presented by patient lymphoma cells in the context of HLA-A(*)0201 molecules. Taken together, our work identifies cyclin D1 as a potentially important antigen for immunotherapy of MCL.

VITATOPS, the VITAmins TO prevent stroke trial: rationale and design of a randomised trial of B-vitamin therapy in patients with recent transient ischaemic attack or stroke (NCT00097669) (ISRCTN74743444)

BACKGROUND

Epidemiological studies suggest that raised plasma concentrations of total homocysteine (tHcy) may be a common, causal and treatable risk factor for atherothromboembolic ischaemic stroke, dementia and depression. Although tHcy can be lowered effectively with small doses of folic acid, vitamin B(12) and vitamin B(6), it is not known whether lowering tHcy, by means of B vitamin therapy, can prevent stroke and other major atherothromboembolic vascular events.

AIM

To determine whether the addition of B-vitamin supplements (folic acid 2 mg, B(6) 25 mg, B(12) 500 microg) to best medical and surgical management will reduce the combined incidence of stroke, myocardial infarction (MI) and vascular death in patients with recent stroke or transient ischaemic attack (TIA) of the brain or eye.

DESIGN

A prospective, international, multicentre, randomised, double blind, placebo-controlled clinical trial.

SETTING

One hundred and four medical centres in 20 countries on five continents.

SUBJECTS

Eight thousand (6600 recruited as of 5 January, 2006) patients with recent (<7 months) stroke (ischaemic or haemorrhagic) or TIA (brain or eye).

RANDOMISATION

Randomisation and data collection are performed by means of a central telephone service or secure internet site.

INTERVENTION

One tablet daily of either placebo or B vitamins (folic acid 2 mg, B(6) 25 mg, B(12) 500 mug).

PRIMARY OUTCOME

The composite of stroke, MI or death from any vascular cause, whichever occurs first. Outcome and serious adverse events are adjudicated blinded to treatment allocation.

SECONDARY OUTCOMES

TIA, unstable angina, revascularisation procedures, dementia, depression. STATISTICAL POWER: With 8000 patients followed up for a median of 2 years and an annual incidence of the primary outcome of 8% among patients assigned placebo, the study will have at least 80% power to detect a relative reduction of 15% in the incidence of the primary outcome among patients assigned B vitamins (to 6.8%/year), applying a two-tailed level of significance of 5%.

CONCLUSION

VITATOPS aims to recruit and follow-up 8000 patients between 1998 and 2008, and provide a reliable estimate of the safety and effectiveness of folic acid, vitamin B(12), and vitamin B(6) supplementation in reducing recurrent serious vascular events among a wide range of patients with TIA and stroke throughout the world.

Depression associated with sexually transmitted infection in Canada

OBJECTIVE

This study was conducted to determine the association between sexually transmitted infection (STI) and the prevalence of depression among the general Canadian population.

METHODS

The analysis was based on data from the Canadian Community Health Survey conducted in 2003 and included 21,560 participants aged 15-49 years. A logistic regression model was used to examine the association between depression and STI history after taking confounding factors (gender, age, marital status, household size, income, education, immigrant status, alcohol use, smoking status and number of chronic diseases) and effect modifiers into consideration.

RESULTS

Of the study subjects, 5.3% reported having a history of STI and 7.9% had depression. STI history was significantly associated with depression, with an odds ratio of 1.5 (95% CI 1.1 to 2.2) for men and 1.8 (95% CI 1.4 to 2.3) for women. The association was significant in men younger than 35 years but was not significant in older men. The association tended to be stronger in men who had a high level of income. The association between STI and depression was relatively consistent among female subpopulations.

CONCLUSION

There is a significant association of depression with STI. Health professionals should be aware that groups of STI patients are more likely to have depression and deal with it accordingly.

Clinical-grade myeloma Ag pre-loaded DC vaccines retain potency after cryopreservation

BACKGROUND

The use of myeloma Ag-loaded mature DC vaccines, cryopreserved in single-use aliquots, is an attractive immunotherapeutic strategy. In this study we investigated the retention of phenotype, viability and potency of DC vaccines after freezing and thawing.

METHODS

Plastic-adherent monocytes, derived from a steady-state leukapheresis, were cultured in serum-free media containing GM-CSF and IL-4. DC were loaded on day 6 with myeloma lysate (ML) or idiotype (Id) Ag and keyhole limpet hemocyanin (KLH), induced to mature on day 7 with CD40-ligand and cryopreserved on day 9. Seventeen clinical-scale cultures were evaluated for DC yield, recovery and immunophenotype after potency was validated with allogeneic mixed lymphocyte culture and Ag presentation assays.

RESULTS

We produced 88 individual vaccines from 17 clinical-scale cultures. Median DC yield at harvest was 131 x 10(6) (range 37-375 x 10(6)) and median recovery of viable DC after thawing was 69% (range 11-100%). We confirmed viability (7AAD-), phenotype (CD14-, CD83+/CD40+, CD83+/CD80+, CD83+/CD86+, CD83+/CD54+, HLA-DR++) and the ability of the DC to present Ag and stimulate allogeneic T cells post-thawing.

DISCUSSION

We have validated a serum-free culture system for the production of DC. Cryopreservation did not interfere with DC activity, allowed time for rigorous quality control (QC) and flexible scheduling of intranodal vaccination, and reduced the time to prepare multiple vaccines.

Venous thromboembolism in association with features of the metabolic syndrome

BACKGROUND

Central obesity, diabetes mellitus, dyslipidaemia and chronic hypertension--features of the metabolic syndrome--have been individually associated with venous thromboembolism (VTE). However, whether each of these factors additively increases the risk of VTE is uncertain.

AIM

To determine whether features of the metabolic syndrome independently increase the risk of VTE.

DESIGN

Prospective cohort study derived from the Heart Outcomes Prevention Evaluation 2 (HOPE-2) randomized clinical trial.

SETTING

One hundred and forty-five clinical centres in 13 countries.

METHODS

We studied 5522 adults aged > or =55 years with cardiovascular disease or diabetes mellitus. At enrollment, 35% had 0-1 features of the metabolic syndrome, 30% had two, 24% had three and 11% had four. We defined symptomatic VTE as an objectively confirmed new episode of deep-vein thrombosis or pulmonary embolism.

RESULTS

VTE occurred in 88 individuals during a median 5.0 years of follow-up. The incidence rate of VTE (per 100 person-years) was 0.30 with 0-1 features, 0.36 with two features, 0.38 with three features and 0.40 with four features of the metabolic syndrome (trend p = 0.43). Relative to the presence of 0-1 features of the metabolic syndrome, the adjusted hazard ratio (95%CI) for VTE was 1.22 (0.71-2.08) with two features, 1.25 (0.70-2.24) with three features, and 1.26 (0.59-2.69) with four features.

DISCUSSION

The number of features of the metabolic syndrome present was not a clinically important risk factor for VTE in older adults with vascular arterial disease.

Bortezomib is synergistic with rituximab and cyclophosphamide in inducing apoptosis of mantle cell lymphoma cells in vitro and in vivo

Mantle cell lymphoma (MCL) is an aggressive B-cell lymphoma with poor clinical outcome. Although front therapy induces a high rate of complete remission (CR), relapse is inevitable and new regimens are much needed for relapsed MCL. The proteasome inhibitor bortezomib (BTZ) induces apoptosis and sensitizes MCL cells to chemotherapy in relapsed MCL, but CR rates are low, with a short duration of response and severe toxicity. Here we evaluated whether BTZ is additive or synergistic with cyclophosphamide (CTX) and rituximab (RTX). Increasing doses of BTZ with a fixed dose of RTX and CTX (BRC regimen) resulted in markedly synergistic growth inhibition of MCL cells. BRC significantly enhanced apoptosis in MCL cell lines and primary tumor cells compared with single-agent treatment. Furthermore, western blotting analysis indicated that BRC induces apoptosis earlier via activation and cleavage of caspases-8, -9 and -3, and poly (ADP-ribose) polymerase, than single-agent treatment. The pan-caspase inhibitor completely blocked apoptosis induced by BRC. In vivo studies showed that BRC eradicated subcutaneous tumors in MCL-bearing SCID mice and significantly prolonged the long-term event-free survival in 70% of the mice. Hence, our study demonstrates that cytoreductive chemotherapy with both BTZ and anti-CD20 antibody may offer a better therapeutic modality for relapsed MCL.

Association between phosphodiesterase 4D gene and ischaemic stroke

BACKGROUND

An association between the phosphodiesterase 4D (PDE4D) gene and risk of ischaemic stroke in an Icelandic population has been suggested by the deCODE group.

METHODS

A case-control study of 151 hospitalised patients with first-ever ischaemic stroke and 164 randomly selected age-matched and sex-matched community controls was conducted. PDE4D genotypes for the six single-nucleotide polymorphisms (SNPs) previously reported to be independently associated with stroke were determined, common haplotypes were inferred using the expectation-maximisation algorithm, and SNP and haplotype associations with stroke were examined. A meta-analysis of published studies examining the association between PDE4D and stroke was also carried out.

RESULTS

Our study of Australian patients with stroke showed an independent association between ischaemic stroke and PDE4D SNP 89 (CC: odds ratio (OR) 5.55, 95% confidence interval (CI) 1.02 to 30.19; CA: OR 1.68, 95% CI 0.96 to 2.96; AA: OR 1 (reference)), SNP 87 (CC: OR 2.13, 95% CI 1.08 to 4.20; TC: OR 1.64, 95% CI 0.89 to 3.00; TT: OR 1 (reference)) and SNP 83 (TT: OR 2.16, 95% CI 1.08 to 4.32; TC: OR 1.37, 95% CI 0.77 to 2.43; CC: OR 1 (reference)), and between ischaemic stroke and PDE4D haplotypes at SNP 89-87-83 (A-C-C: OR 2.13, 95% CI 1.15 to 3.96; C-C-T: OR 2.25, 95% CI 1.29 to 3.92), but no association between ischaemic stroke and PDE4D SNP 56, SNP 45 or SNP 41, or with PDE4D haplotypes at SNP 56-45-41. A meta-analysis of nine case-control studies (including our current results) of 3808 stroke cases and 4377 controls confirmed a significant association between stroke and PDE SNP 87 (pooled p = 0.002), SNP 83 (0.003) and SNP 41 (0.003). However, there was statistical heterogeneity (p < 0.1) among the studies in the direction of association for each of the individual SNPs tested.

CONCLUSIONS

Our results and the pooled analyses from all the studies indicate a strong association between PDE4D and ischaemic stroke. This strengthens the evidence that PDE4D plays a key part in the pathogenesis of ischaemic stroke. Heterogeneity among the studies in the direction of association between individual SNPs and stroke suggests that the SNPs tested are in linkage disequilibrium with the causal allele(s).

Enhanced antiplatelet effect of clopidogrel in patients whose platelets are least inhibited by aspirin: a randomized crossover trial

OBJECTIVE

We aimed to determine whether adding clopidogrel to aspirin in patients at high risk of future cardiovascular events would suppress laboratory measures of the antiplatelet effects of aspirin; and have greater platelet inhibitory effects in patients with the least inhibition of platelets by aspirin.

METHODS

We performed a randomized, double-blind, placebo-controlled, crossover trial, comparing clopidogrel 75 mg day(-1) versus placebo, in 36 aspirin-treated patients with symptomatic objectively confirmed peripheral arterial disease.

RESULTS

The addition of clopidogrel to aspirin did not suppress platelet aggregation induced by arachidonic acid, urinary 11 dehydro thromboxane B2 concentrations, or soluble markers of platelet activation markers (P-selectin, CD40-ligand) and inflammation (high sensitivity serum C-reactive protein, interleukin-6). Clopidogrel significantly inhibited platelet aggregation induced by ADP (reduction 26.2%; 95% CI: 21.3-31.1%, P < 0.0001) and collagen (reduction 6.2%; 95% CI: 3.2-9.3%, P = 0.0003). The greatest inhibition of collagen-induced platelet aggregation by clopidogrel was seen in patients with the least inhibition of arachidonic acid induced aggregation by aspirin [lower tertile of arachidonic acid-induced platelet aggregation: 2.8% (95% CI: -0.8 to 6.3%) reduction in mean collagen-induced aggregation by clopidogrel; middle tertile: 4.0% (95% CI: 0.4-7.6%); upper tertile 12.6% (95% CI: 4.5-20.8%); P-value for interaction 0.01].

CONCLUSIONS

The greatest platelet inhibitory effect of clopidogrel occurs in patients with the least inhibition of arachidonic acid-induced platelet aggregation by aspirin. This raises the possibility that the clinical benefits of adding clopidogrel to aspirin may be greatest in patients whose platelets are least inhibited by aspirin. Confirmation in clinical outcome studies may allow these patients to be targeted with antiplatelet drugs that inhibit the ADP receptor, thereby overcoming the problem of laboratory aspirin resistance.