Racial differences in coagulation studies in stroke

Identifying Genetic and Biological Determinants of Race-Ethnic Disparities in Stroke in the United States

In the United States, causes of racial differences in stroke and its risk factors remain only partly understood, and there is a long-standing disparity in stroke incidence and mortality impacting Black Americans. Only half of the excess risk of stroke in the United States Black population is explained by traditional risk factors, suggesting potential effects of other factors including genetic and biological characteristics. Here, we nonsystematically reviewed candidate laboratory biomarkers for stroke and their relationships to racial disparities in stroke. Current evidence indicates that IL-6 (interleukin-6), a proinflammatory cytokine, mediates racial disparities in stroke through its association with traditional risk factors. Only one reviewed biomarker, Lp(a) (lipoprotein[a]), is a race-specific risk factor for stroke. Lp(a) is highly genetically determined and levels are substantially higher in Black than White people; clinical and pharmaceutical ramifications for stroke prevention remain uncertain. Other studied stroke risk biomarkers did not explain racial differences in stroke. More research on Lp(a) and other biological and genetic risk factors is needed to understand and mitigate racial disparities in stroke.

Cerebral venous thrombosis in a Caribbean population

INTRODUCTION

Cerebral venous thrombosis (CVT) is a rare affliction characterized by a wide diversity in its clinical expression and etiologies. Data from black populations concerning CVT are limited. We examined the clinical, radiological, and etiological aspects as well as the outcome of CVT in Guadeloupe, a French Overseas Department in the Caribbean.

METHODS

All patients hospitalized between 2000 and 2011 at the University Hospital of Pointe-à-Pitre and diagnosed with CVT were retrospectively studied. Forty-five patients, each having had a medical imaging confirming the diagnostic, were retained.

RESULTS

The frequency of CVT in Guadeloupe was estimated at 15 to 20 per 100,0000 per year in our survey. Our patients were largely composed of young women (73.3%). The average patient age was 40 years (14 to 80), with an incidence peak for women in the 20 to 50 years age range. The onset was sub-acute in 69% of cases, where headaches represented 93% of initial symptoms. Thrombosis of the SLS (60%), and of the lateral sinuses (64.4%) were the most frequently encountered. We observed a majority of mild clinical forms with a good functional prognosis. The main etiological factors were oral estro-progestative contraception (40%), and a positive thrombophilia test (33.3%). The thrombophilia factors in Guadeloupe differed from those in Caucasian populations, with a higher frequency of protein S deficit.

CONCLUSION

The clinical and radiological characters are similar to those described in classical studies. Our study suggests a higher incidence of CVT in Guadeloupe, compared to results from Western countries. Further investigation is necessary to better characterize the thrombo-embolic venous risk factors in the black population. Protein S deficit appears to be the most frequent cause of thrombophilia in our population.

Bronchoalveolar lavage fluid D dimer levels are higher and more prevalent in black patients with pulmonary sarcoidosis

BACKGROUND

Abnormalities of lung coagulation and fibrinolysis in sarcoidosis are thought to play a role in the pathogenesis of this disease.

OBJECTIVE

We previously showed that bronchoalveolar lavage fluid (BALF) D dimer directly correlated with various measures of severity in sarcoidosis. Here, we analyze our observation that BALF D dimer was more frequently found at higher levels in African-American patients with pulmonary sarcoidosis.

METHODS

BALF D dimer was measured in 55 subjects with pulmonary sarcoidosis and 31 healthy volunteers by enzyme immunoassay. The healthy group established a normal range of BALF D dimer with 71 ng/ml as the highest measured level. This was the cut point for comparisons among the patients with sarcoidosis.

RESULTS

High BALF D dimer levels (>71 ng/ml) were found in younger patients with sarcoidosis and were associated with a significantly lower percent predicted forced expiratory volume in 1 s and greater numbers of BAL lymphocytes. Black patients with sarcoidosis had higher BALF D dimer levels (median 131, range 0-2,040 ng/ml) than white patients (median 18, range 0-605 ng/ml; p = 0.011). Higher than normal BALF D dimer levels were found in 61% of the black subjects with sarcoidosis, but in only 20% of the white individuals (chi(2) = 5.539, p = 0.019). BALF D dimer was the only disease measure that discriminated black from white individuals with sarcoidosis.

CONCLUSION

BALF D dimer is an indicator of lung fibrin formation and degradation in sarcoidosis. The relationship of high D dimer levels with greater BAL lymphocytosis and worse lung function may be a marker of active sarcoidosis, especially in African-Americans who tend to suffer a more serious form of the disease.

Ethnic differences in markers of thrombophilia: implications for the investigation of ischemic stroke in multiethnic populations: the South London Ethnicity and Stroke Study

BACKGROUND AND PURPOSE

The role of hypercoagulable states in the pathogenesis of ischemic stroke in black subjects is not known, and data on normal reference ranges in black populations are lacking. This study estimated ethnic-specific reference ranges in a community population to determine the prevalence of thrombophilic states in a multiethnic stroke population.

METHODS

Free protein S, protein C, antithrombin III, activated protein C resistance, IgG anticardiolipin antibodies, and lupus anticoagulant were determined in 130 consecutive ischemic stroke cases < or =65 years of age (50 black Caribbeans, 30 black Africans, 50 whites) and 130 community controls.

RESULTS

Black African controls had significantly lower protein S (P<0.001) and protein C (P=0.049) and a trend toward lower antithrombin III (P=0.056) levels compared with white controls. Black Caribbean and African controls had higher diluted Russell's viper venom time ratios compared with whites (P=0.001, P<0.001). Using ethnic-specific reference ranges, 8 controls (6.3%) and 11 cases (8.5%) had thrombophilia abnormalities (odds ratio [OR], 1.39; 95% confidence interval [CI], 0.54 to 3.57; P=0.50). ORs were 0.96 (95% CI, 0.18 to 4.99; P=0.96) for whites, 1.57 (95% CI, 0.41 to 5.94; P=0.51) for black Caribbeans, and 2.07 (95% CI, 0.18 to 24.2; P=0.95) for black Africans.

CONCLUSIONS

Failure to account for ethnic differences in the normal reference ranges for thrombophilia markers may lead to inappropriate diagnosis and investigation of hypercoagulable states in black individuals. Protein S and protein C deficiencies and lupus anticoagulant may contribute to stroke risk in a minority of black cases, but they are unlikely to be major contributors to the excess stroke risk seen in young individuals of African and African-Caribbean descent.

Age, functional status, and racial differences in plasma D-dimer levels in community-dwelling elderly persons

BACKGROUND

Dysregulation of immunologic and coagulation systems is common in elderly persons and is associated with many diseases of aging. Thrombotic events are a major cause of morbidity and mortality in the elderly population. This study assesses whether D-dimer, a marker of fibrinolytic activity, varies systematically by demographic, health, and functional measures, and derives a prediction model for factors related to D-dimer in a sample of community-dwelling elderly persons.

METHODS

D-dimer levels were assessed in a random sample of 1,727 community-dwelling elderly persons from five rural and urban counties in North Carolina in 1992, as part of the Established Populations for the Epidemiologic Studies of the Elderly (Duke University). All subjects were 72 years or older at the time of the blood draw. In addition, all subjects were surveyed yearly by telephone or in person each year from 1986 to 1992 for a variety of health, functional, and social factors. Levels of D-dimer in 1992 were related cross-sectionally to demographics (age, race, education, income, gender, smoking), function (Nagi, Rosow-Breslau, Katz, Older Americans Resources and Services procedures instrumental activities of daily living), life satisfaction and self-rated health, self-reported diseases (heart attack, cancer, stroke, diabetes, and hypertension), and weight change from 1986 to 1992.

RESULTS

D-dimer levels increased with increasing age and functional disability. Among the health variables, only high blood pressure was predictive of D-dimer level. D-dimer levels were dramatically higher in blacks. Blacks were nearly four times more likely to have an extreme value of D-dimer (>600 microg/l) than whites when high D-dimer (yes/no) was analyzed, and blacks had an average level that was nearly 40% higher than whites in analyses of the continuous version of the outcome. This racial effect was not substantively affected in multivariable analyses with demographic and socioeconomic variables controlled. Race, age, functional status, current smoking, high blood pressure, and weight loss were related to level of D-dimer, and race, age, and functional status were related to the presence of a high D-dimer level (in the top 10% of the sample).

CONCLUSIONS

Black, older, and functionally impaired persons had significantly higher levels of D-dimer in this sample of community-dwelling elderly persons. The findings for race were particularly striking and persisted even after controlling for smoking and other factors known to be related to thrombosis and were not mediated by social factors. This result may contribute to our understanding of the increased levels of thrombotic events found in these groups.

Plasma fibrinogen of black South Africans: the BRISK study

OBJECTIVE

To describe the distribution of plasma fibrinogen and relationships with other risk factors for coronary heart disease (CHD) and stroke in the black population of the Cape Peninsula.

DESIGN

A cross-sectional survey of a stratified proportional sample of randomly selected black men and women.

SETTING

Households in Gugulethu, Langa, Nyanga, New Crossroads, KTC, Old Crossroads and Khayelitsha in the Cape Peninsula, South Africa.

SUBJECTS

One subject per household (352 men and 447 women), aged 15-64 years, voluntarily participated. Visitors, pregnant, lactating, ill, mentally retarded and intoxicated subjects were excluded.

RESULTS

Mean fibrinogen (thrombin time coagulation method) of men and women were higher than published data for Europeans but slightly lower than values of black Americans. Women aged 45-54 years had the highest level (3.13+/-0.89 g l(-1)) and men aged 15-24 years had the lowest (2.13+/-0.88 g l(-1)). Fifteen per cent of the men and 12% of the women had a level greater than 1 standard deviation of the mean for their age group. Univariate and multivariate analyses revealed significant (P<0.05) positive correlations of fibrinogen with smoking habit, age, body mass index (BMI), total and low-density lipoprotein (LDL) cholesterol, triglycerides, blood pressure and white blood cell count, and significant negative correlations with high-density lipoprotein (HDL) cholesterol, gamma glutamyl transferase (GGT), serum iron and ferritin. The correlations with BMI, serum lipoproteins, iron, ferritin, and GGT suggest that nutritional status and therefore diet influences plasma fibrinogen.

CONCLUSION

Relatively high fibrinogen levels, tending to cluster with other, including diet-related, risk factors for CHD and stroke, were observed in black South Africans. It is suggested that fibrinogen may contribute to the high stroke incidence of this population group.

Impact of race and ethnicity on ischemic stroke. The University of California at San Diego Stroke Data Bank

BACKGROUND AND PURPOSE

As the US minority population continues to grow, increasing numbers of nonwhite citizens are at risk for stroke. A better understanding of how ischemic stroke differs in the minority populations may lead to more effective clinical management.

METHODS

We prospectively evaluated 542 consecutive patients (416 whites, 71 Mexican Americans, 55 blacks) presenting to the University of California at San Diego Medical Center or the San Diego Veterans Affairs Hospital with presumed acute ischemic stroke or transient ischemic attack.

RESULTS

Whites had a higher proportion of transient ischemic attacks (32% versus 18% and 17% for blacks and Mexican Americans, respectively) and had the lowest prevalence of diabetes mellitus (17% versus 29% and 40% for blacks and Mexican Americans, respectively). Mexican Americans had higher initial serum glucose levels (178 versus 133 and 131 mg/dL for whites and blacks, respectively). Blacks were youngest (average age, 56 years). There were no differences among the groups in the prevalence of prior stroke, hypertension, myocardial infarction, or smoking; initial systolic blood pressure, serum cholesterol levels, and functional deficit also were similar. Although it did not reach statistical significance, there was a trend toward relatively late presentation in the black stroke subpopulation: only 53% of blacks (compared with 73% of both Mexican Americans and whites) reached medical attention within 24 hours of stroke onset. All groups had similar diagnostic evaluations and functional outcome at 1 week. With the exception of a higher frequency of stroke of unknown cause in Hispanics, the distributions of stroke etiologies did not differ significantly among the groups.

CONCLUSIONS

These data suggest that there are significant clinical differences in populations with ischemic stroke and transient ischemic attack that are related to race and ethnic origin, but in our population these differences did not include the extent of diagnostic evaluation undertaken or stroke severity.