Inflammatory markers and platelet aggregation tests as predictors of hemoglobin and endogenous erythropoietin levels in hemodialysis patients

Approach to the Assessment of Platelet Function: Comparison between Optical-based Platelet-rich Plasma and Impedance-based Whole Blood Platelet Aggregation Methods

Platelet aggregation studies play an important role in the assessment of hereditary and acquired platelet function defects. The first aggregation test introduced into laboratory practice used platelet-rich plasma (PRP) where aggregation was detected by an optical method. The assessment of platelet function using whole blood (WB) aggregation by an impedance method followed up nearly 20 years later. The WB impedance aggregation assay appears to be superior to the optical method because it 1) evaluates platelets in a physiologic milieu in the presence of red and white blood cells, which are known to modulate platelet function; 2) is faster; 3) has higher sensitivity; and 4) does not require centrifugation, thus avoiding injury to platelets and loss of giant thrombocytes. These two assays were compared. Clearly, the WB impedance aggregation methodology has many advantages over the optical PRP assay for the assessment of the hyperactive platelet syndrome and the effects of anti-platelet drugs.

Oncostatin M receptor β and cysteine/histidine-rich 1 are biomarkers of the response to erythropoietin in hemodialysis patients

Biomarkers that evaluate the response to erythropoietic-stimulating agents largely measure inflammation and iron availability. While these are important factors in modifying an individual's response to these agents, they do not address all aspects of a poor response. To clarify this, we isolated peptides in the serum of good and poor responders to erythropoietin in order to identify biomarkers of stimulating agent response. Ninety-one candidate biomarker targets were identified and characterized using mass spectrometry, of which tandem mass spectroscopy provided partial amino-acid sequence information of 17 different peptides for 16 peptide masses whose abundance significantly differed between poor and good responders. The analysis concluded that three peptides associated with a poor response were derived from oncostatin M receptor β (OSMRβ). The 13 serum peptides associated with a good response were derived from fibrinogen α and β, coagulation factor XIII, complement C3, and cysteine/histidine rich 1(CYHR1). Poor response was most strongly associated with the OSMRβ fragment with the largest molecular weight, while a good response was most strongly associated with CYHR1. Immunoblots found the abundance of intact OSMRβ and CYHR1 significantly differed between good and poor responders. Thus, two measurable biomarkers of the response to erythropoietic-stimulating agents are present in the serum of treated patients.

Prognostic importance of hemoglobin in hypertensive patients with electrocardiographic left ventricular hypertrophy: the Losartan Intervention For End point reduction in hypertension (LIFE) study

BACKGROUND

The prognostic importance of hemoglobin is controversial. We investigated the prognostic importance of baseline and in-treatment hemoglobin in the LIFE study.

METHODS

Eight thousand one hundred ninety-four LIFE patients with hypertension and left ventricular hypertrophy with available baseline hemoglobin measurements were randomized to losartan- or atenolol-based treatment and followed for 4.8 years for end points of all-cause mortality and composite of cardiovascular death, nonfatal stroke, or nonfatal myocardial infarction.

RESULTS

U-shaped relations were observed between deciles of baseline hemoglobin and all-cause mortality and the composite end point. In univariate Cox models, baseline hemoglobin in the lowest gender-specific decile (women/men: <12.5/13.4 g/dL) was associated with all-cause mortality (hazard ratio [HR] 2.01, 95% CI 1.64-2.64) and the composite end point (HR 1.53, 95% CI 1.27-1.85, both P < .001), whereas hemoglobin in the highest gender-specific decile (women/men: > or =15.0/16.2 g/dL) was not. The decrease in hemoglobin was higher (P < .001) in patients allocated to losartan- (14.3-13.8 g/dL) versus atenolol-based treatment (14.3-14.0 g/dL). In Cox models with the same gender-specific definitions for high and low hemoglobin as time-varying covariates with adjustment for treatment allocation and established risk factors and diseases, hemoglobin in the lowest decile was associated with higher rates of all-cause mortality (HR 3.03, 95% CI 1.89-4.85, P < .001) and the composite end point (HR 1.36, 95% CI 1.08-1.71, P < .01), whereas hemoglobin in the highest decile was not.

CONCLUSIONS

After adjusting for other risk factors, relatively low, but not high, hemoglobin during antihypertensive treatment was associated with higher incidence of all-cause mortality and the composite end point.

[Thrombocytopathy and blood complications in uremia]

Bleeding diathesis and thrombotic tendencies are characteristic findings in patients with end-stage renal disease. The pathogenesis of uremic bleeding tendency is related to multiple dysfunctions of the platelets. The platelet numbers may be reduced slightly, while platelet turnover is increased. The reduced adhesion of platelets to the vascular subendothelial wall is due to reduction of GPIb and altered conformational changes of GPIIb/IIIa receptors. Alterations of platelet adhesion and aggregation are caused by uremic toxins, increased platelet production of NO, PGI(2), calcium and cAMP as well as renal anemia. Correction of uremic bleeding is caused by treatment of renal anemia with recombinant human erythropoietin or darbepoetin alpha, adequate dialysis, desmopressin, cryoprecipitate, tranexamic acid, or conjugated estrogens. Thrombotic complications in uremia are caused by increased platelet aggregation and hypercoagulability. Erythrocyte-platelet-aggregates, leukocyte-platelet-aggregates and platelet microparticles are found in higher percentage in uremic patients as compared to healthy individuals. The increased expression of platelet phosphatidylserine initiates phagocytosis and coagulation. Therapy with antiplatelet drugs does not reduce vascular access thrombosis but increases bleeding complications in endstage renal disease patients. Heparin-induced thrombocytopenia (HIT type II) may develop in 0-12 % of hemodialysis patients. HIT antibody positive uremic patients mostly develop only mild thrombocytopenia and only very few thrombotic complications. Substitution of heparin by hirudin, danaparoid or regional citrate anticoagulation should be decided based on each single case.

Erythropoietin-deficient anemia associated with autoimmune polyglandular syndrome type I

Autoimmune polyglandular syndrome type I (APS1), a relatively common disorder in some populations, is frequently associated with adrenal insufficiency, hypoparathyroidism, and other endocrine and skin abnormalities. We describe an 18-year-old male with APS1, as documented by genotyping, who presented with hypoparathyroidism and a normocytic, hypoproliferative, isolated anemia. An extensive hematological work-up revealed a low serum erythropoietin, without any other hematological abnormalities. His renal function was normal, and he did not have many of the laboratory or clinical findings associated with an anemia of chronic disease. His anemia was responsive to superphysiologic doses of erythropoietin. We thus suggest that erythropoietin deficiency may be one of the endocrine abnormalities associated with APS1, and clinicians should be cognizant of the association of treatable anemia in patients with APS1.

Chronic kidney disease, anemia, and incident stroke in a middle-aged, community-based population: the ARIC Study

BACKGROUND

Chronic kidney disease (CKD) has been linked to higher stroke risk. Anemia is a common consequence of CKD, and recent evidence suggests anemia may increase risk of cardiovascular events. The combined effect of CKD and anemia on stroke risk, however, has not been investigated thoroughly. We analyzed data from a middle-aged, community-based cohort to determine if CKD and anemia interacted to affect stroke risk.

METHODS

Data on 13,716 participants in the prospective Atherosclerosis Risk in Communities (ARIC) Study were analyzed to assess the joint effect of CKD and anemia on risk of incident stroke during a 9-year follow-up period. CKD was defined as a creatinine clearance of <60 mL/min. Anemia was defined as hemoglobin levels of <13 g/dL for men or <12 g/dL for women.

RESULTS

Overall, CKD was associated with an increase in stroke risk after adjustment for other factors [hazard ratio HR) 1.81; 95% CI 1.26 to 2.02]. However, this association was modified substantially by anemia. In the presence of anemia, CKD was associated with a substantially higher risk of stroke compared to no CKD (HR 5.43; 95% CI 2.04 to 14.41). In contrast, when anemia was not present, CKD was associated with only a modest, nonsignificant elevation in stroke risk (HR 1.41; 95% CI 0.93 to 2.14). The interaction between CKD and anemia on risk of stroke was statistically significant (P < 0.01).

CONCLUSION

Among middle-aged, community-based persons, the combination of CKD and anemia was associated with a substantial increase in stroke risk, independent of other known risk factors for stroke.