1. Skip to Menu
  2. Skip to Content
  3. Skip to Footer

Platelet Aggregation

Platelet aggregation testing is useful in the evaluation of usefull link http://it-rechtsanwalt.at/cialis100mg suspected hereditary and low cost alternatives to viagra acquired disorders of platelet function. Activation of platelets causes them to change shape, secrete their intracellular granules, and aggregate with each other. Platelets normally contain two major types of granules – alpha and dense granules. These granules contain substances which promote hemostasis when secreted from platelets at the site of vascular injury. The alpha granules contain fibrinogen, factor V, and von Willebrand factor while the dense granules contain platelet factor 4, ADP, ATP, calcium and serotonin.

Abnormalities of platelet function may be hereditary or acquired. Hereditary platelet function disorders include rare defects of adhesion (Bernard Soulier syndrome), rare defects of aggregation (Glanzmann thrombasthenia), and more common defects of secretion (alpha or dense granule deficiency, aspirin-like defects, or other primary secretion defects).

Platelet Disorder

Biochemistry

Clinical Findings

Von Willebrands

Decreased vWF

Mild to severe bleeding

Bernard Soulier

Gp1b defect

Adhesion defect

Autosomal recessive

Mild to moderate bleeding

Glanzmann’s Thrombasthenia

GpIIb/IIIa defect, Decreased fibrinogen binding

Aggregation defect

Autosomal recessive

Moderate to severe bleeding

Normal platelet count, long bleeding time

Storage Pool Disease

Dense granule defect

Autosomal recessive

Mild to severe bleeding

Hermansky Pudlak

Dense granule

Secretion defect

Autosomal recessive

Albinism, poor vision, mild bleeding

Wiskott-Aldrich

Structural abnormality

Eczema, infections

Chediak Higashi

Lack dense bodies & ADP

Albinism, infections, hemorrhage

Gray Platelet syndrome

Deficiency of http://www.furtheryourpassion.ca/levitra-dosage-recommended alpha granules

Mild bleeding

Acquired platelet function disorders are more common than the hereditary disorders and include drug-induced platelet dysfunction (including aspirin, NSAID’s, clopidogrel, antibiotics, various cardiovascular and psychotropic drugs), uremia, and myeloproliferative disorders.

Classically, platelet function has been tested in the laboratory by testing platelet aggregation in platelet rich plasma upon addition of various agonists such as ADP, collagen, arachidonic acid, epinephrine and ristocetin. Using modern platelet aggregometers, it is viagra injectable possible to evaluate platelet secretion simultaneously, by measuring release of ATP by the aggregating platelets. Measurement of platelet secretion allows the cialis facts laboratory diagnosis of secretion defects with greater sensitivity than platelet aggregation testing alone. Platelet aggregation may be normal in some cases, and measurement of platelet secretion may be critical for diagnosis.

The following concentrations of each agonist are used: ADP (2uM and 5uM), collagen (1ug/mL), arachidonic acid (1mM) and ristocetin (1.25 mg/mL). For von Willebrand disease evaluation, dilute ristocetin (0.625 mg/mL) is also added. Evaluation of thrombocytosis (platelet count >400,000/uL) includes epinephrine (10uM). Platelet secretion is measured together with aggregation for all agonists except ristocetin.

Typical results of aggregation and where buy cialis secretion testing in some of the platelet function disorders are shown in the following table.

Platelet Aggregation and Secretion Responses

Platelet Disorder

ADP*

Collagen

Arachidonic

Acid

Ristocetin

Bernard Soulier

N

N

N

D

Glanzmann’s Thrombasthenia

D***

D

D

N

Storage Pool Disease

D**

D

N/D

N

Von Willebrand Disease

N

N

N

D

Aspirin

N/D

N/D

D

N/D

*Response to buy cialis once daily one or both concentrations of ADP, **Decrease in 2nd wave aggregation, *** Absent aggregation (1st and 2nd wave). Rule out platelet inhibitory drug, e.g. Clopidogrel, †Responses shown refer in most cases to both aggregation and secretion; in some case only secretion may be abnormal, N = Normal, D = Decreased

Decreased response to ristocetin and normal aggregation with the other agonists is seen in von Willebrand's disease and Bernard Soulier syndrome. For diagnosis of von Willebrand disease, platelet response to both concentrations of ristocetin must be evaluated together with von Willebrand disease screening tests such as ristocetin cofactor, von Willebrand disease antigen, and factor VIII assay. Glanzmann's thrombasthenia is characterized by absent aggregation with ADP, collagen and arachidonic acid and normal response to ristocetin. Inherited disorders of platelet secretion usually demonstrate a decreased secondary aggregation wave with ADP, decreased response to collagen and variable response to arachidonic acid; however, the pattern is not always typical.

Aspirin and other non-steroidal anti-inflammation drugs produce an absent secondary wave of aggregation with ADP, and decreased response to collagen and arachidonic acid. Antibiotics and cheap cialis find other drugs produce variably decreased platelet aggregation. The abnormal platelet function commonly seen in patients with uremia, dysproteinemia and liver disease is also associated with variably decreased platelet aggregation. Epinephrine induced aggregation and secretion may be absent in thrombocytosis secondary to chronic myeloproliferative disorders, in addition to the presence of a variety of other aggregation abnormalities.

Indications for ordering platelet aggregation and secretion testing include a bleeding diathesis secondary to suspected platelet dysfunction, especially if the PFA-100 platelet function screening test is abnormal and drug-induced platelet dysfunction is online viagra prescription ruled out. If the patient is taking aspirin, NSAID’s or other platelet-inhibitory drugs, the drug should be discontinued for at least 2 weeks prior to aggregation testing.

Seven 4mL sodium citrate (light blue-top) tubes of blood are required for full aggregation and secretion testing. Platelet aggregation testing alone (without secretion) may be ordered and requires four 4mL tubes of blood.

Reference value is normal aggregation with ADP, arachidonic acid, collagen, and ristocetin. A clinical pathologist interprets results.

Other Articles of no prescription needed cialis Interest
AddThis Social Bookmark Button

Stay Informed

Amazon Book

Our Sponsors

Login Form

Mobile Applications

iPad mini Horz Vert 300w

Get it for: iPhoneiPad

ClinLab Navigator Information

McAfee SECURE sites help keep you safe from identity theft, credit card fraud, spyware, spam, viruses and online scams
© 2012 ClinLab Navigator, LLC.