Comprehensive platelet aggregation studies are a standard and accepted part of any coagulation work-up following initial screening tests, PT/INR, aPTT and von Willebrand factor testing. Platelet function testing is an important part of the evaluation of common and rare bleeding disorders [1, 2, 3, 8]. Platelet function testing has been a part of clinical laboratory practice since early in the 20th century (8). Machaon Diagnostics measures platelet aggregation by light transmission aggregometry (LTA) which is the current GOLD STANDARD test for measuring platelet function [4, 5, 6, 8]. We test 7 different platelet activators or agonists, some at multiple concentrations, for a total of 11 platelet aggregation tests as part of our comprehensive platelet function assessment. Each agonist is tested individually against platelets suspended in platelet rich plasma environment and at a standardized platelet concentration (250,000 platelets/μL). The concentrations of agonists included in our assessment have been selected from those recommended by platelet aggregation testing guidelines published by the College of American Pathologists (CAP), Clinical and Laboratory Standards Institute (CLSI), North American Specialized Coagulation Laboratory Association (NASCOLA) and the British Society of Haematology[1, 2, 3, 8].
Platelets promote hemostasis by 4 interconnected mechanisms: 1.) adhering to sites of vascular injury or artificial surfaces, 2.) releasing compounds from their granuales, 3.) aggregating together to form a hemostatic platelet plug, and 4.) providing a procoagulant surface for activated coagulation protein complexes on their phospholipid membranes . Platelet aggregation testing is performed to assess each of these mechanisms by exposing platelets to stimuli that mimic physiologic situations encountered during vascular injury and hemolytic processes . Since the activation of platelets is a multiphasic reaction involving different membrane bound receptors and intracellular signaling pathways it is essential to test multiple agonists at multiple concentrations. Lastly, there is good correlation between defects in platelet aggregation and bleeding disorders in affected individuals [1, 2, 3, 7, 8].
# of Aliquots
Pref. Sample Type
citrated whole blood
Ristocetin-induced Platelet Aggregation
Draw Kits Available?
Light Transmission Aggregometry
Special Instructions & Forms
Patients should be fasting (no food or drink, water is OK) for 6 hours prior to the blood draw.
1. Hayward C, Moffat K, Raby A, Israels S, Plumhoff E, Flynn G, Zehnder J. Development of North American consensus guidelines for medical laboratories that perform and interpret platelet function testing using light transmission aggregometry. Am J Clin Pathol 2010;134:955-963.
2. Kottke-Marhcant K and Corcoran G. The laboratory diagnosis of platelet disorders; an algorithmic approach. Arch Pathol Lab Med 2002;126: 133-146.
3. Guidelines on platelet function testing: The British Society for Haematology BCSH Haemostasis and Thrombosis Task Force. J Clin Pathol. 1988;41: 1322-1330.
4. Karon B and Jaben E. Platelet Function; Laboratory methods for evaluating effectiveness of anti-platelet therapy. Clinical Laboratory News. 2011 April;37(4).
5. Lordkipanidze M, Pharand C, Shampaert E, Palisaitis DA, Diodati JG. Evaluation of the platelet count drop method for assessment of platelet function comparison with “gold standard” light transmission aggregometry. Thromb Res 2009 Sep;124(4): 418-422. Epub 2009 Feb 28.
6. White MM, Krishan R, Kueter TJ, Jacoski, MV, Jennings LK. The use of the pint of care Helena ICHOR/Plateletworks and the Accumetrics Ultegra RPFA for assessment of platelet function with GPIIB-IIIa antagonists. J Thromb Thrombolysis 2004 Dec;18(3): 163-169.
7. Jackson S. The growing complexity of platelet aggregation. Blood 2007 June 15;109(12).
8. CLSI. Platelet Function Testing by Aggregometry; Approved Guidelines. CLSI document H58-A. Wayne, PA: Clinical and Laboratory
Standards Institute; Vol. 28 No. 31., 2008.
Specimen processing is one of the most important aspects in the generation of accurate and reliable lab results. Many variables, such as, anticoagulant ratio, storage time and temperature, and surface of containers and drawing components can affect test results.
Machaon Diagnostics follows and recommends the use of the third edition of the National Committee for Clinical Laboratory Standards (NCCLS) guideline H21-A3: Collection, Transport, and Processing of Blood Specimens for Coagulation Testing and General Performance of Coagulation Assays.
Frozen Citrated Plasma
Frozen citrated plasma is the specimen of choice for clotting assays and some ELISA testing. The anticoagulant used for these assays is 105 – 109 mmol/L, 3.13% – 3.2% of the dihydrate form of trisodium citrate (Na3C6H5O7 2H2O), buffered or nonbuffered.
Patients with hematocrit values above 55% should have their final citrate concentration corrected using the following equation:
X = (100 – PCV) / (595 – PCV) WB Volume
Where X is citrate volume required to prepare a whole blood volume (WB Volume) from a patient with a certain percent packed cell volume (PCV).
Please follow the listed suggestions for collection of citrated plasma samples.
A 1:9 ratio of anticoagulant to whole blood is imperative
Blood should be drawn directly into anticoagulant if possible
Syringe draws should be added to anticoagulant within 1 minute
Syringe draws should use no more that a 20mL volume syringe
A two-syringe technique is preferred for syringe draws
Coagulation draws should be the 2nd or 3rd tube drawn
Catheter draws should be avoided or under the advice of the attending physician
All tubes should be inverted at least 4 times to ensure adequate mixing
Suitable needle gauges range from 19 – 22 for coagulation and platelet testing
Cell-free plasma must contain less than 10,000 platelets/µL
Centrifugation should be performed at 1,500 × g for 15 or more minutes
Aliquots are frozen (<= -20ºC) promptly to minimize factor degradation
Specimens are shipped frozen on dry ice (-78.5ºC)
Frozen serum is the specimen of choice for most immunoglobulin detecting assays and many ELISA based tests. Whole blood is drawn into a glass or plastic tube possibly containing an activator. Please follow the tube manufacturer’s guidelines for tube handling and processing.
Please follow the listed suggestions for collection of serum samples.
Plastic tubes containing an activator should be inverted at least 4 times
Glass tubes without activator should be clotted for 2 hours at room temperature
Suitable needle gauges range from 19 – 22 for the serum based tests
Centrifugation should be performed at 1,500 × g for 15 or more minutes
Aliquots are frozen (<= -20ºC) before shipping and shipped on dry ice (-78.5ºC)
EDTA Whole Blood
EDTA anticoagulated whole blood is the specimen of choice for molecular genetic tests.
Please follow the listed suggestions for collection of genetic samples.
Blood should be drawn directly into anticoagulant if possible
Extracted DNA is acceptable if received from CLIA-certified labs
This must be a closed system draw to prevent contamination
All tubes should be inverted at least 4 times to ensure adequate mixing
Suitable needle gauges range from 19 – 22 to prevent cell lysis
A minimum of 2mL of whole blood is needed for genetic assays
No processing is required for this sample type
Ship this type of specimen at room temperature
Submitting multiple aliquots (plasma or serum) for testing is an important aspect of clot, chromogenic and ELISA based tests. Aliquots of 1mL are requested for most of our assays. These should be frozen prior to shipment in a <= -20 C freezer or colder. Tubes should be placed into a rack to ensure the samples are frozen properly in the base of the tube. Freezing should occur within 1 hour of the time of draw. Please refer to the preferred number of aliquots when submitting samples.
Shipment is a crucial aspect of clinical testing. Please follow the below instructions for easy shipments to the lab.
Machaon Diagnostics contracts with Medical Couriers, Inc. (MCI). who service the entire San Francisco Bay Area and surrounding areas. MCI has a fleet of specially trained drivers that will visit your lab, clinic or office during specified times. Couriers carry dry ice, cold packs and room temperature containers for receipt of all specimen types.
Medical Couriers, Inc. can be phoned for individual pickup requests at the below number.
Medical Couriers, Inc. (800)-652-1147
Place prepared samples and order forms in a shipping bag with Machaon and specimen type written in a clear and visible location.
Please collect the following items:
Test Order Form
Packing material or newspaper
Styrofoam container, possibly with outer cardboard box
Airbill for overnight shipments
ORM-A label for dry ice shipments (UN1845)
Dry ice (-78.5ºC) sufficient for transit time (5lb. per day)
Specimens in biohazard specimen transport bag
Place the biohazard bag containing samples and the test order form into a Styrofoam container followed by dry ice. Fill remaining container space with packaging material and seal with packaging tape. Adhere a completed airbill and dry ice labels to the exterior of container in a visible location. Telephone your preferred overnight courier to request a pickup or place container in designated pickup area.
37th Annual Meeting of the Histiocyte Society Meeting
Antiphospholipid Syndrome: criteria, non-criteria and triple positive testing – a video with Dr. Brad Lewis and Dr. Sciascia.
Platelet Functional Defects, from the clinic to genetics (a webinar given by Dr. Brad Lewis, Feb. 24, 2017)
Diagnosing Thrombotic Microangiopathies: TTP and atypical HUS: (A Grand Rounds presentation at Mattel Children’s Hospital, UCLA, to Pediatric Nephrology with Dr. Brad Lewis.)
A guide to the video content:
00:24 – Introduction (Why we should care about diagnosis of aHUS and TTP)
1:00 – What is microangiopathic hemolytic anemia (MAHA)?
1:16 – Blood smear with schistocytes
1:40 – Von Willebrand’s protein synthesis
02:09 – ADAMTS-13 and TTP pathophysiology
02:43 – How to interpret ADAMTS-13 activity testing and advantage of doing ADAMTS-13 activity testing with Machaon Dx
03:48 – Use of ADAMTS-13 testing to diagnose “Occult” TTP
04:40 – Ruling in or out aHUS with ADAMTS-13 activity testing
05:20 – Plasma exchange for aHUS patients
05:57 – The complement cascade and aHUS pathophysiology
08:04 –aHUS patients respond to eculizumab therapy
08:45 – Unlike TTP, aHUS has triggers in 70% of cases
09:26 – aHUS is a multisystem microvascular disease (aHUS-induced organs damage)
10:09 – aHUS presentation
11:41 – Can we differentiate TTP and aHUS clinically?
12:15 – 5 reasons why you should care about aHUS patients genotyping
14:17 – Advantage of doing aHUS genetic testing with Machaon Dx
14:52 – The punchline: aHUS and TTP diagnosis algorithm
Shapiro, AD. et al. Plasminogen replacement therapy for the treatment of children and adults with congenital plasminogen deficiency. Blood. 2018;131(12):1301–1310.
Stromsness B. et al. Physician Interpretation of Equivocal Results for aHUS Genetic Testing Varies Greatly and is Frequently at Odds with Laboratory Views. J Clin Apheresis. 2019; (abstract P-82).
Ero, MP, Kain, JS, inventors; Machaon Diagnostics, Inc., assignee. 2018 Dec 18. Method of diagnosis of complement-mediated thrombotic microangiopathies. United States patent US 10,155,983.
Tao J. et al. A rare case of Alport syndrome, atypical hemolytic uremic syndrome and Pauci-immune crescentic glomerulonephritis. BMC Nephrology. 2018;19:355.
Kain J. et al. Additional Genes Associated with Atypical Hemolytic Uremic Syndrome. ASN 2018 Abstract TH-PO713. 2018; (abstract).
Switala L. et al. Complement factor abnormalities detected in patients with suspected Heparin-induced Thrombocytopenia (HIT) but not in Thrombotic Thrombocytopenia Purpura (TTP). ISLH 2017 Abstract Proceedings. 2017; (abstract).
Ipe T. et al. An extremely rare splice site mutation in the gene encoding complement factor I in a patient with atypical hemolytic uremic syndrome. J Clin Apheresis. 2017;32(6):584-588.
Alge J. et al. Hemolytic uremic syndrome as the presenting manifestation of WT1 mutation and Denys-Drash syndrome: a case report. BMC Nephrology. 2017;18(1): 243.
Zhang K. et al. Atypical hemolytic uremic syndrome: a brief review. Hematology Reports. 2017;9(2):7053.
Jensen G. et al. Consumption of nattokinase is associated with reduced blood pressure and von Willebrand factor, a cardiovascular risk marker: resultd from a randomized double-blind, placebo-controlled, multicenter North American clinical trial. Integrated Blood Pressure Control. 2016;9:95-104.
Stromsness B. et al. Perceived clinical utility of ADAMTS-13 testing decreases quickly when turnaround time extends beyond two days. Int J Lab Hematol. 2015; (abstract).
Ero M. et al. Novel variant detection is essential when attempting to genetically confirm the clinical diagnosis of complement-mediated thrombotic microangiopathies (TMA). J Clin Apheresis. 2015; (abstract O-09).
Harbert J. et al. Inhibitory effects of fish oil on platelet-associated thrombin generation as measured by the calibrated automated thrombogram: an in vitro study. Int Soc Thromb Hemost 2014; (abstract 604).
Ero M. et al. Impact of telavancin on prothrombin time and activated partial thromboplastin time as determined using point-of-care coagulometers. J Thromb Thrombolysis. 2013;38(2):235-240.
Beattie DT. Et al. An in vitro investigation of the cardiovascular effects of the 5-HT4 receptor selective agonists, Velusetrag and TD-8954. J Thromb Thrombolysis. Vascular Pharmacology. 2013;58:150–156.
Ero M. et al. A pilot study on the serum pharmacokinetics of nattokinase in humans following a single oral daily dose. Alternative Therapies. 2013;19(3): 18-21.
Higgins D. et al. The inability of tegaserod to affect platelet aggregation and coronary artery tone at supratherapeutic concentrations. Archives of Pharmacology. 2012;385(1):103-9.
Ng C. et al. Oral bioavailability of nattokinase (NSK-SD). Am J Clin Pathol. 2010;134(suppl):11.
Lakshmi P. et al. Flavocoxid, an anti-inflammatory agent of botanical origin, does not affect coagulation or interact with anticoagulation therapies. Adv Ther. 2010;27(7):1-12.
Jeske WP. et al. Isolation and characterization of heparin from tuna skins. Clin Appl Thromb Hemost. 2007 Apr;12(2):137-45.
Fareed D. et al. Nitric oxide levels are upregulated in patients with malignancy-associated hypercoagulable state. Int J Lab Hematol. 2005; (abstract).
Jeske WP. et al. A survey of venous thrombosis models. Methods Mol Med. 2004;93:221-37.
Sahud et al. von Willebrand factor-cleaving protease inhibitor in a patient with human immunodeficiency syndrome-associated thrombotic thrombocytopenic purpura. Br J Haematol. 2002; 116(4):909-911.
Fenton JW. et al. Statin drugs and dietary isoprenoids downregulate protein prenylation in signal transduction and are antithrombotic and prothrombolytic agents. Biochemistry. 2002;67(1):85-91.
Ero M. et al. Comparative effects of a novel sulfated pentamannan oligosaccaride mixture (PI-88), heparin and related agents on the tissue factor-induced platelet activation and aggregation profile in whole blood. Thromb Haemost. 2001; (abstract 6260).
Ero M. et al. An antiplatelet drug, ticlopidine, inhibits heparin-induced thrombocytopenia responses as measured by platelet aggregometry and 14C serotonin release. Thromb Haemostasis. 1997; (abstract).
Clinical Trial Services
Machaon Diagnostics is a clinical reference laboratory, specializing in the diagnosis and monitoring of coagulation, platelet, rare disease and genetics. What makes us unique is our ability to provide high quality custom testing with unmatched speed.
Our Mission is to save more lives with lab tests.
Since 2003, we have grown into a team of clinicians, scientists, consultants and technologists bringing over 400 years of aggregated expertise to the field of laboratory medicine.
Our areas of clinical expertise include: Rare Disease Genetics, Advanced Hemostasis, (Platelets and Coagulation), Complement Disorders, Nephrology, Hematology / Oncology, Ophthalmology, Cardiology, Immunology, and Medical Devices.
Our esoteric and additional routine testing menu applies to a wide variety of disorders and clinical situations and, therefore, draws attention from both a national and an international clientele. Our clients include university medical centers, health system networks, community hospitals, commercial and research laboratories, doctor’s offices, biotechnology firms and pharmaceutical companies of all sizes.
Machaon Diagnostics provides a rapid and complete solution for companies in need of clinical trial services, contract research and independent marketing claim validation. We have been performing studies on pharmaceuticals and medical devices since 2003. Design, subject recruitment, sample collection/storage, testing, statistical analysis, study reporting and manuscript preparation are all included in our comprehensive service. We have an extensive database of well-characterized study volunteers, allowing us to complete some IRB-approved clinical trials in as little as 5 weeks. Our subject database includes normal adult, rare disease, elevated risk of cardiovascular disease, high blood pressure, metabolic syndrome and other populations. We frequently collaborate with our larger CRO partners to aid in global clinical trials.
Research & Development
Machaon Diagnostics is the largest independent specialized coagulation lab in the US. We are a privately-owned company, staffed by MDs, PhDs, licensed clinical laboratory scientists (CLSs) and medical technologists.
As a clinical lab, we provide a unique testing environment for evaluating thrombotic and fibrinolytic potential. Pharmaceutical, device and biotech compounds and materials can be studied within established, validated and controlled clinical assays with verified reference ranges. Our clinical tests are further controlled within our quality assurance and proficiency testing policies and procedures. All tests can be modified or re-designed for best-fit analysis.
The Machaon Diagnostics laboratory facility is located on a medical center campus in Berkeley, California with a second lab site in New Orleans, Louisiana. Our scientists are published in and passionate about the field of laboratory medicine.
Our staff has had extensive experience designing unique testing systems or applying the proper testing system to answer the clinical trial questions quickly and accurately.
Custom-built assays, from ELISAs to NGS, from Sanger to Flow Cytometry, from TEG to Electrophoresis, we build custom assays to complement our pre-existing testing capabilities to fit your testing needs.
Machaon Diagnostics is a multi-state licensed, CLIA-accredited, College of American Pathologists (CAP)-accredited clinical laboratory authorized to provide high complexity clinical laboratory services. All laboratory testing is controlled within our Quality Assurance Program and studies are offered in a Good Laboratory Practices (GLP, 21CFR Part 58)/ EN 13612 environment.
Machaon (pronounced may-chay-on) is a character from Homer’s Iliad (800 B.C.) and a key figure in the Trojan War. Described as a warrior, surgeon and healer, Machaon was revered for saving the lives of Menelaus, King of Sparta, husband Helen, and that of Philoctetes, the famed Achaean leader. Under the direction of King Agamemnon, Machaon saved these and many other warriors during the fierce Greek and Trojan War.
What you need to know
If you are reading this page, it likely means your doctor has ordered a bleeding or clotting test for you and would like you to get this test run at Machaon Diagnostics. Machaon Diagnostics is a clinical reference lab specializing in bleeding and clotting testing, one of the few independent coagulation labs in the country. We run very specific, unique blood tests which are often critical in helping doctors determine the correct course of treatment.
Machaon Diagnostics provides specialized lab testing to hospitals and doctors all over the country and is recognized for the speed and quality of our testing.
It is important to know that your insurance may or may not cover your testing. We have a long track record of working with patients to ensure they get the testing they need and we will work with you to help find a solution should your insurance not cover the testing we would provide.
If you are coming in to Machaon for a test, here are some things you will need to have with you:
Your doctors lab order
Your insurance information
A list of your current medications
If you are coming in for a Platelet Aggregation, please remember you must fast before this test.
Machaon Diagnostics was founded in 2003 and is a California-licensed, CLIA-accredited, College of American Pathologists (CAP)-accredited clinical laboratory authorized to provide high complexity clinical laboratory services. All laboratory testing is controlled within our Quality Assurance Program and studies are offered in a Good Laboratory Practices (GLP, 21CFR Part 58)/ EN 13612 environment.