Automated Platelet Function Analyzer

What is the Automated Platelet Function Analyzer?

An automated platelet function analyzer aspirates citrated whole blood through a capillary coated with collagen and an agonist under high shear, and reports the time until the aperture occludes as the closure time. It suits screening of platelet dysfunction and monitoring of antiplatelet therapy.

Overview

The cartridge contains a capillary coated with collagen plus adenosine diphosphate or epinephrine and a membrane with a small aperture. Blood is aspirated at a controlled shear rate, platelets adhere and aggregate at the coated surface, and a thrombus forms until flow stops; the time to cessation is the closure time. The instrument requires only a sample application step and a short wait, typically two to five minutes per test, and two cartridges can be run in parallel to test two pathways at once. Results are compared with locally established reference intervals, and a prolonged closure time indicates a defect in platelet adhesion or aggregation or the presence of an inhibitor, but not the specific cause, so confirmation requires aggregation studies.

How does it work?

Platelet function testing uses two main approaches. In aggregation methods, platelet-rich plasma or whole blood is stirred at 37 degrees Celsius with an agonist such as adenosine diphosphate, collagen, arachidonic acid or ristocetin. In light transmission aggregometry the sample clarifies as platelets clump and the increase in transmitted light is recorded as an aggregation curve. In impedance aggregometry platelets adhere to electrode wires and the rise in electrical impedance between them is recorded. In luminescence aggregometry, ATP released from dense granules reacts with luciferin-luciferase reagent and the emitted light is measured alongside the aggregation trace. In high-shear systems, blood is aspirated through a capillary coated with collagen and adenosine diphosphate or epinephrine, and the time until the aperture occludes is reported as the closure time. All methods depend on controlled temperature, agonist quality and prompt processing of citrated samples.

What are the key features?

• High-shear aspiration through a coated capillary
• Cartridges with collagen plus ADP or epinephrine coatings
• Closure time reported in seconds
• Parallel testing of two cartridges for two pathways
• Simple sample application with minimal operator training
• Screening result requiring aggregation studies for confirmation

What are the technical specifications?

A typical automated platelet function analyzer configuration offers measurement principle of High-shear flow with aperture occlusion time, cartridge types of Collagen/ADP and collagen/epinephrine, sample volume of About 800 µL citrated whole blood per cartridge, test time of 2–5 min per cartridge, reporting range of Up to 300 s, above which flow non-closure is reported and temperature of 37 °C ±0.5 °C. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Automated Platelet Function Analyzer is used in screening for von Willebrand disease, pre-operative platelet function screening, monitoring of antiplatelet therapy and investigation of unexplained bleeding. Across the wider Platelet Analyzers class, laboratories also deploy it for investigation of inherited platelet disorders, testing for aspirin and P2Y12 inhibitor response and diagnosis of von Willebrand disease with ristocetin.

Which standards and certifications apply?

Relevant standards and methods include ISO 15189, CLSI H58, CLSI EP05, ICSH recommendations on platelet function testing, IEC 61010-1 and IEC 61010-2-101. Certification candidates for this model are CE, ISO 13485 manufacturing and NMPA class II registration; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Collect blood into citrate or hirudin as specified, avoid traumatic venepuncture and process samples within one to four hours, because platelet reactivity declines with time. Keep the aggregometer at 37 degrees Celsius, verify the temperature with an external thermometer and ensure the stir bar rotates at the specified speed. Reagents must be reconstituted and stored exactly as instructed, since degraded agonists give falsely low aggregation. Verify performance with normal control samples and review curves for shape and amplitude, not only the maximum value. Low platelet counts, hemolysis, lipemia and certain drugs affect results, so medication history should be documented before testing.

How do I select the right Automated Platelet Function Analyzer?

Specify this analyzer when a rapid, simple screen is needed before confirmatory aggregation studies, or when monitoring antiplatelet therapy with a standardised method. In the RFQ confirm the cartridge menu and shelf life, the reference interval study supplied, the hematocrit and platelet count limits, and the expected rate of non-closure results.

How does it compare with other Platelet Analyzers variants?

Choose the method according to the clinical question. Light transmission aggregometry is the classical approach and allows a full agonist panel, while impedance aggregometry accepts whole blood and is less affected by low platelet counts and lipemia. Luminescence aggregometry adds dense granule storage pool assessment. High-shear closure time systems are simple to operate and useful for screening and for monitoring antiplatelet therapy, but they give limited mechanistic information. Consider sample volume, which matters for pediatric patients, the number of channels available per run, and the reagent or agonist supply. Confirm whether your laboratory can maintain proficiency in interpretation, because aggregation curves require experience, and take part in external quality assessment where a scheme exists.