Impact-R is a cone and plate analyzer which tests platelet function under arterial flow conditions. It can detect defects in platelet adhesion, extension and aggregation such as can be seen in platelet storage pool diseases like a-SPD and s-SPD.

What is d-SPD?

Platelet.

Storage pool disease involving the dense granules was first described in 1972. On Wright-stained smears, the platelets are morphologically normal but are shown to lack d-granules on EM (electron microscopy).  Since these granules are the storage sites for serotonin, ADP and ATP, their lack also means a lack of the said substances.  ADP and ATP are enhancers of platelet aggregation by activation of more platelets which in turn release their dense granule substances and recruit more platelets. Low levels of platelet ADP, ATP result in bleeding diathesis. Examples of bleeding are: easy bruising, epistaxis, post-surgical bleeding, heavy menstrual bleed.

Use of Impact-R in the Diagnosis of d-SPD

Recent studies of platelet adhesion under high-shear stress have been done on patients with d-SPD. One of these is the Impact-R machine. They show a reduced secondary wave of aggregation when stimulated by ADP, epinephrine or thrombin.

Impact-R may be used in platelet function studies of patients with Storage Pool Disease.

Platelet Storage Pool Disease(SPD) involves disorders with reduction in the number and contents of platelet granules. These may be a-granules, d-granules, or a combination of both. The most common of which is d-SPD, and  the rarest is ad-SPD. The Gray Platelet Syndrome is an a-SPD where there is severe reduction of the number and contents of a-granules. The defect can be

Hermansky-Pudlak syndrome.

of two modalities, one wherein the SPD is restricted to the platelets and another where it is part of systemic syndromes with defective assembly and packaging of granules. An example would be Hermansky-Pudlak syndrome where the patient has oculocutaneous albinism, bleeding disorders, and cellular storage disorders.

SPD is an autosomal recessive trait but can also be an acquired disorder.  It may be seen in patients with myeloproliferative disorders, myelodysplasia, acute leukemia, and even systemic lupus erythematosus (SLE).  Treatment is supportive, and may involve platelet transfusions.

IMPACT-R is a cone and plate analyzer that can be used for the study of platelet function, either hyper- or hypo-function. It is an important screening tool for platelet abnormalities and may be used as a monitoring tool for therapeutic response in patients being treated.