Reference Values

Collagen/epinephrine (C/Epi):  80-180 seconds

Collagen/ADP (C/ADP):  60-120 seconds

If the C/Epi is normal, then platelet function is interpreted as normal. If the patient history or physical examination are suggestive of a bleeding disorder, than repeat testing for confirmation is indicated. If repeat test is still normal and there is a high suspicion for a bleeding disorder, suggest performing further testing as discussed below. Normal PFA-100® test results do not exclude disorders of primary hemostasis (including platelet function abnormalities) or secondary hemostasis. If the PFA-100® results suggest aspirin ingestion (prolonged C/Epi but normal C/ADP) and history confirms this, the physician should make the determination whether or not to proceed with surgery. The presence or magnitude of the PFA-100® abnormality is not necessarily related to the probability of bleeding during surgery. If the C/Epi and C/ADP closure times are prolonged, the results are consistent with abnormal platelet function. However, thrombocytopenia (<150 K) and anemia (hematocrit <35%) should first be excluded. If platelet count and hematocrit are normal, the abnormal PFA-100® results indicate an abnormality of platelet function that should be followed up. Note, however, that some patients taking long-term aspirin may also have a modest prolongation of the C/ADP time. The most common causes of an abnormal C/ADP test are heart valve disease, severe vessel stenosis, renal failure, or von Willebrand disease. If there is no clinical or laboratory explanation (anemia, thrombocytopenia, cardiovascular disease, or renal disease) for the prolonged C/Epi and C/ADP, then surgery should be postponed, if possible, until the underlying reason for the abnormality is determined.

Numerous drugs can prolong the PFA-100® results and may be associated with clinical bleeding including aspirin and other non-steroidal anti-inflammatory drugs and antiplatelet drugs. However, please note that PFA-100® testing is not reliable and is not indicated for detecting the platelet effect of drugs such as Plavix®. Myriad other drugs can prolong the PFA-100® result but are usually not associated with bleeding.

Interfering Substances:

Conditions and substances, in addition to aspirin and anti-glycoprotein IIb/IIIa antagonists, include low hematocrit, low platelet count, hemolysis, and blood specimen with increased sedimentation properties, as in severe sepsis, chemotherapy, hemodiluted specimen obtained during cardiopulmonary bypass, etc.