Q. I am in my 70s. Every year when I go for my yearly physical examination, my blood test results come back that my platelets are "clumped," so they have a hard time getting an accurate count on them. Several years ago, they sent the sample of the platelets to a dermatologist who said they appear normal. Is there something I can take to help this clumping?
A. Before describing the role of platelets in both health and disease, I need to indicate that the specialist who should be looking at blood is a hematologist, not a dermatologist.
The prevention of bleeding is a complicated process. First, when there is a penetrating injury to a blood vessel, the vessel itself constricts so blood flows out more slowly. Also, the blood outside the vessel at the injury site presses against the wound and further reduces blood flow.
At the same time, blood clotting factors or proteins like collagen, thrombin and fibrinogen arrive at the injury site and begin "activating" platelets.
Platelets, also called thrombocytes, are the small cells in the bloodstream there to help stop bleeding.
When the platelets are activated by the proteins, they change their shape from round to spiny, stick to each other and to the damaged vessel wall and begin to plug the break. Fibrin forms a net in and around this clot to entrap still more platelets and red cells.
After the blood vessel has been plugged, other proteins activate to stop the clotting process and dissolve the clot as the injury heals. Both platelets and blood vessel wall cells secrete chemicals that inhibit platelet clotting.
Obviously, any problem in this delicately balanced "hemostatic" process is going to cause trouble. When clotting doesn't proceed normally, even a minor blood vessel injury can result in a substantial loss of blood (hemorrhage) or blood clots can form that cut off blood flow.
Hemorrhage can be due to a deficiency of platelets (e.g., thrombocytopenia); malfunctioning platelets (e.g., Von Willebrand's disease); deficiency in one of the clotting proteins (e.g., hemophilia); or a depletion of clotting proteins. Hereditary factors, drugs and abnormal autoimmune reactions also can play a part.
Sometimes, though, there's too much clotting. Platelets may adhere to blood vessel walls that are only slightly damaged. High blood pressure, high serum cholesterol or smoking seem to increase this happening. This aggregation can cause vascular blockage and contribute to thromboses, strokes and heart attacks.
This hypercoagulability is usually the result of an imbalance of the clotting factors or proteins, but it can be caused by some cancer, inflammatory disorders and congenital deficiency of proteins as well.
All this is not to say that the clumping seen in the blood tests of your exams will result in this level of vascular problems for you. The fact that you've had clumping for some time without other symptoms and your platelets were found to be normal suggests a milder complication.
Nevertheless, I would pursue answers. If the problem is with coagulability, anticoagulants like aspirin or warfarin may be appropriate. A recent study suggests that garlic (raw is more potent than cooked) significantly inhibits human platelet aggregation.
Write to Dr. Douma in care of the Chicago Tribune, Room 400, 435 N. Michigan Ave., Chicago, IL 60611.