Here is the latest update on Yasser Arafat:

Yasser Arafat underwent medical tests on Saturday and a senior Palestinian official said doctors had ruled out for the time being that the PLO leader was suffering from leukemia . . .

Palestinian officials said the first of a battery of tests for cancers and other disorders showed no immediate risk of the 75-year-old dying. They said a full analysis could take until as late as Wednesday . . .

Arafat went into the French hospital with an abnormally low count of blood platelets — a condition that can be caused by leukemia — but the number of platelets had since doubled, a Palestinian official said . . .

There are many causes for a low platelet count – otherwise known as thrombocytopenia. The normal platelet count in adults ranges from 150,000 to 450,000/microL – thrombocytopenia is defined as a platelet count less than 150,000/microL.

A complete blood count (documenting the low platelet count as well as the counts for the other blood lines) and a peripheral smear are the initial tests. The diseases to rule out immediately are thrombotic thrombocytopenic purpura-hemolytic uremic syndrome and acute leukemia – each of these diseases require relatively rapid treatment.

Causes of low platelets involve decreased production (acute leukemia, bone marrow invasion with tumor or fibrosis, myelodysplastic state, vitamin B12 or folic acid deficiency) or increased destruction (disseminated intravascular coagulation (DIC), chronic lymphocytic leukemia, or Hodgkin’s disease).

A presumptive diagnosis of idiopathic thrombocytopenic purpura (ITP) is made when the history, physical examination, complete blood count, and examination of the peripheral blood smear do not suggest other etiologies for the low blood count. If this is the case, treatment is normally with steroids or intravenous immune globulin.

The most comprehensive test would be bone marrow aspiration and biopsy, and I’m sure this test will be done if not already. We’ll see in the coming days.