Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1185 page)

   Combined abnormal PT and PTT is found under two circumstances:

   Medical: administration of oral anticoagulants, DIC, liver disease, vitamin K deficiency, massive transfusions

   Coagulation factor abnormalities: dysfibrinogenemias; factors V, X, and II defects

   Limitations

   Preanalytic errors:

   Partially clotted specimens due to poor mixture with the anticoagulant (3.2 sodium citrate, as offered by manufacturers’ blue top vacuum tubes)

   Over- or underfilled test tubes, altering the ratio of blood (9 parts) to anticoagulant (1 part)

   Analytic errors: Hemolyzed, lipemic, or icteric plasma may interfere with photoelectric measuring instruments (assay may have to be repeated on a mechanical clot measuring instrument)

PYRUVATE KINASE (PK), RED BLOOD CELL

   Definition

   PK is an enzyme involved in glycolysis. Genetic defects of this enzyme cause the disease known as PK deficiency. This deficiency is one of the most common enzymatic defects of the erythrocyte. The disorder manifests clinically as a hemolytic anemia, and the symptomatology is less severe than hematologic indices indicate. The clinical severity of this disorder varies widely, ranging from a mildly compensated anemia to severe anemia of childhood. Most affected individuals do not require treatment. Individuals who are most severely affected may die in utero of anemia or may require blood transfusions or splenectomy, but most of the symptomatology is limited to early life and to times of physiologic stress or infection.

   
Normal range:
9.0–22.0 U/g Hb.

   Use

   Evaluation of nonspherocytic hemolytic anemia