Iron Studies
Ferritin:
An iron storage protein. Serum levels usually correlate with tissue iron stores. Should be decreased in iron deficiency and normal to increased in the anemia of chronic disease. Serum ferritin levels can be elevated by inflammatory states and thus not accurately reflect tissue stores.
Serum iron:
Just like it sounds. Should be low in iron deficiency but also low in the anemia of chronic disease.
TIBC (total iron binding capacity):
A measure of iron binding capacity in serum. This essentially measures transferrin activity. Should be elevated in iron deficiency and decreased to normal in the anemia of chronic disease.
Coagulation Studies
Platelet aggregation studies:
When a functional platelet defect is suspected with a normal platelet count, you can assess platelet function by measuring aggregation after stimulation with various agents. In this way you can study qualitative platelet defects.
PT (prothrombin time):
The coagulation system in patient plasma is activated using tissue factor. This activates factor VII of the extrinsic pathway, and the test measures the time required to generate a fibrin clot. Coumadin affects vitamin K dependent factors including factor VII. Thus, Coumadin prolongs the pro-time and the PT is used to monitor Coumadin anticoagulation.
PTT (partial thromboplastin time):
The coagulation system in patient plasma is activated by a reactive surface like kaolin. This activates factor XII and then proceeds through the intrinsic pathway. The test measures time from kaolin being added to a fibrin clot formed. Heparin inactivates factors IXa and Xa and thus prolongs the PTT.
Heparin anticoagulation is monitored with the PTT.
Hemolysis Studies
Bone marrow aspirate and biopsy
After local anesthesia (Novocaine) and a bullet to bite on, a needle is placed in the marrow space - usually the posterior iliac spine. Marrow cells are aspirated and a core biopsy sample (approximately one inch long with a diameter of pencil lead) are obtained. Despite what you hear, it’s not that bad. Total procedure takes about 30 minutes and is performed in the outpatient clinic.
Coombs test:
This tests for antibodies directed against red cell surface antigens. The direct test starts with patient red cells which may have antibodies stuck on them. A crosslinking anti-antibody (Coombs reagent) is added and the test looks for red cells to clump. Clumping confirms antibody on the surface of the cell. The indirect test starts with patient serum which may have anti-red cell antibody in it. This is mixed with normal red cells then the crosslinking anti-antibody (Coombs reagent) is added and clumping is looked for.
Hemoglobin electrophoresis
Hemoglobin can be electrophoresed in a gel and its movement in the gel is a function of size and charge of the molecule. Alteration of amino acids in the globin chains can alter the migration of hemoglobin through a gel. Normal hemoglobin A can be distinguished from hemoglobin S and other abnormal hemoglobins with this method.
LDH (lactate dehydrogenase):
This enzyme is located in many tissues including a fair concentration in red cells. Thus in hemolysis, LDH is released and serum LDH rises. As LDH lives in many tissues, elevation of serum LDH is NOT specific for hemolysis.
Reticulocyte count:
Reticulocytes are "new" red blood cells in the circulation. Non-extruded material in new red cells stains with methylene blue and is the basis of the assay. In hemolytic processes, there is an increased red cell production and thus an increased reticulocyte count.
Reticulocyte index:
Sure the reticulocyte count is a little high, but is it appropriate for the level of anemia? To correct for the degree of anemia, the reticulocyte count is multiplied by the patient hematocrit over normal hematocrit. The resulting number is the reticulocyte index. A value of less than one is consistent with inadequate marrow response to anemia. A value of 1 to 3 is an appropriate marrow response to anemia. A value of greater than 3 is an excessive response to anemia as occurs in hemolysis.
Schilling test
In this test, you are trying to determine the reason someone is B12 deficient. It does not make the diagnosis of B12 deficiency but may provide clues as to how B12 deficiency developed.
Parenteral B12 is injected to saturate all serum B12 binding sites. Next, a labeled oral dose of vitamin B12 is taken. If the B12 is absorbed, it finds all serum binding sites filled and is excreted in the urine. Thus the urine is collected for the next 24 to 48 hours and urine radioactivity is measured. If more than 10% of the oral dose of radiolabeled B12 comes out in the urine, normal GI absorption has occurred. If poor GI absorption is found, you can see if adding intrinsic factor to the oral labeled dose will correct absorption, etc.
Serum and erythrocyte folate
The serum level of folate rapidly changes with folate ingestion and absorption. Thus, someone who is folate deficient and eats a healthy meal just before you draw the test may have a normal level. Red cell folate levels do not change quickly and reflect the folate level during the red cell life span (120 days).
Serum B12
Just like it sounds. Serum B12 levels usually accurately reflect body stores. They do not change quickly like folate levels can.
Serum haptoglobin:
Haptoglobin is a hemoglobin binding protein. It binds free hemoglobin in the bloodstream and carries it to the liver for catabolism. In hemolysis, the serum haptoglobin level is low.
Total and direct bilirubin:
In hemolysis, the hemoglobin being released is catabolized to bilirubin. This bilirubin is usually unconjugated (indirect). In hemolysis we expect that the total bilirubin is elevated and that the majority of bilirubin is indirect.