LEC 15 BLOOD TESTS

How is hemoglobin concentration derived?

Hemoglobin is converted to cyanmethemoglobin with Drabkin's reagent, then measured in a photometer at 540 nm.

Hematocrit is a ratio of ___ over ___.

Volume of RBCs over volume of whole blood.

What is red blood cell (RBC) count?

A count of the actual number of red blood cells per volume of blood.

Define WBC count.

A count of the actual number of white blood cells per volume of blood.

True or False? An increase or decrease in WBCs can be significant.

True

Define white blood cell differential.

It identifies the types of white blood cells present.

How many different types of WBC are there?

Five

What does Hemoglobin (Hgb) measure?

The amount of oxygen-carrying protein in the blood.

What does Hematocrit (Hct) measure?

The percentage of red blood cells in a given volume of whole blood.

What is a quick screening test for anemia?

The hematocrit test.

How is the hematocrit test performed?

A drop of blood is drawn into a small glass capillary tube and centrifuged to pack the red blood cells at the bottom with plasma on top.

What does hematocrit measure?

The percentage of blood volume that consists of erythrocytes.

What is the ratio of the hematocrit?

The ratio of packed red blood cells to total blood volume.

What percentage is a normal hematocrit?

About 45% (46% for men and 38% for women).

What is a measurement of the average size of your RBCs?

Mean corpuscular volume (MCV).

What is elevated when RBCs are larger than normal?

Mean corpuscular volume (MCV).

What is the term for larger than normal RBCs?

Macrocytic.

Name one condition where MCV is elevated.

Anemia caused by vitamin B12 deficiency.

What is the term for smaller than normal RBCs?

Microcytic.

What is a calculation of the average amount of oxygen-carrying hemoglobin inside a red blood cell?

Mean corpuscular hemoglobin (MCH).

What is a calculation of the average concentration of oxygen on the hemoglobin molecules inside a red cell?

Mean corpuscular hemoglobin concentration (MCHC).

What is the term for decreased MCHC values?

Hypochromia.

What is the term for increased MCHC values?

Hyperchromia.

What is a calculation of the variation in the size of your RBCs?

Red cell distribution width (RDW).

What is platelet count?

The number of platelets in a given volume of blood.

What can thrombocytophilia and thrombocytopenia indicate?

Both increases (thrombocytophilia) and decreases (thrombocytopenia) can indicate abnormal conditions of excess bleeding or clotting.

What is Mean Platelet Volume (MPV) and how does it relate to the age of platelets?

MPV is the average size of platelets. New platelets are larger, so an increased MPV indicates increased platelet production.

What are the uses of PT and PTT tests, and which coagulation factors do they evaluate?

PTT investigates unexplained bleeding or clotting and evaluates all coagulation factors except factor VII. PT evaluates factor VII.

How is heparin used as anticoagulant drug therapy?

• Heparin is given IV or by injection

• prevents and treats blood clots

• PT/PTT are used to monitor therapy

  • too much = excessive bleeding

  • too little = continued clotting

What primary diseases are monitored by a CBC, and what are the parts of a Complete Blood Count (CBC)?

CBC screens for anemia, infection, and many other diseases. It includes: WBC count, WBC differential, RBC count, hemoglobin, hematocrit, MCV, MCH, MCHC, RDW, and platelet count. PT and PTT are separate tests.