ESR, PCV ( Haematocrit), and absolute values Physiology lab7 ESR, PCV ( Haematocrit), and absolute values

The erythrocyte sedimentation rate (ESR): Is a measure of the settling of red blood cells in a tube of blood during one hour. The rate is an indication of inflammation and increases in many diseases.

Mechanism of ESR: Fall of RBCs depends on the following factors: Rouleaux formation: the erythrocytes sediment in the tube because their density is greater than that of plasma. Concentration of fibrinogen in plasma. Concentration of α and β globulins. Length of the tube. Ratio of RBCs to plasma. Bore of the tube. Position of the tube.

Phases in ESR: ESR takes place in the following 3 phases which are carried in one hour: Phase of rouleaux formation: initial period of 10 minutes, and there is little sedimentation. Phase of settling: in the next 40 minutes, settling of RBCs occurs at constant rate. Phase of packing: in the last 10 minutes sedimentation slows and packing of the RBCs to the bottom occurs. That is why ESR by all methods is expressed as mm/ first hour

Methods of ESR: Westergren’s method. Wintrobe’s method. Micro ESR method. The result of an ESR is reported as the millimeters of clear fluid (plasma) that are present at the top portion of the tube after one hour (mm/hr).

Description The ESR test is a simple test. A specific amount of diluted, unclotted blood is placed in a special narrow tube and left undisturbed for exactly one hour. The red cells settle towards the bottom of the tube, and the pale yellow liquid (plasma) rises to the top. After 60 minutes, measurements are taken of the distance the red cells traveled to settle at the bottom of the tube. Most laboratories use the Westergren method. Normally red cells don't settle far toward the bottom of the tube. Many diseases make extra or abnormal proteins that cause the red cells to move close together, stack up, and form a column (rouleaux). In a group, red cells are heavier and fall faster. The faster they fall, the further they settle, and the higher the ESR.

ESR is said to be a non-specific test because an elevated result often indicates the presence of inflammation but does not tell the health practitioner exactly where the inflammation is in the body or what is causing it. An ESR can be affected by other conditions besides inflammation. For this reason, the ESR is typically used in conjunction with other tests, such as C-reactive protein. ESR is used to help diagnose certain specific inflammatory diseases, temporal arteritis, systemic vasculitis and polymyalgia rheumatica. A significantly elevated ESR is one of the main test results used to support the diagnosis This test may also be used to monitor disease activity and response to therapy in both of the above diseases as well as some others, such as systemic lupus erythematosus (SLE).

A low ESR can be seen with conditions that inhibit the normal sedimentation of red blood cells, such as a high red blood cell count (polycythemia), significantly high white blood cell count (leukocytosis), and some protein abnormalities. ESR and C-reactive protein (CRP) are both markers of inflammation.

Westergren method: Westergren pipette is a straight pipette 30 cm long , open at both ends with internal bore diameter of 2.5 mm, and calibrated from 0-200 mm from top to bottom. Anticoagulant Trisodium citrate as 3.8/dl liquid is used. It is used in concentration of 1:4 ( 4 parts of blood added to one part of anticoagulant). Take 1.6 ml of patient blood and mix with 0.4 ml of citrate. Fill the tube up to mark 0 with the help of rubber teat. Fix it in a rack vertically and let it stand for 1 hour . The reading is taken at the upper meniscus of the RBCs .

Normal values: Males 3-5 mm/ 1st hour. Females 4-7 mm/1st hour.

Packed cell volume (PCV) or haematocrit: Defined as : Ratio of volume of RBCs to that of whole blood and is expressed as percentage. Methods: Macro – method (Wintrobe method) Micro-method Electronic method.

Macro ( Wintrobre ) method: In this method PCV is measured by tube which has a length of 110 mm and internal bore of 2.5 mm and graduated from 0-10 cm on both directions. Fill the tube up to mark 10 cm with well mixed anticoagulated blood (EDTA). Centrifuge the tube at 2000-2300 g for 30 minutes. Note the lower most height of column layer of RBC and express it as percentage.

mean corpuscular volume, or mean cell volume (MCV) :is a measure of the average volume of a red blood corpuscle (or red blood cell). The measure is attained by multiplying a volume of blood by the proportion of blood that is cellular (the hematocrit), and dividing that product by the number of erythrocytes (red blood cells) in that volume. In patients with anemia, it is the MCV measurement that allows classification as either a microcytic anemia (MCV below normal range), normocytic anemia (MCV within normal range) or macrocytic anemia (MCV above normal range).

Normally, MCV is expressed in femtoliters (fL, or 10−15L), and [RBC] is the quantity expressed in millions per microliter (106 / μL). The normal range for MCV is 80–100 fL.

mean corpuscular hemoglobin (MCH), or "mean cell hemoglobin" (MCH) : is the average mass of hemoglobin per red blood cell in a sample of blood. It is calculated by dividing the total mass of hemoglobin by the number of red blood cells in a volume of blood. MCH=(Hgb*10)/RBC A normal value in humans is 27 to 31 picograms/cell. It depends on hemoglobin synthesis. It decreases when Hb synthesis reduces

Mean corpuscular hemoglobin concentration: a measure of the concentration of hemoglobin in a given volume of packed red blood cells. It is calculated by dividing the haemoglobin by the haematocrit. Reference ranges for blood tests are 32 to 36 g/dL