Laboratory Investigation Of Anemia

LAB. INVESTIGATIONS OF ANEMIA

1)Hematologic

•       Hb

•       Hematocrit/PCV

•       Red cell count

•       Red cell indices: MCV, MCH, MCHC,RDW

•       Reticulocyte count

•       Red cell morphology on a stained peripheral smear

•       Differential leucocyte count

•       Platelet number and morphology

•       Leucocyte count

•       ESR

•       Bone marrow evaluation, bone marrow iron

•       Serum iron, ferritin and trasferrin saturation

•       Other investigations for hemolytic anemias

2) urinalysis

•       Color, pH, specific gravity

•       Protein, sugar, ketones

•       Bilirubin, urobilinogen

•       Hb in urine                                                                 

•       Microscopic examination for red cells hematuria

3) STOOL

•       Occult blood

•       Examination for ova and cysts

•       4) OTHERS

•       Blood urea nitrogen, S. creatinine

•       S. bilirubin, SGOT, SGPT, S.  Alkaline phosphatase

•       Chest X- ray

•       Barium studies for GIT lesions in esophagus/stomach/small intestine/large intestine depending upon history and clinical features.

•       USG abdomen for any lump, kidneys, spleen and liver.

•       CT/MRI scan in suspected malignancies.

Hemoglobin:

•       Low Hb value is pathognomonic of anemia but does not give information regarding etiology.

•       Further investigations- required to discover cause of anemia.

•       PCV/ Hct: Measures percentage of volume of blood occupied by red blood cell.

•                   Normal :40-55% in males

•                                 :35-48% in females

Red cell count:

•        An estimation of number of red cells present in 1ml of whole blood.

•       Normal red cell count varies according to age and sex.

•                               5.4±1.0 million/ cu mm in men

•                               4.8±1.0 million/ cu mm in women

RED CELL INDICES

1) Mean cell volume (MCV):

•        Measurement of average size of red cells. Normal range: 80-99fl.

•       MCV=Hct(%) X10

                         RBC count

•       A reduced MCV is termed microcytosis.

•       An increased MCV- macrocytosis.

2) MCH( Mean corpuscular hemoglobin):

•       Amount of Hb per red cell.

•       MCH=Hb (g/dl) x10

•                    RBC count

•       Normal range:26-34 pg

•       Higher MCH-Macrocytic anemia (because macrocytes are larger and carry more Hb)

•       Lower MCH-Microcytic hypochromic anemias

3) MCHC (Mean corpuscular hemoglobin concentration):

•       Average concentration of hemoglobin in red cells.

•       MCHC=HbX100

•                     Hct

•       Normal range: 31-37 g/dl

•       <31 g/dl: hypochromic red cells

•       >37 g/dl: hyperchromic red cells but usually red cells do not have more Hb.

4) Red cell distribution width:

•       Measures variation of RBC width; as part of a standard complete blood count.

•       Red blood cells-standard size: 6–8 μm.

•       Higher RDW values indicate greater variation in size.

•       Normal range: 11–15%.

•        RDW = (Standard deviation of MCV ÷ mean MCV)                 × 100

•       If anemia is observed, RDW test results are used together with MCV results to determine possible causes of anemia.

•       Mainly used to differentiate anemia of mixed causes from an anemia of a single cause.

•       Vitamin B₁₂deficiency-macrocytic anemia with normal RDW. However, iron deficiency anemia initially presents with a varied size distribution of red blood cells, and shows increased RDW.

•       In mixed iron and B₁₂ deficiency, there will be mix of both large cells and small cells, causing RDW elevated.

Reticulocyte count

•       Normal red cells undergo maturation process within bone marrow. During this process cells shed their nuclei and all cytoplasmic structures concerned with protein synthesis (a mature RBC cannot synthesize proteins).

•      A small percentage of relatively immature RBCs-normally present in circulating blood. These have shed their nuclei but still retain RNA-known as reticulocytes.

•       Useful indirect index of marrow erythropoiesis (red cell formation).

•       Reticulocytes in routine blood film as large, slightly blue-staining RBCs-polychromatic; polychromatophilia: indicator of high rectic count in peripheral smear.

•       To count reticulocytes requires a special stain-Briliant cresyl blue stain.

•       Manual counts (by microscopy)-reported as percentages (of all RBCs).

•       Reticulocyte%:No. of reticulocte in “n” fieldsX100

           Total no. of RBCs in “n” fields

•       Normal range: 0.2-2%

•       New borns: 2-6%

High retic count:

            -hemolytic anemias

            -following therapy to iron/folic acid/vit b12 deficiency anemias, reflects marrow response to hematinics.

Low retic count:

            -aplastic anemia

            -pure red cell aplasia

•       Red cell morphology on a stained peripheral smear-Already discussed.

•       Differential leucocyte count.

•       ESR: Erythrocyte sedimentation rate is the rate at which red blood cells sediment in a period of 1 hour.

            1) Westergren:0-15 mm 1^st hour, 0-20 mm 1^st hour.

            2) Wintrobe: 0-7 mm 1^st hour, 0-14 mm 1^st hour.