Interpretation of Common Investigations LC Gupta, Abhishek Gupta, RD Chauhan
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SECTION 1

Blood1

The interpretation of investigations in haematology is better grasped with a little knowledge of the basic procedures and principles of various tests.
 
HAEMOGLOBIN ESTIMATION
In modern times of automation age-old Sahli’s method of haemoglobin estimation still has relevance and deserves a description. Sahli’s acid haematin method for estimation of haemoglobin is based on the principle of converting haemoglobin of blood to acid haematin by adding acid. Acid haematin is coloured. The intensity of the colour of solution is compared with a comparator by diluting the solution with water. The Sahli’s haemoglobinometer consists of a comparator, a haemoglobin tube, a stirrer and a haemoglobin pipette that sucks up 0.02 ml of blood till the specified mark on it.
The haemoglobin tube is filled up to mark 20 with N/10 HCl and the blood filled till the specified mark is expelled into the dilute HCl in the tube. Acid haematin is allowed to be formed from 10–40 minutes and the solution is stirred up occasionally. The acid haematin formed is diluted with distilled water drop by drop until its colour matches with2 he coloured columns provided on either side. The Hb reading is taken on the gm percent scale on the haemoglobin tube. If the Hb concentration is less than 2 gm percent then double the amount of blood can be taken and the ultimate result halved to get the actual concentration.
 
Cyanmethaemoglobin Method
The method is more reliable than Sahli’s method, since it does not require viewer’s judgement. Here the intensity of colour produced is compared by measuring its optical density by colourimeter. In 5 ml of Drabkin’s solution 0.02 ml of blood is added. The tube is shaken and allowed to stand for 10–30 minutes for Cyanmethaemoglobin to form. Later the optical density is read against a Drabkin’s blank set to zero at wavelength 540. At the same time OD of a standard solution is also taken and thereby Hb concentration of the unknown is calculated.
 
Haemoglobin Colour Scale
A new method for haemoglobin estimation has been developed which is like the strip test used for urine examination. It is being used in western countries.
It is a simple, reliable tool developed by WHO which allows screening for anaemia. It is convenient and easy to perform. The test consists of a small card with six shades of red, representing haemoglobin levels at 4,6,8,10,12 and 14 g/dl and a test strip (Fig. 1.1).
The test is performed by placing a blood drop on the test strip, waiting 30 seconds and then compare the colour of the blood spot against one of the hues on the scale.3
zoom view
Fig. 1.1: Haemoglobin colour scale strip test for haemoglobin estimation
Internationally validated, the test has a sensitivity of 95 percent and a specificity of 99.6 percent in severe anaemia.
Haemoglobin
Normal values:
12–18 gm percent
Adult males
14–18 mg percent
Adult females
12–16 mg percent
The values are lowered in anaemias and raised in polycythaemia.
 
NORMAL BLOOD CELL COUNTS
A haemocytometer is used to do TLC, RBC and platelet counts. When seen under low power, the new improved Neubauer’s chamber shows a large square with 3 mm sides. This is further subdivided into 9 smaller squares (each 1 mm square in area), except for the central all4 others are subdivided into 16 smaller squares. The central (1 mm square) square is divided into 25 equi-dimensional squares. The 4 corner (1 mm square) squares are used for TLC count. The corner squares and the central square of the 25 equi-dimensional squares are used for RBC and platelet counts.
The other components of a haemocytometer are a thick cover slip which when kept at the appropriate place over the counting region of the chamber provides a chamber depth of 1/10 mm. In addition, there are 2 pipettes:
 
TLC
EDTA anticoagulated blood is used and pipette is filled with shaken (well mixed) blood till 0.5 mark. Next the WBC diluting fluid is sucked up to 11 mark. The pipette is then gently shaken or rolled to allow proper mixing and dispersal of cells in it. Keep in mind that blood mixing has occurred in the bulb only and not in the proximal tube of the pipette so while charging the chamber, discard few initial drops that come out, care must be taken not to spill the diluted blood over the cover-slip or overcharge the chamber. After charging the chamber, let the cells settle and count after a couple of minutes. Reduce the light intensity reaching the chamber and count using the low power objective. The stained nuclei of the WBC’s would be visible. The pattern of counting should be 5uniform so that no cell is counted twice or more number of times. Multiply the number of cells counted with 50 (the dilution factor) to obtain cell count per cubic mm of blood. An absolute increase in total leukocytes is referred to as leukocytosis.
Normal total leucocyte count
4000 to 11000/ cu. mm of blood.
 
WBC Count-Interfering Factors
  1. In newborn and infants count is high values reaches at normal at puberty.
  2. Physical activity, food, pain and emotional disturbance will slightly increase the count.
  3. Chronic leukaemia may decrease the count.
  4. Early morning values are low during evening hours are high.
 
RBC Counts
The normal RBC counts of 4.5 to 5.5 are difficult to measure accurately by routine methods. Therefore these counts are not being asked for in routine cases. The use of Blood Cell Counter has to larger extent reduced the problem of accurate counting. For routine testing fill the RBC pipette with thoroughly but gently shaken blood till the 0.5 mark and after cleaning the tip of the pipette with a cotton swab, fill till the 101 mark with RBC diluting fluid. Gently roll the pipette bulb to ensure proper mixing of contents. As for TLC, discard the first 5–8 drops and then charge the chamber. Count the number of red cells as described earlier and multiply by 6dilution factor, viz. 10,000 to get the RBC count in million/cubic mm of blood.
Normal RBC counts
Men
4.5 to 5.6 millions/cu. mm.
Women
3.9 to 5.6 millions/cu. mm.
 
RBCs-Interfering Factors
  1. i.In lying position count is low
  2. Excitement and exercise raises the count
  3. Count is highest in morning then falls with in 2–4 months and reaches at peak at the age of 14
  4. At high altitude count is higher.
 
Haemoglobin-Interfering Factors
  1. It increases at higher altitude in children
  2. Excessive fluid intake and in pregnancy count will be low
  3. Gentamycin and methyldopa increases the values.
 
PLATELET COUNTS
 
Definition
A platelet count is a diagnostic test that determines the number of platelets in the patient’s blood. Platelets, (thrombocytes), are produced in the bone marrow and involved in the process of blood clotting. Normal level in peripheral blood is 150,000–450,000 /ml. Low platelet counts or abnormally shaped platelets are associated with bleeding disorders. High platelet counts sometimes indicate disorders of the bone marrow.7
 
Purpose
The counts are usually asked for, to assist in the diagnosis of bleeding disorders and to monitor patients who are being treated for any disease involving bone marrow failure. Patients who have leukaemia, polycythaemia vera, or aplastic anaemia are given periodic platelet count tests to monitor their health.
Signs of bleeding due to a low platelet count include:
  • Easy bruising
  • Haematuria
  • Black, tar-like stools or frank bleeding with bowel movements
  • Haematemesis
  • Syncope or visual disturbances due to intracranial bleeding
  • Gingival bleeding
  • Heavy vaginal bleeding
  • Unusual or heavy nosebleeds
 
Technique
Platelet counts use a freshly collected blood specimen to which EDTA has been added to prevent clotting before the test begins. About 5 ml of venous blood is drawn. Venous blood helps to produce a more accurate count than blood drawn from a fingertip.
After collection, the mean platelet volume of EDTA-blood will increase over time. This increase is caused by a change in the shape of the platelets after removal from the body. The changing volume is relatively stable for a period of one to three hours after collection. This period is the best time to 8count the sample when using electronic instruments, because the platelets will be within a standard size range.
 
Counting Methods
Platelets can be observed in a direct blood smear for approximate quantity and shape through a light microscope. Accurate assessment of the number of platelets requires other methods of counting. There are three methods used to count platelets; haemocytometer, voltage-pulse counting, and electro-optical counting.
 
Haemocytometer Counting
The microscopic method uses a phase contrast microscope to view blood on a haemocytometer slide. A sample of the diluted blood mixture is placed in a haemocytometer, with a grid etched into its surface to guide the counting. For a proper count, the platelets should be evenly distributed in the haemocytometer. Counts made from samples with platelet clumping are considered unreliable. Clumping can be caused by several factors, such as clotting before addition of the anticoagulant and allowing the blood to remain in contact with a capillary blood vessel during collection. Errors in platelet counting are more common when blood is collected from capillaries than from veins.
 
Electronic Counting
Electronic counting of platelets is the most common method. There are two types of electronic counting, voltage-pulse and 9electro-optical counting systems. In both systems, the collected blood is diluted and counted by passing the blood through an electronic counter. The instruments are set to count only particles within the proper size range for platelets. The upper and lower levels of the size range are called size exclusion limits. Any cells or material larger or smaller than the size exclusion limits will not be counted. Any object in the proper size range is counted, however, even if it isn’t a platelet. For these instruments to work properly, the sample must not contain other material that might mistakenly be counted as platelets. Electronic counting instruments sometimes produce artificially low platelet counts. If a platelet and another blood cell pass through the counter at the same time, the instrument will not count the larger cell because of the size exclusion limits, which will cause the instrument to accidentally miss the platelet. Clumps of platelets will not be counted because clumps exceed the upper size exclusion limit for platelets. In addition, if the patient has a high white blood cell count, electronic counting may yield an unusually low platelet count because white blood cells may filter out some of the platelets before the sample is counted. On the other hand, if the red blood cells in the sample have burst, their fragments will be falsely counted as platelets.
 
Important
Because platelet counts are sometimes ordered to diagnose or monitor bleeding disorders, patients with these disorders should be cautioned to watch the puncture site for signs of additional bleeding.10
 
Normal Results
The normal range for a platelet count is 150,000–450,000 platelets per ml of blood.
 
Abnormal Results
An abnormally low platelet level (thrombocytopenia) may result from increased destruction of platelets, decreased production, or increased usage of platelets. In idiopathic thrombocytopenic purpura (ITP), platelets are destroyed at abnormally high rates. Hypersplenism is characterized by the collection (sequestration) of platelets in the spleen. Disseminated intravascular coagulation (DIC) is a condition in which blood clots occur within blood vessels in a number of tissues. All of these diseases produce reduced platelet counts.
 
Thrombocytopenia (Below 150,000/cumm)
  • Idiopathic thrombocytopenic purpura
  • Leukaemia (Usually acute leukaemias)
  • Aplastic anaemia
  • Multiple myeloma
  • Hypersplenism
  • Drug reactions
  • Megaloblastic anaemia.
Abnormally high platelet levels (thrombocytosis) may indicate either a benign reaction to an infection, surgery, or certain medications; or a disease like polycythaemia vera, in which the bone marrow produces too many platelets too quickly.11
 
Thrombocytosis
  • Polycythaemia vera, essential thrombocythaemia
  • After splenectomy
  • After haemorrhage
  • After parturition
  • After severe injuries, major surgical operations.
 
DIFFERENTIAL LEUKOCYTE COUNTS
A thin well-prepared smear (a Lood smear is thin and tongue shaped) is stained with Giemsa/Leishman’s stain. After staining it is ascertained that the smear is will spread and there is no tailing. 100 cells are counted at region where RBCs are just touching (and not overlapping) each other. Counting should be done along the short axis of the slide and not from tail to the head of the slide. High power objective is enough but for less experienced oil immersion objective may be necessary. At the same time note the size, shape, Hb concentration of RBCs, inclusion bodies within them including malarial parasites. Look for any immature or atypical cells. A well-prepared smear provides enough indication about the number of platelets, i.e. whether they are decreased, adequate or increased in number. Other haemoparasites should also be searched for if history is indicative. A rough estimate of TLC can also be obtained by studying a well spread smear (Fig. 1.2).
Normal differential counts
12
zoom view
Fig. 1.2: Peripheral blood smear, normal
Neutrophilia (increased neutrophils) seen in Physiological
  • In muscular activity.
  • Infants during first few days.
  • During last week of pregnancy.
  • Emotional disturbances.
  • Extreme heat and cold.
 
Polymorphs-Interfering Factors
  1. In children neutrophilia develops more prominently in case of infection.
  2. Weak debilitated people fail to respond with neutrophilia in infection.
  3. ACTH, myelosuppressive chemotherapy don’t allow proportionate neutrophilia in infection.
 
LEUKOPENIA
A reduction in the number of leukocytes below 4000/cu. mm may be suggestive of various conditions.
Infections. In severe infections when body’s immunity is compromised instead of leukocytosis we may encounter low counts.
  • Bacterial
    Typhoid fever, paratyphoid fever brucellosis and miliary tuberculosis
  • Viral
    Influenza, measles, infective hepatitis
  • Protozoal
    Malaria, kala azar, relapsing fever
Bone marrow diseases
The counts may also be decreased in many conditions involving bone marrow like
  • Defective bone marrow function
    Aplastic anaemia
    Megaloblastic anaemia
  • Bone marrow involvement
    Secondary carcinoma
    Malignant lymphoma
    Multiple myeloma14
Sensitivity to drugs (Agranulocytosis)
  • Sulphonamides
  • Thiouracil
  • Amidopyrine
  • Phenylbutazone
  • Chloramphenicol
Shock
  • Traumatic
  • Anaphylactic
Irradiation
  • Exposure to X-ray and radioactive substances.
 
LYMPHOPENIA
  • Administration of ACTH
  • In conditions of stress and carcinomatosis
  • Excessive radiations15
 
MONOCYTOSIS
Bacterial infections
  • Tuberculosis, typhoid, brucellosis
  • Subacute bacterial endocarditis
Protozoal
  • Malaria, Kala azar, amoebiasis
  • Monocytic leukaemia
  • Hodgkin’s disease
 
EOSINOPHILIA
 
Absolute Eosinophil Count
Done in the same manner as for total leukocyte count except that eosinophil count diluting fluid is used and fresh blood is added. The count is done as soon as possible. The normal range of absolute eosinophil count is from 40–400 cells/cu. mm of blood.
Allergic Disorders
  • Asthama, drug allergy
  • Serum sickness
  • Urticaria
Parasitic Infestations
  • Intestinal worms
  • Hydatid cyst
  • Bilharziasis16
Drug Administration
(With or without drug allergy)
  • Liver extract, penicillin
  • Chlorpromazine
  • Streptomycin
Skin Diseases (Allergy type)
  • Eczema
  • Exfoliative dermatitis
Pulmonary Eosinophilia
  • Tropical eosinophilia
  • Loeffler’s syndrome
Blood Dyscrasias
  • Eosinophilic leukaemia
  • Chronic myeloid leukaemia
  • Following irradiation
  • Hodgkin’s disease.
 
EOSINOPENIA
The condition is clinically not very significant but however may be encountered in following conditions.
  • Administration of ACTH, Adrenaline and ephedrine
  • Response to stress:
    • Traumatic shock,
    • Surgical operations,
    • Burns 17
    • Acute emotional stress,
    • Exposure to cold.
    • Endocrine disorders Cushing’s diseases and acromegaly
    • Aplastic anaemia,
    • SLE.
 
Eosinophilia-Interfering Factors
  1. Eosinophil count is lowest in morning
  2. Burns, electric shock, postoperative states will result in decreased count.
  3. ACTH reduces count.
 
Plasma Cells
These are normally not present in peripheral blood, but may be found in:
  • Measles,
  • Chicken Pox (Plasmacytoid lymphocytes)
  • Multiple myeloma with spillover
  • Plasma cell leukaemia18
 
RED CELL MORPHOLOGY
 
Hypochromia (Increase in central pallor) (Fig. 1.3)
  • Iron deficiency anaemia
  • Thalassaemia
  • Sideroblast anaemia
  • Anaemia’s of chronic diseases
zoom view
Fig. 1.3: Hypochromic RBCs in peripheral blood film
19
 
Macrocytes (larger than small lymphocytes) (Fig. 1.4)
  • Megaloblastic anaemia
  • Hepatic disease
  • Vitamin B6 deficiency
  • Aplastic anaemia
  • Congenital dyserythropoietic anaemia
  • Pure red cell aplasia.
zoom view
Fig. 1.4: Peripheral blood smear, megaloblastic anaemia
 
Spherocytes (Fig. 1.5)
Spherocytes are small cells, which stain darkly and lack central pallor. They result from membrane damage due to either a problem extrinsic to the red cells or an abnormality intrinsic to the red cells. Hereditary spherocytosis is caused by a genetic defect in the red cell membrane. An abnorality of membrane skeletal proteins causes progressive loss of membrane, making the red cells less deformable. The red cells then get trapped within the cords of the splenic red pulp and are destroyed by the splenic macrophages. Spherocytes are not unique to hereditary spherocytosis, and are seen in other haemolytic states also like
  • Autoimmune haemolytic anaemia
  • Cl. Welchii infection
  • Post burn patients.
zoom view
Fig. 1.5: Blood smear, hereditary spherocytosis
 
LEUKO ERYTHROBLASTIC PICTURE
Normally no immature red cells should be seen in peripheral blood. Their presence therefore is always pathological. When 21immature myeloid and erythroid cells appear in peripheral blood it is termed as leuko-erythroblastic picture. The condition is seen in
  • Myeloproliferative disorders
  • Polycythaemia vera
  • Myelofibrosis
  • Haemolytic anaemias
  • Leukaemias
  • Bone marrow involvement with Hodgkin’s disease or in lymphomas
  • Leukaemoid reactions.
 
RETICULOCYTE COUNT
Supravitally stained these cells appear as bluish strands in cytoplasm due to precipitation of ribosomes and RNA. These are suggestive of increased bone marrow activity. Normally 0.1–2 percent of total RBCs may be reticulocytes.
They are increased in
  • Haemolytic anaemias
  • Nutritional anaemia on therapy
Reduced
  • Aplastic anaemia
  • PNH
 
INCREASED PLASMA HAEMOGLOBIN (NORMAL 0.4 MG/100 ML)
  • G-6 PD deficiency
  • PNH22
  • Black water fever
  • Cold haemoglobinuria
  • Autoimmune haemolytic anaemia
 
LEUKOCYTE ALAKALINE PHOSPHATASE SCORE (LAP SCORE)
Increased in
  • Infection
  • Leukaemoid reaction
  • Myelofibrosis
  • Aplastic anaemia
  • Polycythaemia vera
Decreased
  • Chronic myeloid leukaemia
  • Paroxysmal nocturnal haemoglobinuria
 
COOMBS’ TEST
It is positive in autoimmune haemolytic anaemia
  1. Idiopathic
  2. Secondary to
    • Lymphoma
    • Infectious mononucleosis
    • Mycoplasma pneumonia
    • Cold agglutinin disease.
 
LUPUS ERYTHEMATOSUS (LE) CELLS
Positive LE cells are found in
  • Systemic lupus erythematosus (70–80%)
  • Rheumatoid arthritis (10%)23
  • Occasionally other collagen disorders
  • Malaria
  • Drug induced–hydralazine and procainamide. Mycoplasma pneumonia
 
ESR
Two methods are used for the purpose. Westergren Method and Wintrobe method.
Normal value
Westergren method
  • 0–5 mm in men
  • 0–7 mm in women
Wintrobe method
  • 0–9 mm in males
  • 0–20 mm in females
Decreased in
  • Polycythaemia vera
  • Congestive cardiac failure
  • Whooping cough dehydration
24The ESR may increase very rapidly in following conditions
  • Temporal arteritis
  • Kala azar
  • Some cases of multiple myeloma
  • Rheumatoid arthritis
  • Leukaemia
  • Haemolytic anaemia
  • Chronic renal disease
  • Sarcoidosis
ESR may be useful in the diagnosis of following conditions
  • To distinguish functional from organic disease
  • In active rheumatoid arthritis, acute gout and infective arthritis, it is markedly raised while in osteoarthritis it remains practically normal.
  • In myocardial infarction it is raised while in angina it is not.
  • It may be differentiating indicator in cancer of stomach from peptic ulcer.
  • It is raised in pelvic inflammation and not in unuttered ectopic gestation.
 
ESR in Prognosis and Treatment
  • In fevers, a rising ESR suggests progress of the disease
  • In rheumatic fever it is a sensitive index of persistent rheumatic infection
  • In coronary thrombosis repeated determinations serve as a guide of healing and in management of patient’s activities
  • In acute nephritis, the rate remains high in patients passing into chronic stage.25
 
ESR Interfering Factors
  • Blood should not be allowed for more than 2 hours.
  • Refrigeration increases rate of ESR.
  • Young children, menstruation, high globin, dextran, methyldopa, oral contraceptives, Vit. A increases ESR.
  • High blood sugar, ethambutol, quinine salicylates, cortisone decreases blood ESR.
 
FRAGILITY OF ERYTHROCYTES
The test is usually asked for in suspected cases of heredity spherocytosis and other related disorders having haemolytic anaemia. It works on the principle that spherocytes being already round are unable to swell much and therefore are more fragile and rupture even when very small amount of water has entered it. On the other hand red cells in thalassaemia and iron deficiency anaemia can withstand more water entering them.
Increased
  • Hereditary spherocytosis
  • Congenital haemolytic jaundice
  • Autoimmune anaemia (ABO and Rh ) incompatibility.
Decreased
  • Pernicious spherocytosis
  • Thalassaemia
  • Hypochromic anaemia
  • Obstructive jaundice
  • After splenectomy26
 
BLEEDING TIME
The bleeding time estimation although simple is an important investigation which gives information regarding the condition of platelets (number and function) and that of vascular system of the body. The normal value may vary as per the method of estimation. It is 1–6 minutes by Dukes method (where a deep puncture is made on ear lobe or a fingertip and drops of blood are removed using a filter paper). The normal bleeding time is 2–10 minutes by Ivy’s method (10 mm long and 1 mm deep cut is made on the forearm which is free of visible veins after putting a Blood Pressure cuff inflated to 40 mm Hg and readings are taken every 30 seconds).
 
Bleeding Time—Interfering Factors
  • Touching of incision will prolong bleeding time
  • Heavy alcohol consumption increases bleeding time to be increased
  • Dextran, streptokinase, mithramycin increases bleeding time.27
 
Functional Platelets Defects
(Platelets sometimes may be adequate in number but defective in function leading to increase in bleeding time).
  • Glanzmann’s thrombocythaemia
  • Storage pool disease
  • Bernard Soulier’s disease
  • Cyclo oxygenase deficiency
  • Thromboxane synthetase deficiency
 
Coagulation Time
The Lee and White test tube method for coagulation (normal 5–10 minutes) requires venous blood drawn by syringe. It is more reliable than skin puncture methods in which tissue fluids may contribute thromboplastid, which accelerates coagulation. This is the method of choice in heparinised patients.
 
Method
Here we place 3 clean, dry test tubes (13 × 100 mm with internal diameter of 11 mm) in a rack at 37°C water bath. With a clean, dry syringe and needle 6 ml of venous blood is drawn and 2 ml is put into each test tube. Record time at which blood was drawn after 5 minutes, till the first tube can be inverted without loss of blood. Agitation accelerates coagulation, so the end point is determined in tubes 2 and 3. Now test the second tube by tilting and note the time after drawing of the blood when a firm clot is formed; check with third tube. This constitutes the clotting time.
Normal values for clotting time are 9–15 minutes28
 
Reduced
  • After meals
  • In typhoid
  • After haemorrhage and general anaesthesia
  • In endocarditis
  • After splenectomy.
 
COAGULANT FACTOR DEFECTS
 
Haemophilia
(Factor VIII pro-coagulant activity deficiency)
Mild
- 5.25 percent of normal
Moderate
-1.5 percent of normal
Severe
-< 1 percent of normal
 
Haemophilia B
Christmas disease due to factor IX deficiency.
Both haemophilia A and B are ‘X’ linked diseases transmitted by female carriers.
 
Von Willebrand’s Disease
It is due to deficiency of factor VIII related antigen deficiency.29
 
PACKED CELL VOLUME (PCV)
  1. Using a Wintrobe’s tube centrifuge hole blood for 15 minutes at 3500 rpm (or longer at lower speeds) until packing is complete. After centrifuging, the blood is separated into 3 layers a tall bottom layer of packed red cells, a narrow, middle layer of WBCs & platelets and a top layer of liquid plasma. The percentage of the height of the column of blood occupied by packed red cells constitutes the haematocrit.
  2. Micro-haematocrit methods are used commonly these days. Capillary tubes coated with anticoagulant can be filled with blood obtained by finger puncture or from a vein or with blood already treated with anticoagulant. One end is sealed with clay and the tube centrifuged for 3 minutes in a special high-speed centrifuge. By reading the packed cell height and the total height of the entire specimen, the haematocrit can be determined. Special reading devices are available.
Normal value
Male
47 percent (47–54)
Female
42 percent (36–47)
 
MEAN CORPUSCULAR HAEMOGLOBIN (MCH)
zoom view
Raised in 30
Microcytic anaemias.
Low in
Hypochromic anaemia.
 
MEAN CORPUSCULAR HAEMOGLOBULIN CONCENTRATION (MCHC)
zoom view
Raised
Not possible since red cell stroma cannot hold greater than normal concentration of Hb.
Low
Iron deficiency.
 
MEAN CORPUSCULAR VOLUME (MCV)
zoom view
Raised
Macrocytic anaemia
Low
Microcytic hypochromic anaemia.31
 
COLOUR INDEX (CI)
Hb expressed as a percentage of normal
Raised
Pernicious anaemia.
Low
Iron deficiency anaemia.
 
Haematological Diagnosis of Leukaemia
The diagnosis of various leukaemias is dependent on the presence of myeloblasts or lymphoblasts in the peripheral blood film. Myeloblasts are10–25 mm in diameter, round to oval nucleus 2/3rd of cell size, chromatin strands with 2 or more nucleoli, auer rods present. Lymphoblasts are 10–20 mm in diameter and have 1–2 nucleoli. The chromatin is more compact with less cytoplasm.
 
Cytochemical Characteristics
Acute myeloblastic leukaemia
  • Myeloperoxidase positive
  • Siedor black positive
  • Chlorazepate elastase positive
Acute monoblastic leukaemia
  • Non specific estrase positive
    32
ALL Acute Lymphoblastic leukaemia
  • Periodic acid Schiff (PAS) positive
Hairy cell leukaemia
  • Tartrate resistant acid phosphatase positive
Acute megakaryoblast leukaemia
  • Platelet peroxidase positive
Leukaemoid reaction
The total leukocyte count is often in the range of 50,000 cu/mm mimicking leukaemia.
  1. Infections
    1. Myelocyte or myeloblastic
      • Pneumonia
      • Meningitis
      • Diphtheria
      • Tuberculosis
    2. Lymphocytic
      • Whooping cough
      • Chicken pox
      • Infectious mononucleosis
      • Tuberculosis
      • Benign lymphocytosis
  2. Intoxications
    • Eclampsia
    • Burns
    • Mercury poisoning
  3. Malignant disease with bone marrow metastasis
    • Multiple myeloma
    • Myelofibrosis
    • Hodgkin’s disease
  4. Following severe haemorrhage, sudden haemolysis.33
 
Haemoglobin Electrophoresis
It is done for diagnosis of abnormal haemoglobins like HbS, C, D, E, H, Barts. The test is very helpful in the diagnosis of various conditions like sickle cell disease, etc.
In alkaline pH electrophoresis (pH 8–9)
Slowest moving Hb– HbA, C, E
Fastest moving Hb– HbH, Barts
Haemoglobin (A)
Normal 2.0–2.9
Increase
  • Beta thalassaemia trait
  • Myeloblastic anaemia
  • Haemoglobinopathies
Decrease
  • Iron deficiency anaemia
Haemoglobin-F
(Normal 0.1%)
Increase
Physiological
:
Foetal life
Pathological
:
Thalassaemia
:
Haemoglobinopathies
:
Hereditary persistent haemoglobin
:
Juvenile CML
:
Fanconi’s anaemia.
 
IMMUNOGLOBULIN ESTIMATION
IgG
:
1200 mg/dl
IgA
:
280 mg/dl
34
IgM
:
100 mg/dl
IgD
:
3 mg/dl
IgE
:
10–20 gm/dl
IgG
:
70%, IgG2 18%, IgG3 8%
IgG
:
4%, IgA1 75%, IgA2 25%
All immunoglobulins are decreased in
IgA deficiency
  • Bronchiectasis and chronic lung infections
  • Giardiasis
  • SLE and rheumatoid arthritis
IgM deficiency
  • Wiskott-Aldrich syndrome.
Blood tests for worm infestations
Disease
Test
Dilution
Specificity
Invasive amoebiasis
IHA
1:256
90%
Cysticercosis
IHA
1:128
90–95%
Echinococcosis
IHA
1:256
90–95%
Toxocariasis
ELISA
1:32
92%
Trichuriasis
BFT
1:5
90%
IHA: Iso haemagglutination
ELISA: Enzyme linked immunosorbent assay
BFT: Bentonite Flocculation test.