Overview of Anemia & Hematology

Overview of Anaemia

• Haematology is the study of blood-forming tissues, circulating blood components, and blood illnesses.

Functions of Blood

• Delivers nutrients, oxygen, and hormones to tissues via red cells.
• Collects waste from cellular metabolism utilizing white blood cells (WBCs).
• Delivers cells to tissues for protection against the external environment with WBCs.
• Prevents leakage from blood vessels with platelets and clotting factors.
• Circulating blood accounts for 5-7% of total body weight and is composed of cellular and fluid elements.

Cellular and Fluid Elements of Blood

• Cellular elements include red blood cells, white blood cells, and platelets.
• Fluid elements consist of plasma (obtained from anticoagulated blood) vs. serum, water, electrolytes, and proteins like clotting factors, antibodies, along with transport proteins.

Diagnosis of Haematological Disorders

• Diagnosis involves history, physical examination, and peripheral blood measurements.

History

• Emphasizes bleeding, infections, and constitutional symptoms (fever, night sweats, weight loss).
• Includes exposure to toxins or chemicals like lead, which may suppress haematopoiesis.
• Reviews systems and family history to assess potential inherited causes (e.g., G6PD deficiency).

Physical Examination

• Focuses on skin, mucosae, eyes looking for pallor, jaundice, petechiae, purpura, and ecchymoses.
• Checks for organomegaly (hepatomegaly, splenomegaly), lymphadenopathy, and bony tenderness, especially in the sternum.

Peripheral Blood Measurements

• Can be done manually or automated.

Specimen Collection

• Blood is collected in tubes containing anticoagulant such as EDTA (purple top tube, used for CBC).
• Trisodium citrate (blue top tubes are used for coagulation tests).

Haemoglobin Levels

• Normal Hb levels are around 11.5g/dl
• Women are normal
• Men are considered anaemic if below this level.

Further Lab Studies

• Tests include molecular studies, cytogenetics, and lymphocyte counts using heparin (green top).
• The ratio of blood to anticoagulant must be appropriate to avoid affecting lab results.
• Blood can be stored for testing later, with appropriate storage conditions being crucial.
• Request forms must be complete and accurate.

Cell Counts

• Manual counts lack precision and are time-consuming
• Automated counts detect changes in impedance in electrical flow and light scatter properties.

Other Information from Blood Tests

• Haematocrit (HCT or PCV): volume of red cells as a percentage of total blood.
• Haemoglobin concentration (Hb).
• Mean corpuscular volume (MCV).
• Mean corpuscular haemoglobin concentration (MCHC) amount of Hb in a volume of cells.
• Mean corpuscular haemoglobin (MCH): concentration of Hb in cells.
• Red cell distribution width (RDW): measures variation in RBC size.

White Blood Cell Counts

• Automated methods could be inaccurate due to clumping of particles, aggregated platelets, nucleated red cells, incomplete lysis of red cells, or WBC agglutination.

Leucocyte Differentials

• Automated methods are more accurate as they count more cells, however, abnormal cells might not be identified.
• Flagging alerts the lab to look at the blood film.

Platelet Analysis

• Automated methods are more reliable.
• Errors can occur from platelet clumps or small red cell fragments; manual counts can confirm accuracy.

Morphology of Blood Cells

• Slides are prepared from anticoagulated blood or fingerstick blood.
• Blood is smeared on a glass slide and stained with Wright or May-Grunwald-Giemsa stain.
• Smear should be scanned at 10 to 20x objective before a higher power is used for WBC differentials.
• Assessment includes size, shape, haemoglobin distribution, and inclusions.

Red Blood Cell Morphology Assessment

• Assess in areas where cells are just touching, avoiding overlap.
• Normal cells are round with a central area of pallor.
• Anisocytosis is variation in size
• Poikilocytosis is variation in shape.
• Hypochromia: poor haemoglobinisation (low MCH), decreases mean corpuscular Hb.
• Spherocytes: lack a central area of pallor.
• Macrocytes: cells are larger than normal (high MCV), increasing mean corpuscular volume.

MCV Interpretation

• The MCV relates to cell size.
• Microcytes are smaller than normal (low MCV).

RDW and MCV Interpretation

• Normal RDW and Low MCV: may indicate anaemia of chronic disease or heterozygous thalassemia.
• Elevated RDW and Low MCV: suggests iron deficiency or S-thalassemia.
• Normal RDW and High MCV: indicates aplastic anaemia, liver disease, or chemotherapy/alcohol use.
• Elevated RDW and High MCV: may indicate folate/B12 deficiency or myelodysplastic syndrome.
• Normal RDW and Normal MCV: seen in anaemia of chronic disease or acute blood loss/haemolysis.
• Elevated RDW and normal MCV: indicates early iron, B12, folate deficiency, chronic liver disease, or sickle cell disease.

Assessment of Platelets and White Blood Cells

• Platelet numbers and morphology should be assessed.
• Leucocyte morphology and distribution require the counting of at least 100 white cells, including neutrophils, eosinophils, basophils, monocytes, and lymphocytes.
• Immature WBCs include bands, metamyelocytes, myelocytes, promyelocytes, and blasts.

Bone Marrow Examination

• It involves cytology from aspirate along with assessment of cellularity and infiltration from biopsy.
• Indications include evaluation/staging of primary bone marrow tumors, assessing abnormalities from peripheral blood smears, and investigating infectious/metabolic storage diseases.
• Sites: Anterio-medial tibia in children. Sternum, anterior and posterior iliac crest.

Bone Marrow Staining

• Wright or May-Grunwald-Giemsa stain.
• Haematoxylin and eosin for biopsy.
• Special stains along with cytochemical and immunohistochemical stains.

Erythrocyte Sedimentation Rate

• ESR is commonly done but nonspecific.
• Reflects how quickly blood settles in certain disease states.
• Rate increases with plasma fibrinogen, immunoglobulins, and acute phase reactive proteins.
• Influenced by red cell shape and numbers, age, and is a poor screening in asymptomatic people.
• Useful in monitoring diseases like rheumatoid arthritis or Hodgkin's
• Measured via Westergren or Wintrobe method in mm/hr

Anaemia Definition

• It is not a diagnosis, but a sign of underlying issues.
• A disorder characterized by tissue hypoxia due to reduced oxygen-carrying capacity, often shown by reduced haemoglobin or red cell count.

Identification

• Requires knowledge of normal haematological values, varying by age, sex, and altitude.

Red Cell Count Normal Values

• Men: 5.5 ± 1.0 x 10^12/l
• Women: 4.8 ± 1.0 x 10^12/l
• Infants (full-term, cord blood): 5.0 ± 1.0 x 10^12/l
• Children, 1 year: 4.4 ± 0.8 x 10^12/l

Haemoglobin Normal Values

• Men: 15.5 ± 2.5 g/dl
• Women: 14.0 ± 2.5 g/dl
• Infants (full-term, cord blood): 16.5 ± 3.0 g/dl
• Children, 1 year: 12.0 ± 1.0 g/dl
• Children, 10-12 years: 13.0 ± 1.5 g/dl

PCV Normal Values

• Men: 0.47 ± 0.07 (l/l).
• Women: 0.42 ± 0.05 (l/l).
• Infants (full-term, cord blood): 0.54 ±0.10 (l/l).
• Children, 3 months: 0.38 ± 0.06 (l/l).
• Children, 10-12 years: 0.41± 0.04 (l/l).

Anaemia Classification

• Pathogenetic/aetiological, based on the cause.
• Morphological, based on red cell characteristics.
• Clinical investigation involves both classifications to determine the morphological type and the underlying cause.

Aetiological Classification

• Subdivided into hypo-regenerative and hyper-regenerative types.
• Anaemia occurs due to failure of bone marrow production of red cells (hypo-regenerative).
• Anaemia can occur through increased red cell destruction and consumption with increased red cell production (hyper-regenerative).
• Reticulocytes help characterize anaemia and indicates how the bone marrow is responding.

Reticulocytes

• Approximately 0.8% of the red cell pool needs replacement by young erythrocytes daily.
• Larger than mature red cells, contain polyribosomal RNA material, and are detected via supravital stains.
• Reticulocyte count helps implicate whether the marrow or periphery is the source of anaemia.

Further Investigation

• Guided by whether reticulocytosis is present to determine between bone marrow issues vs loss/haemolytic abnormalities.

Reticulocyte Count and Anaemia

• Anaemia + Low reticulocyte count = Hypo-regenerative anaemia.
• Anaemia + High reticulocyte count = Hyper-regenerative anaemia, due to high maturation or destruction rate.
• Typically shown as a percentage of red cells, with normal counts of 0.2-2.0% (adults/children) and 2-6% (infants).
• Percentage increase happens when there are more reticulocytes and fewer mature red cells.

Red Cell Production

• Rate control is the arterial blood's oxygen content, as decreased oxygen stimulates erythropoiesis, and an increased oxygen level suppresses it.
• Red cell mass is maintained through erythropoietin feedback.
• Blood loss or haemolytic destruction causes erythropoietin overdrive -> reticulocytosis.
• Reticulocytes under erythropoietin stimulation persist in peripheral blood longer.

Reticulocyte Index (RI)

• Reticulocyte count (%) x Patient PCV (l/l) / Normal PCV (l/l).
• Reticulocyte Maturation Time is proportional to PCV.

Hypo-regenerative anaemia RI

• RI <2.
• Indicates something affects the rate at which bone marrow produces cells

Hyper-regenerative anaemia RI

• RI >3.
• Indicates cells are being destroyed by other processes(e.g. hemolytic anemia).

Morphological Classification

• Involves red cell morphology, size, and staining characteristics.
• Red cells can be normocytic, macrocytic or microcytic.
• Cells stained with pink and a central pallor not exceeding 1/3 the cell diameter are normochromic
• If a pallor area exceeds 1/3 the diameter, it is considered hypochromic.

Classifying Anaemia

• Hypochromic/microcytic.
• Normochromic/normocytic.
• Macrocytic.
• Size and staining can be measured via mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), and mean corpuscular haemoglobin concentration (MCHC).

Formulae for Measurements

• MCV (fl) = PCV (l/l) x 1000 / RCC (10^12/l)
• MCH (pg) = Haemoglobin (g/dl) x 10 / RCC (10^12/l)
• MCHC (g/dl) = Haemoglobin (g/dl) / PCV (l/l)

Normal MCV values

• Adults: 85 ± 8 fl.
• Infants (full-term, cord blood): 106 fl (mean).
• Children, 1 year: 78 ± 8 fl.
• Children, 10-12 years: 84 ± 7 fl.

Normal MCH values

• Adults: 29.5 ± 2.5 pg.

Normal Values for MCHC

• Adults and children: 33 ± 2 g/dl.
• Absolute values and blood film examination are important for assessing anaemic patients.

Clinical Features of Anaemia

• Symptoms relate to the anaemia itself.
• Symptoms relate to the disorder causing the anaemia.
• Haemoglobin level symptoms depend on the rate of anaemia and the patient's age.

Fast-developing Anaemia

• Symptoms appear at higher haemoglobin levels such as acute haemorrhage.

Older People

• Older patients and those with cardiovascular compromise have a lower tolerance.

Symptoms and Signs

• Tiredness, fatigability, and muscle weakness are common early symptoms.
• Pallor.

Jaundice with pallor

• Indicates hemolytic anaemia.

Lemon yellow pallor

• Indicates Pernicious anaemia.

Waxy dead like whiteness + Cold and moist palms

• Indicates acute blood loss.

Cardio-pulmonary symptoms

• Cardio-pulmonary includes dyspnoea or palpitations.
• Angina can stem from myocardial ischemia or pre-existing coronary stenosis.
• May include murmurs and water retention/oedema.

Neuromuscular issues

• Can result in Headache, vertigo, tinnitus, faintness, lack of mental concentration, drowsiness, restlessness, and muscular weakness.

Neuromuscular symptoms

• Can be caused by cerebral hypoxia

Alimentary System/gastrointestinal issues

• Includes duodenal ulcers or glossitis and atrophy of the tongue papillae, especially in nutritional anaemia.

Fever with anaemia

• Mild fever may occur without a clear cause.

Physiological Adjustments to Anaemia

• The main function of haemoglobin is to transport oxygen from the lungs to the tissues.
• Anaemia reduces the oxygen-carrying capacity of the blood and results in tissue hypoxia.
• Body responses occur first in the red cell and then circulation.

Red Cell Changes

• Primary function of red cells is to transport oxygen so diffusion from the blood occurs rapidly.
• The oxygen-dissociation curve plots percent saturation against partial pressure and is sigmoid.
• Shifts to the left increase oxygen affinity while shifts to the right decrease it (partial pressure when saturation is 50% = 27 mmHg).
• Binding and release of oxygen are affected by phosphates such as 2,3 diphosphoglyceric acid (2,3DPG). Increases in 2,3 DPG are seen in chronic anaemia. These increase facilitates oxygen delivery by lowering Hb affinity in capillaries; the curve then shifts right.

Circulation Changes

• Includes increases in cardiac output and circulation rate, mainly via increased stroke heart volume.
• Cardiac output rises when haemoglobin drops below 7 g/dl, with stroke volume and heart increasing when it falls below 5g/dl, especially with exercise.
• Total volume is kept normal by expanding plasma volume.
• Blood flow is redistributed away from less oxygen-demanding tissues, increasing flow to cerebral and muscle tissues.
• These mechanisms make the patient asymptomatic, although exertion may cause symptoms.

Management of Anaemia

• Three questions include: "Is the patient anaemic?", "What is the type of anaemia?", and "What is the cause of the anaemia?".
• Principles are treating the underlying disorder and treating the anaemia itself.