Hematological function tests

Content

•       Various hematological function tests

•       Normal reference ranges of various lab parameters

•       Various disease conditions correlated with hematological function tests

Objective

After completion of this lecture, student will be able to:

•       Explain the various hematological function tests

•       Explain the normal reference ranges of various lab parameters

•       Explain the various disease conditions correlated with hematological function tests

Hematological function tests

Introduction

•       Complete blood count (CBC) or Complete Blood Examination (CBE) is routinely ordered test

•       Provides useful information on cellular and non-cellular elements of blood

•       Helps in diagnosis of multiple haematological disorders

Routine tests

•       RBC count

•       WBC count

•       Hemoglobin (Hb)

•       Hematocrit (Hct)

•       RBC indices (specifically assess RBCs)

              -Mean cell volume (MCV)

              -Mean cell hemoglobin (MCH)

              -Mean cell hemoglobin concentration (MCHC)

Reference range

•       RBC count:

                                -Male: 4.6 to 6.2 X10⁶ cells /mm³

                                -Female: 4.2 to 5.4 X10⁶ cells /mm³

•       WBC count:

                                5000 to 10,000 cells /cu mm of blood

 

•       Hemoglobin (Hb):

                                -Male: 14 to 18g/dl

                                -Female: 12 to 16g/dl

•       Hematocrit (Hct) / Packed cell volume (PCV):

                It is the percentage volume of blood that is composed of erythrocytes

                                Range:

                                                -Male: 42 to 52 %

                                                -Female: 37 to 47%

•        Mean cell volume (MCV):

                -It is an estimate of the average volume of RBCs

                -Derived by dividing Hct by RBC count

                                Range:

                                                -Male: 80 to 96 fl (femtolitres – 10 ^{-- 15})

                                                -Female: 82 to 98 fl

                - Microcytic anaemia:                     âMCV

                - Macrocytic anaemia:                    áMCV  

•       Mean cell haemoglobin (MCH):

                - It is the percent volume of Hb per RBC

                - Derived by dividing Hb by RBC count

                                Range: 27 to 33 pg /cell [picograms = 10 ^–12]

                - Increase in folate deficiency & decrease in iron deficiency

                -A low MCH corresponds with hypochromic RBCs - as seen in iron deficiency anaemia

•       Mean cell haemoglobin concentration (MCHC):

                -It is derived by dividing Hb by Hct

                                                Range: 31 to 35 g/dl

                -Iron deficiency is the only anaemia in which the MCHC is low

Assessment of anaemia

Possible causes

•       Macrocytic anaemia:

                                -Vitamin B₁₂ deficiency

                                -Folic acid deficiency

                                -Drug induced bone marrow toxicity

•       Normocytic anaemia:

                                -Acute blood loss

                                -Haemolytic anaemia

                                -Drug induced

 

•       Microcytic anaemia:

                                -Iron deficiency

                                -Drug induced

Laboratory findings

Erythrocyte sedimentation rate (ESR):

                -Rate at which the erythrocytes settle down

                                Range:

                                                -Male: 1 to 15 mm / hour

                                                -Females: 1 to 20 mm / hour      

                -Much physiological condition alters the normal values of ESR

Physiological condition that alters the normal values of ESR

Increased ESR	Decreased ESR
Advanced age Female gender Infection Macrocytic anaemia Normocytic anaemia Pregnancy Rheumatoid arthritis	Congestive cardiac failure Microcytic anaemia Sickle cell anaemia Drugs like corticosteroids

White Cell Count (WCC)

White Cell Count (WCC)

•       Describes the number of leucocytes circulating in peripheral blood

Total WCC subdivided into

1. Granular white cells-N,E,B
2. Mono-nuclear cells-Lymphocytes and monocytes

•       Leucopoenia – WCC is significantly lower than reference range

•       A specific cell maybe low ( neutropenia, lymphopaenia)

Causes for Leucopoenia

Ø  Neoplastic disease- malignant cells compromise granulopoesis

Ø  Drugs as an adverse effect

•       Cytotoxic drugs

•       Immunosuppressant drugs

•       Antibiotics (Minocyclin)

•       Anti-convulsants (Lamotrigine)

•       DMARDS

•       Psychotropic agents- clozapine

Ø  Exposure to ionizing radiations

Ø  Exposure to pesticides or herbicides

Causes for elevated WCC

Ø  Infections such as

•       UTI

•       Bacterial pneumonia

•       TB

•       Meningitis

Ø  Drugs (iatrogenic increase)

•       Corticosteroids

•       Lithium

Ø  Hematological malignancy like Leukemia, Lymphoma

•       Eosinophilia- elevated eosinophils

•        WCC also monitored as a guide to the response to treatment of an infection

Platelet count

Platelet count (reference range 150-450 x 10³ /microliter)

•       Minor to moderate increase – surrogate marker of inflammation

•       Thrombocytopenia – decreased platelet count

Causes of Thrombocytopenia

•       Severe iron deficiency anemia

•       Liver disease

•       Fulminant infectious diseases

•       Drug induced- heparin, quinine and thiazide diuretics

Other laboratory data

CRP & ESR - Markers of inflammation

•       Serum amylase – acute pancreatitis

•       Creatine kinase – muscle cells damage         

Summary

•       RBC count:

                                -Male: 4.6 to 6.2 X10⁶ cells /mm³

                                -Female: 4.2 to 5.4 X10⁶ cells /mm³

•       A low MCH corresponds with hypochromic RBCs - as seen in iron deficiency anaemia

•       Much physiological condition alters the normal values of ESR

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