Understanding Medical Lab Test Reports

Introduction

Departments of Medical lab
A standard medical or pathology lab consists of following departments:

Hematology
Study of blood, blood forming organs and diseases of blood

Clinical pathology
Includes test on urine and stool (feaces)

Biochemistry
Study of chemistry of human body or chemistry of a human cell

Serology
It is the study of In vitro (inside the lab) Antigen / Antibody reactions

Antigen (foreign particles): a substance protein in nature which when enters the body provokes the production of antibodies. Antigen can be a bacteria, virus, fungus, pollen etc.

Antibody (body's defense): a substance protein in nature which is produced in response to an antigen in the human body, they are also called protective proteins eg IgG, IgM etc

Histopathology
Histopathology is the examination of tissues from the body under a microscope to spot the signs and characteristics of disease.

Microbiology
Is the study of microorganisms such as bacteria, virus, fungus and parasite

Hematology

Blood CP (blood complete picture)

The test includes following parameters

Red blood cells (RBC) count
RBC'S are the blood cells which carry and transport oxygen in the body, they do not have a nucleus and are red in color due to the presence of a pigment called hemoglobin

RBC count is lower than normal in most of the cases of anemia
Normal values:
Male: 4.5 to 5.5 million / L
Female: 3.8 to 4.8 million / L

Hemoglobin
It is a red colored pigment found in red blood cells its function is to bind with oxygen and carry it to each and every cell of the body.
Normal values:
Male: 13 to 17 gram / dl
Female: 12 to 15 gram / dl

Anemia
It is defined as lack of hemoglobin below normal levels for the age, sex and environment of an individual. Causes:

– Changes in bone marrow such as;
1. Aplasia (bone marrow failure)
2. Dyshemopoeisis (disorder in formation of blood cells)

– Changes in circulation
1. Hemolysis (reduced life span of red blood cells eg in malaria)
2. Acute hemorrhage

Types:
– Iron deficiency anemia
– Megaloblastic anemia
– Hemolytic anemia
– Anemia due to acute blood loss

Symptoms of anemia:
– Pallor of skin
– Dyspnoea specifically on exertion
– Lethargy
– Pain and numbness of lower limbs

Note
The most common type of anemia found worldwide is the iron deficiency anemia, the causes for iron deficiency anemia include:

1. Poor nutrition
2. poverty
3. Multiple pregnancies
4. malabsorption

It is also the most common type of anemia affecting the pregnant women

Red cell indices:

– MCV (mean cell volume)
MCV demonstrates the normal size of a red blood cell. In case of Iron deficiency anemia the size of a cell is reduced which means a low MCV (microcytic picture)
While in Megaloblastic anemias the MCV is increased (macrocytic)
Normal value: 80 to 10O fL

– MCH (mean cell hemoglobin)
MCH is the total amount of hemoglobin in RBC'S
In case of Iron deficiency anemia the mean cell Hb is reduced alongwith a low MCV (microcytic picture)
While in Megaloblastic anemias the MCH remains low or can be normal
Normal value: 27 to 34 pg

– MCHC (mean cell hemoglobin concentration)
It is the concentration of Hb in the red blood cell
Normal values: 33 to 36 g / dl

– PCV (packed cell volume)
It is the percentage of blood volume occupied by red blood cells
Normal values:
Male: 40 to 54%
Female: 37 to 47%

WBC count (leucocytes)
The total number of wbc's found in one liter of blood. The function of WBC'S is to provide immunity to the body against bacteria, virus and other organisms, they form the first line of defense against infection and they provide immunity to the body.

The normal value of WBC count is the same in both male and female that is: 4,000 to 11,000 / L

The value of leucocytes increases above normal level that is more than 11,000 / l in the following conditions:
– Acute infection
– TB
– Bacterial infections
– Viral infections
– Inflammation

AND if the value is very high that is near or above 20,000 than it should be investigated further for:

– Leukemia (blood cancer)
A decrease in the number of leucocytes occurs in case of typhoid and diabetes mellitus

Platelet count
Platelets are the blood cells which help in forming the clot after injury or bleeding.

Their value is same in both male and female that is: 150,000 to 40,0000 / L. When the value of platelet is decreased below normal (thrombocytopenia), blood looses its ability to clot, it occurs in following conditions:

– Liver diseases such as; Hepatitis and Chronic liver disease
– Cloting disorders

The value of platelets may also increase in certain conditions such as;

– Disseminated intravascular coagulation (DIC)
– Drug reactions

ESR (erythrocyte sedimentation rate)
ESR is a routine investigation which is mostly requested along with blood CP, it is a non specific investigation because it does not have any diagnostic value, it carries more of a prognostic value.
Serial ESR examinations are performed to assess the progress of disease.

Its value increases in the following conditions;
– Tissue damage
– Pregnancy
– TB
Typhoid
– Arthritis
– Acute infections
– Fractures

The value of ESR decreases in;
– Sickle cell anemia
– Polycythemia

Normal value:
Male: 4 to 10 mm / hour
Female: 6 to 12 mm / hour

Coagulation profile

1. Bleeding time / Clotting time:
These test are done for the diagnosis of bleeding disorders but both the tests are non specific and specifically the bleeding time is only prolonged in severe platelet deficiency

These tests do not give a clear picture of the coagulation pathway but only provide evidence of severe platelet disorder

Bleeding time and clotting time is prolonged in;
– Severe platelet deficiency (thrombocytopenia)
– Platelet function defects
– Warfarin therapy
– Aspirin ingestion

Normal value: <9 minutes

2. PT / APTT (Prothrombin time / Activated partial thromboplastin time)
These tests are also performed for the diagnosis of bleeding disorders BUT they provide a clear picture of the whole coagulation pathway which makes them more specific

Prothrombin time / Activated partial thromboplastin time are prolonged in;
– Clotting factor deficiency
– DIC (disseminated intravascular coagulation)

Normal value:
PT: 10 – 13 second
APTT: 28 – 38 second

Blood grouping
Blood group are antigens found on the surface of red blood cells, a person having 'A' antigen on the surface of his / her RBC'S will be having 'A' blood group just a person having 'B' antigen on the surface of his / her RBC'S will be having 'B' blood group

Classical ABO blood group system:
This is the most common blood group system found in the world, it is explained as under;

Blood group
Antigen on RBC Antibody in serum
AAB
BBA
AB AB Nil
O Nil AB

Blood group 'AB' is 'Universal recipient' and blood group 'O' is the 'universal donor'
Blood grouping is performed before going for "Blood transfusion"