Morphology with smear – purpose and course of examination, indications, norms

A blood smear test is a laboratory test that provides information about the types and amounts of white blood cells, red blood cells, and platelets in your blood. These results are presented as percentages and absolute values ​​and compared with reference ranges to determine if the values ​​are valid, low, or high. Changes in the number of white blood cells can help diagnose many medical conditions, including viral, bacterial and parasitic infections, and blood disorders such as leukemia. We divide the morphology with a smear into an automatic morphology with a smear performed by an automatic analyzer and a morphology with a manual smear, examining blood smears under a microscope.

There are two types of morphology with a smear:

1. automatic morphology with smear – performed by a special device;
2. morphology with manual smear – examining blood smears under a microscope.

The smear morphology looks at the percentages and numbers of different types of white blood cells and looks for irregular cells. White blood cells are also called leukocytes. The bone marrow produces five major types of white blood cells, namely neutrophils, lymphocytes, monocytes, eosinophils, and basophils.

Neutrophils – usually make up the largest number of circulating white blood cells. They move to the area of ​​damaged or infected tissue, where they absorb and destroy bacteria and sometimes fungi.

Lymphocytes – they are found both in the blood and in the lymphatic system. They are broadly divided into three types, but the study does not distinguish between them. Differentiation counts and reports all lymphocytes together. To distinguish these three types, separate specialized tests (such as immunophenotyping) must be performed:

1. B lymphocytes – Produce antibodies that help protect against infections. Plasma cells are fully differentiated B lymphocytes that produce antibodies, immune proteins that attack and destroy bacteria, viruses, and other foreign antigens.
2. T lymphocytes – They finish to mature in the thymus and consist of several different types. Some T cells help the body distinguish between “self” and “non-self” antigens. Others initiate and control the extent of the immune response, strengthening it as needed, then slowing it down as the condition subsides. Other types of T cells directly attack and neutralize virus-infected or cancerous cells.
3. NK cells – Directly attack and kill abnormal cells such as cancerous or virus-infected cells.

Monocytes – like neutrophils, travel to the area of ​​infection and absorb and destroy bacteria. They are more often associated with chronic infections than with acute infections. They are also involved in tissue repair and other functions related to the immune system.

Eosinophils – react to infections caused by parasites, play a role in allergic reactions (hypersensitivity) and control the range of immune responses and inflammation.

Basophils – These usually make up the smallest number of circulating white blood cells and are thought to be involved in allergic reactions.

See also: Percentage formula of white blood cells (peripheral blood smear)

A blood smear morphology may be performed when we have signs and symptoms that the doctor believes may be related to a blood and / or bone marrow disease, autoimmune disease, or other immune disorder.

Morphology with a smear – the course of the study

In the case of a complete blood count, your doctor checks your white blood cell count by testing a blood sample. A healthcare worker in a laboratory uses a small needle to draw blood from your arm or hand. No special preparation before the test is necessary.

The specialist places a drop of blood from the sample on a clear slide and smears it to distribute the blood. The blood smear is then stained with a dye which helps to distinguish between the types of white blood cells in the sample. The number of each type of white blood cell is then counted. Your doctor may perform a manual smear morphology, visually identifying the number and size of cells on the slide. The doctor may also use an automated blood smear morphology. In this case, the machine analyzes blood cells based on automatic measurement techniques. In the latter case, a special device uses electrical, laser or photo-detection methods to provide a very accurate picture of the size, shape and number of blood cells in the sample.

However, it should be noted that the levels of eosinophils, basophils, and lymphocytes may not be accurate if the patient is taking corticosteroid medications such as prednisone, cortisone, and hydrocortisone at the time of testing. In this case, you should inform your doctor before the examination.

Morphology with smear – norms

The test collects a lot of information from your blood sample.

1. Number and types of white blood cells (WBC) – A high number of white blood cells or a certain type of white blood cell could mean that there is an infection or inflammation somewhere in the body. A low white blood cell count could mean you are at risk of infection.
2. Red blood cell count (RBC) – They carry oxygen throughout the body and remove excess carbon dioxide. Too few red blood cells can be a sign of anemia or other diseases. In rare cases, too many red blood cells can cause problems with blood flow.
3. Erythrocyte volume distribution width (RDW, RDW-CV or RDW-SD) – you may have larger variations in red blood cell volume if you are anemic.
4. Hematocrit (HCT) – is the fraction of red blood cells in a certain amount of whole blood. Low hematocrit may be a sign of excessive bleeding. Or it could mean we have iron deficiency or other disorders. Higher than normal hematocrit may be caused by dehydration or other disorders.
5. Hemoglobin (Hgb, Hb) – Hemoglobin is the protein found in red blood cells. It carries oxygen from the lungs to the rest of the body. Abnormalities can be a sign of problems ranging from anemia to lung disease.
6. Average red blood cell volume indicator (MCV) – increases when the volume of red blood cells is greater than normal. This happens if you have anemia caused by low levels of vitamin B12 or folate. If the red blood cell volume is lower, it could be a sign of other types of anemia, such as iron deficiency anemia.
7. Platelet count (PLT). Platelets are cell fragments that play a role in blood clotting. Having too few platelets in your blood may mean you are at greater risk of bleeding. Too many of them can mean many possible conditions.
8. Average hemoglobin mass in the erythrocyte (MCH) – measures how much hemoglobin our red blood cells have.

The results may vary depending on the age, gender, test method, etc. And it may not necessarily be a medical condition, so always discuss your test results with your doctor.

The standard for blood smear morphology is:

1. red blood cells (RBC): 3,93 to 5,69 million per cubic millimeter (million / mm3);
2. erythrocyte volume distribution range (RDW, RDW-CV, RDW-SD): 11,5% to 14,5%;
3. white blood cells (WBC): 4,5 to 11,1 thousand per cubic millimeter (thousand / mm3)
4. platelets (PLT): 150 to 450 thousand / mm3;
5. hemoglobin (Hb or Hgb): 11,7 to 16,1 grams per deciliter (g / dL) for women, 13,2 to 17,3 for men;
6. hematocrit (HCT): 34% to 46% for women, 36% to 52% for men.

The normal range for white blood cell counts can vary from lab to lab, but overall is as follows:

1. neutrophils: 40%-70%;
2. lymphocytes: 22% -44%;
3. monocytes: 4%-11%;
4. eozynofile: 0%-8%;
5. basophils: 0%-3%.

See also: Blood morphology – what is this test, what are the standards?

Morphology with a smear – complications after the examination

Tests such as blood smear morphology do not carry much risk. After the examination, the patient may have bruises at the injection site, but he does not have to worry about any problems or complications. Some people may experience moderate pain and burning when collecting blood, and some may feel nauseous or dizzy during or after the blood is drawn. For these reasons, it is recommended to remain seated after the examination until the feeling has passed.

Very rarely, but some people who have had blood collected may develop a hematoma, which is a collection of blood directly under the skin. Some people may also develop a skin infection at the site of collection, but this is also extremely rare.