Peripheral Blood Smear
A peripheral blood smear is a process, involving spreading some blood directly onto a glass slide. Then it will be treated with a special dye and examined under a microscope. 1
This blood test is a significant method used to check for abnormalities in the blood cells. The test check for three main blood cells, which are:
• White cells, that work against inflammatory diseases
• Red cells, that carry the oxygen
• Platelets, that play an important role in blood clot
The test is showing detail information regarding the shape and number of these cells, helping doctors diagnose blood disorders and other medical conditions. 2
Interpretation and evaluation and of a peripheral smear
Red blood cells
The normal size of RBCs is equal to the nucleus size of a small lymphocyte with a mean diameter of 7.5 ?m. Based on this mean diameter, RBCs are classified into:
• normocytic (normal sized).
• microcytic (smaller than normal)
• macrocytic (larger than normal)
This morphological estimation is useful for classifying the notable types of anemias, including thalassemia, Iron deficiency anemia, sideroblastic anemia show microcytic RBCs, and anemia of chronic disorders.
The anemia due to folic acid and vitamin B-12 deficiency, alcoholism or liver disease is one of macrocytic type. Hemolytic anemias are usually considered one of the normocytic types. The variation in the size of RBCs is known as anisocytosis.
Color and Pallor
The shape of normal RBCs is a disc shaped and has a central pallor area, having cell’s diameter around one-third. These normal erythrocytes are called normochromic RBCs. If RBCs have a pallor area that is larger than the normal, they are known as hypochromic. This can be found in anemia of chronic diseases, hemoglobinopathies, and iron deficiency anemia.
Normal RBCs are biconcave discs. Many diseases can result in abnormal shapes of red blood cells; identification of which provides important clues to the underlying disorder. Variation in the shape of RBC is called poikilocytosis.
The normal red blood cells are biconcave discs. Many diseases can cause abnormal shapes of the red blood cells. The variation in the RBCs shape is known poikilocytosis. The following is some of the abnormalities in RBC shapes:
Red blood cells become more spherical, cannot see central pallor, and there is a lot of hemoglobin materials.
Post- transfusion reaction and hereditary spherocytosis
RBCs shaped as Oval
hereditary ovalocytosis, thalassemia, and sickle cell anemia.
Half-moon shaped red blood cells, having more than one spicules.
G6PD deficiency and disseminated intravascular coagulation.
Red blood cells with uniformly spaced pointed projections on their surface.
Hemolytic and megaloblastic anemia, and uremia.
Red cell agglutinate
Red blood cells are found in irregular clumps
Warm autoimmune hemolysis and cold agglutination
An abnormal rise in the proportion of immature leucocytes is called a left shift, can be seen in some infections or leukemias.
Myeloblasts are the earliest granulocyte procedures. They are large with a round to oval nucleus, have basophilic cytoplasm, have 2-5 nucleoli and a fine reticular chromatin pattern. Myelocytes are smaller with oval nucleus, have no nucleoli, have a lot of cytoplasm and condensed chromatin. Promyelocytes are slightly larger with primary granules, more condensed chromatin pattern and faint nucleoli.
The normal number of platelets are around 2-4 by 0.5 microns in size, having coarse cytoplasmic granules. Usually, in a normal individual, around 7-15 platelets are found per oil immersion field. A lot of fields should be counted to estimate platelets count and reduce sample bias.
Thrombocytopenia is a low platelet count that may occur in specific infections, such as aplastic anemia, hypersplenism, dengue fever, and idiopathic thrombocytopenic purpura.
Thrombocytosis is a high platelet count that can be seen in idiopathic thrombocythemia, chronic myeloid leukemia, and post-hemorrhage. Also, thrombasthenia is a term for qualitative abnormalities of platelets, that require platelet functional studies to identify them.
Giant platelets are platelets about the normal size of red blood cells or more, caused by hyperactivity of the megakaryocytes. If there is a stimulus that causes increase the demand for platelets production by inducing the bone marrow to form platelets, some larger and younger platelets are made and thrown into the circulation. This is found in some inherited conditions, such as May-Haggelin anomaly, Bernard Soulier syndrome, and Wiskott Aldrich syndrome. 3
1-Heather Ross, and Tim Jewell. “Blood Differential Test: Purpose, Procedure & Complications.” Healthline. Accessed September 15, 2018. https://www.healthline.com/health/blood-differential#1.
2- “Peripheral Blood Smear Examination.” DoveMed. June 4, 2013. Accessed September 16, 2018. https://www.dovemed.com/common-procedures/procedures-laboratory/peripheral-blood-smear-examination/.
3- Mahajan, Surbhi, and Surbhi MahajanDr Surbhi Mahajan. “Peripheral Blood Smear Procedure and Interpretation.” Medcaretips.com. November 11, 2017. Accessed September 16, 2018. https://medcaretips.com/peripheral-blood-smear-procedure/.