Test Detail
Interpreting Results

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Written by
Dr. Shreya Gupta
BDS, MDS - Oral and Maxillofacial Pathology
Reviewed by
Dr. Ashish Ranjan
MBBS, MD (Pharmacology)
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Peripheral Smear Examination

You need to provide
This test is for
Male, Female
Test Preparation
  1. No special preparation required
  2. Provide brief clinical history/ doctor's prescription at the time of sample collection


What is P/S?

Peripheral Smear Examination test evaluates the different components of the blood. The smear evaluates the red blood cells, white blood cells, and platelets as well as other abnormalities such as the presence of parasites. The blood smear test is ordered to diagnose the cause of unexplained jaundice, unexplained anemia, unknown fever, and severe infection.

The number and the appearance of blood cells can be affected by a variety of diseases such as the smaller size of RBCs may indicate a type of anemia whereas increased number of WBCs may indicate infection.

A blood smear test is said to be normal when the sample contains an optimum number, size and shape of blood cells. The results are considered abnormal when cells have an abnormality in shape, size, and number.

Why is P/S done?

The peripheral smear examination is done:

  • In case of signs or symptoms of anemia such as weakness, fatigue, pale complexion, unexplained jaundice, and enlargement of the spleen.

  • In case the results of complete blood count or WBC differential is abnormal. 

  • In case of signs or symptoms of conditions affecting red blood cell production.

What does P/S Measure?

The peripheral smear examination evaluates the red blood cells (RBCs), white blood cells (WBCs), platelets and determines their relative percentages in the blood. It also helps in detecting, diagnosing, and monitoring deficiencies. Along with that, it detects diseases and disorders which involves the production of blood cells, their function, and lifespan.

To make a peripheral smear, a drop of blood is taken from the patient’s blood sample and is spread in a thin layer onto a glass slide. The slide is then stained with special stains. After the staining, the slide is examined and evaluated under the microscope for blood cells. 

The following cells can be evaluated in the slide:

  • White blood cells (WBCs or leukocytes) - Their function is to fight infections and participate in immune responses.  

  • Red blood cells (RBCs, erythrocytes) - Their function is to carry oxygen to the tissues. 

  • Platelets (Thrombocytes) - These are small cell fragments which play an important role in blood clotting.

Platelets are produced and mainly mature in the bone marrow just like RBCs and WBCs. They are released into the stream of blood whenever required. 

The peripheral smear examination helps to:

  • Compare the size, shape, and general appearance of WBCs along with determining its five different types and their relative percentages.

  • Detects the size, shape, and color of the RBCs.

  • Evaluates the number of platelets. 

The number and the appearance of blood cells can be affected by a variety of diseases and conditions such as the smaller size of RBCs may indicate a type of anemia, increased number of WBCs may indicate infection or any other condition.

Interpreting P/S results


The abnormal results depend upon the type of blood cell affected.

The abnormal red blood cells can be seen in conditions like:

  • Iron deficiency anemia

  • Sickle cell anemia

  • Hemolytic uremic syndrome

  • Polycythemia rubra vera

The abnormal white blood cells can be seen in conditions like:

  • Acute or chronic leukemia

  • Lymphoma

  • Hepatitis C virus infection

  • HIV

  • Viral infections like Dengue

  • Fungal infections such as candidiasis

  • Parasitic infections such as pinworm

  • Other lymphoproliferative diseases

The abnormal platelets can be seen in conditions like:

  • Thrombocytopenia

  • Myeloproliferative disorders

Answers to Patient Concerns & Frequently Asked Questions (FAQs) about P/S

Frequently Asked Questions about Peripheral Smear Examination

Q. How is the blood sample taken?
The healthcare provider takes a blood sample from the arm. The site from where the blood is to be withdrawn is cleaned with a swab of rubbing alcohol. This is then followed by inserting a small needle which has a tube attached to it for collecting blood. Once the sufficient blood for analysis is withdrawn, the needle is removed. The site is then covered with a gauze pad.
Q. Is there any risk associated with the withdrawal of blood sample procedure?
As such there is no risk but in few cases, bruising, bleeding, and infection at the puncture site can be seen. In very few cases, there can be swelling of the vein after the blood is withdrawn.
Q. What are the signs and symptoms of a blood disorder?
The signs and symptoms of a blood disorder include weakness, fatigue, pale complexion, fever, unexplained jaundice, episodes of bleeding, easy bruising, frequent nose bleeds, spleen enlargement, and bone pain.
Q. What conditions can affect the red blood cells?
The conditions which can affect the red blood cells include different types of anemia, myeloproliferative or myelodysplastic neoplasms, and bone marrow disorders.
Q. What type of RBCs irregularities can be seen on a smear in case of a condition affecting the RBC?
The most common RBC irregularity includes anisocytosis in which variable size of red blood cells is seen such as in case of anemia. If the size of the RBC is smaller than normal, it is called as microcyte while if it is larger than normal, it is called as macrocyte. If there is a variation in the shape of the RBCs, it is known as poikilocytosis. Examples include burr cells, rouleaux, sickle cells, elliptocytes, target cells, teardrop cells, and schistocytes. If there is variability in the size as well as shape of RBC, it is known as anisopoikilocytosis.
Q. What conditions can affect the absolute or relative number of WBCs and their appearance?
The conditions which can affect the absolute or relative number of WBCs and their appearance include infections and/or inflammation, bone marrow disorders, allergies, leukemia, myelodysplastic syndrome, or myeloproliferative neoplasm.
Q. In what conditions abnormal size of platelets can be seen?
The abnormal size of platelets can be seen in conditions like myeloproliferative neoplasms, immune thrombocytopenia, and in case the immune system inappropriately produces antibodies directed against platelets.
Q. What additional tests are advised in case of abnormal results are seen on the blood smear?
The additional tests include iron tests, folate tests, and flow cytometry immunophenotyping. The other tests could be bone marrow aspiration and bone marrow biopsy, BCR-ABL1, and hemoglobinopathy evaluation.
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