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Blood smear

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Anonymous

14y ago
Updated: 6/22/2024
Definition

A blood smear is a blood test that gives information about the number and shape of blood cells.

Alternative Names

Peripheral smear

How the test is performed

Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

The blood sample is sent to a lab, where the health care professional looks at it under a microscope. Or, the blood may be examined by an automated machine. The smear shows the number and kinds of white blood cells (differential), abnormally shaped blood cells, and gives a rough estimate of white blood cell and platelet counts.

How to prepare for the test

No special preparation is necessary.

How the test will feel

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed

This test may be performed as part of a general health exam to help diagnose many illnesses. Or, your doctor may order this test if you have signs of a blood disorder.

Other conditions under which the test may be performed:

Normal Values

Red blood cells normally are the same in size and color and have a lighter-colored area in the center. The blood smear is considered normal if there is:

  • Normal appearance of cells
  • Normal white blood cell differential

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

What abnormal results mean

Abnormal results mean there is an abnormality in the size, shape, color, or coating of the red blood cells.

Some abnormalities may be graded on a 4-point scale:

  • 1+ means 25% of cells are affected
  • 2+ means half of cells are affected
  • 3+ means 75% of cells are affected
  • 4+ means all of the cells are affected

The presence of target cells may be due to:

The presence of sphere-shaped cells (spherocytes) may be due to:

The presence of elliptocytes may be a sign of hereditary elliptocytosisor hereditary ovalocytosis.

The presence of fragmented cells (schistocytes) may be due to:

The presence of a type of immature red blood cell called a normoblast may be due to:

The presence of burr cells (echinocytes) may indicate:

The presence of spur cells (acanthocytes) may indicate:

The presence of teardrop-shaped cells may indicate:

  • Leukoerythroblastic anemia
  • Myelofibrosis
  • Severe iron deficiency
  • Thalassemiamajor

The presence of Howell-Jolly bodies may indicate:

The presence of Heinz bodies may indicate:

  • Alpha thalassemia
  • Congenital hemolytic anemia
  • G6PD deficiency
  • Unstable form of hemoglobin

The presence of slightly immature red blood cells (reticulocytes) may indicate:

  • Anemia with bone marrow recovery
  • Hemolytic anemia
  • Hemorrhage

The presence of basophilic stippling may indicate:

The presence of sickle cells may indicate sickle cell anemia.

What the risks are

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

  • Excessive bleeding
  • Fainting or feeling light-headed
  • Hematoma (blood accumulating under the skin)
  • Infection (a slight risk any time the skin is broken)
Special considerations

The accuracy of this test depends, in part, on the experience of the person looking at the sample. Experienced cell examiners can get a lot of information from the blood smear.

References

Newland J. The peripheral blood smear. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 161.

Reviewed By

Review Date: 02/09/2010

David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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13y ago

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Continue Learning about Biology

What is blood smear?

A blood smear is a sample of blood that is spread thinly on a glass slide, stained, and examined under a microscope. It is used to evaluate the number, morphology, and size of different types of blood cells such as red blood cells, white blood cells, and platelets. This test helps in diagnosing various blood disorders and infections.


Is there any difference if the prepared smear is too thick or too thin?

Thin smears of blood are needed to investigate hematological problems or disorders of the blood. It is also used to identify the parasite within the blood. Thick films enables the microscopist to screen the blood of a larger volume. They are more sensitive than the thin film.


Why do you have to use NSS instead of water in preparing fecal smear?

NSS (normal saline solution) is used instead of water in preparing a fecal smear to prevent lysis (rupturing) of red blood cells in the sample. Using water can cause hemolysis, which may interfere with the accurate interpretation of the fecal sample. Normal saline is isotonic and helps maintain the integrity of the red blood cells in the smear.


What causes smudge cells?

Smudge cells are caused by the mechanical disruption of fragile cells, such as lymphocytes, during the slide preparation process for blood smear examination. This can occur due to rough handling, poor staining techniques, or improper smear creation. Smudge cells are often seen in samples with high white blood cell counts and do not represent pathological changes in the cells themselves.


Why are white blood cells in a stained blood smear usually counted at low power under a microscope?

Due to the limited field of vision of microscopes, it is comparatively easier to count the number of white blood cells in a stained blood smear under low power than under high magnification. Although the individual cells would be smaller and thus more difficult to count, there would be more in view at any given time.

Related Questions

What makes up blood smear?

Blood


What does blood in your pap smear mean?

It's not unusual for women to have a small amount of bleeding with their pap smear. On its own, blood in the pap smear has no clinical significance.


What is the important of thin blood smear?

lllpp


The area of a blood smear that is tested is called the?

The area of a blood smear that is tested is called the peripheral blood smear. It is a sample of blood that is spread thinly on a glass slide for examination under a microscope to evaluate the number, shape, and size of blood cells.


Do they take your blood when you have a pap smear?

A blood sample is not part of the pap smear, which screens for cervical cancer. Blood tests may be recommended for patients at the office for their annual exams, however.


What white blood cell is most numerous in a normal blood smear?

Neutrophils


I had blood on the swob when you had a smear even thought you were not on a period and have been taking hormone tablets to stop me bleeding so i could have a smear test done but i have a cyst?

Blood on the swab is not unusual during a pap smear and has no clinical significance.


What is blood smear?

A blood smear is a sample of blood that is spread thinly on a glass slide, stained, and examined under a microscope. It is used to evaluate the number, morphology, and size of different types of blood cells such as red blood cells, white blood cells, and platelets. This test helps in diagnosing various blood disorders and infections.


Do you have information about frog blood smear?

a frog blood smear reveals that its red blood cells are ovoid in nature as compared to the human RBCs that are spherical in nature. i think that's the main difference that u will find with a frog blood smear


What would be observed in the blood smear of patient who has malaria?

sBoth thick and thin blood smears are taken from the finger tip of earlobe of malaria patient. This smear is kept in water to dissolve and remove the haemoglobin from the slide. The slide is stained and visualised under oil immersion lens to see the malaria parasites directly.


Where should blood be taken from to perform a smear?

from the body or blood bank. dont get from anywhere else


What are the five factors that can affect the quality of a blood smear?

i just want the answer