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Testing for Lupus: Complete Blood Count

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Updated July 14, 2014

When determining if someone has lupus, your physician has several diagnostic tools available to help her make a diagnosis. The most common include a complete medical history, physical examination, skin and kidney biopsies, as well as various lab tests, which might be referred to as bloodwork.

Typical lab tests include:

And while all of these are important for helping diagnosis lupus, typically the first lab test a physician will request is the complete blood count (CBC). The reason why? Because blood can tell the doctor a lot about a person’s condition right from the get-go.

As you might expect, blood is collected by the healthcare professional, typically from a vein at the inside of the elbow or the back of the hand. A smaller tool, called a lancet, is used for infants and young children.

A CBC is comprised of tests and is commonly used as a broad screening tool. It has several components, including

  • White blood cell count (WBC) White blood cells aid the body in fighting infections, and can be indicators of infection, as well. This test measures the number of white blood cells in the blood. Either too many white blood cells or too few can both be significant indicators.
  • White blood cell differential This test counts the various types of WBCs.
  • Red blood cell count (RBC) Simply, the number of red blood cells present. Red blood cells contain hemoglobin and function as oxygen carriers. As with white blood cells, both increases and decreases in number can matter.
  • Red cell distribution width Measures the variation in the size of red blood cells.
  • Hemoglobin Hemoglobin is the protein in red blood cells that carries oxygen. This measures how much of that oxygen-carrying protein is in the blood.
  • Mean corpuscular hemoglobin Tells how much hemoglobin is inside a red blood cell.
  • Mean corpuscular hemoglobin concentration Measures the average concentration of hemoglobin inside a red blood cell.
  • Hematocrit The percentage of red blood cells in whole blood.
  • Platelet count The number of platelets in the blood. Platelets are a type of blood cell that prevents bleeding by forming clots.
  • Mean platelet volume Measures the size of platelets and can give information about platelet production in bone marrow.

Results might tell a doctor that you have issues with fluid volume, like dehydration or blood loss, and it can aid in the diagnoses of infection, allergies, and problems with blood clotting. It can also indicate various types of anemia.

For those wondering if they have lupus, the doctor will focus on your RBC and WBC counts. Low RBC counts are frequently seen in autoimmune diseases like lupus. But they can also indicate blood loss, bone marrow failure, kidney disease, hemolysis (RBC destruction), leukemia, malnutrition and more.

Similarly, low WBC counts can point toward lupus, as well as bone marrow failure and liver and spleen disease.

If a CBC comes back with high numbers of RBCs or a high hematocrit, it could be indicative of issues such as lung disease, blood cancers, dehydration, kidney disease, congenital heart disease (and other heart problems. Low RBCs indicate autoimmune diseases

High WBCs, called leukocytosis, may indicate an infectious disease, inflammatory disease, leukemia, stress, and more.

Sources:

CBC. Lab Tests Online. February 2009.

Handout on Health: Systemic Lupus Erythematosus The National Institute of Arthritis and Musculoskeletal and Skin Diseases. August 2003.

CBC Medline Plus Medical Encyclopedia. January 2009.

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