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Living with immune thrombocytopenia (ITP) usually means regular blood draws and waiting for your latest platelet count. But if you develop new symptoms or changes in your blood counts, your doctor may order a direct Coombs test to look for another immune-related condition.
If you have both ITP and autoimmune hemolytic anemia (AIHA), which affects red blood cells, you may be diagnosed with Evans syndrome. This rare condition occurs when the immune system mistakenly targets more than one type of blood cell.
This article covers what the direct Coombs test checks for, how Evans syndrome relates to ITP, signs that may point to Evans syndrome, and when to talk with a hematologist (a doctor who specializes in blood disorders).
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Also called the direct antiglobulin test (DAT), the direct Coombs test checks whether antibodies or other immune proteins are attached to red blood cells. It can help diagnose AIHA, in which the immune system mistakenly destroys red blood cells.
If you already have ITP, your doctor might order a direct Coombs test if you develop signs or symptoms that ITP alone doesn’t explain, such as unusual fatigue, pale skin, or anemia (a low level of healthy red blood cells). Other blood tests can also look for signs that red blood cells are breaking down too quickly.
If these tests show AIHA along with ITP, your doctor may diagnose Evans syndrome.
How Are ITP and Evans Syndrome Related? ITP and Evans syndrome are connected, but they’re not the same condition. Understanding the difference starts with knowing what Evans syndrome is.
Evans syndrome is a rare autoimmune disorder in which the immune system attacks more than one type of blood cell at once. It most often involves platelets and red blood cells, but sometimes white blood cells called neutrophils, which help fight infections, are also affected.
Doctors call these conditions autoimmune cytopenias, meaning the immune system causes certain blood cell counts to drop. They can include ITP (low platelets), AIHA (affects red blood cells), and autoimmune neutropenia (low neutrophils).
Researchers estimate that Evans syndrome affects 1 to 9 people per million each year, making it far less common than ITP or AIHA alone. The two conditions don’t have to occur at the same time. One (usually ITP) may develop months or years before the other.
If you already have ITP, doctors may look for Evans syndrome if a routine complete blood count (CBC) reveals a sudden, unexplained drop in your red or white blood cells. New symptoms, such as unusual fatigue, pale skin, or frequent infections, may also lead your doctor to investigate further.
No single test can confirm Evans syndrome. Doctors diagnose this condition by looking for autoimmune blood cell problems, such as ITP and autoimmune hemolytic anemia, and ruling out other possible causes. Tests for antibodies against platelets or neutrophils aren’t always needed and may not give clear results.
ITP on its own tends to cause bruising and bleeding-related symptoms. Evans syndrome can cause additional symptoms because red blood cells are also affected.
With ITP alone, you might notice easy bruising, petechiae (tiny red or purple spots caused by bleeding under the skin), or bleeding gums. Evans syndrome may cause additional symptoms tied to hemolysis (the breakdown of red blood cells):
Tell your doctor if you develop any of these symptoms. Jaundice and dark urine, in particular, can be signs that red blood cells are breaking down too quickly.
Beyond your platelet count, several lab results can point to hemolysis. One sign is a drop in hemoglobin, the oxygen-carrying protein in red blood cells, that can’t be explained by bleeding. A high reticulocyte count can also be a sign that your bone marrow is making more red blood cells to replace those being destroyed.
Doctors may also check lactate dehydrogenase (LDH), haptoglobin, and bilirubin. Levels of these three markers shift when red blood cells are breaking down too quickly.
A peripheral blood smear, which involves looking at your blood under a microscope, may show spherocytes. These unusually round red blood cells can be seen with warm AIHA, the most common type of AIHA.
Doctors consider these lab results together rather than relying on any one result. They may look at them along with your platelet count, symptoms, and direct Coombs test results to determine whether you have AIHA in addition to ITP.
How Is Evans Syndrome Diagnosed and Treated? Evans syndrome usually requires more testing than ITP alone, and treatment is tailored to each person.
Diagnosing Evans syndrome may involve a direct Coombs test, reticulocyte count, and tests for LDH, haptoglobin, and bilirubin to look for hemolysis. Doctors may also check neutrophil counts if autoimmune neutropenia is a concern.
Because Evans syndrome is a diagnosis of exclusion, doctors also rule out other possible causes. These can include thrombotic thrombocytopenic purpura (TTP), a different blood disorder that can cause low platelets and the breakdown of red blood cells.
Other steps may include a bone marrow biopsy, imaging, or additional blood tests. These tests can help look for conditions associated with Evans syndrome, such as systemic lupus erythematosus (SLE, a broader autoimmune disease) or autoimmune lymphoproliferative syndrome (ALPS, a rare inherited immune disorder).
Evans syndrome can be more difficult to treat than ITP or AIHA alone. Treatment may need to address more than one type of low blood cell count.
Common first-line treatments are corticosteroids, such as prednisone, and intravenous immunoglobulin (IVIG). IVIG is made from antibodies collected from donated blood plasma and is given through a vein.
If these treatments don’t work well enough, doctors may consider other options based on which blood cells are affected and a person’s overall health. These may include rituximab or other medicines that affect the immune system.
For ongoing ITP, options may include fostamatinib or thrombopoietin receptor agonists, which help the body make more platelets. Certain types of AIHA may require different treatments, such as sutimlimab.
Treatment is highly individualized, and relapses are common. Regular monitoring helps doctors see how treatment is working and adjust the care plan when needed.
Most people with ITP can receive routine care, but certain changes may call for a closer look from a hematologist. These include:
If any of these occur, a hematologist can look for possible causes, including Evans syndrome, and recommend next steps. Because Evans syndrome may require more testing and treatment, involving a hematologist early can help guide your care.
A direct Coombs test doesn’t diagnose ITP or Evans syndrome on its own. Instead, it helps doctors diagnose AIHA, which can occur along with ITP as part of Evans syndrome.
Keep track of new symptoms, such as fatigue, jaundice, or dark urine, so you can describe changes clearly to your doctor. If you develop symptoms that seem different from your usual ITP pattern, ask whether additional testing, including a direct Coombs test, may be appropriate.
If your doctor suspects Evans syndrome, ask whether you should see a hematologist for a full evaluation. An accurate diagnosis can help you and your healthcare team determine the treatment plan that best fits your needs.
On myITPteam, people share their experiences with immune thrombocytopenia, get advice, and find support from others who understand.
If you’ve had a direct Coombs test, what led your doctor to look beyond ITP in your case? Let others know in the comments below.
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