Restless Legs Syndrome and Related Disorders - Diagnosis

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Diagnosing Iron Deficiency Anemia and Its Causes

Because of the high association between restless legs syndrome and iron deficiency, a test for low iron stores should be part of the diagnostic work-up in RLS. There are two steps in making this diagnosis:

• The first step is to determine if a person is actually deficient in iron.
• If iron stores are low, the second step is to diagnose the cause of the iron deficiencies, which will help determine treatment.

Determining if Iron Stores are Low: The following findings are important in determining that a person is iron deficient:

• Blood cells viewed under the microscope are pale (hypochromic) and abnormally small (microcytic). They are also mostly uneven in shape. (These findings suggest iron deficiency, they but can also appear in anemia of chronic disease and thalassemia.)
• Hemoglobin and iron levels are low. (These findings further suggest iron deficiency, but they can also occur in cases due to anemia due to chronic disease.)
• Ferritin levels are low. Ferritin is a protein that binds to iron and low levels typically mean reduced iron stores. (However, high levels in the blood do not always mean sufficient iron stores. For example, pregnant women may have high ferritin levels into their third trimester but still be iron deficient. Ferritin levels may also be normal or even elevated in patients with inflammation from anemia of chronic disease, even if they also have low iron stores.)
• A test that measures a factor called serum transferrin receptor (TfR) is proving to be very sensitive in identifying iron deficiency in problematic patients, including the elderly with chronic diseases and possibly pregnant women.

Determining Causes of Iron Deficiency. When iron deficiency anemia is diagnosed, the next step is to determine what causes the iron deficiency itself.

• Dietary iron deficiency is most common in children and infants. It is rare in adults.
• Heavy menstrual or abnormal uterine bleeding is usually the cause of iron deficiencies in young women. Increased need for iron during pregnancy is also a common cause in this population.
• If internal bleeding is suspected as the cause, the gastrointestinal tract is usually the first suspect as the source. A diagnosis in such cases can be often be made if the patient has noticed blood in the stools, which can be black and tarry or red-streaked. Often, however, bleeding may be present but not visible. In such cases, stool tests for this hidden (occult ) blood are required. Additional tests may then be needed to diagnose the precipitating condition. Endoscopy, in which a fiber optic tube is used to view into the gastrointestinal tract, may be used, particularly when the source of bleeding is unclear.