Laboratory Studies
All patients with symptoms of restless legs syndrome (RLS) should be tested for iron deficiency. [3, 4] At a minimum, a ferritin level should be obtained. A complete iron panel, including iron levels, ferritin, transferrin saturation, and total iron binding capacity, is preferable because the ferritin level can be falsely elevated in acute inflammatory states.
Patients whose RLS is well controlled but who develop reemergence or augmentation of symptoms should undergo repeat evaluation of their iron status. Augmentation is defined the presence of 1 or more of the following:
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Earlier onset of symptoms during the evening or after assumption of a restful position
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Increased intensity of symptoms in the morning
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Extension of symptoms to the upper part of the body
If a secondary cause of RLS is suspected on the basis of the history, abnormal findings on neurologic examination, or a poor response to treatment, other laboratory tests should be done. These include a complete blood count (CBC) and measurement of levels of the following:
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Blood urea nitrogen (BUN)
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Creatinine
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Fasting blood glucose
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Magnesium
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Thyroid-stimulating hormone (TSH)
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Vitamin B-12
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Folate
Other Studies
Needle electromyography (EMG) and nerve conduction studies should be considered if polyneuropathy or radiculopathy is suspected on clinical grounds, even if the results of the neurologic examination are apparently normal. [5]
Polysomnography (PSG) may be necessary to quantify periodic leg movements of sleep (PLMS) or to characterize sleep architecture, especially in children and in patients who continue to have significant sleep disturbances despite relief of restless legs syndrome (RLS) symptoms with treatment. PSG should also be used in patients with other suspected sleep comorbidities.
Imaging studies are not routinely used in the diagnosis of patients with RLS and are currently investigational in this setting.
