How do blood tests help diagnose MS?

Multiple sclerosis (MS) is a chronic disease of the central nervous system. Symptoms vary from person to person. Problems with vision, balance, coordination, and fatigue are among the most common symptoms.

Approximately 2.3 million people worldwide have MS. There’s no US national registry, but it’s estimated to affect about 400,000 Americans.

Blood tests are often an effective way to eliminate or confirm other diagnoses. Blood tests can help your doctor rule out conditions such as Lyme disease that trigger some of the same symptoms as MS. This puts your doctor one step closer to making an accurate diagnosis.

Since symptoms come and go, and there isn’t one test that provides a conclusive diagnosis, it can take a long time to diagnose MS. A new type of blood test shows a great deal of promise, but more clinical studies are needed.

While the wait may be frustrating, each test will help eliminate or confirm other potential causes for your symptoms.

A number of conditions cause symptoms similar to those of MS. All of these should be investigated. Some, like progressive multifocal leukoencephalopathy (PML) virus and brain tumors, can be identified with an MRI.

Blood tests can help provide clues to other MS mimics, such as:

Lyme disease

Tingling or numbness in your arms, hands, legs, and feet are common symptoms of both MS and Lyme disease. Lyme disease is a tick-borne infection that can spread to the central nervous system. With Lyme disease, you’re likely to also have a skin rash.

While not 100 percent accurate, enzyme-linked immunosorbent assay and Western-blot blood tests can detect the presence of Lyme disease infection in the blood. Although some symptoms are the same, the treatments for MS and Lyme disease are different. Early-stage Lyme disease can often be cured with a course of oral antibiotics.

Systemic lupus erythematosus

Lupus is an inflammatory autoimmune disease that can affect your central nervous system. Symptoms that lupus and MS share include:

  • numbness
  • tingling
  • fatigue
  • vision problems

Like MS, there isn’t a single test for lupus. A blood test that is positive for antinuclear antibodies and other antibodies may indicate lupus or some other autoimmune disease, but not MS. Treatment for lupus depends on your symptoms.

Devic’s disease

Neuromyelitis optica, better known as Devic’s disease, is a rare immunological disorder that is strikingly similar to MS. The two conditions share many symptoms, including:

  • blurred or lost vision
  • weakness
  • numbness
  • bladder problems
  • spasticity

A test called the NMO-IgG blood test will be negative in people with MS, but positive in 70 percent of people with Devic’s disease. Devic’s disease doesn’t respond to the same disease-modifying medications as MS. It can be treated with steroids and other immune-suppressing drugs.

Vitamin deficiencies

Certain vitamin deficiencies, such as a lack of vitamin B-12, can cause symptoms that mimic those of MS.

Demyelination, common in both B-12 deficiency and MS, is damage to the protective covering that surrounds nerve fibers within the central nervous system. Symptoms of vitamin B-12 deficiency include numbness and tingling in the hands and feet, weakness, and fatigue.

Copper, zinc, and vitamin E deficiencies can also cause neurological symptoms.

A simple blood test can check the levels of essential vitamins in your blood. Your doctor can walk you through treatment plan with supplements and dietary changes.

To reach the diagnosis of MS, your doctor must find:

  • damage in two distinct areas of the central nervous system
  • that the areas of damage developed at two different points in time
  • that all other possible diagnoses are ruled out

Generally, a series of tests are needed to meet the criteria for diagnosis. In addition to symptom history and blood tests, your doctor might also order the following tests.


An MRI is painless, noninvasive, and can produce detailed images. Performed both with and without contrast dye, an MRI can identify lesions on the brain and spinal cord. The images can show if the lesions are old, new, or currently active. In addition to diagnosis, an MRI can help monitor disease progression.

Spinal tap

Although lumbar puncture can’t rule out or confirm MS, it can help with diagnosis. Spinal fluid is obtained from a needle inserted between the bones of your lower spine. In people with MS, the spinal fluid sometimes contains elevated levels of IgG antibodies or proteins called oligoclonal bands, which could also be caused by some other diseases. About 5 to 10 percent of people with MS have no spinal fluid abnormalities.

Visual evoked potentials

This test involves staring at a screen with an alternating checkerboard pattern. This helps determine if there’s any impairment of your optic nerve pathways.

After diagnosis, the next step is to discuss treatment options with your doctor. There’s a growing list of disease-modifying drugs designed to reduce relapses and slow disease progression in relapsing MS. These drugs haven’t been shown to work for progressive types of MS.

These powerful drugs must be taken consistently to be effective, and they can have serious side effects. Be sure to discuss the pros and cons of each with your doctor. Other symptoms, such as fatigue, can also be treated.

Your doctor can refer you to local resources to learn about MS. You may find it helpful to join an MS support group, either online or in person. Although everyone’s experiences with MS are different, it might help to share your experiences with others.

There’s no cure for MS, so management is a lifetime commitment. In addition to your general doctor, you’ll also need a neurologist on your healthcare team to evaluate symptoms and monitor disease progression.

Sometimes MS can lead to severe disability, but most people continue to have a good quality of life and can expect a normal lifespan.