Multiple sclerosis is an autoimmune health condition that affects the central nervous system. It develops when the immune system accidentally attacks the myelin sheath, which covers nerve fibers.  This  causes disrupted communication between the brain and the rest of the body. The condition can be managed if it is detected in time. But diagnosing it requires a combination of tests to overrule other conditions that can cause similar symptoms.

Diagnostic criteria
Multiple sclerosis diagnoses are primarily based on the McDonald criteria. They are named after the neurologist W. Ian McDonald, who led a panel to  come up with  recommendations for diagnosing the condition.

1. Dissemination in space (DIS)
This  criterion focuses on the parts of the body affected by multiple sclerosis. The scarring associated with the condition must be observed in multiple key central nervous system areas that are typically affected by multiple sclerosis. DIS can be demonstrated through an MRI.

2. Dissemination in time (DIT)
This diagnostic criterion focuses on the  progression of the condition . It requires evidence that new lesions have formed at different points in time.  This  can be checked through follow-up MRIs that reveal new lesions  that were  absent in previous scans.

The McDonald criteria have evolved to incorporate more precise diagnostic tools, making it possible to test the impact of multiple sclerosis earlier and with greater accuracy.

Diagnostic tests
A self-test for the condition may not suffice, as a combination of methods is used to help doctors accurately diagnose multiple sclerosis. Each multiple sclerosis test provides valuable information that contributes to a better understanding of the condition and severity of symptoms.  This  then helps  determine  the appropriate management options for the condition.  

1. Clinical evaluation
Clinical evaluation is the first step toward diagnosing any medical condition. If one suspects multiple sclerosis,  they  would be referred to a neurologist who would perform these tests. The examination would primarily focus on two things:

Medical history:  Those with a family history of the condition are more likely to develop it. Also, reviewing a family history of conditions like diabetes, autoimmune disorders, and other health issues can help doctors determine the risk of multiple sclerosis.  This  is accompanied by a detailed health review, which helps doctors identify patterns and potential triggers associated with symptom flare-ups. 

Neurological examination:  Multiple sclerosis primarily affects the central nervous system. So, a neurological examination is crucial for confirming the presence of the condition. Here, the doctor will check the reflexes, muscle strength, balance, coordination, sensory abilities, and vision. Any abnormalities here could be a sign of multiple sclerosis. For instance, abnormal eye movements, muscle weakness, or changes in sensation often indicate the condition.

2. MRI
MRI is an imaging tool for diagnosing various conditions, including multiple sclerosis. It detects lesions or plaques, i.e.,  areas of demyelination in the brain and spinal cord. Also, the contrast agents used for MRI scans highlight active inflammation .

Brain MRI:  It provides detailed images of the brain structure, enabling the identification of lesions, if any. Multiple sclerosis lesions often appear as bright spots.  The scan can reveal  the  size, number, and location  of these lesions .

Spinal MRI:  This focuses on lesions in the spinal cord. Spinal cord lesions can lead to significant disability, such as motor weakness or sensory deficits, so checking for them can help doctors determine the severity of symptoms and how to deal with them.

MRI scans also help monitor the  progression of the disease and the effectiveness of treatment .   Regular follow-up MRIs may be performed to track  changes in  inflammation, damage, and scarring.

3. Spinal tap
A spinal tap (or lumbar puncture) helps extract cerebrospinal fluid (CSF), which is then analyzed to check for specific markers of multiple sclerosis. For instance,  the presence of  certain proteins, called oligoclonal bands, in the spinal  fluid  can indicate inflammation in the central nervous system. An increased IgG (immunoglobulin G—an antibody) index in the CSF also suggests an immune response within the central nervous system. Elevated levels of IgG are a sign of chronic inflammation or immune activation. So, a spinal tap is particularly useful when MRI findings are inconclusive, providing additional evidence to support a diagnosis of MS.

4. Blood tests
Blood tests may not detect the neurological condition but can help rule out other issues that mimic multiple sclerosis symptoms. These tests often help rule out  conditions like  infections, inflammatory diseases, and vitamin deficiencies.

Vitamin B12 deficiency:  Extremely low levels of vitamin B12 can cause health issues like tingling and numbness in the extremities, which are also observed when dealing with multiple sclerosis.

Lyme disease : This tick-borne illness can cause neurological symptoms

Lupus:   This is an autoimmune disease known to  cause symptoms like fatigue and pain, which are also observed in multiple sclerosis.

5. Optical coherence tomography (OCT)
Another imaging test, OCT, provides detailed pictures of the retina—a light-sensitive tissue at the back of the eye. The test  can detect the thinning of the retinal nerve fiber,  which is frequently observed in those with optic neuritis, a condition associated with multiple sclerosis.