A diagnostic test for multiple sclerosis (MS) developed by a group of neurologists in Spain was recently scrutinized in a group of patients,1 and doctors report very positive results.
A Test With a Unique Approach
It's called oligoclonal immunoglobulin G (IgG) band testing (OCGB), a test that looks for levels of an antibody known as immunoglobulin G in a person's spinal fluid as evidence of multiple sclerosis. Immunoglobulin G is one of the most common antibodies found in humans, even when no illness is present. However, it also plays a role in the apparent immune system attacks on the central nervous system that make up the pathology of MS.2,3
Experts believe it mediates the damage against myelin, a fatty sheath that covers nerve endings in the brain and spinal cord. This damage results in the symptoms found in MS.4
Other standard tests used to diagnose MS include magnetic resonance imaging, or MRI. This gives doctors a detailed image of the brain and can show lesions that have resulted from the disease. Evoked potential tests are other screening methods to verify the presence of MS. These tests measure how quickly and accurately a person's nervous system responds to certain stimulation. Patients suspected of having MS may also undergo a spinal tap, in which doctors remove a sample of spinal fluid to look for signs of the illness.5
A More Sensitive Diagnostic Test
A team of medical researchers headed by neurologist Luisa Villar, MD, at the Hospital Ramon y Cajal in Madrid, Spain, wrote in the journal Archives of Neurology that they recently developed a new, more sensitive, diagnostic test to detect levels of IgG in the cerebrospinal fluid of people suspected of having MS. This test "in conjunction with magnetic resonance imaging, can help in the early diagnosis of MS," the study investigators wrote. The aim of this research, therefore, was to determine the efficacy of the test in a group of people diagnosed with various neurologic disorders.
Three-hundred eighty five patients being evaluated in a hospital neurology department were recruited into this observational study. Each patient underwent the OCGB test to search for levels of IgG.
Few False Positives/False Negatives
At the end of the study, Villar and her colleagues found the test was positive for IgG in 127 patients with MS, a 96% sensitivity. The antibody was also found in just over a third of patients with central nervous system infections, and in one patient with motor neuron disease, the investigators reported. There were two patterns uncovered by the test that detected levels of IgG; one pattern showed IgG only in cerebrospinal fluid, which was found predominately in people with MS. The second pattern was found in both cerebrospinal fluid and in blood samples, which was more common in people with central nervous system infections, Villar's group noted.
In all, the test was more than 96% sensitive and had a specificity of over 92%, the researchers reported. When they considered the value of the test in only the MS patients, the study investigators found it still provided 96% sensitivity and more than 99% specificity. While the test has a specificity similar to that provided by MRI tests, it has a higher sensitivity, Villar explained. Sensitivity represents the probability of a screening test to correctly diagnose a disease. By contrast, specificity represents the ability of such a test to rule out a disease in a patient.
"The accuracy of this OCGB method reinforces the value of cerebrospinal fluid studies in the differential diagnosis of MS," wrote Villar and her colleagues.
If this test continues to show promise, it could be effectively used as a diagnostic test in conjunction with certain clinical data, Villar told Priority Healthcare.
1. Villar LM, Masjuan J, Sadaba MC et al. Early differential diagnosis of multiple sclerosis using a new oligoclonal band test. Arch Neurol 2005 Apr;62(4):574-7.
2. Durelli L, Ricci A, Verdun E. Immunoglobulin treatment of multiple sclerosis: future prospects. Neurol Sci 2003 Oct;24 Suppl 4:S234-8.
3. Losy J. Oliogclonal antibodies in the diagnosis of multiple sclerosis and other diseases of the nervous system. Neurol Neurolchir Pol 1991 May-Jun;25(3):363-70.
4. National Multiple Sclerosis Society. What is Multiple Sclerosis? Available at: http://www.nationalmssociety.org/What%20is%20MS.asp. Accessed August 22, 2005.
5. National Multiple Sclerosis Society. Diagnosis. Available at: http://www.nationalmssociety.org/Diagnosis.asp. Accessed August 22, 2005.
John Martin is a long-time health journalist and an editor for Priority Healthcare. His credits include overseeing health news coverage for the website of Fox Television's The Health Network, and articles for the New York Post and other consumer and trade publications.
