Possible Blood Tests to Identify and Monitor FM

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Category: Medical Info and Drug Trials

Published on Thursday, 08 March 2012 15:03

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When it comes to diagnosing fibromyalgia one of the problems is that there is no simple blood test. Despite the published diagnostic criteria for FM, the tender point test can often be used as a last resort after you have undergone every blood test and scan known to man with no positive results. This can be extremely frustrating and lead to a long delay in getting a diagnosis. Wouldn't it be wonderful to simply be able to have a blood test that told you whether you had fibromyalgia or not?

Several researchers have been working towards this aim. A team led by Dr Alan Light at the University of Utah, USA have been investigating possible markers that can distinguish FM and CFS and can be measured in a blood sample¹. They looked at three different groups of people: those with FM only, those with CFS or CFS and FM, and healthy controls. They put these three groups of people through an exercise challenge involving working out on a bike ergometer for 25 minutes. Blood tests were taken prior to the test and at 30 minutes, 8 hours, 24 hours and 48 hours after the exercise. In general, this modest level of exercise caused post-exertional fatigue and pain lasting 48 hours in all the CFS and FM patients, whereas the healthy controls were not affected at all.

What they found is that the FM-only group could be distinguished from the CFS group and healthy controls by differences in the levels of three markers in the blood, an immune system messenger called cytokine interleukin-10 (IL-10) and sensory receptors P2X4 and TRPV1. What was interesting is that these differences were apparent before the exercise challenge and the levels did not change during or after exercise. This was quite different to what happened in the CFS group. Compared with the healthy controls and the FM-only group, the CFS group showed increases in seven different biomarkers following the exercise challenge. The more severely affected the patient was by CFS and more dramatic the increase.

The advantage of the lack of change after exercise in the FM proposed biomarkers is that you would only need a single blood test and would not have to undergo an exercise challenge! These are certainly exciting results and if they can be replicated and confirmed may offer a real possibility of a simple blood test to aid in the diagnosis of FM.

Other similar exciting research is being carried out by a team led by Dr Dennis Ang at Indiana University, USA who are looking at using biomarkers in the blood to measure FM disease severity, focusing on pain levels in particular². The idea would be to monitor how a particular treatment is really working, offering a non-subjective test to show that pain levels are increasing or decreasing.

Much research into FM has demonstrated that certain substances to do with pain severity are elevated in the central nervous system (spinal cord and brain). These include substance P and corticotropin-releasing hormone (CRH) which are at least double the level they should be. The problem is that these substances do not show up as abnormal in the blood and the only way of measuring them accurately is by performing a spinal tap to obtain a sample of spinal fluid. Such procedures however are expensive to perform, can be risky, not commonly used and certainly not available at your local GP surgery.

Dr Ang and his team have been searching for a simple way to measure the levels of these chemicals and they may just have come up with something. The elevated levels of substance P and CRH in the central nervous system stimulate immune system cells called mast cells which are located all over the body. These mast cells release chemicals called IL-8 and monocyte chemotactic protein-1 (MCP-1) into the bloodstream which can easily be measured. Previous research has already indicated that IL-8 and MCP-1 are elevated in people with FM compared with healthy controls and it is possible that these chemicals could reflect what is going on with the levels of substance P and CRH in the central nervous system.

Dr Ang’s team put a group of 16 fibromyalgia patients through a 6-week course in pain and stress management and took blood samples at week 1 and week 12 to measure the levels of IL-8 and MCP-1. They asked all the fibromyalgia patients to complete a Brief Pain Inventory questionnaire at these time points to assess whether their pain levels had increased or decreased. The idea was to see if decreases in reported pain from the patients matched decreases in IL-8 and MCP-1 levels.

They found that improvements in pain reported by the patients did correspond to reductions in both IL-8 and MCP-1, implying that the levels of substance P and CRH in the central nervous system had decreased as a result of the treatment. Although these results are only preliminary and involved only a small group of patients, they indicate that it may be possible to measure FM pain severity levels objectively with a simple blood test. This could be used for monitoring treatment responses in the future and possibly predicting a patient's prognosis. What a substantial leap forward that would be!

By Kathy Longley

References:

1. 1.Light AR, Bateman L, Jo D, Hughen RW, VanHaitsma TA, White AL, Light KC. Gene expression alterations at baseline following moderate exercise in patients with chronic fatigue syndrome and fibromyalgia syndrome. Journal of Internal Medicine, 2011 May 26.
   1. 2.Ang DC, Moore MN, Hilligoss J, Tabbey R. MCP-1 and IL-8 as Pain Biomarkers in Fibromyalgia: A Pilot Study. Pain Medicine, 2011 August; 12(8):1154–61.