Early detection and aggressive treatment ofrheumatoid arthritis (RA)are vital to prevent joint damage. To spot RA and measure its progression, rheumatologists test the blood for certain biomarkers that are characteristic of RA. Although several biomarker tests – the erythrocyte sedimentation (sed) rate, the C-reactive protein (CRP), and rheumatoid factor (RF) – indicate inflammation, they are fairly non-specific to RA. So, the development of more specific biomarker tests is important. These tests allow earlier detection of RA and also pave the way for more customized care.
Below are descriptions of more specific biomarker tests that are being used to diagnose and monitor RA disease activity.
Polyglutamate Testing: Measuring Methotrexate’s Effectiveness
What It Is:Methotrexate is one of the most commonly prescribed and effective drugs for RA. Once it enters the cells, it is converted to methotrexate polyglutamates, explains rheumatologist Maria I. Danila, MD, assistant professor of medicine at the University of Alabama at Birmingham.
Unless that conversion occurs, methotrexate won’t work its therapeutic magic. Because 30–40% of patients do not respond to methotrexate, the measurement of methotrexate polyglutamates in the blood may show if a person if being adequately or inadequately treated. The measurement is taken three months after someone begins taking methotrexate.
Why It’s Different:It can take months for methotrexate to have an effect on how you feel. The theory is that measuring methotrexate polyglutamate levels at three months may indicate earlier whether the methotrexate is working.
What It Means for Personalized Medicine.测量甲氨蝶呤多谷氨酸水平可以让医生调整甲氨蝶呤的剂量，以提高或降低每个患者的多谷氨酸水平，直到达到治疗水平——或者完全改变药物的选择。
Vectra DA: A Multi-Biomarker Test
What It Is:Vectra DA is a blood test that measures 12 biomarkers of RA. The test is not used to diagnose RA but to monitor disease activity and to help predict joint damage.
Why It’s Different:这是第一个同时测量RA的多种生物标志物的测试。“它揭示疾病活动的方式与我们通常测量的方式相关联，”医学博士杰弗里·柯蒂斯说，他是阿拉巴马大学伯明翰分校的医学教授，也是Vectra DA制造商Crescendo生物科学公司的科学顾问委员会成员。“它还能很好地预测与超声波和核磁共振成像相关的关节损伤和耀斑。”
What It Means for Personalized Medicine.柯蒂斯博士说:“这是医生可以用来优化风湿性关节炎患者护理的又一条信息。”他还强调，并不是每个患有风湿性关节炎的人都需要这种测试:“只有在不确定风湿性关节炎的活跃程度或医生不确定是否要改变治疗方法时，才需要这种测试。”
Anti-CCP2 Test: More Accuracy
What It Is:This is the second generation of the first anti-CCP test, which has been around since the late 1990s, says John Griffiths, founder and CEO of Gold Standard Diagnostics, the manufacturer of the test. Antibodies of cyclic citrullinated peptides (CCP) are often present in the early stages of RA, even before clinical signs of RA appear.
Why It’s Different:The second generation test was developed by selecting the CCPs that best detected RA, making it a more sensitive and specific test than the first generation.
What It Means for Personalized Medicine:Although the test doesn’t have much impact on personalized medicine, it is an additional tool in the diagnosis and management of patients with RA.
Anti-MCV: Looking for Antibodies Common in Early RA
What It Is:This blood test checks for antibodies to mutated citrullinated vimentin, or MCV. MCV is a protein “that drives RA,” says Martin Fleck, MD, chief physician of the clinic for rheumatology and clinical immunology for the Asklepios Clinic in Bad Abbach, who has been involved in the research of anti-MCV.
Why It’s Different:“MCV antibodies are highly specific and may be detectable several years before the RA [is clinically obvious],” says Dr. Fleck. “You won’t find these antibodies in healthy people.” He notes that the MCV test is a better predictor of aggressive disease or erosions than the anti-CCP test. Because the CCP test and MCV test measure different antibodies, both tests are given along with a test for rheumatoid factor.
What It Means for Personalized Medicine:“The MCV test extends the repertoire of biomarkers for RA,” says Dr. Fleck. “And the [quick version] helps identify immediately RA patients among patients presenting with [other forms of] arthritis.”
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