What are the values for a CCP test for RA?

I have had severe pain in my joints...hands, wrists, elbows, back, hips, knees, ankles, and feet. My primary care physician sent me to a Reumotologist. He ordered many X-rays. The tests came back negative. The blood work he ordered all came back negative for RA also except the value of 48 on my CCP test. He has ordered an MRI for my right hand and said if it comes back negative he can not help me at all. He explained the importance of treating RA if I have it though told me the MRI is a subjective test. If he chose the wrong limb for the MRI and it comes back negative for RA then he could possibiltiy miss the correct diagnosis for RA if I have it in other places. I am extremely confused. In past X-rays I was diagnosed with Osteoarthritis in my hands but now am told I do not have it based on X-rays. I need some advice. What does the numerical value of 48 mean on a CCP test?
I have scanned the internet and have not found answers. Does anyone have any experience with a situation similiar to mine.
Thank you in advance for your help.