Blood Tests to Diagnose Arthritis
What Does It Mean if Muscle Enzymes Are High?
When muscle enzymes -- creatine phosphokinase (CPK) and aldolase -- are high, it indicates a possible inflammatory muscle disease. Higher levels of CPK can also be seen after trauma, injections into a muscle, muscle disease due to an underactive thyroid, and while taking certain medications such as cholesterol-lowering statin drugs.
What Are Antineutrophil Cytoplasmic Antibodies (ANCA)?
ANCA are abnormal antibodies found in the blood in most people with Wegener's granulomatosis, a disease that affects the upper respiratory tract, lungs, and kidneys. They are uncommon in other diseases, which makes them useful in diagnosing this particular disease. ANCA levels are sometimes used to follow the course of Wegener's granulomatosis.
What Is the Complement System?
The complement system is made up of a network of proteins that involve the immune system and inflammation. Decreased levels of various components of complement -- C3, C4, or CH50 -- can be seen in lupus. Other diseases that involve inflammation of the blood vessels -- called vasculitis -- also often have decreased levels of complement in the blood. In lupus, complement levels are used to follow the illness, because they rise and fall according to the activity of the disease.
What Are Cryoglobulins?
Cryoglobulins are antibodies that may be high in a variety of different diseases, including rheumatoid arthritis, lupus, Sjögren's syndrome, Waldenstrom's macroglobulinemia, multiple myeloma, lymphoproliferative disorders, hepatitis B and C, and other infections.