A variety of blood tests may be used to determine base levels of substances in blood or to screen for or identify certain conditions, many of which are characterized by inflammation. These include lupus and many forms of arthritis, such as rheumatoid arthritis and gout. These common blood tests include:

• Autoantibody testing such as an antinuclear antibody test (ANA test). Checks blood levels of antibodies that are often present in patients with certain autoimmune disorders such as lupus. According to the American College of Rheumatology, nearly everyone with lupus tests positive for antinuclear antibodies. However, other conditions (including rheumatoid arthritis, Sjogren’s syndrome, polymyositis and scleroderma) and the use of certain medications may also result in a positive ANA test. Further testing is necessary to establish a diagnosis.
  
  
• Basic metabolic panel (BMP). A group of tests that are often ordered in hospital emergency rooms because their components provide important information about a patient’s kidneys, electrolytes and acid/base balance, in addition to glucose (blood sugar) levels. Significant changes in these test results can indicate acute conditions, such as kidney failure, insulin shock or diabetic coma, respiratory distress or changes in heart rhythm.
  
  
• Blood differential. Also called a white blood cell (WBC) count. Measures the numbers of white blood cells in a blood sample. This test also includes information about abnormal cell structure and the presence of immature cells. A patient’s WBC count may increase as a result of infection or decrease with use of certain medications or in response to certain diseases, such as lupus. In addition, a low level of WBCs indicates that a patient may be at higher risk for infections.
  
  
• C-reactive protein test. A nonspecific test for detecting general inflammation. An elevated level of this protein produced by the liver suggests an inflammatory disease such as rheumatoid arthritis.
  
  
• Coagulation test. Measures how long it takes a person’s blood to clot (coagulate). This test is ordered for disorders that interfere with coagulation and to monitor patients taking anticoagulant drugs. Patients using anticoagulants may also be monitored with a test called INR (international normalized ratio).
   
• Complement. Measures the blood levels of a group of proteins (complement) that helps destroy foreign substances that enter the body. Patients with lupus often exhibit low blood levels of these proteins. This type of blood test is also useful in evaluating kidney damage and in monitoring the progression of a disease.  
  
  
• Complete blood count (CBC). Measures the number of red blood cells, white blood cells and platelets in a patient’s blood as well as the amount of hemoglobin (a substance that carries oxygen throughout the body) in the red blood cells and a number of other factors. Some rheumatic conditions or certain drugs used in the treatment of arthritis are associated with low counts of white blood cells (leukopenia), red blood cells (anemia) or platelets (thrombocytopenia). Patients who take medications that affect the CBC must have periodic blood testing for monitoring.
  
  
• Electrolyte panel. Measures various minerals, abnormal levels of which can suggest conditions ranging from cancer to kidney disease. 
  
  
• Enzyme test. A group of blood tests that measure enzyme (proteins required for chemical reactions to take place in cells) levels in the blood. These tests assess how well the body’s systems are functioning and whether any tissue damage has occurred. For example, cardiac enzyme tests are used in making the diagnosis of a heart attack and determining the extent to which the heart muscle was damaged.
  
  
• Genetic tests. Screen for genetic abnormalities that may indicate a risk of certain diseases, such as cancer.
  
  
• Glucose test. Measures the amount of sugar (glucose) in a patient’s blood sample. Glucose levels are measured mostly to diagnose diabetes and to monitor its control and treatment. In rare cases, greater-than-normal levels (hyperglycemia) may indicate acromegaly, a painful metabolic disorder that causes enlargement of a patient’s bones. Diabetic patients generally undergo a glycohemoglobin test every few months to assess long-term management of their condition.
  
  
• HLA–B27 antigen test. Checks for a genetic marker in white blood cells. Its presence may indicate many inflammatory conditions including ankylosing spondylitis and Reiter’s syndrome.
  
  
• Lipid profile (cholesterol test). A group of tests that measure total cholesterol, “good” HDL cholesterol, “bad” LDL cholesterol, “very bad” VLDL cholesterol and triglycerides. These tests are good indicators of a patient’s risk of heart attack or stroke.
  
  
• Liver function test. Used to assess the functioning of the liver and to diagnose various disease associated with liver.
  
  
• Lyme serology. A group of blood tests that confirm a diagnosis of Lyme disease. These tests detect a patient’s immune response to the infectious agent that causes the inflammatory disease.
  
  
• Rheumatoid factor test. Detects the presence of rheumatoid factor (RF), an antibody found in the blood of many patients with rheumatoid arthritis. RF may also be found in other autoimmune conditions such as Sjögren syndrome and sometimes in healthy people. Also, this test may be negative in some cases of rheumatoid arthritis when the disease is in remission, with no flare–ups of inflammation. Therefore, further testing may be necessary to confirm a diagnosis.
  
  
• Sedimentation rate (sed rate). Measures the rate at which red blood cells (erythrocytes) separate from the liquid part of blood (plasma) and fall to the bottom of a test tube, forming sediment. Higher sed rates indicate the presence of inflammation and are typical of many forms of arthritis (e.g., rheumatoid arthritis, ankylosing spondylitis) and many of the connective tissue diseases (e.g., lupus).
  
  
• Sickle cell test. Indicates the presence or absence of the abnormal hemoglobin (a substance in the red blood cells that carries oxygen throughout the body) that causes sickle cell anemia, a painful condition characterized by abnormalities in a patient’s red blood cells.
  
  
• Serum myoglobin. Determines damage to muscle, such as from a traumatic injury or heart attack, and predicts a recurrence of polymyositis.
  
  
• Thyroid test. Measures thyroid hormones to help diagnose thyroid diseases.
  
  
• Total serum protein. Measures the levels of protein to help diagnose conditions including kidney disease, liver disease, heart failure and high blood pressure.
  
  
• Tumor marker tests. Detect substances that may be produced by cancer cells, such as prostate specific antigen (PSA). Conditions including prostatitis can also elevate PSA. 
  
  
• Waste product test. A group of blood tests that measure the levels of specific waste products in a patient’s blood sample. They commonly test for uric acid, creatinine and blood urea nitrogen (BUN). When the kidneys are not working properly, waste products can build up in the body. The results of these tests can be used during the diagnosis of several diseases, including gout and lupus, as well as to monitor for underlying kidney disease.