Tests

Blood Tests

Various blood tests may be used to help diagnose RA, determine its severity, and detect complications of the disease.

Rheumatoid Factor. In RA, antibodies that collect in the synovium of the joint are known as rheumatoid factor. In about 80% of cases of RA, blood tests reveal rheumatoid factor. It can also show up in blood tests of people with other diseases. However, when it appears in patients with arthritic pain on both sides of the body, it is a strong indicator of type 2 RA. The presence of rheumatoid factor plus evidence of bone damage on x-rays also suggests a significant chance for progressive joint damage.

Erythrocyte Sedimentation Rate Test. An erythrocyte sedimentation rate (ESR or sed rate) measures how fast red blood cells (erythrocytes) fall to the bottom of a fine glass tube that is filled with the patient's blood. The higher the sed rate the greater the inflammation. In addition to rheumatoid arthritis, the sed rate can be high in many conditions ranging from infection to inflammation to tumors. The test is used, then, not for diagnosis, but to help determine how serious the condition is.

C-Reactive Protein. High levels of C-reactive protein (CRP) are also indicators of active inflammation.

Anti-CCP Antibody Test. The presence of antibodies to cyclic citrullinated peptides (CCP) can identify RA years before symptoms develop. In combination with the test for rheumatoid factor, the CCP antibody test is the best predictor of which patients will go on to develop severe RA. Used in Europe, it is now beginning to be used somewhat more commonly in the US. US laboratories have not yet developed consistent standards for interpreting the test, however.

Tests for Anemia. Anemia is a common complication and blood tests should be taken that determine the amount of red blood cells (hemoglobin and hematocrit) and iron (soluble transferrin receptor and serum ferritin) in the blood.

Possible RA Markers in Synovial Fluid

Analyzing the synovial fluid might prove to be helpful in detecting markers of joint destruction, but this is not commonly performed. Some investigational examples include the following:

An enzyme called MMP-3 (matrix metalloproteinase 3) is involved with the degradation of cartilage. Its presence in synovial fluid is strongly associated with progressive joint destruction in patients with chronic RA.
High levels urocortin, a member of the peptide family involved in the stress response, may also be a major player in the RA inflammation.

Imaging Techniques

X-Rays. X-rays generally have not been helpful to detect the presence of early rheumatoid arthritis because they cannot show images of soft tissue. The use of a technique known as dual energy x-ray absorptiometry, however, may be useful in detecting early bone loss in rheumatoid arthritis (between two and 27 months after onset). Evidence of damage on x-rays along with elevated rheumatoid factor is a significant predictor for progressive joint destruction.

Ultrasound. Special ultrasound techniques called power Doppler ultrasonography (PDUS) or quantitative ultrasound (QUS) may be helpful in RA. PDUS may be reliable for monitoring inflammatory activity in the joint. QUS, which is used for osteoporosis, has been used to detect bone loss in fingers, which may prove to be a good indicator of early RA.

Magnetic Resonance Imaging. Specially designed magnetic resonance imaging (MRI) equipment called extremity MRI may be able detect bone erosions in the hands of RA patients where x-rays cannot. Further evaluation is necessary.

Ruling Out Other Disorders

Symptoms of rheumatoid arthritis can be mimicked by things as benign or as serious as cancer. A number of rare genetic diseases attack the joints. Physical injuries, infections, and poor circulation are among the many problems that can cause aches and pains. It would be impossible to discuss in this report the dozens of other conditions that present themselves with symptoms of joint aches and pains.

Osteoarthritis. Osteoarthritis requires some special mention because it is the most common form of arthritis. It differs from RA in several important respects.

Osteoarthritis usually occurs in older people.
It is located in only one or a few joints. (In fact, osteoarthritis is probably most often confused with rheumatoid arthritis if it affects multiple joints in the body.)
The joints are less inflamed.
Progression of pain is almost always gradual.

Gout. Gout also causes swelling and severe pain in a joint, although most commonly starting in one joint. It is particularly difficult to distinguish chronic gout in older people from rheumatoid arthritis, however, since gout in this population can occur in a number of joints. A proper diagnosis can be made with a detailed medical history, laboratory tests, and detection in the affected joint of a salt called monosodium urate (MSU), which identified gout.

Laboratory studies initially may not contribute to the diagnosis. The rheumatoid factor assay is initially negative in many patients--and in up to 30%,the assay is never positive. The ESR may or may not be elevated at presentation,the elevation may not occur for weeks and even months. Elevated ESR may be found in other,certain diseases.

Erythrocyte sedimentation rate -ESR (sed rate)--The most often used measurement of inflammation is the E.S.R. This test is based on how quickly red blood cells settle out on the bottom of a test tube. In inflammatory conditions of any type (arthritis included), red blood cells settle out more quickly.

The "sed rate" is a useful test and most physicians use it. A normal rate is about 20 millimeters per hour or less,but in some forms of arthritis it may as high as 80 millimeters per hour.

A high sedimentation rate can confirm suspicions of inflammation, but,like many other tests,the results may be elevated in conditions other then arthritis,and sometimes in normal people. Many physicians use it to follow disease course,but to the question,"Is the patient getting better or worse". A few questions and a quick exam may be better at times.

The CRP (C-reactive protein) is a blood test that is starting to be used more often now. It can be automated so it's cheaper to perform,and it's less likely to be fooled by non-inflammatory conditions than the sed rate.

Rheumatoid Factor--This test determines whether RF is present in the blood. Rheumatoid Factor is an antibody found in the blood of most people who have RA. RF may be found in many other diseases beside RA,and sometimes in normal healthy people .

Eighty % of patients with RA have an increased level of the RF in their blood. The RF is elevated in most patients with RA. An elevated RF is consistent with,but does not prove that RA is present. However,a negative RF,particularily early on in the disease does not exclude RA.

Most patients with moderate or severe RA develop a positive RF within the first 6 months to 1 year of contacting the disease. Some patients with a family history of RA will test positive all their lives.

The more positive the test,the greater likelihood of RA being present. However,most doctors have seen patients with strongly positive tests and no other evidence of arthritis. Unfortunately,early on in the disease and in patients with the mild form of the disease,the RF is often very low,or even negative.

Urinalysis-- In this test,a urine sample is studied for protein,red blood cells,white blood cells,or casts. These abnormalities indicate kidney diseases which may be seen in several rheumatic diseases such as lupus or vasculitis (RA) Some DMARDs can also cause abnormal findings on urinalysis. Gold therapy requires this test to be conducted regularly.

Complete blood count (CBC)--This test determines the number of white blood cells,red blood cells,and platelets present in a sample of blood. Some drugs used to treat arthritis are associated with a low white blood count (leukopenia),low red blood count (anemia),or low platelet count (thrombocytopenia). when doctor's prescribe medications that affect the CBC,they periodically check the patient's blood.

Since red blood cells carry oxygen from the lungs to the body,white blood are one of the body's main means of dealing with infection,and platelets are very important in blood clotting,problems with any one of them may cause real trouble.

Anemia (a low red blood cell count ) is common in inflammatory arthritis. Usually this reflects the fact that the bone marrow,which is where blood cells are made,just isn't able to keep up production when inflammation is present,even if it has all the ingrediants,including enough iron. But anemia can be due to arthritis medicine,particuarly NSAIDs such as ASA,which may cause bleeding from the stomach or duodenal ulcer,and a resulting low red blood cell count.

Low white blood cell counts and low number of platelets may occur, separately or together,in some kinds of arthritis. Unfortunately, similar problems may be caused by some of the drugs used to treat the disease, so the sitution can be confusing at times.

White blood cell count (WBC)--This test determines the number of white blood cells present in a sample of blood. The number may increase as a result of infection or decrease in respose to certain medications or with certain diseases such as lupus.

Low number of white blood cells increase a person's risk of infection. The white cell count is usually normal in patients with RA,but can be mildly elevted secondary to inflammation similarily,the platelet count is usually normal,but thrombocytosis occurs in response to inflammation

X-rays and other imaging procedures--to see what the joint looks like the doctor may order x-rays or other imaging devices. Other nonivasive imaging devices such as computed tomography (CT or CAT),magnetic resonance imaging (MRI),and arthrograpy (joint x-ray) show the whole joint.

The doctor may use a arthroscope (a small,flexible tube that transmits a image, of the inside of a joint, to a monitor to examine damage to a joint). The arthroscope is inserted into the affected joint through a very small incision in the skin. This procedure called arthroscopy allows the doctor to see inside the joint. Doctors also use arthroscopy to perform surgery for some types of joint injury.

Creatine--This blood test is commonly ordered in patients who have rheumatic diseases to moniter for underlying kidney disease.

Complement--this test measures the level of complement,a group of proteins in the blood. complement helps destroy foreign substances such as germs that enter the body. A low level of blood complement is usually found in people who have lupus.

Hematocrit (PCV packed cell volume) This test and the test for hemoglobin (a substance in the red blood cell that carries oxygen through the body) measure the number of red blood cells present in a sample of blood. A decrease in the number of red blood cells (anemia) is common in people with inflammatory arthritis.

Arthrocentesis--Arthrocentesis or joint aspiration is done to obtain a sample of synovial fluid. The doctor injects a local anesthetic,inserts a thin,hollow needle into the joint and removes the synovial fluid into a syringe. The test provides important diagnostic information.

Antinuclear antibody (ANA)--This test checks blood levels of antibodies that are often present in people who have connective tissue diseases or other autoimmune disorders such as lupus. Since the antibodies react with material in the cell's (control center),they are referred to as antinuclear antibodies.

There are also tests for individual types of ANA's that may be more specific in people with certain autoimmune disorders. ANA's are sometimes found in healthy people. Therefore having ANA's in the blood does not necessarily mean that a person has a disease.

It is more helpful in determining if inflammatory disease is present or not. However, the antiinuclear antibody test is often positive without any underlying disease present.

Complete bone count test ( approximately 250 bones in the body)procedure is not taught at the family physician level in medical school training. The rheumatoligist training provides this test but a complete bone count is not often done,and the time factor may be involved. The complete test may take over an hour.

Synovial Fluid Assessment--If the joints are very swollen,the physician may take a small amount of fluid from the swollen joint for testing . Normal synovial fluid is clear,thick,and oily,which helps to lubricate the joints.

In RA (not OA),the fluid becomes cloudy because it is infiltrated with cells,usually white blood cells and debris. These cells break down the oily substance (hyaluronic acid) and make it very watery. By looking at the fluid the physician can tell if it is normal or the presence of inflammation. In the laboratory the presence of inflammation can be determined.

Chemistry is normal in RA,with the exception of a slight decrease in albumin,and increase in protein,reflecting the chronic inflammatory process. Renal and liver function should be checked prior to therapy.

Diagnosing rheumatic diseases can be difficult because some symptoms and signs are common to many different diseases. A general practisioner or family doctor may be able to evaluate a patient or refer him or her to a rheumatoligist

The doctor will review the patient's medical history,conduct a physical examination and obtain laboratory tests and x-rays or other imaging tests. The doctor may need to see the patient more than once to make a accurate diagnosis. In patients with any evidence of ongoing disease activity,a plain film of the most severly affected joints can be very helpful. Documentation of progressive joint destruction would permit earlier intervention with aggressive therapy.

There are two common tests used to monitor the progress of inflammatory arthritis. A hemoglobin test measures your red blood cell count: During a flare of inflammatory activity,normal hemoglobin levels drop. This "low blood" differs from the anemia of "iron poor blood",since it can occur even if you're storing adequate amounts of iron.

How successfully your DMARD therapy is at reducing inflammation determines whether your hemoglobin returns to normal levels. The other test is called a sedimentation (or "sed") rate: It measures certain proteins in the blood that indicate inflammatory activity. The lower the score the better.

X-rays provide a baseline. After one or two years,the physician can obtain another x-ray to see whether the disease has continued to progress radiographically. This can occur independently of clinical manifestations,even patients whose symptoms have responded well to therapy may continue to show radiographic progression. If erosions or joint space narrowing had already been present,it would help to predict the disease course and to determine the therapeutic strategy (one of the many aids in therapy).

It is vital for people to give the doctor a complete medical history. Answers to the following questions will help the doctor make a accurate diagnosis:

Is the pain in one or more joints?

When does the pain occur?

How long does the pain last?

When did you first notice the pain?

What were you doing when you first noticed the pain?

Does activity make the pain better or worse?

Have you had any illnesses or accidents that may account for the pain?

Is there a family history of any arthritis or rheumatic disease?

What medicine(s) are you taking?

It may be helpful for people to keep a daily journal to describe the pain. Patients may write down what the affected joint looks like,how it feels,how long the pain lasts,and what they were doing when the pain started.

The doctor will examine all of the patient's joints for redness, warmth, deformity, ease of movement,and tenderness. Because some forms forms of arthritis like lupus,and RA may affect other organs,a complete physical examination including the heart, lungs , abdomen,nervous system,and eyes, ears, and throat may be necessary. The doctor may order some laboratory tests to help confirm a diagnosis. Samples of blood,urine,or synovial fluid (fluid foud in the joints) may be necessary for the tests.

Acute phase reactants (white blood cell count,platelets,ESR,and C-reactive protein) may not be always elevated in patients with active arthritis,especially in an elderly patient. A sometimes-useful strategy is to obtain and analyze synovial fluid,which should show features of disease activity.

Usually,the patients who are prone to joint destruction are rheumatoid factor positive,but not all patients. Only in about 70 to 80 % of individuals with RA is the blood test,the rheumatoid factor,actually positive. In 30 % or so of patients, that blood test is negative--seronegative rheumatoid arthritis. i.e., an individual who has rheumatoid arthritis,but the blood test is negative. They have a sophisticated testing in research for a positive test,but not of a type that can be picked up on the commercially available rheumatoid tests done in most labs.

The diagnosis of rheumatoid arthritis is what physicians call a clinical diagnosis. It's based on the history and what the physician sees. There's a certain distribution and type of arthritic changes they like to see. There are things they like to see on x-ray as well as on exam.

Treatments for arthritis include rest and relaxation,exercise,proper diet, medication,and instruction about the use of joints,and to conserve energy. Other treatments may include the use of pain relief methods ,and assistive devices (if necessary).

The doctor may delay using medications until a definite diagnosis is made, because medications can hide important symptoms (such as fever and swelling) and thereby interfere with diagnosis. Patients taking any medication,either prescription or over the counter should always follow the doctors instructions. The doctor should be immediately notified if the medication is making the symptoms worse or causing any problems such as a upset stomach,nausea,or headache. The doctor may be able to change the doseage or medicine to reduce these side effects.

Unfortunately "bone-count" is not a regular program taught to doctors at the medical training level,therefore many physicians are not properly trained in this procedure. Another factor is the time factor,a complete "bone count" may involve 1 hour of testing (the bone count involves manually feeling each bone joints for inflammation). This important fact was written by a medical school graduate--now an writer about medical conditions such as rheumatoid arthritis)

Basline laboratory evaluations should include complete blood cell count (CBC),platelet count,chemistry profile,RF measurement,and measurement of ESR or CRP. Evaluation of renal and hepatic function is necessary since many antirheumatic agents have renal or heotic toxicity,and may be contraindicated if these organs are impaired. As explained elsewhere and repeated,initial x-rays (radiographs) of the hands/feet should be obtained since structural damage cannot be deducted by physical examination alone.

Arresting and preventing structural damage is a primary goal of therapy,and repeat radiographic studies of sentinel or major involved joints may be needed periodically. Rheumatoid arthritis can attack any joint in the body,and tends to do so in a symmetric pattern (left and right side).

Advisory And Tests:

Analegesics (pain relievers) such as aspirin,other NSAIDs such as ibuprofin (Motrin,Advil,Nuprin),and acetaminophen (Tylenol) are used to reduce the pain caused by many rheumatic conditions. Aspirin and NSAIDs have the added benefit of decreasing the inflammation associated with arthritis. Certain anagesics,such as aspirin and NSAIDs,can have side effects,such as stomach irritation,that can be reduced by changing doseage or the medication.

The doseage will vary depending on the particular illness and the overall health of the individual The doctor and patient must work together to determine which analgesic to use and the appropriate amount. If analgesics do not ease the pain,the doctor may use other medications,depending on the diagnosis.

Pain is one symptom virtually everyone will have regardless of which form of arthritis they have. For that reason,analgestic (pain-relieving) medications play an important role in the arthritis treatment plan. One of the most commonly used analgesics is acetaminophen. The ACR recommends it as a first-line option against osteoarthritis pain. Unlike NSAIDs,acetaminophen,and other pure analgesics con't relieve inflammation.

Yet recent studies suggest acetaminophen relieves arthritis pain-even severe pain-as effectively as NSAIDs without NSAIDs risk of GI side effects. At one time,acetaminophen was the only analgesic many doctors prescribed for arthritis pain. But that is changing. It provides the benifit of aspirin without it's GI side effect. The amount of doseage needed for efficacy may be of some concern. There are clinical trials presently going on to address this question. Eight tablets,daily may be the maximum safe doseage.

Research Article: Development of an instrument to measure pain in rheumatoid arthritis: Rheumatoid Arthritis Pain Scale (RAPS)

Objective: To develop a valid and reliable clinical instrument for measuring pain in adult patients with rheumatoid arthritis. The resulting Rheumatoid Arthritis Pain Scale (RAPS) is a quantitative,single-score,self-report 24-item report.

Methods: Psychometric evaluations of RAPS was conducted following estimation of content validity and a pilot study. The actual study used a convience sample of 120 adults,18 years of age or older,with pain of at least 3 months duration. The setting was a large rheumatology private practise in a metrpoplitan southwestern city.

The gate control and effective motivational theories of pain served as a framework guiding the development of RAPS, which includes items suggestive of the mutidirectional pain experience in rheumatoid arthritis. Four subscales, physiological,affective,sensory-discriminative, and cognitive,evaluated numerous pain factors.

Results: Findings indicates a high estimate for internal consistency for the total scale and a moderate to high estimate of internal consistency for projected subscales. Data were analyzed using Cronbach's coefficient alpha,Pearson product-moment correlation coefficients,and exploratory factor analysis.

Using Cronbach's coefficient alpha,RAPS showed an internal consistency reliability coefficient of 0.92,a strong indicator of reliability. Reliability assessment for the 4 subscales also indicate reliability,with Cronbach's coefficients ranging from 0.65 to 0.86. Exploratory factor analysis yielded 3 factors with criteria for factor loadings 0.4.

Conclusion: The study's findings provided support for RAPS as a reliable and valid measurement of rheumatoid arthritis pain. Assessment of rheumatoid arthritis pain and it's relationship to treatment outcomes could significantly impact the treatment interventions.

The hand radiograph as a diagnostic discriminant between seropositive and seronegative rheumatoid arthritis: A controlled study --Pub Med - indexed for Medline. T.M. Burns, A. Calin.

Although traditional teaching emphasises that 70-80 % of patients with rheumatoid arthritis have positive serological tests for rheumatoid factor,a review of the evidence sugests that the serological group has distinctive charachteristics. In a blinded and controlled evaluation of hand and wrist films the researchers correctly identified the serological status of 43 out of 46 patients satisfying the ARA criteria for "definite RA".

The radiographic appearances of the seronegative group differed significantly from those of the seropositive group in 1) degree of juxtalesional osteosclerosis (p < 0.001); 2) the relative absence of classical subchondral erosions (p < 0.001); 3) presence of new bone formation (p< 0.001); 4) more fusion (p< 0.001); 5) more asymmetrical joint involvement (p< 0.001); and 6) predominant carpel involvement (p < 0.001). The nature of the destructive process,as defined radiologically,may be different in patients with seropositive rheumatoid arthritis from that seen in individuals with so-called "seronegative rheumatoid arthritis".

In response to the continuing debate as to whether seronegative rheumatoid arthritis and seropositive RA are part of the same disease spectrum or are distinct disorders, scientists evluated 720 patients with definite and classic RA,of whom 53 subjects had definite persistently seronegative destructive disease. For all but 1 seronegative RA patient,a seropositive case control was identified and matched for age,disease duration,degree of destruction on hand radiographs,and disease modifying drug therapy.

DR typing was undertaken on those 105 patients,together with scoring of hand radiographs. The frequency of DR4 was 69% in seropositive patients and 60% in seronegative RA patients (p=0.22),versus 36% in 318 healthy controls (p=0.008 and p=0.007 versus seropositive and seronegative RA,respectively). Patients were matched and rematched with different controls in a series of subanalyses in order to make comparison of hand radiograoh scores.

Researchers found that HLA-DR4 was associated with destructive RA in both seropositive and seronegative RA patients. In general,DR4 + patients had a more severe disease by radiologic criteria than did DR4 - patients. Thus,HLA-DR4 may be an additive to the serologic status and may be more closely related to disease severity than disease susceptibility.

To help confirm a diagnosis or check on the status of disease activity, your doctor may order a biopsy (or removal of a small piece of tissue) to be examined under a microscope. Three of the most common biopsies include skin, muscle, and kidney biopsies.

Skin biopsies

These are usually done to aid the diagnosis of lupus , vasculitis (inflammation of blood vessels), psoriatic arthritis (inflammation of joints and scaly, inflamed skin), or other forms of arthritis that involve the skin. After using a local anesthetic, a tiny piece of skin is removed.

Muscle biopsies

These are similar to skin biopsies, except the surgeon must go deeper into tissue. Muscle biopsies are used to look for signs of damage to the muscle fibers. This information can help confirm the diagnosis of polymyositis or vasculitis.

Kidney biopsies

These are usually done to check for signs of damage from a disease such as lupus . They are usually done by passing a needle through the back and withdrawing a bit of tissue for examination.

Other biopsies

Other biopsies are done on a less frequent basis. These include synovial, lung, salivary gland, and blood vessel biopsies. Liver biopsies are occasionally done to check for signs of damage in people receiving methotrexate for rheumatoid arthritis .

Rheumatoid factor (RF, Latex)

This measures whether a certain amount of abnormal antibody called rheumatoid factor is in the blood. The majority of people with rheumatoid arthritis (a common disease of inflamed joints that can cause joint alignment problems and loss of function) have a large amount of rheumatoid factor in their blood.

However, up to 20 percent of adults with rheumatoid arthritis may never have any rheumatoid factor in their blood.

In contrast, about 85 percent of children with juvenile rheumatoid arthritis (ERA) are negative for rheumatoid factor (ERA is a group of diseases, similar to rheumatoid arthritis, that begin in childhood). It is important to note that having a positive rheumatoid factor will assist in the diagnosis, but the test alone is not conclusive.

Methodologies

Latex agglutination testing is still widely used although it is being supplanted by other methods including ELISA and nephelometry that are capable of being done by machine rather than by hand to hopefully improve standardization and reproducibility. Nephelometry uses laser light scatter to measure the formation of immune complexes in this case, rheumatoid factor and human IgG.

Normal range

The latex test is reported in a titer with most labs considering > 1:40 as positive. The nephelometry test is usually reported in international units and the normal range is dependent on the specific laboratory usually < 20 IU.

Utility

Rheumatoid factor is not sensitive nor specific enough to rule in or out rheumatoid arthritis. The rheumatoid factor is present in 70-80% of patients who have RA. This means that 20-30% of patients with RA are seronegative for rheumatoid factor. It is most useful as a prognostic indicator in patients with RA.

People with RA who are rheumatoid factor positive typically have a more aggressive disease. It is also useful in confirming one's clinical impression that a polyarthritis that looks like RA is even more likely to be RA. It is also followed in patients with Sjogren's disease to predict the development of lymphoma. Rheumatoid factor production may be a way for the immune system to enlarge immune complexes to make them more easily removed by the spleen and other immune organs.

Antinuclear antibody tests (ANA)

These detect a group of autoantibodies that are found in most people with lupus and scleroderma and in a few people with rheumatoid arthritis . These autoantibodies react with antigens in the nuclei of cells. The antibodies suggest that an autoimmune illness may be present, although many people test positive and have little evidence of serious disease.

Specific antinuclear antibody tests are helpful in the diagnosis of certain rheumatic diseases that involve abnormalities in the immune system. The names of the following tests are abbreviations of more complicated-sounding tests. The diseases for which they are used include:

systemic lupus erythematosus (multiple-system illness, may involve the skin, joints, kidney, etc.); anti-dsDNA, anti-Sm, anti-Ro/SS-A, and antihistone tests help confirm the diagnosis.
scleroderma (a marked thickening of the skin); the anti-Scl-70 test helps confirm the diagnosis.
polymyositis (inflammation of muscles, resulting in muscle weakness, sometimes with joint inflammation); anti-Jo-l and anti-PM-l tests may help confirm the diagnosis.
Sjogren's syndrome (disorder marked by dry eyes and dry mouth); anti-Ro/SS-A and anti-La/SS-B tests may help confirm the diagnosis.
mixed connective tissue disease (a syndrome with a variety of symptoms, including joint inflammation and swollen fingers); the anti-Ul RNP test helps confirm the diagnosis.

Complement tests

These tests measure the amount of complement proteins circulating in the blood. Complement tests involve the reaction of antibodies with antigens. These tests usually are reserved for diagnosing or monitoring people with active lupus . Those people with lupus frequently have lower-than-normal amounts of complement, especially if the kidneys are affected.

Human leukocyte antigen (HLA) tissue typing tests

These tests detect the presence of certain "genetic markers" or traits in the blood. For example, B-27 is a genetic marker that nearly always is present in people with ankylosing spondylitis (a disease involving inflammation of the spine and sacroiliac joint) and Reiter's syndrome (a disease involving inflammation of the urethra, eyes, and joints). This test also is positive in five to 10 percent of the healthy population.