- ANA,FANA (Fluorescent)-Anti-Nuclear Antibody
- Anti-DNA
- anti-Sm antibody-_Antibody to the Smith antigen
- anti RNP-Antibody to the Ribonucleoprotein
- anti-Ro,(=anti-SSA(=anti-Ro))
- anti-La,(=anti-SSB)
- Complement,CH50,C3,C4
- aCL, aPL, lupus anticoagulant
- BUN (Blood Urea Nitrogen)
- Urinary protein, proteinuria, albuminuria
- Platelets- blood cells that aid in clotting.
Are you confused by the names of the blood tests doctors use to diagnose or monitor lupus? Do you know what the tests mean? If you are confused, perhaps the information below will help. In looking at the following information, remember:
An antibody is a protein (such as gamma globulin and other globulins) that the body normally makes to defend itself against bacteria (germs), viruses, and other things that cause harm. In lupus, the body mistakenly makes antibodies against a person's normal tissue.
An antibody is named according to the substance (antigen) which it is made to fight. Thus, an antibody induced by a polio vaccination is called anti-polio virus antibody.
Because the basic abnormality of lupus is an immune system that is in overdrive, most of the tests measure the degree to which the immune system is active.
Other tests measure the function of specific organs such as the kidneys.
A lot of these tests and names are confusing. Don't worry about such designations as mg/dL (milligrams per deciliter). These are technical terms that refer to a specific way of measuring one or another substance. Some laboratories use international units (IUs); some laboratories report the results of chemical tests in mols instead of milligrams. I've given the measurements that are most often used. If your laboratory reports your results in a different way, ask your doctor to explain which units are used and what is normal for that laboratory. I have not given numbers for tests that are either reported as positive/negative, or in cases where there are too many ways of reporting to summarize briefly.
Keep in mind that the statements above are just rough guides. There are always exceptions to every rule. I've listed the most common tests and the most common uses, but they may differ for you. If you are still confused, or you are in doubt, ask your doctor for an explanation.
Test: ANA, FANA (Fluorescent) - Anti-Nuclear Antibody
What test is for: An antibody against the nucleus, or central controlling part of each cell. All organs are made of cells and all cells have nuclei. ANAs have four basic patterns describing the way they look under the microscope. The patterns are "diffuse" (the whole nucleus lights up), "peripheral" or "rim" (only the ring around the nucleus does), "speckled" and "nucleolar" (two very specific spots light up).
What a positive test means: Almost all patients with lupus have a strongly positive test (still positive even when diluted more than 100 times, commonly expressed 1:100). Many normal people also have positive tests, usually less strong (1:10-1:30). The "diffuse" and "speckled" patterns are common in lupus, but are also seen in other diseases and normal people. The "peripheral" pattern is relatively specific for lupus. The "nucleolar" does not often occur in lupus. A positive test means lupus is a possible diagnosis.
What a negative test means: A negative test usually means that a patient does not have lupus, or that lupus is in remission. However, most patients in remission do not have negative ANAs.
Test: Anti-DNA - Antibody to Double Stranded Deoxyribonucleic Acid
What test is for: DNA is the major part of the cell nucleus, and is the stuff of which our genes are made. The anti-DNA antibody is usually the reason for the positive ANA. People who have a positive ANA who do not have anti-DNA have antibodies against other parts of the nucleus.
What a positive test means: An unequivocally positive test in a person with symptoms almost always means lupus is present. The higher the amount, the more likely the disease is active. Rarely, well blood relatives of lupus patients have positive tests, as do some patients with rare other diseases.
What a negative test means: A negative test does not mean that lupus is not present, since other tests can still be positive in a person who has had a positive test; a negative test usually means remission.
Test: anti-Sm antibody - Antibody to the Smith antigen
What test is for: The Smith (first patient) antigen is a protein that helps DNA stay in its correct shape as it goes about its business directing the cell how to do its work. Together, anti-Sm, anti-RNP, anti-Ro/SSA, and anti-La/SSB are known as ENA antigens.
What a positive test means: Like anti-DNA, this test generally means that lupus is present. False positive tests are very rare.
What a negative test means: A negative test does not mean that lupus is not present, since other tests can still be positive. Most persons with lupus have either anti-DNA or anti-Sm antibodies. Negative tests for both generally mean that lupus is not present.
Test: anti-RNP - Antibody to the Ribonucleoprotein
What test is for: The RNP antigen is similar to the Smith antigen, but has a different job in the cell.
What a positive test means: A positive test occurs in some patients with lupus but also in other related diseases. It helps to classify a patient but it is not usually useful to make a specific diagnosis nor to follow for worsening or recovery.
What a negative test means: A negative test excludes a related disease, Mixed Connective Tissue Disease.
Test: anti-Ro, (=anti-SSA (= anti-Ro)) - Antibody to the Rose (first patient) antigen; antibody to the Sjogren's syndrome A antigen; the test was described simultaneously in both lupus and the related disease.
What test is for: The test is designed to look for the Ro/SSA antigen similar to, but this antigen has a different job than the Smith antigen.
What a positive test means: The test is often positive in lupus patients and in patients with other related diseases. In pregnant women, it makes a complication known as neonatal lupus possible. Only about 1/4 of women with this antibody have a child who develops neonatal lupus.
What a negative test means: If both this test and the related anti La/SSB test are negative, the child of a pregnant woman will not develop neonatal lupus.
Test: anti-La, (=anti-SSB) - Antibody to the Lane (first patient) antigen, antibody to the Sjogren's syndrome B antigen.
What test is for: Similar to the Ro/SSA antigen.
What a positive test means: Similar to the Ro/SSA antigen.
What a negative test means: Similar to the Ro/SSA antigen.
Test: Complement, CH50, C3, C4 - Complement is a series of proteins that help antibodies fight antigens: CH50 refers to the amount of complement necessary to destroy 50% of red blood cells in an immune reaction. C3 and C4 are the third and fourth components of the complement proteins.
What test is for: Complement is used up in immune reactions such as lupus.
What a positive test means: Low levels of complement mean the body is undergoing a severe immune reaction, primarily in the kidneys. Lupus is one cause, but there are many others. CH50 is usually 150-300 units. C3 is about 80-150 mg/dL. C4 is about 15-40 mg/dL.
What a negative test means: Normal levels of complement make lupus inflammatory kidney disease unlikely. Other types of kidney disease, such as leaky kidneys or scarring, can still occur even if complement is normal. Other types of lupus do not usually lower complement.
Test: aCL, aPL, lupus anticoagulant, antiphospholipid antibody, aPTT, dRVVT - Antibody to Cardiolipin, antibody to Phospholipid, Activated Partial Thrombosplasin time; Dilute Russell Viper Venom Time.
What test is for: Cardiolipin is a phospholipid (a type of fat that contains phosphate). There are many other phospholipids, but cardiolipin is the one most frequently tested. The test can be performed on clotted blood. The lupus anticoagulant test (for antibodies to clotting factors) can be performed only on fresh blood since it measures the time it takes the blood to clot. Except for the different techniques, the tests measure approximately but not exactly the same things, so it is possible to have a positive aPL test and a negative lupus anticoagulant, and vice versa. The membranes that surround all cells are composed of phospholipids, aPTT and dRVVT are two specific clotting tests used to screen for a lupus anticoagulant antibody.
What a positive test means: An unequivocally and repeatedly positive test means a higher than normal likelihood of developing internal blood clots or problems with pregnancies. Weakly positive tests that come and go are common and generally not important. About 1/3 of lupus patients have either an aPL or lupus anticoagulant test positive. Normal aCL (immunoglobulin G, IgG) is usually under 15 GPL units, for immunoglobulin M (IgM), under 10 MPL units. Normal a PTT is usually under 35 seconds.
What a negative test means: A negative test markedly reduces the likelihood of internal clotting problems or certain types of pregnancy complications.
Test: BUN (Blood Urea Nitrogen), creatinine, creatinine clearance
What test is for: BUN and creatinine are two chemicals normally excreted by the kidneys; creatinine clearance is a determination of how much creatinine the kidneys can excrete in a given period of time.
What a positive test means: BUN and creatinine levels both rise when kidney function fails; creatinine clearance falls. Normal BUN is usually 15 mg/dL or less, creatinine under 1.0 mg/dL, and creatinine clearance more than 80 ml/min.
What a negative test means: Normal levels mean that kidney function is normal, but do not mean that everything about the kidney is normal.
Test: Urinary protein, proteinuria, albuminuria
What test is for: The kidneys do not normally excrete protein.
What a positive test means: Kidneys that leak protein are abnormal. The more they leak the worse the injury. Normal is under 1/4 gram in 24 hours. Over 4 grams a day is high.
What a negative test means: Kidneys that do not leak protein are usually normal or near normal. Rarely, function can be abnormal even without protein in the urine.
Test: Platelets - blood cells that aid in clotting.
What test is for: Platelets are used up in severe clotting and can be reduced in number by antibodies to platelets.
What a positive test means: Low platelets occur for several reasons in lupus. All reasons need to be checked out since very low platelets are associated with spontaneous bleeding. Normal platelet count is around 150,000/cubic mL or blood.
What a negative test means: A normal platelet count means no problems in this system. Platelet function can, at times, still be abnormal, even if the number is normal.
