Different types of blood tests are described in more detail at the links below.
ANCA Test: (Anti-Neutrophil Cytoplasmic Antibody test)
This test is highly specific for certain autoimmune diseases affecting blood vessels (Churg-Strauss Syndrome, Microscopic Polyangiitis and Wegener's Granulomatosis). It is done by separating out neutrophils (one type of white blood cell) and staining them with a dye that will fluoresce when exposed to ultra-violet light. The illuminated neutrophils are then examined by microscope to determine the character of the fluorescing granules in the neutrophils.
One of four findings may result from the ANCA tests:
1. A test result where the fluorescent granules are scattered in the cytoplasm of neutrophils (positive cytoplasmic or C-ANCA)
2. A test result where the fluorescent granules are mostly near the nucleus of neutrophils (positive perinuclear or P-ANCA).
3. A test result where the fluorescent granules are diffuse, both in the cytoplasm and near the nucleus (positive mixed ANCA).
4. A negative ANCA where so little fluorescence is present, it falls below the upper limit of normal.
Points to consider about ANCA:
1. The upper limit of normal C-ANCA ratio varies from lab to lab. The upper normal limit for the test result to be considered a negative may be about 1:16 or 1:32.
2. The C-ANCA test is about 90+% accurate for WG for serious cases, but only 50% or so for light cases).
3. Not all medical labs do the test, so frequently it is a 'send-out' test. A tentative diagnosis made by positive C-ANCA is often confirmed by biopsy.
4. The related P-ANCA test if positive may be an indicator for some other autoimmune diseases, e.g., microscopic polyarteritis (MPA), Churg-Strauss Syndrome (CSS), or crescentic glomerulonephritis.
5. In the case of mixed ANCA, it may require other tests and analysis of symptoms to determine if the cause of the abnormality is vasculitis or some other condition.
6. The C-ANCA and P-ANCA are immunofluorescent (IIF) tests requiring a human microscopic examination and interpretation. Results may vary if different individuals are doing the test. It is best to have these and other tests done at the same lab each time to reduce the possible variations.
7. While a positive C-ANCA is highly diagnostic for Wegener's, some small percentage of Wegener's patients test P-ANCA positive, rather than C-ANCA. Occasionally a Wegener's patient will switch at times from testing positive to one ANCA to the other.
8. ANCAs are titrated tests. Stained blood samples are diluted in steps, progressively until no fluorescence is detected. Results are reported as the dilution level at which fluorescence ceases. These are given as 1:256 or 1/256 for example. The higher the ANCA ratio, the more of the harmful antibodies are present in the patient's blood.
9. ANCA test results can be positive due to conditions other than autoimmune diseases. Amebiasis, ulcerative colitis, mesangiocapillary glomerulonephritis with crescents, improperly cleaned glassware, and both subacute and bacterial endocarditis have been shown to cause transient positive ANCAs.
10. ANCA test samples can show differing results if submitted to different labs. An effort to standardize these tests is underway in Europe by the EUVAS group. False positives or negatives can and do occur due to mishandling or misinterpretation or even effects of medications or other disease conditions.
11. In diagnosis both C-ANCA by immunofluorescence and anti-PR-3 by ELISA result in greater sensitivity than either test alone, and are often both are performed even if only the C-ANCA is ordered.
C Reactive Protein (CRP) :
C-reactive protein is a test that measures the concentration of a protein in serum that indicates acute inflammation.
Complete Blood Counts (CBC):
The complete blood count (CBC) is a very common blood test. It evaluates the three major types of cells in blood: red blood cells, white blood cells, and platelets.
Red Blood Cells (RBC) carry oxygen from the lungs to the rest of the body. Three tests measure red blood cell (RBC) count:
1. The red blood cell count is a measure of the number of RBCs in the body.
2. Hemoglobin is the oxygen-carrying protein in red blood cells. RBCs carry oxygen to all parts of the body.
3. MCV measures the average size of the red blood cells.
4. Other factors analyzed include the hematocrit (HCT), which is the percentage of red blood cells in the blood sample. If a child has anemia, the results for RBC, hemoglobin, and hematocrit will all be low.
White Blood Cells (WBCs) help the body fight infection. Also called leukocytes. These cells are bigger than red blood cells, and there are far fewer of them in the bloodstream. An abnormal white blood cell count may indicate that there is an infection, inflammation, or other stress in the body. For example, a bacterial infection can cause the WBC count to increase or decrease dramatically. There are five types of white blood cells: neutrophils, lymphocytes, eosinophils, basophils, and monocytes. Each has a different job.
1. Neutrophils and lymphocytes are the two major types of WBCs. Neutrophils play a key role in the body's defense against invading bacteria by destroying invading organisms. Someone with insufficient neutrophils is at risk for developing serious infections.
2. Lymphocytes produce antibodies, specific proteins that attack and help destroy specific germs. They are especially important in fighting viral infections, like colds and flu.
3. Eosinophils and basophils in the blood may be increased in allergic conditions. (Churg-Strauss patients have high #s of eosinophils.)
4. Monocytes, the largest white blood cells in the bloodstream, remove dead cells and organisms from the blood.
The Platelets are the smallest blood cells. They play an important role in blood clotting and the prevention of bleeding. When a blood vessel is damaged or cut, platelets clump together and plug up the hole until the blood clots. If the platelet count is too low, a person can be in danger of bleeding in any part of the body.
Erythrocyte (Red cell) Sedimentation Rate (ESR or SED):
ESR (erythrocyte sedimentation rate) is a nonspecific screening test for various diseases. This 1-hour test measures the distance (in millimeters) that red blood cells settle in unclotted blood toward the bottom of a specially marked test tube.