Med lab blog

Test Description The Apt test for swallowed blood is a test to determine if blood in an infant’s stool or vomitus is from the mother or from the infant. The test is based on the fact that a newborn’s blood contains primarily fetal hemoglobin (Hb F). The mother’s blood, unless she has thalassemia major, is primarily Hb A. When blood is seen in a newborn’s stool or vomitus, it must be tested to ensure that the newborn is not having internal bleeding. If bleeding is occurring, immediate treatment is needed. To differentiate the type of hemoglobin in the sample of bloody stool or vomitus, the sample is first mixed with water and then centrifuged, producing a pink solution. This solution is then tested with sodium hydroxide. If the blood is maternal blood, the solution will turn brownish yellow, due to the presence of hematin, a product of the breakdown of Hb A. If the blood is fetal blood, the solution will remain pink. This is because Hb F is resistant to breakdown by al...

Test Description Lipoproteins are important transporters of cholesterol. High-density lipoprotein (HDL or “good cholesterol”) picks up cholesterol in the tissues and transports it back to the liver for either recycling or excretion in the bile. Since it works to get rid of excess cholesterol, high levels of HDL are preferred. Low-density lipoprotein (LDL, or “bad cholesterol”) also transports excess cholesterol, however it has a tendency to transport it to the arteries, where it can result in the development of atherosclerosis. Thus, it is best to have low levels of LDL to decrease the risk of atherosclerotic disease. Apolipoproteins (apo) are the protein components of lipoproteins. Two of the apolipoproteins, apo A and apo B, in particular serve important functions in control of cholesterol in the body. Apo A activates the enzymes that cause movement of cholesterol from the tissues into HDL and also causes HDL to be recognized by receptor sites in the liver where the cho...

Test Description Thyroglobulin is a thyroid glycoprotein that has a role in the synthesis of triiodothyronine (T3) and thyroxine (T4). In some types of thyroid disorders, thyroglobulin may escape from the thyroid gland. Once liberated, these substances appear as antigens to the body. In response, the body produces antibodies against the thyroglobulin, leading to inflammation and destruction of the thyroid gland. Antithyroglobulin antibodies are present in the majority of patients diagnosed with Hashimoto’s thyroiditis. The most dilute serum in which antithyroglobulin antibodies are detected is called the titer. Normal Values     Titer <1:100 Possible Meanings of Abnormal Values Increased Autoimmune hemolytic anemia Diabetes mellitus Type 1 Granulomatous thyroiditis Hashimoto’s thyroiditis Hyperthyroidism Juvenile lymphocytic thyroiditis Myasthenia gravis Myxedema Nontoxic nodular goiter Pernicious anemia Primary hypothyroidism Rheumatoid arth...

Test Description During hemostasis, a substance called thrombin stimulates the formation of fibrin from fibrinogen. This fibrin then forms a stable clot at the site of injury. Any excess amounts of clotting factors, which remain following hemostasis are inactivated by fibrin inhibitors which prevent clotting from occurring when it is not needed. One such substance is antithrombin III (AT-III). AT-III is a naturally occurring protein immunoglobulin that is synthesized by the liver. The action of AT-III is catalyzed by heparin. Its role is to inactivate thrombin and other coagulation factors, thus inhibiting the coagulation process. The proper balance between thrombin and AT-III allows for appropriate hemostasis to occur. If, however, this balance is disrupted, problems can arise. For example, if there is a congenital deficiency of AT-III, coagulation will not be inhibited at an adequate level, resulting in a hypercoagulability state with a high risk of thrombosis. THE...

Test Description Streptolysin-O is an enzyme produced by Group A beta-hemolytic streptococcal bacteria. When confronted by this foreign enzyme, the body produces antibodies against it. The antibodies appear 7 to 10 days after the acute streptococcal infection and continue to rise for 2 to 4 weeks. The ASO level will typically fall to preinfection levels with 6 to 12 months. The antistreptolysin-O (ASO) test is designed to detect these antibodies. If the antibodies are present, the person has had a streptococcal infection. Over 80% of patient with acute rheumatic fever and 95% of those with acute streptococcal glomerulonephritis have elevated ASO levels. ASO levels do not typically rise with cutaneous infections. This test is considered less sensitive than the anti-DNase B test. When both tests are consistently performed on blood samples, 95% of the streptococcal infections can be identified. The test is particularly useful in determining whether such conditions as jo...

Test Description Anti-Ss-A (Ro) and anti-SS-B (La) are autoantibodies formed against ribonucleic acid (RNA) protein particles in the body. These antibodies are most often seen in Sjögren’s syndrome, a disorder with symptoms similar to those of connective tissue disorders such as rheumatoid arthritis, systemic lupus erythematosus (SLE), or scleroderma. The syndrome is characterized by decreased secretion and eventual destruction of the exocrine glands, resulting in dryness of the mucosa and conjunctiva. The test is used in the differential diagnosis of Sjögren’s syndrome, SLE, and mixed connective tissue disease. Normal Values Ro: Negative La: Negative Possible Meanings of Abnormal Values Positive ANA-negative lupus Neonatal lupus Scleroderma Sjögren’s syndrome Interventions/Implications Pretest • Explain to the patient the purpose of the test and the need for a blood sample to be drawn. • No fasting is required before the test. Procedure • A 7-mL blo...

Test Description Antisperm antibodies may form in a male as a result of blocked efferent ducts in the testes. This blockage results in reabsorption of sperm, which can lead to the formation of autoantibodies to the sperm. Antisperm antibodies may also form in a female. Thus, this test may be performed on both males and females as one part of infertility screening. Normal Values Negative Possible Meanings of Abnormal Values Increased      Blocked efferent ducts in the testes Infertility Vasectomy Interventions/Implications Pretest • Explain to the patient the purpose of the test and the specimen samples needed. • No fasting is required before the test. • If a semen sample is to be used, the male should avoid ejaculation for 3 days before the    test. Procedure • The preferred specimen for a male is a semen sample. Provide a plastic container for the    specimen collection. • A 7-mL blood sample is drawn in a red-top...

Test Description The anti-smooth muscle antibody (ASMA) test is used to detect the presence of autoimmune antibodies that have formed against smooth muscle. These antibodies have a tendency to appear in chronic active hepatitis and other diseases in which there is liver damage. The ASMA test is used in the diagnosis of primary biliary cirrhosis and chronic active hepatitis Normal Values Negative at 1:20 dilution Possible Meanings of Abnormal Values Increased Acute viral hepatitis Chronic active hepatitis Infectious mononucleosis Intrinsic asthma Malignancies Primary biliary cirrhosis Viral infection Contributing Factors to Abnormal Values • Hemolysis of the blood sample and the presence of antinuclear antibodies may alter test results. Interventions/Implications Pretest • Explain to the patient the purpose of the test and the need for a blood sample to be drawn. • No fasting is required before the test. Procedure • A 7-mL blood sample is drawn...

Test Description The antiscleroderma antibody is found in individuals with progressive systemic sclerosis (scleroderma) and individuals with CREST syndrome. CREST syndrome is characterized by calcinosis, Raynaud’s phenomenon, esophageal dysfunction, sclerodactyly, and telangiectasia. Positive results with this test are considered highly diagnostic of scleroderma, because the antibody is found only rarely in diseases such as mixed connective tissue disease, rheumatoid arthritis, Sjögren’s syndrome, and systemic lupus erythematosus. Normal Values Negative Possible Meanings of Abnormal Values Positive CREST syndrome Scleroderma Contributing Factors to Abnormal Values • Drugs that may increase antiscleroderma antibody levels: aminosalicylic acid, isoniazid, methyldopa, penicillin, propylthiouracil, streptomycin, tetracycline . Interventions/Implications Pretest • Explain to the patient the purpose of the test and the need for a blood sample to be drawn. ...

Test Description The anti-parietal cell antibody test (APCA) measures the presence of antibodies against gastric parietal cells. When antibodies form against the parietal cells in the stomach, their production of intrinsic factor is disrupted. This results in pernicious anemia due to an autoimmune process. Thus the APCA test is used in the evaluation of pernicious anemia. It may be elevated in atrophic gastritis and in some other autoimmune processes. Normal Values Negative Possible Meanings of Abnormal Values Positive CREST syndrome Scleroderma Contributing Factors to Abnormal Values • Drugs that may increase antiscleroderma antibody levels: aminosalicylic acid, isoniazid,   methyldopa, penicillin, propylthiouracil, streptomycin, tetracycline.    Interventions/Implications Pretest • Explain to the patient the purpose of the test and the need for a blood sample to be drawn. • No fasting is required before the test. Procedure • A 7-mL bl...

Test Description Antinuclear antibodies are antibodies the body produces against nuclear components of its own cells. This results in the development of an autoimmune disease. The antinuclear antibody (ANA) test is commonly used to rule out systemic lupus erythematosus (SLE) because 95% to 99% of SLE patients have positive ANA titers. A titer is the most dilute serum in which the ANA is detected. The ANA test uses an indirect immunofluorescent procedure, which results in several staining patterns: homogeneous, nucleolar, peripheral, and speckled patterns. These patterns assist in diagnosing the specific disease process affecting the individual. Normal Values Negative at 1:8 dilution Possible Meanings of Abnormal Values Positive Bacterial endocarditis Chronic autoimmune hepatitis Cirrhosis Connective tissue diseases Dermatomyositis Discoid lupus erythematosus Drug-induced lupus Infectious mononucleosis Leukemia Malignancy, especially lymphoma Mixed connec...

Test Description The anti-neutrophil cytoplasmic antibody test (ANCA) is used primarily in the diagnosis and monitoring of patients with Wegener’s granulomatosis (WG). WG is an autoimmune disease, which is characterized by inflammation in many tissues of the body, including the upper and lower respiratory system, the kidneys, eyes, ears, and skin. The blood vessels in these areas become inflamed, a condition known as vasculitis, and granulomas develop. Once the diagnosis is confirmed, treatment with cytotoxic agents is usually needed. Normal Values                       ANCA by immunofluorescence: Negative ANCA by EIA: Negative: <21 Units Weak Positive: 21–30 Units Positive: >30 Units Possible Meanings of Abnormal Values Increased Glomerulonephritis Inflammatory bowel disease Polyarthritis nodosa Systemic arthritis Wegener’s granulomatosis Interventions/Implications Pretest • Explain to the p...

Test Description The antimitochondrial antibody (AMA) test is used to detect the presence of autoimmune antibodies that have formed against a lipoprotein component of the mitochondrial membrane. These antibodies have a tendency to attack organs that expend a great deal of energy, such as those of the hepatobiliary system. The AMA test is used in the diagnosis of primary biliary cirrhosis. Normal Values Negative at 1:20 dilution A Possible Meanings of Abnormal Values Increased Cryptogenic cirrhosis Drug-induced jaundice Hepatic obstruction Hepatitis Primary biliary cirrhosis Rheumatoid arthritis Systemic lupus erythematosus Contributing Factors to Abnormal Values • Hemolysis of the blood sample may alter test results. Interventions/Implications Pretest • Explain to the patient the purpose of the test and the need for a blood sample to be drawn. • No fasting is required before the test. Procedure • A 7-mL blood sample is drawn in a red-top collection tub...

Test Description Microsomes are lipoproteins that are normally present within the epithelial cells of the thyroid. In some types of thyroid disorders, these microsomes escape from their normal locations. Once liberated, these substances appear as antigens to the body. In response, the body produces antibodies against the microsomes, leading to inflammation and destruction of the thyroid gland. Antimicrosomal antibodies are present in the majority of patients diagnosed with Hashimoto’s thyroiditis. The most dilute serum in which antimicrosomal antibodies are detected is called the titer. This test is usually performed in conjunction with the antithyroglobulin antibody test Normal Values       Titer < 1:100 Possible Meanings of Abnormal Values Increased Autoimmune hemolytic anemias Granulomatous thyroiditis Hashimoto’s thyroiditis Juvenile lymphocytic thyroiditis Myasthenia gravis Myxedema Nontoxic nodular goiter Pernicious anemia Primary hypo...

Test Description The presence of LKM antibodies is used in conjunction with clinical findings and other laboratory tests to aid in the diagnosis of autoimmune liver diseases such as autoimmune hepatitis type 2. Autoimmune hepatitis occurs primarily in women and is associated with very high transaminase levels and elevated gamma globulins, especially IgG. LKM antibodies are usually evaluated, along with anti-smooth muscle antibody and antinuclear antibody. Normal Values Negative: <20.1 Units A Possible Meanings of Abnormal Values Positive Autoimmune hepatitis type 2 Interventions/Implications Pretest • Explain to the patient the purpose of the test and the need for a blood sample to be drawn. • No fasting is required before the test.   Procedure • A 7-mL blood sample is drawn in a gold-top (serum separator) collection tube. • Gloves are worn throughout the procedure . Post test • Apply pressure at venipuncture site. Apply dressing, periodically as...

Test Description Insulin, whether beef, pork, or human type, contains insulin-related peptides, which may stimulate production of antibodies. With subsequent insulin injections, these antibodies join and neutralize the insulin so that it is no longer able to function appropriately. Larger doses of insulin are then required to attempt to meet the patient’s needs, a phenomenon called insulin resistance. This is indicated by the presence of IgG and IgM anti-insulin antibodies. If the anti-insulin antibodies are found to be IgE, this indicates the body has developed an allergic response to the medication This allergy can result in minor allergy symptoms such as rash, or more severe responses. The insulin antibody test is performed when insulin is no longer controlling the patient’s diabetes or if symptoms of allergy to the insulin are present. Normal Values Undetectable for antibodies Possible Meanings of Abnormal Values Increased Allergy to insulin Factitious hypogl...

Test Description Goodpasture’s syndrome is an autoimmune disease in which antibodies specific for renal structural components, such as the glomerular basement membrane in the kidney, and pulmonary structural components, such as the alveolar basement membrane, are produced. These antibodies then bind to the tissue antigens, resulting in an immune response and the development of such problems as necrotizing glomerulonephritis and hemorrhagic pneumonitis. Because of the renal and pulmonary complications, kidney and lung biopsies may also be performed. Normal Values Negative: <20 units by ELISA Possible Meanings of Abnormal Values Increased                                                   Antiglomerular glomerular nephritis Goodpasture’s syndrome Systemic lupus erythematosus Contributing Factors to Abnormal Values • Drugs that may d...

Test Description The anti-DNA antibody test detects the presence of antibodies to native, or doublestranded DNA. Presence of these antibodies indicates the person has some type of autoimmune disease. The resultant antibody-antigen complexes which form play a major part in the tissue injury involved in autoimmune diseases. These antibodies are particularly prevalent in patients with systemic lupus erythematosus (SLE); thus, this test is useful in the diagnosis of SLE and for monitoring the course of SLE. Normal Values ∎Immunofluorescence method:                Negative at 1:10 dilution ELISA method:                                            Negative<50 IU/mL Borderline                                      ...

Test Description Antidiuretic hormone (ADH), originally known as vasopressin, is a hormone produced by the hypothalamus. It is stored in the posterior pituitary and released when needed as indicated by serum osmolality levels. A high serum osmolality indicates that the serum is concentrated and that the amount of water is limited. When this occurs, ADH is released. ADH increases the permeability of the distal renal tubules and collecting ducts, resulting in water reabsorption. Conversely, a low serum osmolality indicates there is a water excess and that the serum is dilute. In this situation, ADH secretion is reduced, leading to increased excretion of water (diuresis). Certain conditions can result in an abnormal secretion or lack of secretion of ADH, or in a lack of renal response to ADH secretion. In diabetes insipidus, there is either inadequate ADH secretion or the kidneys do not respond appropriately to ADH. Causes of diabetes insipidus include head t...

Test Description Deoxyribonuclease B is an antigen produced by group A streptococci. When the body is confronted by this antigen, it produces antibodies against the antigen. The antideoxyribonuclease-B test is designed to detect these antibodies. If the antibodies are present, the person has had a streptococcal infection. The anti-DNase B level increases after the person has recovered from the infection. This test is considered more sensitive than the antistreptolysin-O (ASO) test. When both tests are consistently performed on blood samples, 95% of the streptococcal infections can be identified. The test is particularly useful in the diagnosis of rheumatic fever and post-streptococcal glomerulonephritis, both sequelae of infections involving group-A beta-hemolytic streptococci. Normal Values Adult:                                        <85 Todd U/mL ...

Test Description CREST syndrome is a variant of scleroderma characterized by calcinosis, Raynaud’s phenomenon, esophageal dysfunction, sclerodactyly, and telangiectasia. The anticentromere antibody has been found in most patients diagnosed with CREST syndrome. Normal Values     Negative  Possible Meanings of Abnormal Values               Positive                                                    CREST syndrome Interventions/Implications Pre test • Explain to the patient the purpose of the test and the need for a blood sample to be drawn. • No fasting is required before the test.   Procedure • A 7-mL blood sample is drawn in a red-top collection tube. • Gloves are worn throughout the procedure.   Posttest • Apply pressure at venipuncture site....

Test Description Cardiolipin antibodies are the most common form of antiphospholipid antibodies. The antibodies play an important role in the blood clotting process. When autoantibodies (anticardiolipin antibodies, or ACA) are formed against cardiolipins, the patient has an increased risk of developing recurrent thrombosis. There are three types of cardiolipin antibodies: IgG, IgM, and IgA. ACA testing is used to determine the cause of thrombosis, thrombocytopenia, and recurrent fetal loss, and in the evaluation of patients with systemic lupus erythematosus. Normal Values IgG Cardiolipin Antibody Negative:         <10 GPL Equivocal:    10–40 GPL High Positive: >40  GPL IgM Cardiolipin Antibody Negative:         <12   MPL Equivocal:       12–40 MPL High Positive:  >40   MPL IgA Cardiolipin Antibody Negative:...