Anti-hemolytic streptococcus "O" test
The anti-streptolysin "O" test, abbreviated as "O", is an antibody produced by the body using streptococcal O as an antigen. By measuring the ASO antibody titer in serum, it can be judged whether the patient has a group A hemolytic streptococcus infection, and can be used as one of the auxiliary diagnostic methods for group A hemolytic streptococcal infectious diseases. However, this test has no specific significance, because group A streptococcus infection can cause a variety of human diseases, such as streptococcal infection caused by corresponding tonsillitis, scarlet fever, acute nephritis, subacute bacterial endocarditis, nephrotic syndrome Etc. can cause ASO to rise. After human infection with hemolytic streptococcus, a variety of antibodies can be present in the serum, such as anti-streptokinase antibodies, anti-hyaluronic acid antibodies and anti-"O" hemolysin antibodies, while anti-"O" hemolysin antibodies are active in detecting rheumatism. A serological diagnostic test is more meaningful. ASO is elevated in 60% to 80% of patients with active rheumatism, and multiple tests are normal to help eliminate rheumatism.Basic Information
Specialist classification: Infectious disease inspection and classification: pathogenic microorganism inspection
Applicable gender: whether men and women apply fasting: fastingTips: Do not eat too greasy, high-protein foods the day before the blood draw, avoid heavy drinking. The alcohol content in the blood directly affects the test results. Normal value
1 hemolytic streptococcal infection, scarlet fever, erysipelas, streptococcal pharyngitis, tonsillitis. It has indirect diagnostic value for rheumatic fever and acute glomerulonephritis. If the results of multiple tests are increased, accompanied by an increase in erythrocyte sedimentation rate (ESR), it may be helpful for diagnosis.
2 A small number of non-hemolytic streptococcus infections such as viral hepatitis, nephrotic syndrome, tuberculosis, connective tissue disease, subacute infective endocarditis, multiple myeloma.
3 cold areas, cold seasons.
(2) Reduction: found in drug (salicylate, adrenocortical hormone, antibiotic).Positive results may be diseases: Streptococcal pharyngitis, intermediate streptococcal infection, streptococcal infection, scarlet fever, erysipelas
First, the precautions before blood draw
1, do not eat too greasy, high-protein food the day before the blood, to avoid heavy drinking. The alcohol content in the blood directly affects the test results.
2. After 8 pm on the day before the medical examination, you should fast, so as not to affect the test of the next day.
3, should relax when taking blood, to avoid the contraction of blood vessels caused by fear, increase the difficulty of blood collection.
4, have a history of halo, please explain in advance, and make special arrangements.
Second, should pay attention after blood draw
1. After blood is drawn, local compression is required at the pinhole for 3-5 minutes to stop bleeding. Note: Do not rub, so as not to cause subcutaneous hematoma.
2, the pressing time should be sufficient. There is a difference in clotting time for each person, and some people need a little longer to clotting. Therefore, when the surface of the skin appears to be bleeding, the compression is stopped immediately, and the blood may be infiltrated into the skin due to incomplete hemostasis. Therefore, the compression time is longer to completely stop bleeding. If there is a tendency to bleed, the compression time should be extended.
3, after the blood draw symptoms of dizziness, such as: dizziness, vertigo, fatigue, etc. should immediately lie down, drink a small amount of sugar water, and then undergo a physical examination after the symptoms are relieved.
4. If there is localized congestion, use a warm towel after 24 hours to promote absorption.Inspection process
1. Laboratory materials: blood
Principle of anti-hemolytic streptococcus "O" test: Streptococcal hemolysin O is unstable to oxygen, and rapidly loses hemolysis activity in the air. When detecting ASO, the streptolysin O is first reduced to restore its hemolysis activity, and then Patients with different dilutions were mixed with serum, followed by O-erythrocytes or rabbit red blood cell suspension as an indicator. If hemolysin O is neutralized by the corresponding antibody in the serum, the added indicator indicates that the red blood cells are not dissolved. If there is no corresponding antibody or the amount of antibody in the serum is insufficient to neutralize the added hemolysin, different degrees of hemolysis occur.
(1) Hemolysin O: It is commercially available. After dilution according to the instructions, the hemolysin O activity (binding unit) must be accurately titrated with the WHO standard anti-hemolysin O antibody prepared by the Danish National Institute of Serum. Hemolysin O is unstable to heat, and can be stored in a refrigerator at 4 to 10 ° C for short-term storage. It should be stored at low temperature for several months or more.
(2) ASO buffer: taking 9.06 g of disodium hydrogen phosphate dodecahydrate, 10.89 g of sodium dihydrogen phosphate dihydrate, and 4.6 g of sodium chloride, so that it is dissolved in a small amount of distilled water and made up to 1000 ml, and the pH is 6.5. .
(3) Red blood cell suspension: Take anti-coagulated rabbit or O-type human blood of sodium citrate, wash 3 times with ASO buffer, after the last wash, it must be centrifuged at 2000r/min for 10-15min, as far as possible after centrifugation The colorless supernatant was aspirated and made up to a 5% suspension in ASO buffer and gently shaken as needed.
(4) Reducing agent: The commercial reducing tablet can be used according to the specification, and its main component is 2:1 anhydrous sodium hydrogen sulfite and anhydrous sodium sulfite. It is also possible to adjust the pH of the ASO buffer to 8.0 with 2 mol/L sodium hydroxide before use, and add 7 g/L of L-cysteine salt to dissolve.
3. Operation method:
(1) The serum samples were diluted with ASO buffer to two dilutions of 1:100 and 1:500.
(2) According to the instructions, prepare 1 binding unit/ml of reduced hemolysin O, accurately absorb a certain amount of hemolysin, first dilute with the reducing agent solution to about 1/3 of the final volume, place for 15min, so that hemolysin is fully reduced, then Accurately dilute to the specified volume and use within 45 minutes.
(3) Take a 70 x 100 mm small test tube and use the standard serum of known ASO units as a control.
(4) Results report: It is mainly observed whether the supernatant has hemolysis phenomenon, and the highest dilution factor of serum which is completely non-hemolyzed is the ASO unit/ml of the specimen.Not suitable for the crowd
Those who do not have an indication for examination should not do this check.Adverse reactions and risks
Generally no complications and harm.