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سؤال عن ASO Test

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  • سؤال عن ASO Test

    ارد شرحا مختصرا عن ASO test

  • #2
    About antistreptolysin-O tests

    The antistreptolysin-O (ASO) test is a blood test that measures levels of ASO in the blood. ASO is an antibody produced to fight streptolysin-O, an enzyme produced by a specific type of bacteria called Group A streptococci (“strep”). This bacteria is related to infections such as endocarditis and rheumatic fever.

    High levels of ASO may remain in the blood for months following the onset of infection, even after the bacteria causing the infection have been eliminated.

    Several strep-related diseases can cause the release of ASO. The test is used to help diagnose or to monitor the treatment of any of the following:

    Endocarditis. A relatively uncommon but potentially dangerous inflammation, usually caused by infection (e.g., strep infection) in vulnerable areas of the endocardium, or the innermost layer of the heart’s chambers and valves. The ASO test is not used as a primary tool for diagnosis, but may be used as in a supporting role.


    Rheumatic fever. A disease that may begin with a streptococcal infection that was not properly treated with antibiotics. It can cause serious damage to the heart, joints and kidneys. About 80 percent of patients with rheumatic fever have elevated ASO titers. However, this is not enough to diagnose rheumatic fever alone and physicians will often run additional antibody tests, as well as follow established criteria to confirm the diagnosis.


    Glomerulonephritis. A type of serious kidney disease that can follow a streptococcal infection. The glomeruli (small, round filters in the kidneys) become inflamed and cannot effectively filter waste products from the bloodstream.


    Scarlet fever. A contagious childhood disease caused by streptococci and marked by a bright red rash that affects the face, throat, skin and tonsils.
    ASO is always present in the body to ward off minor strep infections. Therefore, even healthy patients will have some ASO detectable in their blood. Normal levels of ASO in the blood are 120 Todd units per milliliter for adults and preschoolers, and 170 Todd units per milliliter for school-aged children, although these results may vary somewhat depending on the lab.

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    • #3
      also called Streptococcal antibody tests


      Definition

      Streptococcal infections are caused by a microorganism called Streptococcus. Three streptococcal antibody tests are available: the antistreptolysin O titer (ASO), the antideoxyribonuclease-B titer (anti-Dnase-B, or ADB), and the streptozyme test.

      Purpose

      The antistreptolysin O titer, or ASO, is ordered primarily to determine whether a previous group A Streptococcus infection has caused a poststreptococcal disease, such as scarlet fever, rheumatic fever, or a kidney disease called glomerulonephritis.

      The anti-DNase-B (ADB) test is performed to determine a previous infection of a specific type of Streptococcus, group A beta-hemolytic Streptococcus. Identification of infections of this type are particularly important in suspected cases of acute rheumatic fever (ARF) or acute glomerulonephritis.

      Streptozyme is a screening test used to detect antibodies to several streptococcal antigens. An antigen is a substance that can trigger an immune response, resulting in production of an antibody as part of the body's defense against infection and disease.

      Precautions

      For the ASO test, increased levels of fats, called beta lipoproteins, in the blood can neutralize streptolysin O and cause a false-positive ASO titer. Antibiotics, which reduce the number of streptococci and thereby suppress ASO production, may decrease ASO levels. Steroids, which suppress the immune system, consequently may also suppress ASO production. Also Group A streptococcal infections of the skin may not produce an ASO response. Antibiotics also may decrease anti-DNase-B (ADB) levels.

      Description

      Streptococcal infections are caused by bacteria known as Streptococcus. There are several disease-causing strains of streptococci (groups A, B, C, D, and G), which are identified by their behavior, chemistry, and appearance. Each group causes specific types of infections and symptoms. These antibody tests are useful for group A streptococci. Group A streptococci are the most virulent species for humans and are the cause of strep throat, tonsillitis, wound and skin infections, blood infections (septicemia), scarlet fever, pneumonia, rheumatic fever, Sydenham's chorea (formerly called St. Vitus' dance), and glomerulonephritis.

      Although symptoms may suggest a streptococcal infection, the diagnosis must be confirmed by tests. The best procedure, and one that is used for an acute infection, is to take a sample from the infected area for culture, a means of growing bacteria artificially in the laboratory. However, cultures are useless about two to three weeks after initial infection, so the ASO, anti-DNase-B, and streptozyme tests are used to determine if a streptococcal infection is present.

      Antistreptolysin O titer (ASO)

      The ASO titer is used to demonstrate the body's reaction to an infection caused by group A beta-hemolytic streptococci. Group A streptococci produce the enzyme streptolysin O, which can destroy (lyse) red blood cells. Because streptolysin O is antigenic (contains a protein foreign to the body), the body reacts by producing antistreptolysin O (ASO), which is a neutralizing antibody. ASO appears in the blood serum one week to one month after the onset of a strep infection. A high titer (high levels of ASO) is not specific for any type of poststreptococcal disease, but it does indicate if a streptococcal infection is or has been present.

      Serial (several given in a row) ASO testing is often performed to determine the difference between an acute or convalescent blood sample. The diagnosis of a previous strep infection is confirmed when serial titers of ASO rise over a period of weeks, then fall slowly. ASO titers peak during the third week after the onset of acute symptoms of a streptococcal disease; at six months after onset, approximately 30% of patients exhibit abnormal titers.

      Antideoxyribonuclease-B titer (anti-DNase B, or ADB)

      Anti-DNase-B, or ADB, also detects antigens produced by group A strep, and is elevated in most patients with rheumatic fever and poststreptococcal glomerulonephritis. This test is often done concurrently with the ASO titer, and subsequent testing is usually performed to detect differences in the acute and convalescent blood samples. When ASO and ADB are performed concurrently, 95% of previous strep infections are detected. If both are repeatedly negative, the likelihood is that the patient's symptoms are not caused by a poststreptococcal disease.

      When evaluating patients with acute rheumatic fever, the American Heart Association recommends the ASO titer rather than ADB. Even though the ADB is more sensitive than ASO, its results are too variable. It also should be noted that, while ASO is the recommended test, when ASO and ADB are done together, the combination is better than either ASO or ADB alone.

      Streptozyme

      The streptozyme test is often used as a screening test for antibodies to the streptococcal antigens NADase, DNase, streptokinase, streptolysin O, and hyaluronidase. This test is most useful in evaluating suspected poststreptococcal disease following Streptococcus pyogenes infection, such as rheumatic fever.

      Streptozyme has certain advantages over ASO and ADB. It can detect several antibodies in a single assay, it is technically quick and easy, and it is unaffected by factors that can produce false-positives in the ASO test. The disadvantages are that, while it detects different antibodies, it does not determine which one has been detected, and it is not as sensitive in children as in adults. In fact, borderline antibody elevations, which could be significant in children, may not be detected at all. As with the ASO and ADB, a serially rising titer is more significant than a single determination.

      Preparation

      These tests are performed on blood specimens drawn from the patient's vein. The patient does not need to fast before these tests.

      Risks

      The risks associated with these tests are minimal, but may include slight bleeding from the blood-drawing site, fainting or feeling lightheaded after the blood is drawn, or blood accumulating under the puncture site (hematoma).

      Normal results

      Antistreptolysin O titer:


      adult: 160 Todd units/ml


      child: six months to two years: 50 Todd units/ml; two to four years: 160 Todd units/ml; five to 12 years: 170-330 Todd units/ml


      newborn: similar to the mother's value

      Antideoxyribonuclease-B titer:


      adult: 85 units


      child (preschool): 60 units


      child (school age): 170 units

      Streptozyme: less than 100 streptozyme units.

      Abnormal results

      Antistreptolysin O titer: Increased levels are seen after the second week of an untreated infection in acute streptococcal infection, and are also increased with acute rheumatic fever, acute glomerulonephritis (66% of patients will not have high ASO titers), and scarlet fever.

      Antideoxyribonuclease-B titer: Increased titers are seen in cases of acute rheumatic fever and poststreptococcal glomerulonephritis.

      Streptozyme: As this is a screening test for antibodies to streptococcal antigens, increased levels require more definitive tests to confirm diagnosis.

      Key Terms


      Antibody
      A protein manufactured by a type of white blood cells called lymphocytes, in response to the presence of an antigen, or foreign protein, in the body. Because bacteria, viruses, and other organisms commonly contain many antigens, antibodies are formed against these foreign proteins to neutralize or destroy the invaders.


      Antigen
      A substance that can trigger a defensive response in the body, resulting in production of an antibody as part of the body's defense against infection and disease. Many antigens are foreign proteins not found naturally in the body, and include bacteria, viruses, toxins, and tissues from another person used in organ transplantation.


      Glomerulonephritis
      An inflammation of the glomeruli, the filtering units of the kidney. Damage to these structures hampers removal of waste products, salt, and water from the bloodstream, which may cause serious complications. This disorder can be mild and cause no symptoms, or so severe enough to cause kidney failure.


      Rheumatic fever
      A disease that causes inflammation in various body tissues. Rare in most developed countries, but reported to be on the increase again in parts of the United States. Joint inflammation occurs, but more serious is the frequency with which the disease permanently damages the heart. The nervous system may also be affected, causing Sydenham's chorea.


      Sydenham's chorea
      A childhood disorder of the central nervous system. Once called St. Vitus' dance, the condition is characterized by involuntary, jerky movements that usually follow an attack of rheumatic fever. Rare in the United States today, but a common disorder in developing countries. Usually resolves in two to three months with no long-term adverse effects.

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      • #4
        احسنت على هذا الشرح المفصل
        تحاتي:sm188:

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        • #5
          جزاك الله خيرا
          شكرا جزيلا

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          • #6
            مجهود كبير ورائع

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            • #7
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              • #8
                انا عندى سؤال

                هل اذا كان نسبة asoكانت٦٠٠وبعدة٣ شهور
                460ثم بعد شهر 420 مع الاستمرار في لعلاج بالبنسلين ومن الاطباء من يقول هذه نسبة متناقصة لعدوي منذ فترة وىكفى هذا العلاج ومنهم من يري استكمال العلاج حتى نرجع الي النسبة الطبعبة مع العلم انالطفلة باتفاقهم جمعا لا يوجد عليها الان اي اعراض لاي مرض

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