Streptococcus serologic testing (Antistreptolysin O titer [ASO], Antideoxyribonuclease-B titer, [Anti-DNase-B, ADNase-B, ADB], Streptococcus group B antigen detection, Streptozyme)
المؤلف:
Kathleen Deska Pagana, Timothy J. Pagana, Theresa Noel Pagana.
المصدر:
Mosbys diagnostic and laboratory test reference
الجزء والصفحة:
15th edition , p839-840
2025-09-08
428
Type of test Blood, cerebrospinal fluid (CSF)
Normal findings
Antistreptolysin O titer
Adult/elderly: ≤ 160 Todd units/mL
Child:
Newborn: similar to mother’s value
6 months-2 years: ≤ 50 Todd units/mL
2-4 years: ≤ 160 Todd units/Ml
5-12 years: 170-330 Todd units/mL
Antideoxyribonuclease-B titer
Adult: ≤ 85 Todd units/mL or titer ≤ 1:85
Child:
Preschool age: ≤ 60 Todd units/mL or titer ≤ 1:60
School age: ≤ 170 Todd units/mL or titer ≤ 1:170
Streptozyme
Titer < 1:100
Streptococcus group B antigen
None detected
Test explanation and related physiology
Infection by group A Streptococcus is unique because it can be followed by a serious nonpurulent complication (e.g., rheumatic fever, scarlet fever, glomerulonephritis). Serologic tests are used primarily to determine whether a previous group A Streptococcus infection (pharyngitis, pyodermia, pneumonia) has caused a poststreptococcal disease. These poststreptococcal diseases occur after the infection and after a period of latency during which the patient is asymptomatic.
These antibodies are directed against streptococcal extracellular products that are primarily enzymatic proteins. Serial rising titers of these antibodies over several weeks followed by a slow fall in titers are more supportive of the diagnosis of a previous streptococcal infection than is a single titer.
One such extracellular enzyme produced by streptococcus is called streptolysin O, which has the ability to destroy (lyse) RBC corpuscles. The streptolysin O is antigenic, stimulating the immunologic production of a neutralizing ASO antibody. ASO appears in the serum 1 week to 1 month after the onset of a streptococcal infection. A high ASO titer is not specific for a certain type of poststreptococcal disease (i.e., rheumatic fever versus glomerulonephritis) but merely indicates that a streptococcal infection is or has been present.
Like the ASO titer, ADB is used to detect previous streptococcal infections. Although this test may be more sensitive than the ASO titer, it is not used alone in the evaluation of streptococcal infections because its results are too variable.
The Streptozyme assay detects antibodies to multiple extracellular antigens of group A Streptococcus, including antistreptolysin O, antistreptokinase, and antihyaluronidase. Approximately 80% of specimens positive by streptozyme have antistreptolysin O, and 10% have antistreptokinase and/or antihyaluronidase. The remaining 10% of positive samples are apparently caused by ADB antibodies or other streptococcal extracellular antigens.
Streptococcus group B antigens accumulate in CSF, serum, or urine and provide a direct qualitative detection of bacterial antigens. These antigens indicate acute infection and are not related to poststreptococcal sequelae as described previously. Confirmatory diagnosis of streptococcal infection is done by cultures.
Interfering factors
• Increased beta-lipoprotein levels inhibit streptolysin O and give a falsely high ASO titer.
* Drugs that may cause decreased ASO levels include adrenocorticosteroids and antibiotics.
Procedure and patient care
• See inside front cover for Routine Blood Testing.
• Fasting: no
• Blood tube commonly used: red
Abnormal findings
Increased levels
- Streptococcal infection
- Acute rheumatic fever
- Acute glomerulonephritis
- Bacterial endocarditis
- Scarlet fever
- Streptococcal pyoderma
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