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Anti-streptolysin O (ASO or ASLO) is the antibody made against streptolysin O, an immunogenic, oxygen-labile streptococcal hemolytic exotoxin produced by most strains of group A and many strains of groups C and G Streptococcus bacteria.
Thus, if the initial titer is 1:4 and stable but increases at 26 weeks' gestation to 1:8, assessment with MCA Doppler velocity at that point is reasonable. However, if the patient presents in the first trimester with a 1:8 titer that remains stable at 1:8 throughout the second trimester, continued serial antibody titers are appropriate.
Titers of 1:4 or higher is considered critical for Kell (compared to 1:16 for most other antibodies) and is considered to confer a high risk of fetal anemia. [17] Such high titers may be managed by weekly follow-up by obstetric ultrasound , assessing the peak systolic velocity of the fetal middle cerebral arterial (MCA), amniotic fluid volume ...
ASO analysis is only one of the methods used to detect genetic polymorphisms. Direct DNA sequencing is used to initially characterize the mutation, but is too laborious for routine screening. An earlier method, Restriction Fragment Length Polymorphism (RFLP) didn't need to know the sequence change beforehand, but required that the mutation ...
Thus, if the initial titer is 1:4 and stable but increases at 26 weeks' gestation to 1:8, assessment with MCA Doppler velocity at that point is reasonable. However, if the patient presents in the first trimester with a 1:8 titer that remains stable at 1:8 throughout the second trimester, continued serial antibody titers are appropriate.
The indirect Coombs test is used in prenatal testing of pregnant women and in testing prior to a blood transfusion. The test detects antibodies against foreign red blood cells. In this case, serum is extracted from a blood sample taken from the patient. The serum is incubated with foreign red blood cells of known antigenicity. Finally, anti ...
Post-streptococcus glomerulonephritis is more often associated with group A strep skin infection than it is with strep pharyngitis, so in a patient with suspected post-strep glomerulonephritis with a negative ASO titer, one can then obtain anti-DNase-B titers which are more sensitive for group A strep and for its various strains.
The Widal test is positive if TO antigen titer is more than 1:160 in an active infection, or if TH antigen titer is more than 1:160 in past infection or in immunized persons. A single Widal test is of little clinical relevance especially in endemic areas such as Indian subcontinent, Africa and South-east Asia.