PATHOPHYSIOLOGY
Antistreptolysin – O is an
antibody that appears when a person has Group A streptococcus bacteria in the
blood. These bacteria produce exotoxins called Streptolysin-O, which act as
destroys red blood cells. Antistreptolysin – O (ASO) is the antibodies produced
against these exotoxins .
CLINICAL SIGNIFICANCE
·
Confirms a recent or ongoing infection with
Group streptococcus.
·
Helps diagnose rheumatic fever or a
streptococcal infection in the kidneys.
·
Determine whether a person has rheumatoid
arthritis or rheumatic fever.
Antistreptolysin – O reaction
provides useful information for diagnosis and monitoring of human streptococcal
infections
such as in tonsillitis, otitis, erysipelas scarlet fever , as well as connective
tissue diseases like rheumatic fever , or glomerulonephritis. This test is a
sensitive test for recent streptococcal infection . A rise in titer begins
about one week after infection and peaks two to four weeks later . Streptolysin-O
Antibody (ASO) titer doesn’t rise with
cutaneous infections. In the absence of complications or reinfection, the titer
will fall to preinfection levels within 6 to 12 months. Over 80% of patients
with acute rheumatic fever and 95% of patients with acute glomerulonephritis
have elevated titers o ASO.
Elevated Levels of
ASO indicate :
·
Active streptococcal infection.
·
Bacterial endocarditis, an inflammation in the
lining of the heart.
·
Postreptococcal glomerulonephritis , an
infection in the kidney.
·
Rheumatic fever, a disease that may affect the
heart and kidneys.
·
Scarlet fever, an infection involving the throat
and tongue that causes fever, rash, and rapid pulse .
LIMITATIONS:
Very lipemic samples, wich cannot
be clarified by centrifugation, must not be assayed by this method. In case
of monoclonal gammopathies the
measurement yield false highly elevated ASO concentrations in very few
patients. Such samples should be assayed by another method .