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Paediatric

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CVS

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Regarding ASO titre all are seen except -(AIPG 2012)



A ASO can be increased in school children

B May be negative in post streptococcal Glomerulonephritis

C ASO titre included in major criteria in j ones criteria

D May not be elevated in20% cases of carditis

Ans. C

ASO titre included in major criteria in Jones criteria

Evidence of antecedent group ‘A’ streptococcrl infection

a. Positive throat cultures or rapid streptococcal antigen tests for group A streptococcoci are less reliable for

b. anlecedent infeaion capable of producing rheumatic lever because they do not distinguish between recent

c. infection and chronic pharyngeal carriage (as many people are carrier of this bacteria).

d. Antibody test are the most reliable laboratory evidence of antecedent streptococcal infection capable of producing acute rheumatic fever The onset of clinical ,manifestations of acute rhheumatic fever coincides with the peak ol the streqttococcal antibody response

e. The antibodies used commonly for serological tests are antisrrelrtolysin O (ASO), antideoryribonuclease (Anti-DNAse) and antihyaluronidase.

f. ASO titre is well standardized and therefore is most widely used test. Lt has following features.

i. Elevated in 80% of patient with acute rheumatic fever (So, 20% patieats do not show elevated titre) ) sensitivity is 80%.

ii. It is elevated in 20% of normal individual’s particularly in healthy school children of elementary school age (20% false positive),

iii. ASO tiiers ofat least 333 Todd units in children and 250 Todd units in adults are considered elevated.

iv. It is included in minor criteria of jones criteria (not in major criteria).

g. Anti DNAse B titers of240 Todd units or greater in children and 1200 Todd units or greater in adults are considered elevated.

h. If three aatibody tests (ASO, anti-DNAse and anti-hyaluonidase) are used simultaneously, a titer for at least one antibody iest is elevated in 95% of cases ) Se sitivit! olcombined three antibody tests is 95%.

i. The streptoz: yme test is a simple slide agglutination test for extra-cellular streptococcal antigen absorbed to red blood cells (passive hemagglutination) test. It is almost 100% sensitive but specificity is very low and it is less standardized and less reproducible than the other antibody tests. Therefore, it should not be used as a diagnostic test for evidence of antecedent group A streptococcal infection.

About option B.

a. ASO titre may not be elevated in PSGN if PSGN develops secondary to skin infection.

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