Which test best supports a diagnosis of a recent group A streptococcal infection in suspected acute rheumatic fever?

Which test best supports a diagnosis of a recent group A streptococcal infection in suspected acute rheumatic fever?

• A. Urinalysis
• B. Antistreptolysin-O titer
• C. Electrocardiogram
• D. Hemoglobin electrophoresis

Answer: (B)

In suspected acute rheumatic fever, you need evidence that a group A Streptococcus infection occurred recently. Antistreptolysin-O titer measures antibodies to streptolysin O released by GAS, and these antibodies rise several days to weeks after infection, typically peaking a few weeks later. A high ASO titer supports a recent GAS infection and helps fulfill the criterion that ARF follows a prior strep infection, even if the throat culture is no longer positive by the time ARF signs appear. Urinalysis isn’t used to prove a prior GAS infection; an electrocardiogram assesses heart involvement but not infection history; and hemoglobin electrophoresis screens for blood disorders, not GAS exposure.

In suspected acute rheumatic fever, you need evidence that a group A Streptococcus infection occurred recently. Antistreptolysin-O titer measures antibodies to streptolysin O released by GAS, and these antibodies rise several days to weeks after infection, typically peaking a few weeks later. A high ASO titer supports a recent GAS infection and helps fulfill the criterion that ARF follows a prior strep infection, even if the throat culture is no longer positive by the time ARF signs appear.

Urinalysis isn’t used to prove a prior GAS infection; an electrocardiogram assesses heart involvement but not infection history; and hemoglobin electrophoresis screens for blood disorders, not GAS exposure.