A child has a fever and arthralgia. The primary care pediatric nurse practitioner learns that the child had a sore throat 3 weeks prior and auscultates a murmur in the clinic. Which test will the nurse practitioner order?

A child has a fever and arthralgia. The primary care pediatric nurse practitioner learns that the child had a sore throat 3 weeks prior and auscultates a murmur in the clinic. Which test will the nurse practitioner order?

• A. Throat culture
• B. ASO titer
• C. Anti-DNase B test
• D. Rapid strep test

Answer: (B)

This situation hinges on identifying a delayed complication after a streptococcal throat infection. The fever, arthralgia, and a new heart murmur weeks after a sore throat point to acute rheumatic fever with possible carditis, rather than an active tonsillitis or other current infection. To confirm a prior group A Streptococcus infection when the throat infection has already resolved, you look for antibodies produced in response to the bacteria. The antistreptolysin O (ASO) titer rises about 1 to 3 weeks after a streptococcal infection and can stay elevated for several months, making it the classic test to document recent GAS exposure in the setting of suspected rheumatic fever. This helps establish the link between the prior infection and the current rheumatic process. Throat culture or a rapid strep test detects active infection, which is unlikely to be helpful three weeks after the initial illness. Anti-DNase B is another marker of GAS exposure and can be useful in certain cases (e.g., when ASO is negative or in younger children), but ASO titer is the conventional first-line option used to support the diagnosis in this scenario.

This situation hinges on identifying a delayed complication after a streptococcal throat infection. The fever, arthralgia, and a new heart murmur weeks after a sore throat point to acute rheumatic fever with possible carditis, rather than an active tonsillitis or other current infection.

To confirm a prior group A Streptococcus infection when the throat infection has already resolved, you look for antibodies produced in response to the bacteria. The antistreptolysin O (ASO) titer rises about 1 to 3 weeks after a streptococcal infection and can stay elevated for several months, making it the classic test to document recent GAS exposure in the setting of suspected rheumatic fever. This helps establish the link between the prior infection and the current rheumatic process.

Throat culture or a rapid strep test detects active infection, which is unlikely to be helpful three weeks after the initial illness. Anti-DNase B is another marker of GAS exposure and can be useful in certain cases (e.g., when ASO is negative or in younger children), but ASO titer is the conventional first-line option used to support the diagnosis in this scenario.