This 9-year-old boy was taken to the emergency department with asore throat. On examination, he had redness of the throat andslightly swollen glands. The physician assistant ordered a throatculture and blood drawn for an antistreptolysin-O antibody (ASO).An antibiotic was prescribed for a 10-day period. His mother wastold to make an appointment with his pediatrician for a follow-up.At the follow-up visit 2 weeks later, the results of the laboratorytest revealed a throat culture with a few colonies ofβ-streptococci. The qualitative ASO test result was reported aspositive. The acute serum was frozen at the time of testing. Thepediatrician ordered a convalescent specimen to be testedsemiquantitatively in parallel with the acute specimen for an ASOtiter. The results of the parallel testing of the acute andconvalescent specimens revealed the following: • Acute specimenpositive, 1:1 dilution/titer (IU/mL 200) • Convalescent specimenpositive, 1:4 dilution/titer (IU/mL 800)
Thinking Group Discussion Questions
2. What does a rise in titer mean?
