What does ASO titre in blood mean?

Q: My five years old son was suffering from fever. I consulted a doctor who suggested some blood tests, which showed an ASO titre - 450 IU/ml, CRP - 18 mg/l. What does it mean?

A:The ASO is a blood test report that increases 2-4 weeks after the child has been exposed to an infection with a bacteria called streptococcus. As you child has had fever for 5 days only, it is unlikely to be related. He should have a throat swab done to see the bacterial growth in the throat. The CRP being positive suggests that he has had an infection, likely bacterial.