Streptococcal serology refers to a group of blood tests that detect antibodies produced by the body in response to an infection with Streptococcus bacteria, which can cause a variety of conditions, from strep throat to more serious diseases such as rheumatic fever and post streptococcal glomerularnephritis.
The most common serological tests for streptococcal infections are:
- Antistreptolysin O (ASO) titer: This test measures antibodies against streptolysin O, a toxin produced by group A Streptococcus (GAS). An elevated ASO titer indicates a recent strep infection. It is particularly useful in the diagnosis of rheumatic fever, which can follow untreated or inadequately treated strep throat or scarlet fever.
- Anti-DNase B test: This measures antibodies against the DNase B enzyme, which is also produced by GAS. It can be used in conjunction with the ASO titer to help diagnose recent streptococcal infections, especially when ASO titers are not elevated.
These tests are typically ordered when a patient presents with symptoms that suggest a post-streptococcal complication, such as rheumatic fever or glomerulonephritis, but does not have a current strep infection. The presence of high levels of antibodies suggests a recent infection, even if the bacteria are no longer present.