Final answer:
To diagnose rheumatic fever, a physician may use a combination of lab tests including throat culture, ASO titer, CRP, WBC, and ESR. The ASO titer is particularly useful as it indicates a recent Group A Streptococcus infection, which can lead to rheumatic fever.
Step-by-step explanation:
Diagnosis of Rheumatic Fever
Rheumatic fever is an inflammatory disease that can occur after a Group A Streptococcus pharyngeal infection. It is a serious illness that can affect the heart, joints, skin, and brain. To diagnose rheumatic fever, several laboratory tests are used, as no single test can definitively diagnose the condition. The most reliable tests include:
- Throat culture: To detect the presence of streptococcal bacteria, which can cause rheumatic fever if not treated properly.
- Antistreptolysin-O (ASO) titer: Measures antibodies against streptolysin O, an enzyme produced by Group A Streptococcus. An elevated ASO titer indicates a recent strep infection, which can be associated with rheumatic fever.
- C-reactive protein (CRP): An acute-phase protein that rises in response to inflammation. An increased CRP level can suggest an inflammatory process such as rheumatic fever.
- Elevated white blood count (WBC): Points to an infection or inflammation.
- Erythrocyte sedimentation rate (ESR): Another measure of inflammation that may be elevated in patients with rheumatic fever.
While all of these tests can indicate an underlying inflammatory process, the ASO titer is especially linked to recent streptococcal infection, making it particularly useful in the context of rheumatic fever. The ESR and CRP are non-specific markers of inflammation and might be elevated in various conditions. For an accurate diagnosis, a physician will often use a combination of these tests along with clinical observations and the patient’s medical history.