Final answer:
Lyme disease diagnosis typically involves looking for symptoms like the bull's-eye rash and conducting a blood test, such as the enzyme immunoassay (EIA), followed by an immunoblot or Western blot test if necessary. Antibodies may take a few weeks to become detectable, which can initially result in indeterminate test results.
Step-by-step explanation:
Lyme disease is typically diagnosed through a combination of clinical signs and laboratory testing. The key steps in the diagnostic process include recognizing symptoms such as the distinctive bull's-eye rash (erythema migrans), which occurs in 70%-80% of the cases and is a clear indicator of the disease. Doctors will also consider a patient's possible exposure based on their history (like Ximena's time spent in the woods of the northeastern U.S.), and they may start treatment based on this provisional diagnosis.
For confirmation, an enzyme immunoassay (EIA) is the standard first blood test, which checks for antibodies against Borrelia burgdorferi, the bacteria that causes Lyme disease. If the EIA test results are indeterminate or positive, the Centers for Disease Control and Prevention (CDC) recommends following up with a second test known as an immunoblot or Western blot test. It's important to note that antibodies may not be detectable until a few weeks after infection, hence why Ximena's test results came back as 'indeterminate'—her body may not have had enough time to produce a detectable level of antibodies yet. Additionally, more advanced tests like the PCR test and sequencing of surface protein genes of Borrelia species may also be employed.