Serum or plasma concentration of immunoglobulin G (IgG) antibodies against *Escherichia coli* O157:H7 (E. coli O157:H7 IgG antibody)

Why This Test Might Be Ordered

Your healthcare provider may recommend this test if you’ve had symptoms of a gastrointestinal infection (such as severe diarrhea, vomiting, or bloody stools), recent exposure to contaminated food or water, or if you’re at higher risk for E. coli infections (e.g., young children, elderly adults, or those with weakened immune systems). It may also be used to monitor exposure in outbreaks or research settings.

What to Expect Before the Test

No special preparation is typically needed. You may provide a blood sample (serum or plasma) during a routine clinic visit or lab draw. If you’re tested for urine or other fluids, follow any instructions your provider gives you.

What the Test Results Mean

Positive results suggest your body has detected and responded to E. coli O157:H7 antibodies, indicating past exposure. However, antibody levels alone don’t confirm an active infection. They may be used alongside clinical symptoms, stool testing, or other diagnostics for diagnosis.

Common Causes of Positive Results

Positive IgG antibody results can occur after recovering from an E. coli O157:H7 infection, accidental exposure (e.g., contaminated food), or occupational/environmental contact. False positives are rare but possible if you’ve had prior exposure to similar bacteria or received certain vaccines.