Mycoplasma Infection Can Cause False Positive ANCA Results
Yes, Mycoplasma pneumoniae infection can cause false-positive ANCA results, which may lead to misdiagnosis of ANCA-associated vasculitides if not properly interpreted in clinical context. 1
Mechanism and Clinical Significance
- Mycoplasma infections can trigger antibody production that may cross-react with neutrophil components, leading to false-positive ANCA results in serological testing 1
- In COVID-19 patients with Mycoplasma co-infection, positive Mycoplasma IgM results should be interpreted carefully as they may represent either true co-infection or antibody cross-reactivity 1
- False-positive ANCA results can lead to serious consequences including unnecessary immunosuppressive treatment, resulting in significant morbidity and even mortality in some cases 2
Types of False-Positive ANCA Patterns
- Mycoplasma infection can produce both cytoplasmic (C-ANCA) and perinuclear (P-ANCA) false-positive patterns 2
- These false-positive results may not correlate with specific antigen targets (PR3 or MPO) typically seen in true ANCA-associated vasculitides 3
- Other infectious conditions can similarly produce false-positive ANCA results through cross-reactive antibodies 4
Diagnostic Considerations
- When interpreting ANCA results in patients with suspected or confirmed Mycoplasma infection, clinicians should consider the possibility of false-positive results 1, 4
- Confirmation testing using both immunofluorescence (IIF) and enzyme-linked immunosorbent assay (ELISA) methods is recommended to reduce false-positive results 4
- Only samples positive by both IIF and ELISA methods should be considered truly positive for diagnostic purposes 4
Avoiding Misdiagnosis
- ANCA results should always be interpreted in the clinical context, especially in patients with infectious diseases like Mycoplasma pneumonia 2, 4
- In patients with positive ANCA but without typical clinical features of vasculitis, consider infectious causes like Mycoplasma as potential sources of false-positive results 2
- Additional testing for specific antibodies against PR3 and MPO can help distinguish true ANCA-associated vasculitis from false-positive results due to infections 3
- Supplementary testing on alternative substrates (such as cultured human epithelial cells) can help distinguish true C-ANCA from "pseudo-ANCA" patterns caused by cross-reactive antibodies 5
Clinical Approach to Suspected False-Positive ANCA
- For patients with positive ANCA results and concurrent respiratory symptoms, consider testing for Mycoplasma pneumoniae infection 1
- In patients with positive ANCA but atypical clinical presentation for vasculitis, defer immunosuppressive treatment until infectious causes are ruled out 2
- Follow-up ANCA testing after treatment of the underlying infection may show resolution of false-positive results 4
- Consider applying clinical ordering criteria before requesting ANCA testing to improve test utility and reduce false-positive results 4