From the Guidelines
False positive procalcitonin (PCT) results can be caused by a hyperinflammatory status or cytokine storm induced by SARS-CoV-2 infection, which may result in a higher PCT production than in other viral pneumonia. This is according to a recent study published in 2023 in the Journal of Microbiology, Immunology and Infection 1.
Key Points to Consider
- The use of PCT testing to guide antibiotics treatment in COVID-19 patients is confounded by the hyperinflammatory status or cytokine storm induced by SARS-CoV-2 infection.
- A low PCT level at initial presentation has a high negative predictive value to rule out bacterial coinfections, but an initially high PCT level did not provide additional value to traditional clinical criteria or laboratory data.
- Early PCT sampling, defined as within less than 6 h of admission, may have false negative results, and it is advised to avoid PCT assays on day 0 of admission 1.
Clinical Implications
When interpreting PCT results, clinicians should consider these potential false positives and correlate with clinical presentation, other inflammatory markers, and microbiological findings before making treatment decisions.
- Serial measurements showing trends often provide more valuable information than single values in ambiguous cases.
- The negative predictive value of PCT for bacterial coinfection is expected to be more accurate when sampled on the day after admission. It is essential to consider the clinical context and potential causes of false positive PCT results to avoid misinterpretation and inappropriate treatment decisions, as supported by the study published in the Journal of Microbiology, Immunology and Infection 1.
From the Research
Causes of False Positive Procalcitonin (PCT) Results
- Rheumatoid arthritis: False-positive PCT results can occur in patients with rheumatoid arthritis due to the presence of heterophilic antibodies, as reported in a case series 2.
- Lung cancer: Lung cancer, particularly neuroendocrine cancers or those with multiple metastases, can cause elevated PCT levels, leading to false-positive results 3.
- Other factors: While not directly stated, it can be inferred that any condition that causes inflammation or elevation of PCT levels, such as autoimmune disorders or other malignancies, may potentially lead to false-positive PCT results.
Considerations for Interpreting PCT Results
- Clinical context: PCT results should be interpreted in the context of clinical findings and not relied upon solely to diagnose or exclude infection 4, 5, 6.
- Assay methodology: The choice of assay method, such as semiquantitative immunochromatography or quantitative methods, may affect the accuracy of PCT results 2.