The Diagnostic Trap: When PSA Results Mislead - A Case Report

Immunoassays used in clinical practice can occasionally yield falsely elevated or suppressed results due to assay interference. We present a patient case of metastatic prostate cancer where plasma prostate-specific antigen (PSA) concentrations were falsely low. This was discovered incidentally, when a different laboratory, using another PSA assay, reported significantly higher values.

A 77-year-old man, diagnosed with prostate adenocarcinoma in 2011, developed bone metastases in 2015 and metastatic castration-resistant prostate cancer (mCRPC) in 2016. Between 2016 and 2017, PSA measurements at a different hospital using the Roche Cobas e602 assay, showed significantly higher plasma PSA concentrations compared to those measured at the initial hospital, using the Abbott Architect assay. Due to this discrepancy, which was inconsistent with the patient's clinical status, the clinician contacted the laboratory. Subsequent investigation revealed an assay interference leading to falsely low PSA results with the Abbott Architect Assay.

This case underscores the importance of close collaboration between clinicians and laboratories, as well as the need to consider analytical interference when clinical findings do not match laboratory results. Laboratories must continue working with assay manufacturers to minimize interference risks, and clinicians should remain vigilant for potential diagnostic pitfalls and consult the laboratory when inconsistencies arise.