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Macro-prostatic acid phosphatase in a patient's serum
J A Schifferli1, P Roth, G Steiger
1Department of Medicine, Hôpital Cantonal Universitaire, Geneva, Switzerland.
Clinical Chemistry
|October 1, 1988
Summary
Elevated prostatic acid phosphatase (PAP) levels in a patient's serum were due to PAP bound to IgG autoantibodies, forming "macro-PAP." This complex formation falsely indicated prostate cancer, highlighting the need for clinical evidence beyond PAP measurements.
Area of Science:
- Biochemistry
- Immunology
- Oncology
Background:
- Prostatic acid phosphatase (PAP) is an enzyme used as a biomarker for prostate cancer.
- Elevated serum PAP levels can indicate the presence of prostate cancer.
Observation:
- A patient presented with high serum PAP concentrations despite lacking prostatic carcinoma.
- This elevated PAP was identified as a complex of PAP bound to immunoglobulin G (IgG), termed "macro-PAP".
Findings:
- IgG autoantibodies against PAP were detected in the patient's serum.
- The patient's IgG autoantibodies prolonged the biological half-life of PAP, reducing its catabolism.
- Macro-PAP exhibited slower inactivation in serum compared to free PAP, leading to increased measured enzymatic activity and antigen concentration.
Implications:
- The formation of macro-PAP can lead to false-positive results for prostate cancer based solely on PAP levels.
- Diagnosis of prostatic carcinoma should integrate clinical and histological evidence, not rely exclusively on PAP measurements.
- Understanding macro-enzyme formation is crucial for accurate laboratory diagnostics and appropriate patient management.