Assessment of Agreement between Two Difference Prostate-Specific Antigen Assay Modalities

Area of Science:

• Urology
• Oncology
• Biomarker Analysis

Background:

• Prostate-specific antigen (PSA) is a key biomarker for prostate cancer (PCa).
• Controversy exists regarding PSA's utility due to variability between assay modalities.
• Standardized validation of PSA assay methods is crucial for accurate PCa diagnosis.

Purpose of the Study:

• To evaluate the agreement between two PSA assay modalities.
• To identify specific PSA concentration ranges where agreement is poor.
• To determine the clinical relevance of observed differences in PSA measurements.

Main Methods:

• Analysis of PSA levels from 4810 patients using two distinct assay modalities.
• Statistical evaluation using intra-class correlation coefficient (ICC) and weighted kappa analysis.
• Linear regression to assess the association and predict values between modalities.

Main Results:

• Excellent overall agreement between PSA assay modalities (ICC: 0.999, kappa: 0.951).
• Poor agreement observed in specific PSA sub-groups: 0.05-0.1, 0.15-0.2, 1.5-2.0, and 2.0-2.5 ng/mL.
• Linear regression indicated significant differences, e.g., 0.2 ng/mL in modality B corresponded to 0.258 ng/mL in modality A.

Conclusions:

• While overall agreement is excellent, significant discrepancies exist in critical PSA ranges.
• The observed differences between PSA assay modalities can be clinically meaningful.
• Further validation and consideration of assay-specific values are necessary for reliable PCa biomarker interpretation.