Abnormal Flagging of Prostate Specific Antigen Screening Tests: A Regression Discontinuity Design.

Area of Science:

• Urology
• Medical Diagnostics
• Public Health

Background:

• Prostate specific antigen (PSA) testing lacks defined normal/abnormal levels.
• The "upper limit of normal" (ULN) is a common but limited guideline for interpreting PSA results.
• Physicians' reliance on "abnormal flagging" may drive care irrespective of individual patient risk factors.

Purpose of the Study:

• To investigate the impact of "abnormal flagging" of PSA results above the ULN on subsequent diagnostic pathways.
• To determine if flagging influences repeat PSA testing, urology referrals, and prostate biopsies or MRIs.

Main Methods:

• Utilized a regression discontinuity design on a cohort of 38,042 PSA screening tests.
• Analyzed the association between "abnormal" PSA flagging and downstream medical interventions.
• Adjusted for patient age and PSA level differences.

Main Results:

• 2.7% of PSA tests were flagged as abnormal.
• "Abnormal" flagging significantly increased the odds of repeat PSA testing (OR 14.17), urology referral (OR 10.03), and prostate MRI or biopsy (OR 13.61).
• These associations remained significant after adjusting for covariates.

Conclusions:

• Abnormal flagging of PSA results above the ULN strongly influences clinical decision-making.
• This practice may lead to both over- and under-evaluation of prostate cancer risk.
• Recommends developing improved reporting standards that incorporate patient-specific risk estimates.