Login to Access Video or Poster Abstract: MP86-20
Sources of Funding: None

Introduction

Prostate-specific antigen (PSA) screening in men of average risk remains controversial. Results from PSA clinical trials are widely cited in patient education materials, but patients' ability to incorporate probability and risk data into their decision-making may depend on their numeracy, or facility with quantitative concepts. This study assessed men's numeracy and its impact on their understanding of the risk reduction benefits of PSA screening.

Methods

Cross-sectional survey study. Men 40-75 years old attending a general medicine clinic were invited to complete a survey, which included demographics, personal PSA and prostate cancer (CaP) history, and a validated 3-item numeracy test. Numeracy was scored as the number of items correctly answered (range 0-3). Surveys also presented PSA risk reduction data derived from the European Randomized Study of Screening for Prostate Cancer, framed in 1 of 4 ways: absolute or relative risk reduction (ARR or RRR), with or without baseline risk (BR). Respondents were asked to adjust their perceived risk of CaP mortality using the risk data presented. Accuracy of risk reduction was evaluated relative to how risk data were framed.

Results

200 men completed the survey (60% response rate). Mean age was 60 years, 51% had received a PSA test, and 5% reported a CaP diagnosis. Respondents' demographics were not significantly different among the 4 survey formats. Most men incorrectly answered 1 or more of the 3 numeracy items; half could not convert "1 in 1000" to a percentage, and one-quarter could not calculate "1% of 1000." Overall accuracy of perceived risk adjustment based on PSA data was 20% among all groups. Accuracy varied with how data were framed: when presented with RRR, men were 13% accurate without BR and 31% accurate with BR; when presented with ARR, they were 0% accurate without BR and 35% accurate with BR. Including BR data significantly improved accuracy for both RRR (P=0.03) and ARR groups (P<0.01). Accuracy was significantly related to numeracy; numeracy scores of 0, 1, 2, and 3 were associated with accuracy rates of 6%, 5%, 9%, and 36%, respectively (P<0.01). Neither PSA testing history nor CaP history was associated with accuracy.

Conclusions

Patients' numeracy was significantly associated with the accuracy of interpreting quantitative benefits of PSA screening. Although accuracy improved when the presentation of risk reduction data was framed by baseline risk, numeracy in this screening population of men was poor overall. Alternative methods of communicating concepts of risk to patients may facilitate shared decision-making.

Funding

None