Predictive properties of serum-prostate-specific antigen testing in a community-based setting.

BACKGROUND

Most studies that have described the sensitivity and specificity of prostate-specific antigen (PSA) as a screening test have been conducted in urology practice settings or in media-based screening programs. The control patients from these settings may have a higher prevalence of urologic disorders that increase serum PSA levels than that of the general population in which screening efforts might take place, leading to biased estimates of sensitivity and specificity.

OBJECTIVE

To determine the sensitivity and specificity of serum PSA levels for the early detection of prostate cancer in a population-based setting.

PATIENTS AND METHODS

This population-based case-control study was conducted in Olmsted County, Minnesota, where the Rochester Epidemiology Project could identify all incident cases of prostate cancer through passive surveillance of medical care provided to local residents. Case patients were all 177 men (age range, 50-79 years) who were newly diagnosed as having prostate cancer from 1990 through 1992 and had a prediagnostic serum PSA determination (90% of all incident cases). Control patients were randomly selected from the Olmsted County population and had undergone a clinical examination to exclude prostate cancer.

RESULTS

The median (25th and 75th percentiles) of serum PSA levels was 9.4 ng/mL (5.4 and 18.6 ng/mL, respectively) for case patients and 1.2 ng/mL (0.7 and 2.1 ng/mL, respectively) for control patients (P < .001). When sensitivity was plotted against 1-specificity, the area under the receiver operating characteristic curve was 0.94 (SE, 0.01). The predictive power declined somewhat with age, with areas under the curve of 0.96, 0.94, and 0.90 for men in their 50s, 60s, and 70s, respectively. When cases were restricted to the 155 men with clinically localized disease, the area under the curve was essentially unchanged (0.94; SE, 0.01) and still much greater than the estimates of 0.75 that were reported from urology practice- and media-based settings.

CONCLUSIONS

In a community-based setting, serum PSA levels provide better discrimination between men with and without clinically localized prostate cancer than has been observed in studies that were conducted in urologic practices. These results suggest that previous decision analyses may have underestimated the predictive value of PSA for the detection of prostate cancer in a primary care or community-wide screening program.