A total of 189,823 PSA tests were performed at Group Health between 1997 and 2008. The analysis cohort, which excluded short-term repeat tests within 11 months of a prior test, included 59,738 subjects and 121,591 index tests. Tests for patients aged >85 years or <35 years (n=2338) and tests for subjects who did not have 12 months of follow-up (n=900) were excluded. Tests with missing or indeterminate PSA levels (n=803), missing comorbidity data (n=554) and missing census tract family income information (n=312) were also excluded. The final sample included 111,369 index tests among 54,831 subjects. The tests were ordered by 1089 unique providers (18 urologists), with 208 providers ordering at least 100 tests. The mean number of index tests per subject was 2.03 (median = 2.0) with 27,329 men (49.8%) having a single test in the current sample, 12,681 having two index tests (23.1%), and 14,821 having three or more tests (27.0%).
The characteristics of the analysis cohort are described in . The majority of PSA tests were ordered by primary care providers (85.2%) and were <2.5 ng/mL (78.3%). While 11.7% of tests were suspicious, most (7.0%) were between 4.0 and 6.9 ng/mL, with 2.2% between 7 and 9.9 ng/mL, and 2.5% at 10 ng/mL or above. Unadjusted trends in receipt of biopsy, frequency of urology visit and additional PSA testing within 12 months are shown in . Overall, 28.0% of tests with a PSA value ≥4.0 ng/mL led to a biopsy within 12 months, and 38.6% of tests ≥4.0 ng/mL were followed-up by a urologist within 12 months but did not result in a biopsy. The frequency of biopsy among men with tests with mild to moderately elevated PSA levels (2.5–3.9 ng/mL) was 2.9% across years, and fewer than 0.4% of tests with a PSA level <2.5 ng/mL led to a biopsy within 12 months.
Characteristics of 111,369 PSA tests among 54,831 enrollees
Type of follow-up received within 12 months of an index PSA test (unadjusted), %
In unadjusted analyses, biopsies were slightly more common in the earliest years of the study compared to later years among tests ≥4.0 ng/mL (29.7%) and <2.5 ng/mL (0.9%) but there was no difference in biopsy rates over time for men with mild to moderate PSA levels (2.5–3.9 ng/mL) (data not shown). In adjusted analysis, the relative risk of biopsy was 13% higher for the early period 1998–2001 (RR 1.13, 95% CI=1.06, 1.20) compared to 2002–2004 (). The interaction with PSA category and calendar year was not significant (Wald p=0.206), indicating that there did not appear to be a change over time in the threshold used for biopsy referral.
Multivariable model: Factors associated with biopsy within 12 months of index PSA test
Older age was associated with a lower biopsy rate. Approximately 11% of the PSA tests were conducted among men aged ≥75 years; however, these men were less likely to undergo biopsy if the test was elevated (RR 0.42, 95% CI=0.38, 0.46) compared to men aged 55–64 years. Tests ordered by urologists (13%) more likely to result in biopsy compared to those ordered in primary care (RR 1.13, 95% CI=1.05, 1.21). Men living in neighborhoods with higher income levels were more likely to undergo biopsy compared to those living in lower-income areas.
Comorbidity score was not associated with biopsy frequency. Results were similar in sensitivity analyses which excluded tests ordered by urologists. For example, 28.2% of tests ≥4.0 ng/mL ordered by primary care providers led to a biopsy within 12 months. In analyses excluding second or later PSA tests focusing only on the 54,831 initial tests, slightly more men (34.9%) with a value ≥4.0 ng/mL received a biopsy in 12 months. All trends in adjusted analyses were similar compared to the primary analyses.
The PSA velocity was strongly associated with biopsy among the subset of tests where prior test information allowed for the calculation of PSA velocity (). PSA velocity was available for 65,372 index tests (58.7%). Among men with PSA tests ≥4.0 ng/mL, those with a rapidly rising velocity were more likely to undergo biopsy, compared to slow-growing velocity, 36.9% vs 21.7% respectively (p<0.001). There was no interaction between calendar year and PSA velocity (Wald test p=0.099), suggesting that the association between velocity and biopsy frequency has been consistent across calendar years in this sample. The associations of the covariates with biopsy frequencies by PSA velocity were consistent with the main analysis and are not presented. The Wald test for the model including interaction terms between ordering provider and PSA velocity leading to biopsy was not significant (p<0.275), suggesting that there was not a distinct pattern in how urologists used velocity compared to other providers in referring tests for a biopsy.