Volume 23
Number 3
2002

[Table of Contents]

Prevalence of PSA testing and effect of clinical indications on patterns of PSA testing in a population-based sample of Alberta men

Abstract

An age-stratified population-based random digit dial (RDD) telephone survey determined awareness and prevalence of prostate-specific antigen (PSA) testing among Alberta men aged 40–74 years, and assessed the role of indications for PSA testing in explaining patterns of PSA testing. The sample of 1984 men (participation rate 65%) with no history of prostate cancer was divided into three age strata: 40–49, 50–59, and 60–74 years. Awareness of PSA tests was low, with fewer than half of the men indicating they had ever heard of PSA tests. The percentage of men who had ever had PSA testing was 4.5%, 13.1%, and 22.2% respectively, in the three age strata. PSA testing was strongly associated with having at least one clinical indication for PSA testing (prevalence 21.8%, 26.9%, and 42.2% respectively). PSA testing rates were very low among men who had no clinical indications for PSA testing, suggesting infrequent PSA screening prior to the survey. PSA testing patterns in this population-based sample were consistent with Alberta clinical practice guidelines.

Key words: mass screening; prevalence; prostate cancer; PSA

Introduction

The introduction of prostate-specific antigen (PSA) testing in the late 1980s has had a dramatic effect on the detection of prostate cancer. Prior to that time, Canadian age-standardized prostate cancer incidence rates were increasing slowly but steadily over a 25 year period.¹ However, starting in 1990, the year significant utilization of PSA tests began in Canada,² there was a rapid increase in prostate cancer incidence, peaking in 1993. The peak was followed by a decline in the age-standardized incidence, although rates remain higher than in the pre-PSA testing era. The early steady increases in incidence in Canada and elsewhere have been attributed to increased detection of incidental prostate cancers found during transurethral resection of the prostate (common in the treatment of benign prostatic disease) with the more recent large and transient increases attributed to the availability of PSA testing.^3–7

Trends in age-standardized incidence rates of invasive prostate cancer in Alberta show the same pattern (Figure 1).

Declines in incidence after an initial rapid increase subsequent to the introduction of PSA testing have been observed in other areas with population-based cancer registries,^8–12 and in administrative data on PSA testing rates. Patterns in incidence correlate most strongly with patterns of first-time PSA testing¹³ consistent with the hypothesis that PSA testing is detecting clinically unapparent cases from an existing prevalence pool.

Figure 1
Invasive prostate cancer*, Alberta, 1973–1999

The Canadian Task Force on the Periodic Health Exam,¹⁴ systematic reviews by provincial health agencies,^15–17 the US Preventive Services Task Force,¹⁸ and the American College of Physicians¹⁹ have concluded that there is insufficient evidence to recommend routine PSA screening of asymptomatic men over 50 years of age. This conflicts with the American Cancer Society²⁰ and the American Urological Association (AUA)²¹ which recommend annual PSA testing and digital rectal examination (DRE) for men aged 50 and over with at least a ten-year life expectancy, with screening beginning earlier for high-risk men. All recommendations include the need to inform men about the potential risks and benefits of screening.

Alberta has always had a very restrictive policy²² on PSA testing. Reimbursement of PSA testing for screening purposes has never been authorized by the provincial health insurance plan. PSA testing in Alberta has been restricted to the monitoring of men who have been diagnosed and treated for prostate cancer; evaluation of patients with “symptoms of prostatism” or an abnormal DRE; and for men at higher risk of prostate cancer based on family history and/or ancestry. The guideline indicates prostatism is a symptom of both benign prostatic hyperplasia (BPH) and prostate cancer.

PSA testing is often used to rule out prostatic carcinoma among men presenting with lower urinary tract symptoms.²³ However, the prevalence of prostatic cancer among men presenting for prostate cancer screening does not vary in men with or without urinary symptoms^24,26 and BPH is not etiologically related to prostate cancer.²⁵ Some health policies actually recommend against the use of PSA testing in men with uncomplicated urinary symptoms.²⁷ In this study, it was hypothesized that the presence of clinical indications for PSA testing including lower urinary tract symptoms would be an important predictor of PSA testing in Alberta because the PSA tests have never been approved for prostate cancer screening purposes.

The purpose of the current study was to determine the age-specific prevalence of PSA testing among Alberta men aged 40–74 years and to describe patterns of PSA testing among men with and without clinical indications for PSA testing.

Methods

An age-stratified population-based random digit dial (RDD) telephone survey was used to assess awareness of PSA testing and self-reported rates of PSA testing among Alberta men. Age strata were 40–49 years, 50–59 years, and 60–74 years. The two oldest age groups were over-sampled to allow for an expected higher prevalence of moderate to severe lower urinary tract symptoms, and hence ineligibility for screening.

The survey (available upon request) covered a variety of topics, and was introduced as concerning men's health to minimize bias due to men declining to participate specifically because of lack of interest in prostate cancer. The 36 questions ascertained information on health status, primary care practices, lower urinary tract symptoms, knowledge and awareness of prostate cancer, and demographics. Questions included awareness of the PSA test, discussion of the PSA test with a doctor, whether the respondent has had a PSA test, and the reason the test was performed. Only men who indicated they were aware of PSA tests were asked about their use of them. Definitions of PSA tests were provided. Some questions were modified from a Canadian RDD telephone survey conducted in January 1995.²⁸ The AUA symptom index²⁹ was used to assess the severity of lower urinary tract symptoms over the previous month and classify men as having mild, moderate, or severe lower urinary tract symptoms. Indications for PSA testing were determined using criteria outlined in the Alberta clinical practice guideline (CPG)²²(Table 1).

The survey instrument was initially pilot tested on 41 male volunteers. Final revisions were made after a second pilot test on 43 RDD selected men.

The RDD computer-assisted telephone interview survey was conducted over a four-week period in November/December 1996. The short time frame for data collection reduced the chances of external influences (e.g., media reports) affecting survey responses. Data collection was contracted to the Population Research Laboratory (PRL), University of Alberta. The sampling frame consisted of a random sample of Alberta telephone numbers from the PRL working bank of residential telephone numbers. Standard protocols were used to determine eligibility, invite participation, and administer the telephone interview. The most recent birthday was used to randomly select the person to be interviewed if there was more than one eligible man in a household. Calls were made over three different time periods on all weekdays and Saturdays and two time periods on Sundays, with up to 12 attempts to reach each phone number.

Age-specific estimates of the prevalence of lower urinary tract symptoms and indications for PSA testing were calculated. Point estimates and 95% confidence intervals for PSA test awareness and prevalence of PSA testing were calculated for the three age groups. The prevalence of PSA testing among men with and without indications for PSA testing was described. Comparisons between the three age groups were made using chi-square tests for categorical variables and Wilcoxon rank sum tests³⁰ for ordinal variables. Exact tests were used for categorical variables when an expected cell frequency was less than five. Logistic regression was used to test for differences in PSA testing rates by age group and indication for PSA testing. Subjects with missing values were excluded from the analysis and the number of missing cases is indicated in the descriptive tables. All analyses were conducted using SAS³¹ and S-PLUS³² statistical software.

Ethical approval for the study was obtained from the Research Ethics Committee of the Alberta Cancer Board and the Conjoint Medical Ethics Review Committee of the Faculty of Medicine, University of Calgary.

Results

There were 2,016 completed interviews (cooperation rate³³ 64.7%). The most common reason for non-response, after excluding ineligible telephone numbers, was household refusal (35.9%) followed by never answered (34.7%). Comparison with Alberta 1996 Census data indicated the RDD sample was reasonably representative of Alberta men of the same age groups (data not shown). Thirty-two men (1.6%) who reported they had prostate cancer were eliminated from further analysis.

Table 2 shows a description of the sample of 1,984 men without a history of prostate cancer. Among men who indicated they had a regular doctor, 96.2% indicated their doctor was a GP or family doctor. The percentage of men who indicated they went for regular checkups increased with age: 65.2%, 76.5%, and 81.0% of men aged 40–49, 50–59, and 60–74 years respectively.

Visits to a urologist and severity of urinary symptoms increased with age (Table 3). Men with a history of prostate problems were more likely to have discussed urinary symptoms with their doctor (66.2% of men with any prostate problem versus 14.5% of men without a prostate problem, age-adjusted OR = 11.2, 95% CI 8.6, 14.5) and to have visited a urologist (53.8% of men with any prostate problem versus 12.9% of men without a prostate problem, age-adjusted OR = 6.8, 95% CI 5.2, 8.8).

The majority of men in all three age groups were scored as having mild lower urinary tract symptoms.

As expected, older men were more likely to have at least one indication for PSA testing (Table 3). A history of BPH, moderate/severe lower urinary tract symptoms, and an abnormal finding on most recent DRE increased with age (all p < 0.001). First degree family history of prostate cancer was present in about 10% of men and did not vary by age group (p = 0.6). African ancestry was very infrequent in this sample (<1% of men in all age groups). At least one indication for PSA testing was common, especially in men aged 60–74 years.

Men who had heard of prostate cancer (n=1,930) were asked whether they had discussed it with their doctor. The percentage of men who had done so increased with age: 24.4%, 32.1%, and 43.6% of men aged 40–49, 50–59, and 60–74 years respectively (p<0.001). The most frequent topics discussed were: general information (52.5%), detection of prostate cancer (47.2%) (only 8.5% specifically discussed PSA testing), and symptoms (32.6%). Treatment options and prognosis (5.7%) and other topics (8.5%) were far less frequently discussed. There were few differences by age group among the topics men discussed with their doctors. Age guidelines for screening were more often discussed in men aged 40–49 years (15.4% 40–49; 6.8% 50–59; 5.9% 60–74 years, p=0.002).

Fewer than half the men had ever heard of PSA tests. Awareness increased with age with 26.7%, 40.0%, and 45.1% of men aged 40–49, 50–59, and 60–74 respectively having heard of the PSA test. Rates of PSA testing were low and strongly associated with increasing age with 4.5%, 13.1%, and 22.2% of men in the same three age groups reporting having had at least one PSA test. Most men (57.0%) had only one PSA test. The mean (median) time since last PSA test was 1.3 (0.9) years and ranged from just over one month to 12.4 years, with 98% reporting their most recent PSA test within the past five years. There was no difference in the median time since the last PSA test among the three age groups (Wilcoxon rank sum test, p=0.5). Nine men could not recall the date of their last PSA test.

Physicians were the most common initial source of information for men who had been tested. This was particularly important for men aged 40–49 years where 74.1% indicated they first learned about PSA tests from their doctor, compared to 50.0% of men 50–59 years and 61.6% of men aged 60–74 years. Reading material such as newspapers and magazines were cited by 18.9% of men aged 50 and older as the next most important way they learned about PSA tests.

Table 4 shows PSA testing rates by whether or not at least one clinical indication for PSA testing was present. PSA testing in men with no indication for PSA testing was considered prostate cancer screening. The majority (63.8%) of PSA tests in these men were done at a routine checkup suggesting these tests were for screening purposes and 9.4% had specifically asked their doctor for a PSA test. Most men had been tested once (55.9%) or twice (15.8%) and this did not vary by age. The most common way these men first learned about PSA testing was from their physician (57.5%) followed by newspapers or magazines (15.0%). Few men aged 40–49 were aware of PSA tests and PSA testing was very infrequent.

Rates of PSA testing were higher in men with at least one clinical indication for PSA testing compared to men with no indications (Table 4). Awareness of PSA tests was similar in all three age groups but rates of PSA testing increased with age. Like the men with no indication for PSA testing, 59.9% of men who had been tested first learned of the PSA test from their doctor. The majority of men reported having had one (57.8%), or two PSA tests (12.7%). The reason for their most recent PSA test was a problem their doctor wanted to check (32.4%), symptoms that were concerning them (16.9%), or a routine checkup (37.3%).

Logistic modeling showed the effect of indication for PSA testing (OR=2.5, 95% CI 1.9, 3.3) was independent of the age effect (OR=3.1, 95% CI 2.0, 4.9 for men aged 50–59; OR=5.2, 95% CI 3.4, 8.1 for men aged 60–74).

Table 5 describes PSA testing practices among the subset of men who were aware of the PSA test. Less than half of these men had discussed PSA tests with their doctors. This pattern varied by age, with older men more likely to have discussed tests. PSA testing rates were higher in men with at least one clinical indication for PSA testing compared to men with no indications in all three age groups. Again, PSA testing was strongly associated with age. The percentage of men who reported having at least one PSA test increased with age for men both with and without an indication for PSA testing. Logistic modeling showed the effect of indication for PSA testing (OR=2.1, 95% CI 1.5, 2.9) was independent of the age effect (OR=2.6, 95% CI 1.6, 4.3 for men aged 50–59; OR=4.6, 95% CI 2.9, 7.5 for men aged 60–74).

This study found that in late 1996, six years after PSA tests had become available, awareness of PSA tests was quite low among Alberta men, as were rates of PSA testing. Patterns of self-reported PSA testing were consistent with trends in incidence data on invasive prostate cancer in Alberta over the same time period. There were few differences by age in the lifetime number of PSA tests and time since last PSA test, reflecting the relatively short time PSA testing had been available. The majority (57%) of men who had been tested reported having a single PSA test, consistent with the introduction of a new screening test and relatively little opportunity yet for serial screening.

Health care utilization records show similar patterns of PSA testing in three Canadian provinces. Large increases in the number of PSA tests ordered have been reported in Saskatchewan (1990–1994)¹⁶ and Ontario (1988–1996).³⁴ Utilization patterns in British Columbia showed the majority of PSA tests were ordered by general practitioners, and 76% of men tested had a single PSA test over the one-year study period, implying PSA testing was used for prostate cancer screening.¹⁵ A linkage study using PSA test records from two laboratories, one private and one hospital based, in Ontario reported a mean (median) of 1.5 (1) PSA tests in men with no diagnosis of prostate cancer.³⁵ Similar to the current study, PSA testing rates were highest in men 50–70 years of age.

PSA testing rates were very low among men who had no clinical indications for PSA testing, suggesting infrequent screening with PSA testing in Alberta up to the time of the RDD survey. Both PSA test awareness and testing were strongly associated with increasing age. This may reflect the increase in prevalence of clinical indications for PSA testing, increasing index of suspicion by physicians, and the increased experience with, and perhaps salience of, prostate cancer as men age. Very little PSA testing, especially in the screening context, occurred in men aged 40–49 years.

The higher rates of PSA testing reported for US men^36,42 may also be due to higher awareness of PSA tests among both men and physicians. A statewide survey of men aged 50 and over in New York State reported 58% were aware of PSA tests and 64% of them had had at least one PSA test.⁴³ Differences in methodology, timeframe, health care settings, and screening policy environments may also explain part of the variation in prevalence estimates.

In contrast to the findings of Mercer et al.²⁸ where physicians and the media played an equal role in PSA test awareness, in the current study physicians were more often cited as the way men first became aware of the PSA test. This difference may be due to the differences in media promotion of prostate cancer screening across provinces with different policies for PSA testing. The use of PSA testing primarily in men who have at least one indication for PSA testing when discussion of PSA tests likely arose in the investigation of a clinical problem, may also explain this.

PSA testing patterns based on self-report in this population-based sample appear to be consistent with the current Alberta clinical practice guideline and previous restrictions of PSA testing in Alberta. The importance of clinical indications for PSA testing in explaining PSA testing rates is shown by the marked differences in PSA testing rate among men with and without an indication for PSA testing in all three age groups. The prevalence of clinical indications for PSA testing are sufficiently high in men aged 50–74 years to have a marked effect on PSA testing rates. The use of PSA testing in men with clinical indications for PSA testing may explain the rapid increase in prostate cancer incidence in Alberta in the early 1990s.

Other surveys have not assessed the role of clinical indications in explaining patterns of PSA testing in a population-based sample. However, PSA testing rates were higher among men with BPH, moderate or severe lower urinary tract symptoms, and a family history of cancer in the Health Professionals Followup Study.⁴⁴ A cross-sectional survey of US primary care physician visits found PSA tests were much more frequently ordered in all age groups for men with lower urinary tract symptoms, a diagnosis of BPH, or attending for a general medical exam.⁴⁵

Two studies of Australian men who had visited their doctors for troublesome lower urinary tract infections showed they were much more likely to have had a PSA test.^46,39 The strongest predictors of PSA testing among a sample of men aged 40–79 years in New South Wales, Australia were age, doctor's recommendation and presence of lower urinary tract symptoms.⁴⁷

The lack of testing in some men with at least one clinical indication for PSA testing may be due to several reasons. Firstly, men may not seek care for symptoms. Not all men with lower urinary tract symptoms seek care.^48–50 Just over one third of British men with severe urinary symptoms and over one half (51.9%) of men with moderate urinary symptoms did not seek advice from their physicians.⁵¹ Secondly, PSA testing may not have been offered to men who sought health care advice for their urinary symptoms. It is also possible that PSA testing was not available at the time they received a diagnosis of BPH. Finally, lack of testing may also be due to men declining a PSA test.

The prevalence of lower urinary tract symptoms in the Alberta sample is somewhat lower than that reported in an Olmsted County study,^52–53 a mailed survey of British men,⁵⁴ and a self-administered survey of a large consecutive sample of Australian men presenting for an office visit.⁵⁵ The higher prevalence of symptoms in the Olmsted County studies may be partly due to non-response bias resulting in a higher prevalence of urological disease among study participants.⁵⁶ Forty percent of the Australian sample were over 70 years of age, which may partly explain the higher estimate due to the increase in prevalence of lower urinary tract symptoms with age.

The lower prevalence of symptoms in the Alberta sample may also be due to the mode of questionnaire administration. Telephone interviews have been found to result in lower AUA symptom scores when compared to scores obtained from self-administered questionnaires.⁵⁷ A telephone survey of a random sample of Australian men reported the prevalence of moderate/severe symptoms of 4%, 11%, 14%, and 18% in men aged 40–49, 50–59, 60–69, and 70–79 years respectively.⁴⁷ These rates are similar to the prevalence rates found in the Alberta sample.

The current study is limited by the fact that the prevalence estimates are based on self-report. The validity of self-reported PSA testing has not been reported for Canadian men. A convenience sample of 276 male patients attending nine primary care offices in northwest Ohio found the sensitivity and specificity for PSA testing was 74% and 65% when compared to medical records.⁵⁸ Thus, 26% of men in the sample were unaware or failed to recall whether they had a PSA test. However, a larger proportion of men (35%) who had no record of a PSA test in the chart audit falsely reported they had been tested.

It is not clear that results from validation studies carried out in the US are generalizable to the Alberta setting. Social desirability bias may cause more US men to falsely report they have been screened in order to seem compliant with recommendations for prostate cancer screening that are more common in the US. A validation study has been carried out as part of this research and will be reported separately.

The classification of men as to whether they had a clinical indication for PSA testing in the current study was also based on self-report including a history of BPH. A comparison of self-report to medical records among controls in a prostate cancer case control study selected from members of a large health maintenance organization found that men tended to over-report genitourinary diseases that lack explicit diagnostic criteria, including BPH.⁵⁹ However, the authors concluded that self-report may provide a more complete estimate of BPH due to lack of completeness of medical records, high inter-physician variation, and inconsistent timeframes covered in the medical records.

The key strengths of the current study are the population-based sample, use of a valid and reliable measure of lower urinary tract symptoms, and a sufficiently large sample size to permit calculation of age-specific rates of PSA testing. Strong age effects were found, highlighting the usefulness of age-specific estimates. The sample size was sufficient to provide reasonably precise estimates of PSA testing in the sub-group of men with no indications for PSA testing who were considered eligible for screening. The cooperation rate of 65% compares favorably with response rates in other RDD surveys in general^60–61 and of men about prostate cancer in particular.^28,43,62 Comparison with census data indicated the RDD sample was representative of Alberta men in these three age groups with respect to demographic characteristics increasing the generalizability of the findings.

Current recommendations emphasize the importance of informing men about the potential harms and benefits of screening for prostate cancer and involving them in the decision-making about whether or not to undergo screening.^63–64 The potential for increased PSA testing as awareness of PSA tests increases is demonstrated by the higher rates of PSA testing in men of all age groups who are aware of PSA tests. The focus of education about prostate cancer screening should be to ensure that due consideration of potential benefits and harms is undertaken as awareness increases. Research on how both physicians and men respond to this potential demand is required.

It is concluded that screening for prostate cancer using the PSA test was infrequent in Alberta six years after PSA testing had become available and just after the release of prostate cancer screening clinical practice guidelines. There is some evidence that a CPG recommending against prostate cancer screening in Saskatchewan reduced the use of PSA tests by family physicians.³⁴ These findings provide baseline data against which to evaluate changes in uptake of prostate cancer screening subsequent to the release of the CPGs and introduction of education and awareness programs about prostate cancer screening.

Acknowledgments

This research was funded by a grant from the National Cancer Institute of Canada (grant #007339) with funds raised by the Canadian Cancer Society.

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Author References

S Elizabeth McGregor, Heather E Bryant, Division of Epidemiology, Prevention & Screening, Alberta Cancer Board

Rollin F Brant, Department of Community Health Sciences, University of Calgary

Peter J Corbett, Department of Oncology, University of Calgary and Tom Baker Cancer Centre

Correspondence: S Elizabeth McGregor, Division of Epidemiology, Prevention & Screening, Alberta Cancer Board, 1331–29th Street NW, Calgary, Alberta, Canada T2N 4N2; Fax: (403) 270-8003; E-mail: elizabeth.mcgregor@cancerboard ab.ca

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