Major inter-laboratory variations in PSA testing practices: results from national surveys in Ireland in 2006 and 2007

Interassay Variability and Clinical Implications of Five Different Prostate-specific Antigen Assays

Background and objective

Prostate-specific antigen (PSA) remains a critical marker for prostate cancer (PCa) detection and monitoring. Recognising historical variability in PSA assays and the evolution of assay technology and calibration, this study aims to reassess interassay variability using the latest generation of five assays in a contemporary cohort of men undergoing prostate biopsy.

Methods

Five different commercially available PSA assays were tested in a blood sample of 76 men before undergoing a prostate biopsy. Total PSA (tPSA) and free-to-total PSA ratio (%fPSA) were compared across assays, using Roche (Basel, Switzerland) as the benchmark, and correlated with biopsy outcome to analyse the impact on PCa diagnosis. The statistical analysis included Passing-Bablok regression and Bland-Altman plots, with a p value threshold of <0.05 for significance.

Key findings and limitations

Among the 76 men, 28 (36.8%) were diagnosed with significant PCa (defined as International Society of Urological Pathology grade ≥2). A high correlation was observed between tPSA and %fPSA values among the different PSA assays tested (r2 ≥ 0.9). The Passing-Bablok analysis showed that tPSA results varied substantially among the assays, with slopes ranging between 0.78 and 1.04. Compared with the tPSA of Roche, tPSA values were on average 20.7% lower by Beckman (Oststeinbeck, Germany), 15.2% lower by Abbott (Chicago, IL, USA), 6.1% lower by Diasorin (Saluggia, Italy), and 9.6% higher by Brahms (Hennigsdorf, Germany; p < 0.001 for all). The %fPSA values by Abbott and Brahms were higher at 15.7% and 10.6%, respectively (p < 0.001), while the Beckman and Diasorin values had minimal differences of -0.3% and 2.3%, respectively (p > 0.05). The variability across assays would have resulted in discrepancies in both the sensitivity and the specificity for tPSA and %fPSA by at least 14%, depending on the cut-offs applied.

Conclusions and clinical implications

Despite the use of the latest PSA assays, relevant variability of tPSA and %fPSA results can be observed among different assays. There is an urgent need for standardised calibration methods and greater awareness among practitioners concerning interassay variability. Clinicians should acknowledge that clinically relevant thresholds may depend on the specific PSA assay and that ideally the same assay is applied over time for better clinical decision-making.

Patient summary

Prostate-specific antigen (PSA) is a critical marker for prostate cancer (PCa) detection and monitoring. However, significant variations were observed in the results of the latest PSA assays. Thus, standardised calibration methods and greater awareness among practitioners concerning interassay variability are needed.

Stability and accuracy of total and free PSA values in samples stored at room temperature

INTRODUCTION

In 2010, an estimated 476,076 total PSA tests were performed in Ireland, at a cost of €3.6 million with the majority ordered by general practitioners. We aimed to replicate storage conditions at room temperature and see if prolonged storage affected total and free PSA values.

METHODS

Blood samples were taken from 20 male patients in four VACUETTE^® Serum Separator tubes (Greiner-Bio-One, Austria) and stored at room temperature (22 °C) for different time intervals (4, 8, 24, 48 h) before being centrifuged and analyzed. Total PSA (tPSA) and free PSA (fPSA) values were determined using the Tosoh AIA 1800 assay (Tokyo, Japan).

RESULTS

Mean tPSA values were measured at 4, 8, 24 and 48 h with values of 7.9, 8.1, 7.8 and 8.0 μg/L, respectively. Values ranged from -1.26 to +2.53 % compared to the initial 4 h interval reading, indicating tPSA remained consistent at room temperature. The tPSA showed no significance between groups (ANOVA, p = 0.283). Mean fPSA values at 4, 8, 24 and 48 h were 2.05, 2.04, 1.83, 1.82 μg/L, respectively. At 24 and 48 h there was 10.73 and 11.22 % reduction, respectively, in fPSA compared to the 4-h time interval, indicating prolonged storage resulted in reduced fPSA values. After 24 h, there was an 8.8 % reduction in the free/total PSA %. The fPSA showed significant differences between groups (ANOVA, p = 0.024).

CONCLUSIONS

Our recommendation is that samples that have been stored for prolonged amounts of time (greater than 24 h) should not be used for free PSA testing.

Prostate specific antigen testing is associated with men's psychological and physical health and their healthcare utilisation in a nationally representative sample: a cross-sectional study

BACKGROUND

Prostate cancer incidence has risen considerably in recent years, primarily due to Prostate Specific Antigen (PSA) testing in primary care. The objective of this study was to investigate associations between PSA testing and the psychological and physical health, and healthcare utilisation of men in a population where PSA testing is widespread.

METHODS

A cross-sectional study was carried out in a population-representative sample of men ≥ 50 years enrolled in The Irish Longitudinal Study on Ageing (TILDA). TILDA participants underwent structured interviews, health assessments and completed standardised questionnaires. Men were classified as ever/never having received a PSA test. Multivariate logistic regression (Odds Ratios (OR) and 95% Confidence Intervals (CI) was used to determine associations between PSA testing, and men's psychological and physical health and healthcare utilisation.

RESULTS

This analysis included 3,628 men, 68.2% of whom ever had a PSA test. In adjusted analysis, men with sub-threshold depression were significantly less likely to have had a PSA test, (OR=0.79, 95% CI 0.64-0.97). Likelihood of having a PSA test was inversely associated with anxiety, but this was not significant (OR=0.79, 95% CI 0.57-1.09). Frailty (OR=0.61, 95% CI 0.31-1.05) and eligibility for free primary care (OR=0.63, 95% CI 0.52-0.77) were also inversely associated with PSA testing. Positive associations were observed between PSA testing and more chronic illnesses (OR=1.11, 95% CI 1.05-1.19), more primary care visits (OR=1.03, 95% CI 1.01-1.05) and preventative health practices, including cholesterol testing and influenza vaccination (OR=1.35, 95% CI 1.13-1.60).

CONCLUSIONS

Men's psychological and physical health and their healthcare utilisation are associated with PSA testing in primary care. The association between poorer psychological health, in particular sub-threshold depression, and reduced likelihood of PSA testing in primary care requires further investigation. These findings may have wider implications for other cancer screening.

The number of tPSA tests continues to rise and variation in testing practices persists: a survey of laboratory services in Ireland 2008-2010

BACKGROUND

Ireland had the highest incidence of prostate cancer in Europe in 2008, due to widespread prostate specific antigen (PSA) testing.

AIMS

To investigate practices and costs of PSA testing in Ireland, 2008-2010.

METHODS

Postal laboratory questionnaire. Results were compared with 2006 and 2007 surveys.

RESULTS

Response rate was 95 % (42/44). In 2010, 37 laboratories measured total PSA (tPSA); 10 measured free PSA (fPSA). Eight assays were used and cut-offs to define 'normal' tPSA varied widely. There was a 9.9 % annual increase in the number of tPSA tests and a -31 % annual decrease in the number of fPSA, 2006-2010. A 100-fold difference in tPSA workload was observed across laboratories. In 2010, the estimated cost of PSA testing was <euro>3,649,984 (95 % CI <euro>2,532,745-<euro>4,767,222).

CONCLUSIONS

Health service costs of PSA testing are significant. The number of tPSA tests continues to rise; fPSA use fell by almost one-third. Inter-laboratory variation in testing practices persists. These have potentially important clinical consequences for men and need to be addressed.

Factors predicting hospital length-of-stay after radical prostatectomy: a population-based study

Background

Radical prostatectomy (RP) is a leading treatment option for localised prostate cancer. Although hospital in-patient stays accounts for much of the costs of treatment, little is known about population-level trends in length-of-stay (LOS). We investigated factors predicting hospital LOS and readmissions in men who had RP following prostate cancer.

Methods

Incident prostate cancers (ICD-O3: C61), diagnosed January 2002-December 2008 in men < 70 years, were identified from the Irish Cancer Registry, and linked to public hospital episodes. For those who had RP (ICD-9 CM procedure codes 60.3, 60.4, 60.5, 60.62) the associated hospital episode was identified. LOS was calculated as the number of days from date of admission to date of discharge. Patient-, tumour-, and health service-related factors predicting longer LOS (upper quartile, >9 days) were investigated using logistic regression. Patterns in day-case and in-patient readmissions within 28 days of discharge following RP were explored.

Results

Over the study period 9096 prostate cancers were diagnosed in men under 70, 26.5% of whom had RP by end of follow-up 31/12/2009. Two of eight public hospitals and eight of forty surgeons carried out 50% of all public-service RPs. Median LOS was 8 days (10th-90th percentile = 6-13 days) and fell significantly over time (2002, 9 days; 2008, 7 days; p < 0.001). In adjusted analyses men who were not married (OR = 1.71, 95% CI 1.25-2.34), had co-morbidities (OR = 1.64, 95% CI 1.25-2.16) or stage III-IV cancer (OR = 2.19, 95% CI 1.44-3.34) were significantly more likely to have prolonged LOS. Those treated in higher volume hospitals (annual median >49 RPs) or by higher volume surgeons (annual median >17 RPs) were significantly less likely to have prolonged LOS (OR = 0.34, 95% CI 0.26-0.45; OR = 0.55, 95% CI 0.42-0.71 respectively).

Conclusion

Median LOS after RP decreased between 2002 and 2008 in Ireland but it remains higher than in both England and the US. Although volumes of RPs conducted in Ireland are low, there is considerable variation between hospitals and surgeons. Hospital and surgeon volume were strong predictors of shorter LOS, after adjusting for other variables. These factors point to a need for a comprehensive review of prostate cancer service provision.

Discussions about prostate cancer screening between U.S. primary care physicians and their patients

OBJECTIVE

This study examined the likelihood that U.S. primary care physicians (PCPs) discuss and recommend prostate cancer screening with their patients and physician-related and practice-related factors associated with this behavior.

METHODS

We analyzed data from the 2007-2008 National Survey of Primary Care Physician Practices Regarding Prostate Cancer Screening (N = 1,256), the most recent and comprehensive survey specifically designed to address issues concerning prostate cancer screening and representing nearly 95,000 PCPs. We evaluated the relationship between PCP behavior regarding prostate cancer screening discussions and covariates, including PCP demographic and practice-related factors. Weighted percentages and Chi-square tests were used to compare use of screening discussions by PCP characteristics. Adjusted odds of discussing screening and recommending the PSA test were determined from logistic regression.

RESULTS

Eighty percent of PCPs reported that they routinely discuss prostate cancer screening with all of their male patients, and 64.1% of PCPs who discussed screening with any patients reported that they attempted to talk their patients into getting the PSA test. In multivariate analyses, encouraging PSA testing was more likely among non-Hispanic black PCPs (OR = 2.80, 95% CI [1.88, 4.16]), PCPs serving 100 or more patients per week (OR = 2.16, 95% CI [1.38, 3.37]), and PCPs spending longer hours per week in direct patient care (31-40 hours: OR = 1.90, 95% CI [1.13, 3.20]; 41 or more hours: OR = 2.09, 95% CI [1.12, 3.88]), compared to their referents. PCPs in multi-specialty group practice were more likely to remain neutral or discourage PSA testing compared to PCPs in solo practice.

CONCLUSIONS

Both individual and practice-related factors of PCPs were associated with the use of prostate cancer screening discussions by U.S. PCPs. Results from this study may prove valuable to researchers and clinicians and help guide the development and implementation of future prostate cancer screening interventions in the U.S.

Impact of PSA testing and prostatic biopsy on cancer incidence and mortality: comparative study between the Republic of Ireland and Northern Ireland

OBJECTIVES

To investigate the impact of different PSA testing policies and health-care systems on prostate cancer incidence and mortality in two countries with similar populations, the Republic of Ireland (RoI) and Northern Ireland (NI).

METHODS

Population-level data on PSA tests, prostate biopsies and prostate cancer cases 1993-2005 and prostate cancer deaths 1979-2006 were compiled. Annual percentage change (APC) was estimated by joinpoint regression.

RESULTS

Prostate cancer rates were similar in both areas in 1994 but increased rapidly in RoI compared to NI. The PSA testing rate increased sharply in RoI (APC = +23.3%), and to a lesser degree in NI (APC = +9.7%) to reach 412 and 177 tests per 1,000 men in 2004, respectively. Prostatic biopsy rates rose in both countries, but were twofold higher in RoI. Cancer incidence rates rose significantly, mirroring biopsy trends, in both countries reaching 440 per 100,000 men in RoI in 2004 compared to 294 in NI. Median age at diagnosis was lower in RoI (71 years) compared to NI (73 years) (p < 0.01) and decreased significantly over time in both countries. Mortality rates declined from 1995 in both countries (APC = -1.5% in RoI, -1.3% in NI) at a time when PSA testing was not widespread.

CONCLUSIONS

Prostatic biopsy rates, rather than PSA testing per se, were the main driver of prostate cancer incidence. Because mortality decreases started before screening became widespread in RoI, and mortality remained low in NI, PSA testing is unlikely to be the explanation for declining mortality.

Do older pedestrians have enough time to cross roads in Dublin? A critique of the Traffic Management Guidelines based on clinical research findings

BACKGROUND

the safety of older pedestrians at urban intersections is a matter of gerontological concern. Many older pedestrians report inability to complete crossings in the time given by pedestrian lights. Standard times for pedestrian lights in Dublin pelican crossings are specified in the Traffic Management Guidelines (TMG). The Technology Research for Independent Living Centre is building a database of gait assessments of Irish community-dwelling older people using GAITRite.

OBJECTIVE

to compare the usual walking speed of our participants against that required by the TMG.

DESIGN

cross-sectional observational study.

SETTING

comprehensive geriatric assessment outpatient clinic.

SUBJECTS

355 community-dwelling older subjects aged > or =60 assessed between August 2007 and September 2008 (mean age 72.7, SD 7.2).

METHODS

linear regression analysis between age and observed walking speed, followed by comparison of predicted walking speeds at four different ages (i.e. 60, 70, 80 and 89) against minimum walking speeds required to cross standard Irish roads when regulated by the pelican system.

RESULTS

age and walking speed had a strong inverse correlation F (1, 353) = 108.48, P < 0.001, R(2) = 0.235. The regression predicted a walking speed of 1.30 m/s (95% confidence interval 1.24-1.35) at the age of 60, 1.10 (1.07-1.13) at 70, 0.91 (0.87-0.94) at 80 and 0.73 (0.66-0.80) at 89. Against these predicted walking speeds, standard crossing times appeared insufficient for very old people.

CONCLUSIONS

as currently defined in the TMG, maximum pedestrian crossing times at pelican crossings may represent a hazard for very old people. This should be addressed within the Irish authorities' plan to improve safety and equality for older people.

Factors prompting PSA-testing of asymptomatic men in a country with no guidelines: a national survey of general practitioners

Background

Increased use of prostate specific antigen (PSA) has been associated with increased prostate cancer incidence. Ireland is estimated to have one of the highest prostate cancer incidences in Europe and has no national guidelines for prostate cancer screening. GPs have a pivotal role in influencing PSA testing, therefore, our aim was to describe GP testing practices and to identify factors influencing these.

Methods

A postal survey, including questions on clinical practice and experience, knowledge and demographics was distributed to all GPs (n = 3,683). The main outcomes were (i) PSA testing asymptomatic men and (ii) "inappropriate" PSA testing, defined as testing asymptomatic men aged < 50 or > 75 years. Factors associated with these outcomes were identified using logistic regression.

Results

1,625 GPs responded (response rate corrected for eligibility = 53%). Most respondents (79%) would PSA test asymptomatic men. Of these, 34% and 51% would test asymptomatic men < 50 and > 75 years, respectively. In multivariate analyses, GPs were more likely to test asymptomatic men if they were ≥ 50 years, in practice ≥ 10 years, female or less knowledgeable about PSA efficacy. Male GPs who would have a PSA test themselves were > 8-times more likely to PSA test asymptomatic men than GPs who would not have a test. GPs who had an asymptomatic patient diagnosed with prostate cancer following PSA testing, were > 3-times more likely to test asymptomatic men. Practice-related factors positively associated with testing included: running 'well man' clinics, performing occupational health checks and performing other tests routinely with PSA. Factors positively associated with 'inappropriate' testing included; being male and willing to have a PSA test, having worked/trained in the UK and supporting annual PSA testing. 91% of respondents supported the development of national PSA testing guidelines.

Conclusion

Our findings suggest that widespread PSA testing of asymptomatic men in primary care is primarily due to a combination of clinical experience, poor knowledge and the support of doctors for PSA testing, as evidenced by the willingness of male doctors to have a PSA test. There is an urgent need for education and support for GPs concerning prostate cancer screening, starting with the implementation of national guidelines.