|A systematic review of the diagnostic accuracy of prostate specific antigen
|Harvey P, Basuita A, Endersby D, Curtis B, Iacovidou A, Walker M
The review concluded that total prostate specific antigen testing had a role as one of several indicators for prostate biopsy. Although the total prostate specific antigen test had adequate sensitivity for finding prostate cancer, it had poor specificity for ruling out cancer; clinicians should understand these limitations. The authors acknowledged the limitations in their review, and their conclusions appear appropriate.
To assess the diagnostic accuracy of total prostate specific antigen testing for prostate cancer.
MEDLINE and EMBASE were searched from 1998 to January 2008 for articles published in English. Search terms were reported.
Analytical studies that assessed the accuracy of total prostate specific antigen testing in predicting the diagnosis of prostate cancer in men of any age were eligible for inclusion. Studies had to provide a full range of total prostate specific antigen (below 4ng/mL to over 10ng/mL) and had to histologically confirm the diagnosis of prostate cancer from a biopsy or resected specimen. Studies had to be conducted in Europe.
The relevant outcomes were sensitivity, specificity, true positives, false positives, true negatives and false negatives.
The included studies examined the diagnostic accuracy of total prostate specific antigen testing of men in Europe. The reference test was a form of prostate biopsy or resected specimen. The index test varied across studies and included chemoluminescent immunometric assay, Immulite, PSA Bayer ADVIA, Roche 2 immunoassay, Tandem-R PSA, Tandem-e PSA, or unspecified prostate specific antigen assay.
Two reviewers independently performed study selection, and disagreements were resolved by discussion with a third reviewer.
Assessment of study quality
Two reviewers independently graded studies according to the QUADAS (Quality Assessment of Diagnostic Accuracy Studies) criteria, which assessed studies on eight quality factors: representative spectrum, acceptable reference standard, partial verification avoided, reference results blinded, index test results blinded, relevant clinical information, uninterpretable results reported, and withdrawals explained.
Data were extracted on sensitivity, specificity, true positives, false positives, true negatives and false negatives. Data were used to calculate positive and negative likelihood ratios, diagnostic odds ratios, together with 95% confidence intervals (CIs).
The number of reviewers that extracted data was not reported.
Methods of synthesis
Data were graphically presented using forest plots and summary receiver operating characteristic (SROC) curves.
Subgroup analyses were undertaken using SROC curves based on study design and year of publication.
Results of the review
Ten studies were included in the review (n=5,373 participants), including seven prospective cohort studies and three retrospective case control studies. The study sample size ranged from 59 to 3,171 (mean=537). Study quality was mixed, with few studies blinding reference test results or index test results, and few studies explained withdrawals or reported uninterpretable results.
The diagnostic sensitivity of total prostate specific antigen testing ranged from 0.78 to 1.00 (potentially failing to diagnose over 20% of prostate cancers); the specificity ranged from 0.06 to 0.66.
Eight studies had positive likelihood ratios above one, but none had ratios above 10 (the threshold for a useful test). Eight studies also had negative likelihood results below one, but only one had a ratio below 0.1 (threshold for a useful test).
The SROC curve was to the left of the diagonal, indicating that the total prostate specific antigen test had value.
Subgroup analyses indicated greater test accuracy in case control studies and in studies published after 1999.
Total prostate specific antigen testing was one of several indicators for prostate biopsy, along with abnormal digital rectal examinations and urinary symptoms. However, the total prostate specific antigen test had a high false positive rate and a statistically significant false negative rate; it is important for clinicians to understand these limitations.
Inclusion criteria for the review were clearly defined. Two relevant databases were searched. Publication bias was not assessed and could not be ruled out. There was potential for language bias, as only English language articles were included. Attempts were made to reduce reviewer error and bias during study selection and quality assessment, but it was unclear if such attempts were made for data extraction.
Quality assessment was conducted using a standard checklist, which indicated the variable quality of the included studies. Study results were presented using forest plots and SROC curves, which was appropriate for diagnostic data. Subgroup analyses were also undertaken for type of study and year of publication.
The authors acknowledged the limitations in their review, such as a lack of generalisability to the screening population and study differences; the resulting conclusions and research recommendations appear appropriate.
Implications of the review for practice and research
Practice: The authors stated that the total prostate specific antigen test should continue in clinical practice as one of several indicators for biopsy, but clinicians should understand the limitations of the test.
Research: The authors stated that further research on prostate specific antigen should be undertaken using the STARD (Standards for Reporting of Diagnostic Accuracy) statement to ensure standardisation and transparency across studies. Research into the use of prostate specific antigen testing in the screening population would be useful, as would subanalysis based on patient’s symptoms. Assessing the role of prostate specific antigen results in General Practitioner decision making would be of interest.
Harvey P, Basuita A, Endersby D, Curtis B, Iacovidou A, Walker M. A systematic review of the diagnostic accuracy of prostate specific antigen. BMC Urology 2009; 9(1):14
Subject indexing assigned by NLM
Humans; Male; Prostate-Specific Antigen /blood; Prostatic Neoplasms /blood /diagnosis; Reproducibility of Results; Sensitivity and Specificity
Database entry date
This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.