12/15/2023 0 Comments Hiv testing elisa vs western blot‘False positive’ denotes subjects with an actual negative outcome who were incorrectly given a positive assignment (i.e., PSA density test-positive, biopsy-negative). ‘True negative’ indicates subjects with an actual negative outcome who were correctly given a negative assignment (i.e., PSA density test-negative, biopsy-negative). In this scenario, ‘true positive’ denotes subjects with an actual positive outcome who were correctly given a positive assignment (i.e., PSA density test-positive, biopsy-positive for prostate cancer). Thus, there exist four basic combinations of ‘assignment status’ (i.e., cancer status according to PSA density) and ‘actual outcome’ (i.e., cancer status according to gold standard prostate biopsy) by which all 2162 subjects may be categorized ( Table 1). After excluding subjects with a PSA outside of the prespecified range (10 ng/mL), or with missing data, a total of 2162 men were included in the final study cohort.įor simplicity, we will assume that prostate biopsy results (‘gold standard’) correctly determined the true disease status (i.e., presence versus absence of clinically significant prostate cancer) in all cases. Only first available biopsy results were included from men with repeat biopsies. PSA was measured prior to biopsy, and prostate volume was determined on transrectal ultrasound at the time of biopsy. The authors obtained institutional review board approval to retrospectively review data collected on 4109 men who underwent transrectal ultrasound-guided prostate biopsy at their institution from January 2002 through May 2017. sought to determine the diagnostic utility of PSA density (i.e., an ‘alternative test’) in detecting clinically significant prostate cancer in men with elevated PSA who underwent prostate biopsy. In a recent study published in the Journal of Urology, Aminsharifi et al. Accordingly, consideration of PSA density is increasingly favored over PSA alone for assessing prostate cancer risk. Unlike the PSA test itself, PSA density accounts for the fact that men with larger prostates generally have higher levels of PSA under normal baseline physiologic conditions (i.e., in the absence of prostate cancer). A newer, related parameter, PSA density, is computed as the serum PSA level (in ng/mL) divided by the volume of the prostate gland (in cubic centimeters (cc)). The PSA test measures the level of PSA in a man’s blood and is widely used to screen for prostate cancer. Prostate-specific antigen (PSA) is a protein produced by cells of the prostate gland. We will also use these data in subsequent sections of this article to explore the concepts of positive predictive value and negative predictive value. We will approach sensitivity and specificity using a recent real-world example from the medical literature. Sensitivity and specificity are the two statistical measures most commonly used to assess the performance of an alternative test against the gold standard. This article will further detail the concepts of sensitivity, specificity, and predictive values using a recent real-world example from the medical literature. Sensitivity and specificity are inversely related, wherein one increases as the other decreases, but are generally considered stable for a given test, whereas positive and negative predictive values do inherently vary with pre-test probability (e.g., changes in population disease prevalence). Negative predictive value reflects the proportion of subjects with a negative test result who truly do not have the outcome of interest. Positive predictive value reflects the proportion of subjects with a positive test result who truly have the outcome of interest. Specificity, which denotes the proportion of subjects correctly given a negative assignment out of all subjects who are actually negative for the outcome, indicates how well a test can classify subjects who truly do not have the outcome of interest. Sensitivity, which denotes the proportion of subjects correctly given a positive assignment out of all subjects who are actually positive for the outcome, indicates how well a test can classify subjects who truly have the outcome of interest.
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