A panel of selected serum protein biomarkers for the detection of aggressive prostate cancer.

Background: Current PSA-based tests used to detect prostate cancer (PCa) lack sufficient specificity, leading to significant overdetection and overtreatment. Our previous studies showed that serum fucosylated PSA (Fuc-PSA) and soluble TEK receptor tyrosine kinase (Tie-2) had the ability to predict aggressive (AG) PCa. Additional biomarkers are needed to address this significant clinical problem. Methods: A comprehensive Pubmed search followed by multiplex immunoassays identified candidate biomarkers associated with AG PCa. Subsequently, multiplex and lectin-based immunoassays were applied to a case-control set of sera from subjects with AG PCa, low risk PCa, and non-PCa (biopsy negative). These candidate biomarkers were further evaluated for their ability as panels to complement the prostate health index (phi) in detecting AG PCa. Results: When combined through logistic regression, two panel of biomarkers achieved the best performance: 1) phi, Fuc-PSA, SDC1, and GDF-15 for the detection of AG from low risk PCa and 2) phi, Fuc-PSA, SDC1, and Tie-2 for the detection of AG from low risk PCa and non-PCa, with noticeable improvements in ROC analysis over phi alone (AUCs: 0.942 vs 0.872, and 0.934 vs 0.898, respectively). At a fixed sensitivity of 95%, the panels improved specificity with statistical significance in detecting AG from low risk PCa (76.0% vs 56%, p=0.029), and from low risk PCa and non-PCa (78.2% vs 65.5%, p=0.010). Conclusions: Multivariate panels of serum biomarkers identified in this study demonstrated clinically meaningful improvement over the performance of phi, and warrant further clinical validation, which may contribute to the management of PCa.

Comparative evaluation of three FDA-approved HIV Ag/Ab combination tests using a genetically diverse HIV panel and diagnostic specimens.

BACKGROUND: HIV Ag/Ab combination assays are recommended by CDC for routine screening and several HIV Ag/Ab combination tests are now FDA-approved. Maintaining high specificity and consistent sensitivity across diverse HIV strains is critical for these assays to accurately detect HIV infection and expedite delivery of patient results. OBJECTIVES: To evaluate performance of three FDA-approved HIV tests: ARCHITECT HIV Combo (Abbott), ADVIA Centaur HIV Combo (Siemens) and BioPlex HIV Ag-Ab (Bio-Rad). STUDY DESIGN: Sensitivity and specificity were evaluated using an extensive panel of 28 HIV infected human specimens and 17 cultured virus isolates representing multiple genotypes, 6 seroconversion panels, 4 human samples with acute infection, WHO p24 standard and 4020 clinical specimens. RESULTS: The p24 limit of detection (LOD) for the WHO standard was 0.19IU/ml, 0.70IU/ml, and 1.77IU/ml in BioPlex, ARCHITECT, and Centaur respectively. The distribution of LODs across 15 HIV-1 isolates was substantially narrower in ARCHITECT (5-33pg/ml) than in BioPlex (11-198pg/ml) and Centaur (6-384pg/ml). All assays detected antibodies to the majority of HIV-1 and HIV-2 variants. However, reduced sensitivity was observed for Centaur in detection of antibodies to HIV-1 group M (CRF02_AG), O and N variants. BioPlex and ARCHITECT showed better seroconversion sensitivity than Centaur, detecting one bleed (3-7 days) earlier in 4 (BioPlex) and 3 (ARCHITECT) of 6 seroconversion panels. ARCHITECT demonstrated the highest specificity (99.90-100%) compared to BioPlex (99.80%) and Centaur (99.42%). CONCLUSIONS: The overall performance of ARCHITECT and BioPlex was superior to Centaur, especially for detection of acute HIV infection.

Short-term stability of the molecular forms of prostate-specific antigen and effect on percent complexed prostate-specific antigen and percent free prostate-specific antigen.

Differences in stability of the free and complexed molecular forms of prostate-specific antigen (PSA) may influence the clinical utility of assays for these forms, as well as the calculated ratios to total PSA (tPSA), such as percent free PSA (fPSA) and percent complexed PSA (cPSA). The objective of this study was to directly compare the short-term stability of fPSA and cPSA under different storage conditions. Specimens (3 with prostate cancer, 3 biopsy-negative without cancer, 2 normal) from 8 men were analyzed at baseline within 2 hours of collection, and at 4 hours, 8 hours, 24 hours, 48 hours, and 1 week after storage at room temperature, 4 degrees C, or -20 degrees C. Serum specimens were analyzed in duplicate on the Bayer Immuno 1 analyzer (tPSA, cPSA) and on the Beckman Coulter Access analyzer (tPSA, fPSA Tandem assays). Baseline tPSA values ranged from 0.7 to 62.0 ng/mL, with a median of 7.9 ng/mL (Immuno 1). Overall, all forms of PSA were stable up to 24 hours at the 3 temperatures, with the exception of fPSA and percent fPSA, which decreased when stored at 4 degrees C. After 1 week, tPSA levels decreased when stored at room temperature and at 4 degrees C, as did cPSA stored at room temperature. Over the 7 days, percent cPSA was stable at room temperature, but increased at 4 degrees C. There were no significant changes in any PSA form or calculated ratio with storage at -20 degrees C for up to 1 week. In summary, in the short term (<1 week), fPSA is less stable with storage than tPSA or cPSA in a time- and temperature-dependent fashion. Thus, specimen handling should be considered when interpreting PSA results. It is recommended that specimens not analyzed the same day (within 8 hours of collection) be stored frozen at -20 degrees C.