Individual risk prediction of high grade prostate cancer based on the combination between total prostate-specific antigen (PSA) and free to total PSA ratio.

OBJECTIVES: Clinical practice guidelines endorse the stratification of prostate cancer (PCa) risk according to individual total prostate-specific antigen (tPSA) values and age to enhance the individual risk-benefit ratio. We defined two nomograms to predict the individual risk of high and low grade PCa by combining the assay of tPSA and %free/tPSA (%f/tPSA) in patients with a pre-biopsy tPSA between 2 and 10 µg/L. METHODS: The study cohort consisted of 662 patients that had fPSA, tPSA, and a biopsy performed (41.3% with a final diagnosis of PCa). Logistic regression including age, tPSA and %f/tPSA was used to model the probability of having high or low grade cancer by defining 3 outcome levels: no PCa, low grade (International Society of Urological Pathology grade, ISUP<3) and high grade PCa (ISUP≥3). RESULTS: The nomogram identifying patients with: (a) high vs. those with low grade PCa and without the disease showed a good discriminating capability (∼80%), but the calibration showed a risk of underestimation for predictive probabilities >30% (a considerable critical threshold of risk), (b) ISUP<3 vs. those without the disease showed a discriminating capability of 63% and overestimates predictive probabilities >50%. In ISUP 5 a possible loss of PSA immunoreactivity has been observed. CONCLUSIONS: The estimated risk of high or low grade PCa by the nomograms may be of aid in the decision-making process, in particular in the case of critical comorbidities and when the digital rectal examinations are inconclusive. The improved characterization of the risk of ISUP≥3 might enhance the use for magnetic resonance imaging in this setting.

Managing the impact of inter-method bias of prostate specific antigen assays on biopsy referral: the key to move towards precision health in prostate cancer management.

OBJECTIVES: We assessed the inter-method bias of total (tPSA) and free (fPSA) prostate-specific antigen (PSA) immunoassays to establish if tPSA-based risk thresholds for advanced prostate cancer (PCa), obtained from one method (Roche) can be converted into the corresponding concentrations assayed by other methods. Then we evaluated the impact of the bias of tPSA and fPSA on the estimation of the %f/tPSA ratio and performed a re-calibration of the proposed thresholds for the %f/tPSA ratio according to the assay used. METHODS: tPSA and fPSA were measured in 135 and 137 serum samples, respectively by Abbott Alinity i, Beckman Access Dxl, Roche Cobas e801, and Siemens Atellica IM analytical platforms. Scatterplots, Bland-Altman diagrams, Passing-Bablok (PB) were used to inspect and estimate the systematic and proportional bias between the methods. The linear equations with confidence intervals of the parameter estimates were used to transform the tPSA risk thresholds for advanced PCa into the corresponding concentrations measurable by the other analytical methods. To construct a correction coefficient for converting the %f/tPSA ratio from one method to the other, PB and non-parametric boostrapping were used. RESULTS: The inter-method bias is not constant but strictly linear allowing the conversion of PSA results obtained from Roche into the other assays, which underestimate tPSA vs. Roche. Siemens and Abbott vs. Roche and Beckman assays, being characterized by a positive and a negative proportional bias for tPSA and fPSA measurements, tend to overestimate the %f/tPSA ratio. CONCLUSIONS: There is a consistent risk to miss advanced PCa, if appropriate conversion factors are not applied.

Definition of Outcome-Based Prostate-Specific Antigen (PSA) Thresholds for Advanced Prostate Cancer Risk Prediction.

We defined prostate-specific antigen (PSA) thresholds from a well calibrated risk prediction model for identifying and excluding advanced prostate cancer (PCa). We retrieved 902 biopsied patients with a pre-biopsy PSA determination (Roche assay). A logistic regression model predictive for PCa including the main effects [i.e., PSA, age, histological evidence of glandular inflammation (GI)] was built after testing the accuracy by calibration plots and Hosmer-Lemeshow test for goodness of fit. PSA thresholds were derived by assuming a diagnostic sensitivity of 95% (rule-out) and 80% (rule-in) for overall and advanced/poorly differentiated PCa. In patients without GI, serum PSA concentrations ≤ 4.1 (<65 years old) and ≤3.7 µg/L (≥65 years old) excluded an advanced PCa (defined as Gleason score ≥ 7 at biopsy), with a negative predictive value of 95.1% [95% confidence interval (CI): 83.0-98.7] and 88.8% (CI: 80.2-93.9), respectively, while PSA > 5.7 (<65) and >6.1 µg/L (≥65) should address biopsy referral. In presence of GI, PSA did not provide a valid estimate for risk of advanced cancer because of its higher variability and the low pre-test probability of PCa. The proposed PSA thresholds may support biopsy decision except for patients with asymptomatic prostatitis who cannot be pre-biopsy identified.

Use of the reticulocyte channel warmed to 41 °C of the XN-9000 analyzer in samples with the presence of cold agglutinins

ABSTRACT Objectives The purpose of this study was to compare data obtained from the reticulocyte channel (RET channel) heated to 41 °C with those obtained from impedance channel (I-Channel) at room temperature in the samples with the mean corpuscular hemoglobin concentration (MCHC) < 370 g/L and in samples with the MCHC > 370 g/L, in the presence of cold agglutinins. Methods In this study, 60 blood samples (group 1) with the MCHC < 370 g/L (without cold agglutinins) and 78 blood samples (group 2) with the MCHC > 370 g/L (with cold agglutinins) were used to compare the two analytical channels of the XN-9000 analyzer in different preanalytical conditions. The parameters evaluated in both groups were the following: red blood cell (RBC), hemoglobin (HGB), hematocrit (HCT), mean cell volume (MCV), RBC-most frequent volume (R-MFV), mean hemoglobin concentration (MCH) and mean cellular hemoglobin concentration (MCHC). Results The results of this study showed an excellent correlation with both channels of the XN-9000 analyzer in samples with and without cold agglutinins, except for the MCHC. The bias between the values obtained in the I-channel and those obtained in the RET channel of both groups was insignificant and remained within the limits of acceptability, as reported by Ricos et al. for all considered parameters, except for MCHC. Conclusions The presence of cold agglutinins in blood samples can be detected by a spurious lowering of the RBC count and by a spurious increase in the MCHC. The RET channel represents a great opportunity to correct the RBC count in a rapid manner without preheating. However, neither methodology can completely solve the residual presence of cold agglutinins in all samples, despite the MCHC values being < 370 g/L.

Verification of Harmonization of Serum Total and Free Prostate-Specific Antigen (PSA) Measurements and Implications for Medical Decisions.

BACKGROUND: Previous studies have shown that the harmonization of prostate-specific antigen (PSA) assays remained limited even after the introduction of WHO International Standards. This information needs updating for current measuring systems (MS) and reevaluation according to established analytical performance specifications (APS) and the characteristics of antibodies used. METHODS: Total (tPSA) and free (fPSA) PSA were measured in 135 and 137 native serum samples, respectively, by Abbott Alinity i, Beckman Access Dxl, Roche Cobas e801, and Siemens Atellica IM MSs. Passing-Bablok regression and difference plots were used to compare results from each MS to the all-method median values. Agreement among methods was evaluated against APS for bias derived from biological variation of the 2 measurands. RESULTS: The median interassay CV for tPSA MSs (11.5%; 25-75th percentiles, 9.2-13.4) fulfilled the minimum APS goal for intermethod bias (15.9%), while the interassay CV for fPSA did not [20.4% (25-75th percentiles, 18.4-22.7) vs goal 17.6%]. Considering the all-method median value of each sample as reference, all tPSA MSs exhibited a mean percentage bias within the minimum goal. On the other hand, Alinity (+21.3%) and Access (-24.2%) were out of the minimum bias goal for fPSA, the disagreement explained only in minimal part by the heterogeneity of employed antibodies. CONCLUSIONS: The harmonization among tPSA MSs is acceptable only when minimum APS are applied and necessitates further improvement. The marked disagreement among fPSA MSs questions the use of fPSA as a second-level test for biopsy referral.

Is pre-biopsy serum prostate specific antigen retesting always justified? A study of the influence of individual and analytical factors on decision making for biopsy referral.

BACKGROUND AND AIMS: We investigated factors influencing pre-biopsy prostate-specific antigen (PSA) retesting as recommended by clinical guidelines. MATERIALS AND METHODS: 333 patients screened for prostate cancer (PCa) repeated PSA (Roche Cobas systems) after a median of 3.9 months, before performing biopsy. Multiple regression models were used to assess effects of patients' characteristics on PSA results and changes over time. RESULTS: PCa [n = 132 (40.7%)] and cancer-free [n = 192 (59.3%)] patients had similar rate of PSA positive results at baseline (84.8% vs. 83.9%, P = 0.931). Their rate of reversion to normal PSA after retesting was negligible (0.9% in PCa and 3.7% in PCa-free patients, P = 0.286). 31.1% of PCa and 31.3% of cancer-free patients (P = 0.426) showed a significant PSA increase after retesting. Age was a confounder since not only PSA increased in older PCa patients, but it was also related to PCa histological grade, in turn associated to PSA increase. In PCa-free patients, glandular inflammation, present in 1/3 of subjects, was also associated to higher PSA concentrations. CONCLUSION: When obtained with the same immunoassay under controlled analytical conditions, a PSA positive result is confirmed after retesting in the great majority of screened patients. Neither analytical factors nor intraindividual variability appeared to justify PSA retesting before biopsy referral.

Serum Prostate-Specific Antigen Testing for Early Detection of Prostate Cancer: Managing the Gap between Clinical and Laboratory Practice.

BACKGROUND: Current clinical practice guidelines (CPGs) for early detection of prostate cancer recommend for clinical decision-making a personalized prostate-specific antigen (PSA)-based management to improve the risk-benefit ratio of the screening strategy. Some important critical issues regarding the PSA determination in the clinical framework are, however, still neglected in current guidelines and a major focus of recommendations on those aspects would be needed to improve their effectiveness. CONTENT: Evidence sources in the available literature concerning the interchangeability of total PSA results measured with different commercial methods were critically appraised. We discuss how the heterogeneity of the measurand, the intermethod bias, and the design and selectivity of immunoassays may affect the diagnostic accuracy of selected PSA thresholds, and how knowledge of the analytical characteristics of assays in service, such as the recognized PSA circulating forms and the cross-reactivity with PSA homologs, is basic for improving both clinical decision-making in cancer screening and the reliability of the clinical interpretation of results at the individual level. SUMMARY: Current CPGs ignore the poor interchangeability of PSA results obtained from different assays and the substantial role of laboratory issues in clinical performance of PSA testing. Involved stakeholders should contribute to fill the existing gap by: (a) preparing commutable reference materials for immunoassay calibration; (b) providing analytical characteristics that may explain the different performance of assays; (c) deriving outcome-based analytical performance specifications for PSA measurement; and (d) giving more focus on laboratory items when CPGs are prepared.

Use of the reticulocyte channel warmed to 41°C of the XN-9000 analyzer in samples with the presence of cold agglutinins.

OBJECTIVES: The purpose of this study was to compare data obtained from the reticulocyte channel (RET channel) heated to 41°C with those obtained from impedance channel (I-Channel) at room temperature in the samples with the mean corpuscular hemoglobin concentration (MCHC)<370g/L and in samples with the MCHC>370g/L, in the presence of cold agglutinins. METHODS: In this study, 60 blood samples (group 1) with the MCHC<370g/L (without cold agglutinins) and 78 blood samples (group 2) with the MCHC>370g/L (with cold agglutinins) were used to compare the two analytical channels of the XN-9000 analyzer in different preanalytical conditions. The parameters evaluated in both groups were the following: red blood cell (RBC), hemoglobin (HGB), hematocrit (HCT), mean cell volume (MCV), RBC-most frequent volume (R-MFV), mean hemoglobin concentration (MCH) and mean cellular hemoglobin concentration (MCHC). RESULTS: The results of this study showed an excellent correlation with both channels of the XN-9000 analyzer in samples with and without cold agglutinins, except for the MCHC. The bias between the values obtained in the I-channel and those obtained in the RET channel of both groups was insignificant and remained within the limits of acceptability, as reported by Ricos et al. for all considered parameters, except for MCHC. CONCLUSIONS: The presence of cold agglutinins in blood samples can be detected by a spurious lowering of the RBC count and by a spurious increase in the MCHC. The RET channel represents a great opportunity to correct the RBC count in a rapid manner without preheating. However, neither methodology can completely solve the residual presence of cold agglutinins in all samples, despite the MCHC values being < 370g/L.

Performance evaluation of a new and improved cuvette-based automated urinalysis analyzer with phase contrast microscopy.

BACKGROUND: The use of phase contrast in urinalysis has been highly recommended. A new system, sediMAX conTRUST PRO, is now available providing simultaneous automated phase contrast and bright field microscopy. This study aimed to evaluate both analytical and diagnostic performance of this new analyzer. METHODS: Results from 504 samples evaluated with the sediMAX conTRUST PRO were compared to those obtained from the same samples by manual microscopy (MM). Analytical and diagnostic performance were assessed according to established guidelines. RESULTS: The concentration of red blood cells (RBCs)and white blood cells (WBCs) at which the LoQ satisfied a CV< 25% was 12 particles per µL (p/µL) and 8 p/µL, respectively. Within one grade of agreement concordance was quite high, 97.8% for RBCs and 98.0% for WBCs, and above 90% for all other particles. Overall, diagnostic sensitivity and specificity were good (>80%) for the particles considered, although lower sensitivities, 70.6% and 61.8%, were respectively found for hyaline and pathological casts. CONCLUSIONS: The sediMAX conTRUST PRO provides very good performance in terms of RBC and WBC recognition and enumeration, and quite good performance for all other particles. Hyaline cast and pathological cast identification is fine and comparable to other automated systems, but could use further improvement.