Early prediction of prostate cancer biochemical recurrence and identification of disease persistence using PSA isoforms and human kallikrein-2.

BACKGROUND: The role of isoforms of prostate specific antigen (PSA) and other kallikrein-related markers in early detection of biochemical recurrence (BCR) after radical prostatectomy (RP) is not well known and serum PSA is currently used in preoperative risk nomograms. OBJECTIVE: The aim of this research was to study pre- and early postoperative levels of important PSA isoforms and human kallikrein-2 to determine their ability to predict BCR and identify disease persistence (DP). METHODS: This study included 128 consecutive patients who underwent RP for clinically localized prostate cancer. PSA, fPSA, %fPSA, [-2]proPSA, PHI and hK2 were measured preoperatively, at 1 and 3 months after RP. We determined the ability of these markers to predict BCR and identify DP. RESULTS: The DP and BCR rate were 11.7%and 20.3%respectively and the median follow up was 64 months (range 3-76 months). Preoperatively, the independent predictors of BCR were PSA (p-value 0.029), [-2]proPSA (p-value 0.002) and PHI (p-value 0.0003). Post-RP, PSA was the single marker correlating with BCR, both at one (p-value 0.0047) and 3 months (p-value 0.0004). PSA, fPSA, [-2]proPSA and PHI significantly correlated to DP at 1 and 3 months post-RP (p-value <  0.05), although PSA had the most significant existing correlation (p-value <  0.0001). CONCLUSIONS: [-2]proPSA and PHI are preoperative predictors of BCR and DP that outperform the currently used serum PSA. At the early postoperative period there is no additional benefit of the other markers tested.

A 4Kscore Cut-off of 7.5% for Prostate Biopsy Decisions Provides High Sensitivity and Negative Predictive Value for Significant Prostate Cancer.

OBJECTIVE: To evaluate the 4Kscore test's low risk cut-off of 7.5% as the indication to proceed with a prostate biopsy by combining data from 2 independent prospective multicentre trials in the United States which have validated the 4Kscore test as a continuous score to predict clinically significant prostate cancer. MATERIALS AND METHODS: We analyzed the data from 2 prospective multicenter trials in the United states to determine the number of men who could safely avoid a prostate biopsy and the presence of clinically significant cancers detected, at a 4Kscore cut-off of 7.5%. We evaluated this in the entire cohort, and 3 subgroups of men aged 45-75 years with a total prostate specific antigen between 3.0 and 10.0 ng/mL, African American, and non-African American men. RESULTS: The analysis included 1378 patients. The combination analysis at a 7.5% threshold to decide upon a prostate biopsy, was associated with a 32% biopsy reduction. A total of 21 men (4.8%) with a low risk 4Kscore had International society of Urological Pathology, prostate cancer Grade group (GG) 2 or 3 cancer, leading to a sensitivity of 94% for detecting GG ≥2 cancer, and a negative predictive value of 95%. There were no GG ≥4 cancers with a low risk 4Kscore. Analyses in various subgroups afforded similar results. CONCLUSION: A 4Kscore test cut-off of 7.5% allowed a significant biopsy reduction, while maintaining high sensitivity and NPV for detecting and ruling out aggressive prostate cancer.

Clinical utility of current biomarkers for prostate cancer detection.

Although prostate-specific antigen (PSA) remains the most used test to detect prostate cancer (PCa), the limited specificity and an elevated rate of overdiagnosis are the main problems associated with PSA testing. Over the last three decades, a large body of evidence has indicated that PSA screening methods for PCa are problematic, although PSA screening significantly reduces PCa-specific mortality. A number of novel biomarkers have been introduced to overcome these limitations of PSA in the clinical setting. These biomarkers have demonstrated an increased ability to select patients for biopsy and identify men at risk for clinically significant PCa. Although a number of assays require further validation, initial data are promising. Forthcoming results will ultimately determine the clinical utility and commercial availability of these assays. Extensive efforts have recently been made to identify and commercialize novel PCa biomarkers for more effective detection of PCa, either alone or in combination with currently available clinical tools. This review highlights the role of existing and promising serum and urinary biomarkers for the detection and prognostication of PCa before prostate biopsy.

Tissue kallikrein: A potential serum biomarker to predict delayed cerebral ischemia in aneurysmal subarachnoid hemorrhage.

BACKGROUND: Delayed cerebral ischemia (DCI) is a severe complication after aneurysmal subarachnoid hemorrhage (aSAH). Tissue kallikrein (TK), a subgroup of serine proteinases, is an important component of the kallikrein-kinin system. Exogenous TK attenuated cerebral vasospasm in a rabbit model of subarachnoid hemorrhage. We intended to discern association of serum TK levels with aSAH-related DCI. METHODS: Serum TK levels were detected in a total of 92 aSAH patients and 92 healthy controls. A multivariate logistic regression model was configured to investigate relationship between TK levels and occurrence of DCI. RESULTS: TK levels were substantially lower in aSAH patients than in controls. TK levels were strongly correlated with World Federation of Neurological Surgeons (WFNS) score and modified Fisher score. Serum TK, WFNS score and modified Fisher score retained as the three independent predictors for DCI. Under receiver operating characteristic curve, predictive capability of TK levels was in the range of WFNS score and modified Fisher score, as well as TK levels could remarkably improve predictive abilities of WFNS score and modified Fisher score. CONCLUSIONS: Serum TK emerges as a potential biomarker for assessment of hemorrhagic severity and prediction of DCI following aSAH.

A critical appraisal of biomarkers in prostate cancer.

PURPOSE: A number of urine and blood-based biomarker tests have been described for prostate cancer, although to date there has only been a limited exploration of the methodology behind the validation studies that underpin these tests. METHODS: In this review, a selection of commercially available urine and blood-based biomarker tests for prostate cancer are described, and the underlying key validation studies for each test are critically appraised using the Standards for Reporting Diagnostic Accuracy (STARD) 2015 statement. RESULTS: The ExoDx Prostate Intelliscore, SelectMDx, Progensa PCA3, Mi-Prostate Score, 4K Score, and Prostate Health Index (PHI) tests were reviewed. Most of the validation studies supporting these tests perform exploratory analyses to determine cut-off values in a post hoc manner, comprise cohorts that are primarily Caucasian, report receiver operating characteristic curves that combine the biomarker's result with established clinical nomograms and are based on a reference standard (prostate biopsy) that lacks central pathology review. Deficiencies in STARD reporting guidelines include frequent failure to provide a published study protocol, prospective study registration in a registry, a flow diagram, justification for sample size determination, a discussion of adverse events with testing, and information on how missing or indeterminate test results should be managed. CONCLUSIONS: Key validation studies that support many commercially available urine and blood-based biomarkers for prostate cancers have deficiencies in transparency based on STARD reporting guidelines, and limitations in methodology must be considered when deciding when these tests should be applied in clinical practice.

Plasma concentrations of tissue kallikrein in normal and preeclamptic pregnancies.

Objective: To investigate maternal plasma concentrations of tissue kallikrein (TK) in normal and preeclamptic pregnancies.Methods: 96 women with singleton pregnancies were categorized into normal, mild preeclampsia and preeclampsia with severe features. Plasma levels of TK were quantified by ELISA and left lateralrecumbencyposition BP measured.Results: Maternal plasma TK concentrations were significantly lower in preeclampsia with severe features compared with mild preeclampsia and normal pregnant. Plasma TK concentrations were negatively correlated with systolic and diastolic blood pressure, and 24-hour urine protein.Conclusion: Lower maternal plasma TK may be a risk marker that reflects the severity of preeclampsia.

Determination of serum tissue kallikrein levels after traumatic brain injury.

BACKGROUND: Tissue kallikrein (TK) plays an important role in the kallikrein-kinin system. Its protective role has been demonstrated in traumatic brain injury (TBI). We attempted to determine relationship between serum TK levels and trauma severity in addition to clinical outcome in TBI. METHODS: We recruited 112 patients with severe TBI (Glasgow coma scale score < 9) and 112 controls. We configured 2 multivariate models to assess the relationship between serum TK levels and 30-day death. Its prognostic predictive ability was analyzed under receiver operating characteristic curve. RESULTS: TK levels were significantly lower in patients than in controls (median 0.148 mg/l, the upper - lower quartiles 0.121-0.185 vs. median 0.258 mg/l, the upper - lower quartiles 0.207-0.342, P < 0.001). TK levels were closely and positively correlated with Glasgow coma scale score (r = 0.550). TK levels <0.148 mg/l independently predicted 30-day mortality with odds ratio value of 4.752 (95% confidence interval (CI), 1.166-19.367) and 30-day overall survival with hazard ratio value of 3.698 (95% CI, 1.026-13.333). TK levels significantly discriminated 30-day mortality with area under curve of 0.822 (95% CI, 0.738-0.887). CONCLUSIONS: Serum TK can represent a potential predictor of clinical outcome in TBI patients.

High Level of Serum Tissue Kallikrein Is Associated with Favorable Outcome in Acute Ischemic Stroke Patients.

BACKGROUND/OBJECTIVES: We sought to assess the association between a serum tissue kallikrein (TK) level and a 90-day outcome in acute ischemic stroke (AIS) patients who received acute reperfusion therapy. METHODS: Consecutive AIS patients within 6 hours after stroke onset between December 2015 and August 2017 were prospectively recruited. Blood samples were collected before acute reperfusion therapy for serum TK measurement. Outcome was modified Rankin scale (mRS) score at 90 days after stroke onset. Binary logistic regression was performed to analyze the association between the baseline TK level and the clinical outcome. RESULTS: Between December 2015 and August 2017, 75 patients (age range from 33 to 91 years, 72.0% male) were recruited in this study. Higher baseline TK was independently associated with a favorable functional outcome (mRS 0-2) (odds ratio 1.01, 95% confidence interval (CI) 1.00-1.02, p = 0.047) and low mortality rate (odds ratio 0.98, 95% CI 0.96-1.00, p = 0.049) at 90 days. Increased TK level was associated with 90 d mRS (0-2) with area under the curve of 0.719 (95% CI 0.596-0.842; p = 0.002). CONCLUSIONS: Serum TK can be a promising predictor of clinical outcome in AIS patients who received acute reperfusion therapy.

Comparing Pathways of Bradykinin Formation in Whole Blood From Healthy Volunteers and Patients With Hereditary Angioedema Due to C1 Inhibitor Deficiency.

Multiple pathways have been proposed to generate bradykinin (BK)-related peptides from blood. We applied various forms of activation to fresh blood obtained from 10 healthy subjects or 10 patients with hereditary angioedema (HAE-1 or -2 only) to investigate kinin formation. An enzyme immunoassay for BK was applied to extracts of citrated blood incubated at 37°C under gentle agitation for 0-2 h in the presence of activators and/or inhibitory agents. Biologically active kinins in extracts were corroborated by c-Fos accumulation in HEK 293a cells that express either recombinant human B2 or B1 receptors (B2R, B1R). Biological evidence of HAE diagnostic and blood cell activation was also obtained. The angiotensin converting enzyme inhibitor enalaprilat, without any effect per se, increased immunoreactive BK (iBK) concentration under active stimulation of blood. Tissue kallikrein (KLK-1) and Kontact-APTT, a particulate material that activates the contact system, rapidly (5 min) and intensely (>100 ng/mL) induced similar iBK generation in the blood of control or HAE subjects. Tissue plasminogen activator (tPA) slowly (≥1 h) induced iBK generation in control blood, but more rapidly and intensely so in that of HAE patients. Effects of biotechnological inhibitors indicate that tPA recruits factor XIIa (FXIIa) and plasma kallikrein to generate iBK. KLK-1, independent of the contact system, is the only stimulus leading to an inconsistent B1R stimulation. Stimulating neutrophils or platelets did not generate iBK. In the HAE patients observed during remission, iBK formation capability coupled to B2R stimulation appears largely intact. However, a selective hypersensitivity to tPA in the blood of HAE patients suggests a role of plasmin-activated FXIIa in the development of attacks. Proposed pathways of kinin formation dependent on blood cell activation were not corroborated.

Classification analyses for prostate cancer, benign prostate hyperplasia and healthy subjects by SERS-based immunoassay of multiple tumour markers.

Prostate cancer (PCa) is a leading cause of cancer-related death among males globally. To date, prostate-specific antigen (PSA), as a typical tumour marker, has been widely used in the early diagnosis of PCa. However, in practical clinical tests, high serum levels of PSA show a high probability for false-positive results, leading to misdiagnoses. In this study, we developed a new classification system for PCa, benign prostate hyperplasia (BPH) and healthy subjects by using a surface-enhanced Raman scattering (SERS)-based immunoassay of multiple tumour markers along with a support vector machine (SVM) algorithm. Silver nanoparticles (AgNPs) as immune probes and SiC@Ag@Ag-NPs SERS as immune substrates were constructed into a sandwich structure to serve as an ultrasensitive SERS-based immunoassay platform of tumour markers. With this assay, the limits of detection for PSA, prostate-specific membrane antigen (PSMA) and human kallikrein 2 (hK2) were as low as 0.46 fg mL-1, 1.05 fg mL-1 and 0.67 fg mL-1, respectively. Furthermore, the serum levels of PSA, PSMA and hK2 in clinical samples were successfully detected using the SERS-based immunoassay platform, and correct classifications of PCa, BPH and healthy subjects were feasible with help of the linear SVM algorithm. These results demonstrate the potential for improving the diagnostic accuracy of PCa. Overall, the linear SVM classification model with multiple tumour markers exhibited good classifications of PCa, BPH and healthy subjects, with a PCa diagnostic accuracy of 70% that was significantly superior to that of the linear SVM classification model based only on the serum level of PSA (50%). Therefore, combining the SERS-based immunoassay with pattern recognition technology can allow for comprehensive analyses of the serum levels of multiple tumour markers to effectively improve the diagnostic accuracy of cancer with potential applications in point-of-care testing.

The effect of digital rectal exam on the 4Kscore for aggressive prostate cancer.

BACKGROUND: The 4Kscore is a new commercially available blood-based diagnostic test which predicts risk for aggressive, clinically significant prostate cancer on prostate biopsy. The 4Kscore is currently restricted to patients who have not had a digital rectal exam (DRE) in the previous 96 h, owing to prior mixed data suggesting that prostate specific antigen (PSA) isoforms may increase by a statistically significant-if not necessarily clinically significant-amount shortly after DRE. Our primary objective was to determine if 4Kscore test results are affected by a preceding DRE. METHODS: Participants at a Prostate Cancer Awareness Week screening event sponsored by the Prostate Conditions Education Council filled out clinical history questionnaires and had blood samples for 4Kscore testing drawn prior to DRE, then 15-45 min following DRE. Patients with prior cancer diagnosis, 5-alpha reductase inhibitor medication use, or lower urinary tract procedures in the prior 6 months were excluded, resulting in a population of 162 participants for analysis. Values were then compared to determine if there was a significant difference in 4Kscore following DRE. RESULTS: A statistically significant increase was seen in levels of 3 kallikreins measured (total PSA, free PSA, and intact PSA; median <0.03 ng/mL for all). This resulted in a small but statistically significant decrease in post-DRE 4Kscore (median absolute score decrease 0.43%). Using a 4Kscore cutoff of 7.5% resulted in reclassification of 10 patients (6.2%), nine of whom were "downgraded" from above the cutoff to below. CONCLUSIONS: If the blood draw for the 4 K score is performed after a screening DRE, there is a statistically significant difference in the 4 K score results, but in the vast majority of cases it would not affect clinical decision making.

Value of Intact Prostate Specific Antigen and Human Kallikrein 2 in the 4 Kallikrein Predictive Model: An Individual Patient Data Meta-Analysis.

PURPOSE: The 4 kallikrein panel, commercially available as the 4Kscore®, is a statistical model that has been shown to accurately predict Gleason Grade Group 2 or greater (high grade) cancer on biopsy and the long-term risk of distant prostate cancer metastases. The panel includes 2 novel markers, namely intact prostate specific antigen and hK2. It has been questioned whether these 2 additional markers add discrimination to the clinical predictors of patient age, digital rectal examination and prior biopsy, and the established molecular markers total and free prostate specific antigen. MATERIALS AND METHODS: We performed an individual patient data meta-analysis of published studies in which the 4 kallikrein panel was measured in men undergoing prostate biopsy. We assess the improvement in discrimination associated with including intact prostate specific antigen and hK2 along with total and free prostate specific antigen in the statistical model. RESULTS: Included in analysis were 14,510 men from a total of 10 studies. The fixed effects meta-analytical estimate of the discrimination of the model without intact prostate specific antigen and hK2 was 0.742 (95% CI 0.727-0.756) compared to 0.813 (95% CI 0.801-0.825) for the full kallikrein model. The 95% CIs did not overlap and the difference in discrimination was highly statistically significant (0.069, 95% CI 0.057-0.080, p <0.0001). Intact prostate specific antigen (increase in discrimination 0.059, 95% CI 0.050-0.069) and hK2 (increase in discrimination 0.024, 95% CI 0.020-0.029, each p <0.0001) added independently to the model. CONCLUSIONS: The clinical value of the panel could not be replicated using data readily available to urologists without measuring intact prostate specific antigen and hK2.

Human tissue Kallikreins: Blood levels and response to radiotherapy in intermediate risk prostate cancer.

OBJECTIVES: Kallikreins are serine proteases over expressed in many malignancies. In this study, we measure changes in serum kallikrein (KLKs) levels during intensity-modulated radiotherapy (IMRT) in prostate cancer patients, and find potential correlations between serum kallikrein level and normal tissues toxicity during radiation. METHODS: Forty-nine patients with prostate cancer were recruited as follows: group 1, definitive standard fractionation IMRT (78Gy in 39 fractions, n=15); group 2, definitive hypofractionated IMRT (60Gy in 20 fractions, n=15); and group 3, IMRT postprostatectomy (66Gy in 33 fractions, n=19). Patients treated with definitive radiation therapy were intermediate risk. Blood samples were collected at baseline and quarterly during IMRT and at each follow-up visit. Acute toxicity was graded weekly during radiotherapy using CTC-AE v4.0 criteria. Multiplexed immunoassays were used to quantify total, free, and intact Prostate Specific Antigen (PSA), as well as Kallikreins 2, 4, 6, and 11. RESULTS: The serum kallikreins, PSA (total, free and intact), KLK2, 6, and 11 change significantly after definitive radiotherapy. KLK2 and intact PSA decrease as fast as two weeks after initiation of radiation, while the first significant decrease in total and free PSA is noted only at the completion of radiation. KLK6 and KLK11 surge temporarily during radiation therapy and decrease below baseline levels at 8weeks and 12months, respectively after completion of radiation. KLK4 levels did not change with radiation. There was no correlation between GU or GI toxicities and serum kallikreins. CONCLUSIONS: PSA, KLK2, 6, and 11, change significantly after definitive prostate radiotherapy, though KLK2 and PSA decrease by the end of the radiation course while KLK6 and KLK11 decrease significantly starting at 2 and 12months, respectively, after radiation. There was no correlation between GU or GI toxicities and serum kallikreins.

Association of serum levels of AngII, KLK1, and ACE/KLK1 polymorphisms with acute myocardial infarction induced by coronary artery stenosis.

INTRODUCTION: The study aims to confirm the association of acute myocardial infarction (AMI) with serum angiotensin II (AngII), kallikrein1 (KLK1), and ACE/KLK1 polymorphisms. MATERIALS AND METHODS: Serum AngII/KLK1 levels and ACE and KLK1 genotypes were determined in 208 patients with AMI and 216 normal controls. Binary logistic regression was used for data analysis. RESULTS: The differences in serum AngII levels were statistically significant between the groups. After adjusting for potential confounding factors, high serum levels of AngII and KLK1 significantly increased the risk of AMI. The individuals with ACE DD and KLK1 GG genotypes significantly increased the risk of AMI compared with those harboring the ACE II and KLK1 AA genotypes (OR = 8.77, 95% CI = 1.74-44.16). CONCLUSIONS: (1) Increasing the serum levels of AngII increased the risk of AMI. (2) The risk of AMI increased significantly when the serum levels of AngII and KLK1 simultaneously increased. (3) Individuals with the combined genotypes of ACE DD and KLK1 GG showed significantly increased risk of AMI compared with those with the combined genotypes of ACE II and KLK1 AA.

Prostate cancer screening in men aged 50-69 years (STHLM3): a prospective population-based diagnostic study.

BACKGROUND: The prostate-specific antigen (PSA) test is used to screen for prostate cancer but has a high false-positive rate that translates into unnecessary prostate biopsies and overdiagnosis of low-risk prostate cancers. We aimed to develop and validate a model to identify high-risk prostate cancer (with a Gleason score of at least 7) with better test characteristics than that provided by PSA screening alone. METHODS: The Stockholm 3 (STHLM3) study is a prospective, population-based, paired, screen-positive, diagnostic study of men without prostate cancer aged 50-69 years randomly invited by date of birth from the Swedish Population Register kept by the Swedish Tax Agency. Men with prostate cancer at enrolment were excluded from the study. The predefined STHLM3 model (a combination of plasma protein biomarkers [PSA, free PSA, intact PSA, hK2, MSMB, MIC1], genetic polymorphisms [232 SNPs], and clinical variables [age, family, history, previous prostate biopsy, prostate exam]), and PSA concentration were both tested in all participants enrolled. The primary aim was to increase the specificity compared with PSA without decreasing the sensitivity to diagnose high-risk prostate cancer. The primary outcomes were number of detected high-risk cancers (sensitivity) and the number of performed prostate biopsies (specificity). The STHLM3 training cohort was used to train the STHLM3 model, which was prospectively tested in the STHLM3 validation cohort. Logistic regression was used to test for associations between biomarkers and clinical variables and prostate cancer with a Gleason score of at least 7. This study is registered with ISCRTN.com, number ISRCTN84445406. FINDINGS: The STHLM3 model performed significantly better than PSA alone for detection of cancers with a Gleason score of at least 7 (p<0·0001), the area under the curve was 0·56 (95% CI 0·55-0·60) with PSA alone and 0·74 (95% CI 0·72-0·75) with the STHLM3 model. All variables used in the STHLM3 model were significantly associated with prostate cancers with a Gleason score of at least 7 (p<0·05) in a multiple logistic regression model. At the same level of sensitivity as the PSA test using a cutoff of ≥3 ng/mL to diagnose high risk prostate cancer, use of the STHLM3 model could reduce the number of biopsies by 32% (95% CI 24-39) and could avoid 44% (35-54) of benign biopsies. INTERPRETATION: The STHLM3 model could reduce unnecessary biopsies without compromising the ability to diagnose prostate cancer with a Gleason score of at least 7, and could be a step towards personalised risk-based prostate cancer diagnostic programmes. FUNDING: Stockholm County Council (Stockholms Läns Landsting).

Human Kallikrein-2, Prostate Specific Antigen and Free- Prostate Specific Antigen in Combination to Discriminate Prostate Cancer from Benign Diseases in Syrian Patients.

BACKGROUND: The high incidence of prostate cancer as the most common malignancy in males in many countries raises the question of developing reliable detection tests. The prostate specific antigen (PSA) test is the most widely used for screening for prostate cancer; however, its low specificity elevates the number of unnecessarily biopsies. Serum human kallikrein-2 (hK2) is considered as a promising marker, and especially its ratio to fPSA, for predicting the presence of malignancy to select the best choice referring to biopsy or surveillance. In this study, we investigated the role of hK2 and its combinations with other markers to discriminate prostate cancer from benign diseases in Syrian patients. MATERIALS AND METHODS: In this prospective oriented cross-sectional cohort study, serum samples were collected from patients referred to many Hospitals in Damascus, Syria, between May 2011 and March 2012, and diagnosed with biopsy proven benign prostate hyperplasia (BPH) or prostate cancer (PCa). Serum was analyzed for hK2, PSA and fPSA, and the ratios of fPSA/PSA and hK2/fPSA were calculated. RESULTS: We found that mean hK2/fPSA ratios were significantly higher (P=0.01) in prostate cancer patients than in the BPH or control groups. Also the ratio hk2/fPSA gave the largest area under the curve (AUC:0.96) which was significantly larger than for fPSA/PSA (AUC:0.41) indicative of higher specificity. CONCLUSIONS: Our results demonstrate that the ratio of hK2/fPSA might be superior to the use of fPSA/PSA alone. The hK2 could be shown to enhance the early detection of prostate cancer; especially the ratio hK2/fPSA improves specificity and hence may reduce the number of negative biopsies.

Tissue Kallikrein Activity, Detected by a Novel Method, May Be a Predictor of Recurrent Stroke: A Case-Control Study.

AIM: Tissue kallikrein (TK) protein content in plasma has been shown to be negatively associated with both incident and recurrent strokes. The aims of this study were to develop a novel method for detecting TK activity and to investigate its association with event-free survival over 5 years in Chinese first-ever stroke patients. METHODS: We designed a case-control study with 321 stroke patients (174: ischemic stroke, 147: hemorrhagic stroke) and 323 healthy local controls. TK activity was measured by a novel assay utilizing the immunological characteristics of TK and the catalysis of benzoyl arginine ethyl ester hydrochloride (BAEE). RESULTS: TK protein levels above 0.200 mg/L in plasma were not associated with urinary TK activity or the risk of stroke recurrence. TK activity was significantly lower in stroke patients compared with controls (1.583 ± 0.673 Eu/mL versus 1.934 ± 0.284 Eu/mL, P < 0.001). After adjusting for traditional risk factors, TK activity was negatively associated, in a dose-response manner, with the risk of overall stroke recurrence and positively associated with event-free survival during a 5-year follow-up (relative risk (RR), 0.69; 95% CI, 0.57-0.84; P < 0.001). CONCLUSIONS: Our findings suggest that urinary TK activity may be a stronger predictor of stroke recurrence than plasma TK levels.

Predicting high-grade cancer at ten-core prostate biopsy using four kallikrein markers measured in blood in the ProtecT study.

BACKGROUND: Many men with elevated prostate-specific antigen (PSA) levels in serum do not have aggressive prostate cancer and undergo unnecessary biopsy. Retrospective studies using cryopreserved serum suggest that four kallikrein markers can predict biopsy outcome. METHODS: Free, intact and total PSA, and kallikrein-related peptidase 2 were measured in cryopreserved blood from 6129 men with elevated PSA (≥3.0ng/mL) participating in the prospective, randomized trial Prostate Testing for Cancer and Treatment. Marker levels from 4765 men providing anticoagulated plasma were incorporated into statistical models to predict any-grade and high-grade (Gleason score ≥7) prostate cancer at 10-core biopsy. The models were corrected for optimism by 10-fold cross validation and independently validated using markers measured in serum from 1364 men. All statistical tests were two-sided. RESULTS: The four kallikreins enhanced prostate cancer detection compared with PSA and age alone. Area under the curve (AUC) for the four kallikreins was 0.719 (95% confidence interval [CI] = 0.704 to 0.734) vs 0.634 (95% CI = 0.617 to 0.651, P < .001) for PSA and age alone for any-grade cancer, and 0.820 (95% CI = 0.802 to 0.838) vs 0.738 (95% CI = 0.716 to 0.761) for high-grade cancer. Using a 6% risk of high-grade cancer as an illustrative cutoff, for 1000 biopsied men with PSA levels of 3.0ng/mL or higher, the model would reduce the need for biopsy in 428 men, detect 119 high-grade cancers, and delay diagnosis of 14 of 133 high-grade cancers. Models exhibited excellent discrimination on independent validation among men with only serum samples available for analysis. CONCLUSIONS: A statistical model based on kallikrein markers was validated in a large prospective study and reduces unnecessary biopsies while delaying diagnosis of high-grade cancers in few men.

Comparison Between the Four-kallikrein Panel and Prostate Health Index for Predicting Prostate Cancer.

BACKGROUND: The four-kallikrein panel and the Prostate Health Index (PHI) have been shown to improve prediction of prostate cancer (PCa) compared with prostate-specific antigen (PSA). No comparison of the four-kallikrein panel and PHI has been presented. OBJECTIVE: To compare the four-kallikrein panel and PHI for predicting PCa in an independent cohort. DESIGN, SETTING, AND PARTICIPANTS: Participants were from a population-based cohort of PSA-tested men in Stockholm County. We included 531 men with PSA levels between 3 and 15 ng/ml undergoing first-time prostate biopsy during 2010-2012. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Models were fitted to case status. We computed calibration curves, the area under the receiver-operating characteristics curve (AUC), decision curves, and percentage of saved biopsies. RESULTS AND LIMITATIONS: The four-kallikrein panel showed AUCs of 69.0 when predicting any-grade PCa and 71.8 when predicting high-grade cancer (Gleason score ≥7). Similar values were found for PHI: 70.4 and 71.1, respectively. Both models had higher AUCs than a base model with PSA value and age (p<0.0001 for both); differences between models were not significant. Sensitivity analyses including men with any PSA level or a previous biopsy did not materially affect our findings. Using 10% predicted risk of high-grade PCa by the four-kallikrein panel or PHI of 39 as cut-off for biopsy saved 29% of performed biopsies at a cost of delayed diagnosis for 10% of the men with high-grade cancers. Both models showed limited net benefit in decision analysis. The main study limitation was lack of digital rectal examination data and biopsy decision being based on PSA information. CONCLUSIONS: The four-kallikrein panel and PHI similarly improved discrimination when predicting PCa and high-grade PCa. Both are simple blood tests that can reduce the number of unnecessary biopsies compared with screening with total PSA, representing an important new option to reduce harm. PATIENT SUMMARY: Prostate-specific antigen screening is controversial due to limitations of the test. We found that two blood tests, the Prostate Health Index and the four-kallikrein panel, performed similarly and could both aid in decision making among Swedish men undergoing a prostate biopsy.