Marja P. van Dieijen-Visser

Reference Population and Marathon Runner Sera Assessed by Highly Sensitive Cardiac Troponin T and Commercial Cardiac Troponin T and I Assays

BACKGROUND Endurance exercise can increase cardiac troponin (cTn) concentrations as high as those seen in cases of minor myocardial infarction. The inability of most cTn assays to reliably quantify cTn at very low concentrations complicates a thorough data analysis, and the clinical implications of such increases remain unclear. The application of recently developed highly sensitive cTn immunoassays may help resolve these problems. METHODS We evaluated the precommercial highly sensitive cardiac troponin T (hs-cTnT) assay from Roche Diagnostics and the Architect cardiac troponin I (cTnI-Architect) assay from Abbott Diagnostics by testing samples from a reference population of 546 individuals and a cohort of 85 marathon runners. We also measured the samples with the current commercial cTnT assay for comparison. RESULTS Although the hs-cTnT and cTnI-Architect assays were capable of measuring cTn concentrations at low concentrations (<0.01 microg/L), only the hs-cTnT assay demonstrated a CV of <10% at the 99th percentile of the reference population and a near-gaussian distribution of the measurements. After a marathon, 86% of the runners had cTnT concentrations greater than the 99th percentile with the hs-cTnT assay, whereas only 45% of the runners showed increased concentrations with the current cTnT assay. cTn concentrations remained significantly increased the day after the marathon. A multiple regression analysis demonstrated marathon experience and age to be significant predictors of postmarathon cTn concentrations (P < 0.05). CONCLUSIONS The hs-cTnT assay was the only assay tested with a performance capability sufficient to detect cTn concentrations in healthy individuals. The number of runners with increased cTn concentrations after a marathon depends highly on an assays limit of detection (LOD). The assay with the lowest LOD, the hs-cTnT assay, showed that almost all runners had increased cTn concentrations. The clinical implications of these findings require further investigation.

Impaired Renal Clearance Explains Elevated Troponin T Fragments in Hemodialysis Patients

Background—Patients with severe renal dysfunction often have unexplained elevated serum concentrations of cardiac troponin T (cTnT). We investigated whether in vivo fragmentation of cTnT could explain these increases. Methods and Results—cTnT, creatine kinase isoenzyme MB, and myoglobin serum concentrations were measured in all 63 dialysis patients of our in-hospital dialysis department. A highly sensitive immunoprecipitation assay, followed by electrophoresis and Western blotting, was used to extract and concentrate cTnT and its possible fragments from serum of these 63 hemodialysis patients. Although creatine kinase isoenzyme MB values excluded recent ischemic myocardial events in 55 of the 63 cases, cTnT fragments ranging in size from 8 to 25 kDa were present in the serum samples of all dialysis patients. Conclusions—cTnT is fragmented into molecules small enough to be cleared by the kidneys of healthy subjects. Impaired renal function causes accumulation of these cTnT fragments and is very likely the cause of the unexplained elevations of serum cTnT found in patients with severe renal failure.

Serum C-Reactive Protein Level Is Associated With Abdominal Aortic Aneurysm Size and May Be Produced by Aneurysmal Tissue

Background—Abdominal aortic aneurysms (AAA) are characterized by extensive transmural inflammation and C-reactive protein (CRP) has emerged as an independent risk factor for the development of cardiovascular disease. Therefore, we evaluated a possible association between serum CRP and aneurysm dimension in patients with asymptomatic AAA. Furthermore, the possibility of CRP production by aneurysmal tissue has been examined. Methods and Results—Serum CRP was determined highly sensitive (hs CRP) and aneurysmal size was measured in 39 patients with AAA. The presence of CRP mRNA was assessed in the aneurysmal tissue of 16 patients. Mean (SD) hs CRP was 3.23 (2.96) mg/L. After log-transformation, hs CRP correlated significantly with aneurysmal size (r =0.477, P =0.002). When the patients were divided into 3 equally sized groups according to hs CRP level, aortic diameter increased from lowest to upper hs CRP-tertile (49 mm, 61 mm, and 67 mm, respectively;P <0.05 for 3rd versus 1st tertile). This association persisted after correction for risk factors. CRP mRNA was found in 25% of aneurysmal aortic tissues. Conclusions—This is the first report showing that serum hs CRP is associated with aneurysmal size and that—in at least some patients—CRP may be produced by aneurysmal tissue. These data underscore the inflammatory nature of AAA formation, suggesting that serum hs CRP may serve as a marker of AAA disease and that CRP produced in vascular tissue might contribute to aneurysm formation.

Renal Clearance of B-Type Natriuretic Peptide and Amino Terminal Pro-B-Type Natriuretic Peptide A Mechanistic Study in Hypertensive Subjects

OBJECTIVES This study sought to compare the renal clearance mechanisms of B-type natriuretic peptide (BNP) and amino terminal pro-B-type natriuretic peptide (NT-proBNP). BACKGROUND The small molecular weight proteins (SMWPs) BNP and NT-proBNP both inversely correlate with glomerular filtration rate (GFR). Whether this association is causal or confounding is unknown and has been the basis of widespread speculation. METHODS We combined measurements of BNP and NT-proBNP concentrations in the renal arteries and veins of 165 subjects undergoing renal arteriography with invasive renal plasma flow (RPF) measurements and echocardiography. Fractional extraction (FE) of BNP and NT-proBNP was computed. RESULTS The BNP and NT-proBNP concentrations correlated similarly to GFR (r = -0.35 and r = -0.30, respectively; p < 0.001 for both) but the NT-proBNP/BNP serum ratio was negatively associated with GFR (r = -0.21, p = 0.008). Median FE(BNP) was 0.21 (interquartile range [IQR] 0.16 to 0.22) for left and 0.22 (IQR 0.17 to 0.29) for right kidneys. Median FE(NT-proBNP) was 0.16 (IQR 0.09 to 20) for left and 0.18 (IQR 0.12 to 0.22) for right kidneys. The FE(BNP) correlated with GFR (left: r = 0.26, p = 0.008; right: r = 0.21, p = 0.03) as did FE(NT-proBNP) (left: r = 0.25, p = 0.005; right: r = 0.20, p = 0.02). Although FE(BNP) and FE(NT-proBNP) correlated strongly with each other (left: r = 0.66; right: r = 0.60; p < 0.001 for both), left and right FE(NT-proBNP/BNP) ratios were not influenced by GFR (r = 0.10, p = 0.30 and r = 0.08, p = 0.43, respectively). Multivariate analyses confirmed that FE was not independently associated with BNP or NT-proBNP concentrations. CONCLUSIONS Contrary to widespread belief (but in line with the renal physiology of SMWP), BNP and NT-proBNP are equally dependent on renal function for their clearance.

Potential usefulness of inflammatory markers to monitor respiratory functional impairment in sarcoidosis

BACKGROUND Sarcoidosis is a multiorgan inflammatory granulomatous disorder of unknown origin for which adequate markers to monitor disease severity are lacking. The aim of this study was to evaluate the potential clinical usefulness of serologic markers of inflammation [high-sensitivity C-reactive protein (hs-CRP) and serum amyloid A (SAA)], T-cell activation [soluble interleukin-2 receptor (sIL2R)], and granuloma formation [angiotensin-converting enzyme (ACE)] for monitoring of sarcoidosis. METHODS Of the 185 sarcoidosis patients who visited the Sarcoidosis Management Center between 1999 and 2002, we selected 144 nonsmoking patients: 73 untreated (group I) and 71 treated (group II). Subgroups of the untreated patients [group Ia (nonchronic group with time since diagnosis < or = 2 years) and group Ib (chronic group with time since diagnosis >2 years)] were evaluated separately. ROC curves and logistic regression analyses were used to compare the diagnostic accuracy of different markers to assess disease severity. Pulmonary disease severity was defined by lung function test results. RESULTS In untreated subgroup Ia and the total untreated group (group I), sIL2R had the largest areas under the curves (AUCs; 0.891 and 0.799, respectively) and the highest sensitivity (82% and 64%), specificity (94% and 88%), and positive (82% and 70%) and negative (94% and 88%) predictive values among the evaluated markers in both untreated groups. Nevertheless, the confidence intervals for sIL2R AUC, sensitivity, and specificity were broad and partly overlapped those of ACE, hs-CRP, and SAA. In the treated group (group II), all four markers appeared to have comparable AUCs, ranging from 0.645 for SAA to 0.711 for sIL2R. CONCLUSION sIL2R appears to be useful for monitoring respiratory disease severity in sarcoidosis. We recommend sIL2R measurement in the follow-up of patients with sarcoidosis.

The Extent of Coronary Atherosclerosis Is Associated With Increasing Circulating Levels of High Sensitive Cardiac Troponin T

Objective—This study explored the relationship between coronary atherosclerotic plaque burden and quantifiable circulating levels of troponin measured with a recently introduced high sensitive cardiac troponin T (hs-cTnT) assay. Methods and Results—Cardiac patients suspected of having coronary artery disease (CAD) but without acute coronary syndrome were studied. Cardiac troponin T levels were assessed using the fifth-generation hs-cTnT assay. All patients (n=615) underwent cardiac computed tomographic angiography (CCTA). On the basis of CCTA, patients were classified as having no CAD or mild (<50% lesion), moderate (50% to 70% lesion), severe (>70% lesion), or multivessel CAD (multiple >70% lesions). As a comparison, high-sensitivity C-reactive protein levels were measured. Progressively increasing hs-cTnT levels were found in patients with mild (median, 4.5 ng/L), moderate (median, 5.5 ng/L), severe (median, 5.7 ng/L), and multivessel (median, 8.6 ng/L) CAD compared with patients without CAD (median, 3.7 ng/L) (all P<0.01). For high-sensitivity C-reactive protein and N-terminal pro-B-type natriuretic peptide, no such relationship was observed. In patients without CAD, 11% showed hs-cTnT levels in the highest quartile, compared with 62% in the multivessel disease group (P<0.05). Multivariance analysis identified hs-cTnT as an independent risk factor for the presence of CAD. Conclusion—In patients without acute coronary syndrome, even mild CAD is associated with quantifiable circulating levels of hs-cTnT.

Inflammation, overhydration and cardiac biomarkers in haemodialysis patients: a longitudinal study

BACKGROUND Inflammation, overhydration and elevated cardiac biomarkers are related to outcome in haemodialysis (HD) patients. Here, we explored the relationship between the body composition (BC), inflammation and cardiac biomarker concentrations in HD patients longitudinally. METHODS A total of 44 HD patients were followed for 6 months. BC was assessed by multifrequency bioimpedance (BIA). Serum concentrations of cardiac troponin T (cTnT), high-sensitive C-reactive protein (hsCRP), brain natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP) were assessed at 2 monthly intervals. The longitudinal data analysis was conducted with a marginal model. RESULTS During the follow-up, the parameters describing the BC were highly predictive of both BNP and NT-proBNP and independent of gender, time, hsCRP and cTnT concentrations. The intracellular water (ICW)/body weight (BW) ratio (reflecting malnutrition) exerted a negative effect, whereas the extracellular water (ECW)/BW ratio (reflecting overhydration) had a positive effect on BNP and NT-proBNP concentrations. HsCRP and cTnT concentrations were significantly associated with each other. Furthermore, NT-proBNP concentrations were predictive of cTnT and hsCRP concentrations. CONCLUSIONS In the present study, we find a significant relation between BIA-derived BC parameters and natriuretic peptide concentrations. This relationship was independent of the cardiac history of the patient and suggests that the natriuretic peptide levels are to some degree modifiable by changing a patients fluid distribution. Moreover, cTnT, BNP, NT-proBNP and hsCRP were significantly related, showing a complex relation between overhydration, malnutrition, inflammation and cardiac biomarkers in dialysis patients.

Tacrolimus pharmacokinetics and pharmacogenetics: influence of adenosine triphosphate‐binding cassette B1 (ABCB1) and cytochrome (CYP) 3A polymorphisms

Tacrolimus, an immunosuppressant used after organ transplantation, has a narrow therapeutic range and its pharmacokinetic variability complicates its daily dose assessment. P‐glycoprotein (P‐gp), encoded by the adenosine triphosphate‐binding cassette B1 (ABCB1) and the cytochrome (CYP) 3A4 and 3A5 enzymes appears to play a role in the tacrolimus metabolism. In the present study, two different renal transplant recipient groups were used to examine the influence of ABCB1 and CYP3A polymorphisms on the daily tacrolimus dose and several pharmacokinetic parameters. In total 63 Caucasian renal transplant recipients divided into 26 early [median (range) of the days since transplantation – 16 (3–74)] and 37 late [median (range) of the days since transplantation – 1465 (453–4128)] post‐transplant recipients were genotyped for ABCB1 and CYP3A polymorphisms. The pharmacokinetic parameters of tacrolimus were determined for all renal transplant recipients and correlated with their corresponding genotypes. A significant difference in allele frequencies of the CYP3A4*1B (P = 0.028) and CYP3A5*1 (P = 0.022) alleles was observed between the early and late post‐transplant recipient groups. Significantly higher dose‐normalized trough levels (dnC0), dose‐normalized area under the curve (dnAUC0−12), and dose‐normalized maximum concentration (dnCmax) were observed for carriers of the CYP3A5*3 variant allele in both renal transplant patient groups. Except for the daily tacrolimus dose (P = 0.025) no significant differences were observed for carriers of the CYP3A4*1B variant allele. Neither the individual ABCB1 polymorphisms nor the ABCB1 haplotypes were associated with any pharmacokinetic parameter. We noticed that patients carrying a CYP3A5*1 allele require a twofold higher tacrolimus dose compared with homozygous carriers of the CYP3A5*3 variant allele to maintain the target dnAUC0−12. Therefore, genotyping for the CYP3A5*3 variant allele can contribute to a better and more individualized immunosuppressive therapy in transplant patients.

Haemodialysis patients longitudinally assessed by highly sensitive cardiac troponin T and commercial cardiac troponin T and cardiac troponin I assays

Background Elevated cardiac troponin (cTn) concentrations predict an increased mortality in patients suffering from end-stage renal disease (ESRD). This study compares the performance of a precommercial high-sensitive cTnT assay (hs-cTnT) with two contemporary cTn assays in detecting cTn elevations in ESRD patients during a six-month follow-up. Methods Thirty-two ESRD patients were followed for six months, during which cTn concentrations were assessed every two months. Baseline biomarker concentrations were compared with those in a simultaneously measured reference population of 501 healthy subjects. Results During follow-up 26 (81%), 32 (100%) and 9 (28%) of the patients showed elevated cTn concentrations according to the current cTnT, the hs-cTnT and the cTnI assays, respectively. The range of concentrations measured in each patient had a median (interquartile range) magnitude of 0.03 μg/L (0.02–0.06), 0.017 μg/L (0.011–0.029) and 0.011 μg/L (0–0.017) according to the aforementioned assays. Conclusion According to the hs-cTnT assay, all of the ESRD patients had elevated cTnT concentrations at least once during the follow-up. As elevated cTn concentrations are highly prognostic of adverse events, the use of serial measurements has thus identified additional patients at risk for such events. The fact that we find cTn concentrations to be higher in patients with a history of cardiac disease is in line with this. Additional studies in ESRD patients are needed to investigate the added diagnostic and prognostic value of the very low cTnT concentrations and variations detected only by the hs-cTnT assay.

Sarcoidosis: assessment of disease severity using HRCT

The value of high-resolution computed tomography (HRCT) in diagnosing and assessing inflammatory activity in sarcoidosis is well established. The aim of the present study was to address the intra- and inter-observer agreements of the HRCT score by Oberstein et al. [8], and to evaluate the relationship between HRCT findings and disease severity expressed in respiratory functional impairment in sarcoidosis. The clinical records of 80 known sarcoidosis patients visiting the outpatient clinic between January 2000 and August 2001, who underwent a HRCT as well as lung function tests (including exercise testing), were reviewed. Two readers scored the first 60 HRCT images twice. Weighted kappa and intra-class correlation coefficient were used to assess the reliability of the HRCT scoring system. Spearmans rank correlation coefficients and multiple regression analyses were performed to evaluate the relationship between HRCT findings (first reading, reader A) and respiratory functional impairment. Intra- and inter-reader reliability demonstrated good agreement. All HRCT subscores, except enlargement of lymph nodes, were correlated to the FEV1, FVC, DLco, Pao2max (all p<0.05) and A-aPo2 max (p<0.001). Furthermore, HRCT abnormalities, but not the chest radiographic stage, were strongly associated with functional parameters. Abnormal changes of lung parenchyma, established by HRCT features, were associated with respiratory functional impairment in sarcoidosis. Moreover, compared with the radiographic stages, HRCT findings appeared to be much more sensitive in depicting respiratory disability, especially abnormal gas exchange.