Øyvind Skadberg

European multicenter analytical evaluation of the Abbott ARCHITECT STAT high sensitive troponin I immunoassay.

Abstract Background: International recommendations highlight the superior value of cardiac troponins (cTns) for early diagnosis of myocardial infarction along with analytical requirements of improved precision and detectability. In this multicenter study, we investigated the analytical performance of a new high sensitive cardiac troponin I (hs-cTnI) assay and its 99th percentile upper reference limit (URL). Methods: Laboratories from nine European countries evaluated the ARCHITECT STAT high sensitive troponin I (hs-TnI) immunoassay on the ARCHITECT i2000SR/i1000SR immunoanalyzers. Imprecision, limit of blank (LoB), limit of detection (LoD), limit of quantitation (LoQ) linearity of dilution, interferences, sample type, method comparisons, and 99th percentile URLs were evaluated in this study. Results: Total imprecision of 3.3%–8.9%, 2.0%–3.5% and 1.5%–5.2% was determined for the low, medium and high controls, respectively. The lowest cTnI concentration corresponding to a total CV of 10% was 5.6 ng/L. Common interferences, sample dilution and carryover did not affect the hs-cTnI results. Slight, but statistically significant, differences with sample type were found. Concordance between the investigated hs-cTnI assay and contemporary cTnI assay at 99th percentile cut-off was found to be 95%. TnI was detectable in 75% and 57% of the apparently healthy population using the lower (1.1 ng/L) and upper (1.9 ng/L) limit of the LoD range provided by the ARCHITECT STAT hs-TnI package insert, respectively. The 99th percentile values were gender dependent. Conclusions: The new ARCHITECT STAT hs-TnI assay with improved analytical features meets the criteria of high sensitive Tn test and will be a valuable diagnostic tool.

Weekly and 90-Minute Biological Variations in Cardiac Troponin T and Cardiac Troponin I in Hemodialysis Patients and Healthy Controls

BACKGROUND Myocardial infarction (MI) is diagnosed by the finding of a single cardiac troponin value above the 99th percentile and a significant time-dependent change in cardiac troponin concentration. The aim of this study was to determine the 90-min and weekly biological variations, the reference change value (RCV), and the index of individuality (II) of high-sensitivity cardiac troponin T (hs-cTnT) (Roche Diagnostics) and hs-cTnI (Abbott Diagnostics) in patients receiving hemodialysis (HD) and in healthy individuals. METHOD Blood samples were collected from 19 HD patients (on an HD-free day) and 20 healthy individuals at 90-min intervals over a 6-h period (between 08:30 and 14:30) and before the midweek HD treatment for 10 weeks. The within-person variation (CVi), between-person variation, RCV, and II were calculated. RESULTS During the 6-h sampling period, the concentrations of hs-cTnT (both groups) and hs-cTnI (HD patients only) decreased on average by 0.8% to 1.7% per hour, respectively. These declining trends were included in the calculation of a 90-min asymmetric RCV: -8%/+5% in HD patients (hs-cTnT), -18%/+21% in HD patients (hs-cTnI), -27%/+29% in healthy individuals (hs-cTnT), and -39%/+64% in healthy individuals (hs-cTnI). The II was low in both groups for both assays. The weekly CVi values were approximately 8% (hs-cTnT) and 15% (hs-cTnI) in both groups. CONCLUSIONS When using a cardiac troponin change of 20%-50% to diagnose an MI, the false-positive rate is likely to be lower for the hs-cTnT assay than for the hs-cTnI assay. The low II suggests that use of a diagnostic cutoff value can be omitted.

Within-subject biological variation of glucose and HbA(1c) in healthy persons and in type 1 diabetes patients.

Abstract Background: Several articles describing within-subject biological variation of fasting glucose and HbA1c in healthy populations have been published, but information about biological variation of glucose and HbA1c in patients with type 1 diabetes is scarce. It is reasonable to assume that type 1 diabetics differ from their healthy counterparts in this matter. The aim of our study was to estimate the biological variation of glucose and HbA1c in healthy subjects and in patients with type 1 diabetes. Methods: Fifteen healthy individuals and 15 type 1 diabetes patients were included. Biological variations were calculated based on blood samples collected weekly for 10 consecutive weeks from the healthy and the eligible of the type 1 diabetes patients. Results: The within-subject variations of glucose were approximately 5% in healthy individuals and 30% in diabetes patients, and for HbA1c they were 1.2% in healthy individuals and 1.7% in diabetes patients. Conclusions: In conclusion, we found a high within-subject biological variation of glucose in diabetes patients as expected compared to healthy individuals (30% vs. 5%). The short-term (2 months) within-subject biological variation of HbA1c did not differ significantly between well regulated type 1 diabetes patients and healthy individuals (1.7% vs. 1.2%).

Defining normality in a European multinational cohort: Critical factors influencing the 99th percentile upper reference limit for high sensitivity cardiac troponin I

OBJECTIVE To establish and critically evaluate the 99th percentile upper reference limit (URL) for high-sensitivity cardiac troponin I (hs-cTnI) in a large healthy European cohort using different selection criteria. METHODS 1368 presumably healthy individuals from 9 countries were evaluated with surrogate biomarkers for diabetes (glycated hemoglobin [HbA1c] < 48 mmol/mol), myocardial (B-type natriuretic peptide [BNP] < 35 pg/mL) and renal dysfunction (estimated glomerular filtration rate [eGFR] >60 mL/min/1.73 m(2)), and dyslipidemia to refine the healthy cohort. The 99th percentile URLs were independently determined by the non-parametric and robust methods. RESULTS The use of biomarker selection criteria resulted in a decrease of the 99th percentile URL for hs-cTnI from 23.7 to 14.1 ng/L and from 11.2 to 7.1 ng/L, when using the non-parametric percentile and robust methods, respectively; a further reduction after exclusion of individuals with dyslipidemia was noted. Male gender, BNP, HbA1c and smoking status were independently associated with hs-cTnI concentration in the presumably healthy population, while the impact of age, present in the univariate analysis, decreased after adjustments for gender and surrogate biomarkers. The BNP-based inclusion criterion had the most pronounced effect on the 99th percentile URL, excluding 21% of the study participants and decreasing its value to 11.0 (7.1) ng/L according to the non-parametric (robust) method. Gender, but not age-specific, differences at 99th percentile URL have been identified. CONCLUSION The selection of a reference population has a critical impact on the 99th percentile value for hs-cTnI. A uniform protocol for the selection of the healthy reference population is needed.

Soluble Klotho and intact fibroblast growth factor 23 in long-term kidney transplant patients.

BACKGROUND Controversies exist whether disturbances in mineral and bone disorder (MBD) normalise or persist after kidney transplantation. We assessed markers of MBD in patients with well-functioning kidney transplants to minimise confounding by reduced transplant function. METHODS In this cross-sectional study, 40 patients aged ≥18 years who received a first kidney transplant more than 10 years ago were included. A well-functioning transplant was defined as an estimated glomerular filtration rate (eGFR) ≥45 ml/min per 1.73 m(2). RESULTS Median time since transplantation was 18.3 years (inter quartile range (IQR) 12.2-26.2). Albumin-corrected serum calcium levels were above upper limit of normal in 15% of the transplanted patients, and serum phosphate levels below lower limit of normal in 31%. The median levels of intact parathyroid hormone (iPTH) and intact fibroblast growth factor 23 (iFGF23) were significantly higher than that in a group of healthy volunteers (11.3 pmol/l (IQR: 8.7-16.2) vs 4.4 pmol/l (IQR: 3.8-5.9), P<0.001 and 75.0 pg/ml (IQR: 53.3-108.0) vs 51.3 pg/ml (IQR: 36.3-67.6), P=0.004 respectively). There was a non-significant reduction in soluble Klotho (sKlotho) levels (605 pg/ml (IQR: 506-784) vs 692 pg/ml (IQR: 618-866)). When compared with a control group matched for eGFR, levels of iPTH were significantly higher (P<0.001), iFGF23 had a non-significant trend towards higher levels and sKlotho towards lower levels. CONCLUSIONS In long-term kidney transplant patients with well-functioning kidney transplants, we found inappropriately high levels of iPTH and iFGF23 consistent with a state of persistent hyperparathyroidism. We speculate that the primary defect, FGF23 resistance, has evolved in the parathyroid gland before transplantation, and persists due to long half-life of the parathyroid cells.

B-type natriuretic peptide is related to histological skeletal muscle abnormalities in patients with chronic heart failure

This study examined the potential association between skeletal muscle histological findings and circulating levels of N-terminal Atrial natriuretic peptide (NT-proANP) and N-terminal B-type natriuretic peptide (NT-proBNP) at rest and during exercise in patients with moderate chronic heart failure. We report a significant correlation between muscle fibre roundness, defined as ratio of fibre perimeter squared to fibre area, and plasma levels of N-BNP. This finding suggests that the degree of intrafibrillar edema is related to the secretion of NT-proBNP.

Measurement of glycated albumin in serum and plasma by LC-MS/MS

Abstract Background Diagnosis of diabetes and monitoring of long-term blood sugar are preferably done by measurement of glycated hemoglobin (HbA1c). Diabetic patients with end stage renal disease (ESRD) may have short-lived red blood cells due to hemodialysis (HD), and thus higher turnover of hemoglobin. The level of glycated hemoglobin (HbA1c) may be lower than expected for these patients, even at increased blood glucose, possibly making glycated albumin (GA) measurement a better alternative. Methods The percentage of GA was measured by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Fast and efficient trypsin digestion of proteins in diluted serum or plasma resulted in a high number of proteotypic peptides from albumin, including KQTALVELVK which was detected both glycated and non-glycated by multiple reaction monitoring (MRM). The percentage of GA was estimated by neat peak area response of glycated peptide divided by the sum of glycated and non-glycated peptide. Results Acceptable method reproducibility (6% CV), repeatability (2–6% CV), limit of quantification (0.75% GA), linearity (R2 = 0.999) and recovery (79 ± 9%) was achieved without using calibration or isotope-labeled internal standard. GA was strongly correlated with HbA1c (r = 0.84) for patients without ESRD. The average ratio of GA/HbA1c was significantly higher (p = 0.0021) for ESRD patients (1.84 ± 0.38, n = 62) compared to other patients (1.67 ± 0.28, n = 225). Conclusion GA measurement by detecting glycation in KQTALVELVK with LC-MS/MS seems to be a useful supplement to HbA1c for detecting increased blood glucose in diabetic patients with ESRD.

Haplotype Analysis of Norwegian and Swedish Patients with Acute Intermittent Porphyria (AIP): Extreme Haplotype Heterogeneity for the Mutation R116W

Acute intermittent porphyria (AIP), the most common of the acute porphyrias, is caused by mutations in the gene encoding hydroxymethylbilane synthase (HMBS) also called porphobilinogen deaminase (PBGD). The mutation spectrum in the HMBS gene is characterized by a majority of family specific mutations. Among the exceptions are R116W and W198X, with high prevalence in both the Dutch and Swedish populations. These two mutations were also detected in unrelated Norwegian patients. Thus, Norwegian and Swedish patients were haplotyped using closely linked flanking microsatellites and intragenic single nucleotide polymorphisms (SNPs) to see if the high frequency of these two mutations is due to a founder effect. Twelve intragenic SNPs were determined by a method based on fluorescent restriction enzyme fingerprinting single-strand conformation polymorphism (F-REF-SSCP). W198X occurred exclusively on one haplotype in both Norwegian and Swedish patients, showing that it has originated from a common gene source. In contrast, R116W was found on three different haplotypes in three Norwegian families, and in five Swedish families on four or five haplotypes. This extreme haplotype heterogeneity indicates that R116W is a recurrent mutation, maybe explained by the high mutability of CpG dinucleotides. This can also explain why it is the only AIP mutation reported to occur in seven different populations (Norway, Sweden, Finland, Netherlands, France, Spain and South Africa).

Natriuretic peptide levels taken following unplanned admission to a cardiology department predict the duration of hospitalization.

Natriuretic peptide (NP) levels are routinely employed as useful diagnostic and prognostic tools in the evaluation of patients with heart failure (HF). As hospitalization is the major consumer of healthcare resources, the prognostic power of admission NPs with regard to the duration of hospitalization deserves further investigation.

High physical fitness is associated with reduction in basal- and exercise-induced inflammation

C‐reactive protein (CRP) increases after strenuous exercise. It has been a concern that prolonged strenuous exercise may be harmful and induce a deleterious inflammatory response. The purpose of this study was to (a) assess and quantify the magnitude of CRP response following an endurance cycling competition in healthy middle‐aged recreational cyclists. (b) Identify important determinants of this response. (c) Identify the relationship between CRP, myocardial damage (cardiac Troponin I (cTnI)), and myocardial strain (B‐type natriuretic peptide [BNP]). (d) Identify the relationship between CRP and clinical events, defined as utilization of healthcare services or self‐reported unusual discomfort. Race time was used as a measure of physical fitness. A total of 97 individuals (43±10 years of age, 74 [76%] males) were assessed prior to and 0, 3, and 24 hours following the 91‐km mountain bike race “Nordsjørittet” (Sandnes, Norway, June 2013). There was a highly significant increase in CRP from baseline to 24 hours (0.9 (0.5‐1.8) mg/L vs. 11.6 (6.0‐17.5) mg/L (median[IQR]), P<.001), with no correlation of CRP to cTnI and BNP at any time‐point. CRP was strongly correlated to race time at baseline (r=.38, P<.001) and at 24 hours following the race (r=.43, P<.001), In multivariate models, race time was an independent predictor of CRP both at baseline and at 24 hours (P<.01). There was no relationship between CRP levels and clinical events. In conclusion, high physical fitness was associated with reduction in both basal‐ and exercise‐induced CRP. No adverse relationship was found between high intensity physical exercise, CRP levels, and outcomes.