Diurnal Rhythm of Cardiac Troponin: Consequences for the Diagnosis of Acute Myocardial Infarction.

BACKGROUND: Interpretation of serial high-sensitivity cardiac troponin (hs-cTn) measurements for the diagnosis of acute myocardial infarction (AMI) assumes random fluctuation of hs-cTn around an individual's homeostatic set point. The aim of this study was to challenge this diagnostic concept. METHODS: Study 1 examined the presence of a diurnal hs-cTn rhythm by hourly blood sampling, day and night, in 24 individuals without a recent history of AMI. Study 2 assessed morning vs evening diagnostic accuracy of hs-cTnT and hs-cTnI in a prospective multicenter diagnostic study of 2782 unselected patients, presenting to the emergency department with acute chest pain. RESULTS: In study 1, hs-cTnT, but not hs-cTnI, exhibited a diurnal rhythm, characterized by gradually decreasing concentrations throughout daytime, rising concentrations during nighttime, to peak concentrations in the morning (mean 16.2 ng/L at 8:30 AM and 12.1 ng/L at 7:30 PM). In study 2, the hs-cTnT rhythm was confirmed by higher hs-cTnT concentrations in early-morning presenters compared to evening presenters with an adjudicated diagnosis of noncardiac disease. The diagnostic accuracy [area under the receiver-operation characteristics curve (AUC)] of hs-cTnT at presentation, 1 h, and for the combination of absolute changes with presenting concentration, were very high and comparable among patients presenting early morning as compared to evening (all AUC >0.93). hs-cTnI exhibited no diurnal rhythm with no differences in AUC among early-morning and evening presenters. CONCLUSIONS: Rhythmic diurnal variation of hs-cTnT is a general phenomenon that is not seen with hs-cTnI. While the diurnal hs-cTnT rhythm does not seem to affect the diagnostic accuracy of hs-cTnT for AMI, it should be considered when using hs-cTnT for screening purposes. CLINICAL TRIAL REGISTRATION: 1. Circadian Variation of Cardiac Troponin, NCT02091427, www.clinicaltrials.gov/ct2/show/NCT02091427. 2. Advantageous Predictors of Acute Coronary Syndrome Evaluation (APACE) Study, NCT00470587, www.clinicaltrials.gov/ct2/show/NCT00470587.

Cardiac Troponin T and I Release After a 30-km Run.

Prolonged endurance-type exercise is associated with elevated cardiac troponin (cTn) levels in asymptomatic recreational athletes. It is unclear whether exercise-induced cTn release mirrors a physiological or pathological underlying process. The aim of this study was to provide a direct comparison of the release kinetics of high-sensitivity cTnI (hs-cTnI) and T (hs-cTnT) after endurance-type exercise. In addition, the effect of remote ischemic preconditioning (RIPC), a cardioprotective strategy that limits ischemia-reperfusion injury, was investigated in a randomized controlled crossover manner. Twenty-five healthy volunteers completed an outdoor 30-km running trial preceded by RIPC (4 × 5 min 220 mm Hg unilateral occlusion) or control intervention. hs-cTnT, hs-cTnI, and sensitive cTnI (s-cTnI) concentrations were examined before, immediately after, 2 and 5 hours after the trial. The completion of a 30-km run resulted in a significant increase in circulating cTn (time: all p <0.001), with maximum hs-cTnT, hs-cTnI, and s-cTnI levels of 47 ± 27, 69 ± 62, and 82 ± 64 ng/L (mean ± SD), respectively. Maximum hs-cTnT concentrations were measured in 60% of the participants at 2 hours after exercise, compared with maximum hs-cTnI and s-cTnI concentrations at 5 hours in 84% and 80% of the participants. Application of an RIPC stimulus did not reduce exercise-induced cTn release (time × trial: all p >0.5). In conclusion, in contrast to acute myocardial infarction, maximum hs-cTnT levels after exercise precede maximum hs-cTnI levels. Distinct release kinetics of hs-cTnT and hs-cTnI and the absence of an effect of RIPC favors the concept that exercise-induced cTn release may be mechanistically distinct from cTn release in acute myocardial infarction.

Clinical Interpretation of Elevated Concentrations of Cardiac Troponin T, but Not Troponin I, in Nursing Home Residents.

OBJECTIVE: Cardiac troponins T (cTnT) and I (cTnI) are the preferred biomarkers to detect myocardial damage. The present study explores the value of measuring cardiac troponins (cTn) in nursing home residents, by investigating its relation to heart failure and 1-year mortality using 1 cTnT and 2 cTnI assays that are widely used in clinical practice. DESIGN: All participants underwent extensive clinical examinations and echocardiographic assessment for the diagnosis of heart failure. cTn was measured using high-sensitive (hs)- cTnT (Roche), hs-cTnI (Abbott), and sensitive cTnI (Beckman) assays. The glomerular filtration rate was estimated (eGFR) using serum creatinine and cystatin C concentrations. Data on all-cause mortality were collected at 1-year follow-up. PARTICIPANTS AND SETTING: Participants were 495 long-term nursing home residents, older than 65 years, of 5 Dutch nursing home organizations. RESULTS: Median (IQR) concentrations were 20.6 (17.8-30.6), 6.8 (4.1-12.5), and 4.0 (2.0-8.0) ng/L for hs-cTnT, hs-cTnI, and cTnI, respectively. In total, 79% had elevated hs-cTnT concentrations, whereas only 9% and 5% of hs-cTnI and cTnI concentrations were elevated. Most important and independent determinants for higher hs-cTnT and hs-cTnI concentrations were heart failure and renal dysfunction. Whereas both heart failure (odds ratio [OR] 3.4) and eGFR lower than 60 mL/min/1.73 m(2) (OR 3.6) were equal contributors to higher hs-cTnT concentrations (all P < .001), hs-cTnI and cTnI were less associated with renal dysfunction (OR of, respectively, 1.9 and 2.1; P < .01) in comparison with heart failure (OR 4.3 and 4.7, respectively, P < .001). Furthermore, residents with higher hs-cTnT or hs-cTnI concentrations (fourth quartile) had respectively 4 versus 2 times more risk of 1-year mortality compared with lower concentrations. CONCLUSION: Regardless of their cardiac health, hs-cTnT but not hs-cTnI concentrations were elevated in almost all aged nursing home residents, questioning the use of the current diagnostic cutoff in elderly with high comorbidity. Nonetheless, measuring cardiac troponins, especially hs-cTnT, had a promising role in assessing future risk of mortality.

A multicenter evaluation of dysthyroxinemia in a defined patient cohort.

BACKGROUND: In the region Limburg (The Netherlands) almost all of the five participating laboratories use a different immunoassay platform to determine thyroid stimulating hormone (TSH) and free thryoxine (FT4). With the frequent transfer of patients within the region, harmonization of test result interpretation is necessary. In this study, we investigated dysthyroxinemia classification between participating laboratories and developed procedures for improvement. METHODS: Two ring surveys with an interval of 2 years were performed. Four patient groups (n=100) with different dysthyroxinemia classification were based on biochemical results of the Autodelphia analyzer. Samples were tested in five participating laboratories. In each group the percentage of patients classified with dysthyroxinemia was calculated and differences were analyzed by the Fisher's exact test. RESULTS: After the first survey, the percentage of patients with hyperthyroxinemia was more than 20% lower in three laboratories compared to the other two. Bhattacharya analysis revealed that the upper reference limit of FT4 was 20%-30% too high in two laboratories. Adjustments of reference ranges appeared to be effective in the second survey. The third laboratory reported significantly lower percentages of patients with hyperthyroxinemia in the second survey. New FT4 reference ranges were determined for this laboratory, resulting in adequate classification of hyperthyroxinemia. CONCLUSIONS: This study illustrates the potential of a multicenter evaluation of dysthyroxinemia in a biochemical-defined patient cohort. In particular, classification of hyperthyroxinemia differed between laboratories. Adjustments of reference ranges resulted in better agreement of dysthyroxinemia classification. Even using internal and external quality assurance programs, application of multicenter ring surveys is advised to prevent inadequate reference ranges.

Increased osteopontin plasma levels in multiple sclerosis patients correlate with bone-specific markers.

The pro-inflammatory cytokine osteopontin has been found to be highly expressed in multiple sclerosis lesions and plasma levels are increased during relapses in relapse-onset multiple sclerosis patients. The objective was to determine the relationship between osteopontin plasma and cerebrospinal fluid levels in relation to the immunoglobulin G index. In addition, osteopontin plasma levels were compared with osteopontin mRNA levels in peripheral blood mononuclear cells and bone-specific markers to analyse whether osteopontin may be peripherally produced. Osteopontin and bone-specific markers were determined in paired plasma-cerebrospinal fluid samples and serum samples of relapse-onset multiple sclerosis patients (n = 36), respectively. Osteopontin mRNA levels were determined by quantitative polymerase chain reaction analysis. Compared to healthy controls (n = 20), plasma osteopontin levels were significantly increased in relapsing-remitting multiple sclerosis patients and correlated (r = 0.43, p = 0.013) with the immunoglobulin G index. In contrast, cerebrospinal fluid osteopontin levels correlated neither with plasma osteopontin in paired samples nor with the immunoglobulin G index. Since osteopontin mRNA levels in peripheral blood mononuclear cells of relapsing-remitting multiple sclerosis patients did not correlate with osteopontin plasma levels, peripheral blood mononuclear cells might not be the major source for the increased osteopontin plasma levels. Osteopontin plasma levels correlated (r = 0.42, p = 0.035) with the bone-specific degradation product C-telopeptide of type-1 collagen. In addition, another immunomodulatory molecule involved in bone metabolism, 25-OH vitamin D, correlated negatively (r = -0.359, p = 0.048) with the immunoglobulin G index. This study suggests that bone-related molecules like osteopontin and vitamin D with important immunomodulatory functions are related to the immunoglobulin G index in relapsing-remitting multiple sclerosis patients.

Why determine only the total prostate-specific antigen, if the free-to-total ratio contains the information?

BACKGROUND: Total prostate-specific antigen (tPSA) is the best available test for the detection of prostate cancer but it lacks specificity. The free-to-total ratio (F/T ratio) is used to increase specificity in the range of tPSA of 4-10 microg/L. MATERIALS AND METHODS: Four hundred and seven biopsy results and quantitative tPSA and F/T ratio data were combined. Using the histological determination, normal/hyperplasia versus malignant as a gold standard, receiver operating characteristic (ROC) curves as well as the areas under the curve (AUC) for tPSA and F/T ratio were determined. The differences between the two AUCs were considered for various tPSA ranges and specificities of F/T ratio and tPSA were calculated. RESULTS: In the total group, there was a gain of specificity of 11% (from 23% to 34%) when the sensitivity was 92% (using a cut-off >0.28 for the F/T ratio and a cut-off >4 microg/L for tPSA). When considering the group of patients for which the F/T ratio is currently used (4-10 microg/L), the gain of specificity was 27% (from 2% to 29%). This implicates that the number of unnecessary biopsies taken will be reduced by 27%. Moreover, the AUC of the F/T ratio was significantly higher at an even broader range of tPSA, i.e. up to 40 microg/L. CONCLUSIONS: This study demonstrates that the F/T ratio has better diagnostic performance than tPSA, not only in the grey zone of tPSA, but also outside the grey zone, i.e. up to 40 microg/L.

A guide to defining the competence required of a consultant in clinical chemistry and laboratory medicine.

A definition has been agreed for the most senior professional (consultant) in clinical chemistry and laboratory medicine. A model job description for a consultant has been determined, which is intended to act as a toolkit to assist employing authorities and professional bodies to define the role of individual consultant posts. A total of 86 competences for a consultant have been designated and expressed in the form of simple generic proficiency standards. These competences have been allocated to six broad areas: clinical [13]; scientific [15]; technical [12]; communication [12]; management and leadership [20]; professional autonomy and accountability [14]. The competences are intended to be illustrative rather than definitive and to enable the duties of any consultant post to be defined. Assessment of competence is likely to entail consideration of qualifications, registration status, continuing professional development and performance review. The project is intended as a guide to European societies of clinical chemistry and laboratory medicine. The guide should be capable of local interpretation to encourage a greater degree of commonality in the role of the consultant whilst protecting national identity. The guide should stimulate international understanding and collaboration and contribute to an overall improvement in the quality of practice.