Ibrahim A. Hashim

Association of Troponin T Detected With a Highly Sensitive Assay and Cardiac Structure and Mortality Risk in the General Population

CONTEXT Detectable levels of cardiac troponin T (cTnT) are strongly associated with structural heart disease and increased risk of death and adverse cardiovascular events; however, cTnT is rarely detectable in the general population using standard assays. OBJECTIVES To determine the prevalence and determinants of detectable cTnT in the population using a new highly sensitive assay and to assess whether cTnT levels measured with the new assay associate with pathological cardiac phenotypes and subsequent mortality. DESIGN, SETTING, AND PARTICIPANTS Cardiac troponin T levels were measured using both the standard and the highly sensitive assays in 3546 individuals aged 30 to 65 years enrolled between 2000 and 2002 in the Dallas Heart Study, a multiethnic, population-based cohort study. Mortality follow-up was complete through 2007. Participants were placed into 5 categories based on cTnT levels. MAIN OUTCOME MEASURES Magnetic resonance imaging measurements of cardiac structure and function and mortality through a median of 6.4 (interquartile range, 6.0-6.8) years of follow-up. RESULTS In Dallas County, the prevalence of detectable cTnT (≥0.003 ng/mL) was 25.0% (95% confidence interval [CI], 22.7%-27.4%) with the highly sensitive assay vs 0.7% (95% CI, 0.3%-1.1%) with the standard assay. Prevalence was 37.1% (95% CI, 33.3%-41.0%) in men vs 12.9% (95% CI, 10.6%-15.2%) in women and 14.0% (95% CI, 11.2%-16.9%) in participants younger than 40 years vs 57.6% (95% CI, 47.0%-68.2%) in those 60 years and older. Prevalence of left ventricular hypertrophy increased from 7.5% (95% CI, 6.4%-8.8%) in the lowest cTnT category (<0.003 ng/mL) to 48.1% (95% CI, 36.7%-59.6%) in the highest (≥0.014 ng/mL) (P < .001); prevalence of left ventricular systolic dysfunction and chronic kidney disease also increased across categories (P < .001 for each). During a median follow-up of 6.4 years, there were 151 total deaths, including 62 cardiovascular disease deaths. All-cause mortality increased from 1.9% (95% CI, 1.5%-2.6%) to 28.4% (95% CI, 21.0%-37.8%) across higher cTnT categories (P < .001). After adjustment for traditional risk factors, C-reactive protein level, chronic kidney disease, and N-terminal pro-brain-type natriuretic peptide level, cTnT category remained independently associated with all-cause mortality (adjusted hazard ratio, 2.8 [95% CI, 1.4-5.2] in the highest category). Adding cTnT categories to the fully adjusted mortality model modestly improved model fit (P = .02) and the integrated discrimination index (0.010 [95% CI, 0.002-0.018]; P = .01). CONCLUSION In this population-based cohort, cTnT detected with a highly sensitive assay was associated with structural heart disease and subsequent risk for all-cause mortality.

Age and Sex Dependent Upper Reference Limits for the High Sensitivity Cardiac Troponin T Assay

OBJECTIVES The study sought to determine the 99th percentile upper reference limit for the high-sensitivity cardiac troponin T assay (hs-cTnT) in 3 large independent cohorts. BACKGROUND The presently recommended 14 ng/l cut point for the diagnosis of myocardial infarction using the hs-cTnT assay was derived from small studies of presumably healthy individuals, with relatively little phenotypic characterization. METHODS Data were included from 3 well-characterized population-based studies: the Dallas Heart Study (DHS), the Atherosclerosis Risk in Communities (ARIC) Study, and the Cardiovascular Health Study (CHS). Within each cohort, reference subcohorts were defined excluding individuals with recent hospitalization, overt cardiovascular disease, and kidney disease (subcohort 1), and further excluding those with subclinical structural heart disease (subcohort 2). Data were analyzed stratified by age, sex, and race. RESULTS The 99th percentile values for the hs-cTnT assay in DHS, ARIC, and CHS were 18, 22, and 36 ng/l (subcohort 1) and 14, 21, and 28 ng/l (subcohort 2), respectively. These differences in 99th percentile values paralleled age differences across cohorts. Analyses within sex/age strata yielded similar results between cohorts. Within each cohort, 99th percentile values increased with age and were higher in men. More than 10% of men 65 to 74 years of age with no cardiovascular disease in our study had cardiac troponin T values above the current myocardial infarction threshold. CONCLUSIONS Use of a uniform 14 ng/l cutoff for the hs-cTnT assay may lead to over-diagnosis of myocardial infarction, particularly in men and the elderly. Clinical validation is needed of new age- and sex-specific cutoff values for this assay.

Blister fluid cytokines in cutaneous inflammatory bullous disorders

Cytokines are important regulators of immune and inflammatory reactions in the skin, and may contribute to inflammatory blister induction. We examined the profiles of interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-alpha) in fluid of spontaneous blisters in the immune-based inflammatory disorders bullous pemphigoid (8 patients), allergic contact dermatitis (5 patients) and toxic epidermal necrolysis (5 patients). These were compared with levels in 9 patients with burns, i.e. inflammatory blisters of non-immune aetiology, and 4 patients with blisters of physical origin. Very high levels of IL-6 were found in bullous pemphigoid and toxic epidermal necrolysis (p<0.001) compared with non-inflammatory and burn blisters. TNF-alpha levels were high in bullous pemphigoid and burns, but undetectable in non-inflammatory blisters. The pattern in bullous pemphigoid (very high IL-6, high TNF-alpha) differed substantially from toxic epidermal necrolysis (very high IL-6, low TNF-alpha), while burns and allergic contact dermatitis showed lesser elevation of both cytokines. Hence, differences in cytokine profiles were identified, although the relevance to underlying pathomechanisms is uncertain.

Cytokine changes in patients with heatstroke during pilgrimage to Makkah

Circulating levels and role of IL-6, IL-1ra, TNFsr-II and CRP in patients with heatstroke is not fully known. This study correlated levels of these mediators with outcome in 26 patients. In survivors (n=20), IL-6 concentration declined on cooling, whereas in non-survivors levels continued to increase at 6 h following admission before declining. Admission TNFsr-II concentrations in survivors were significantly lower than non-survivors and levels continued to rise in both groups. IL-1ra levels were markedly elevated in both groups. Changes in cytokine levels were not influenced by renal function. Elevated C-reactive protein levels were observed for both groups and remained so despite cooling, furthermore, there was no correlation with alanine aminotransferase levels. The study demonstrated the elevation of the above mediators and suggested a role in the pathogenesis of heatstroke. Markedly elevated levels or those that remained elevated despite cooling were associated with mortality.

Cerebrospinal Fluid Interleukin-6 and Its Diagnostic Value in the Investigation of Meningitis

We examined the measurement and the diagnostic value of cerebrospinal fluid interleukin-6 (CSF IL-6) in meningitis. The cytokine was measured by bioassay (B9 hybridoma cell line) and by immunoassay (in-house radioimmunoassay). We compared the diagnostic value of CSF IL-6 determination with that of other biochemical markers of meningitis. Although there was significant correlation between bioactive and immunoactive IL-6 (r = 0·724, P < 0·001), results were frequently different with biological/immunological ratios ranging from 0·2 to 24·3 (mean 4·6). Gel permeation chromatography suggested that the discrepancy in biological and immunological activities was not due to molecular heterogeneity, but may be explained by the presence of a synergistic factor. Interleukin-6 concentration was markedly elevated in CSF from most patients with bacterial meningitis compared to patients with viral meningitis and those without evidence of infection. However, low IL-6 levels by radioimmunoassay did not exclude bacterial meningitis (sensitivity 86%). CSF total protein and CSF glucose were significantly different between all three groups, but there was no significant difference in lactate concentration between virally infected and normal CSF, both of which had lower lactate concentrations than those in bacterial infection. CSF IL-6 measurement had greater sensitivity, specificity and predictive value than these other biochemical markers, and hence a rapid assay for IL-6 in CSF may contribute to the early diagnosis of bacterial infection.

Interleukin-6 (IL-6) production and cell growth of cultured human ameningiomas:- Interactions with interleukin-1β (IL-1β) and interleukin-4 (IL-4) in vitro

Abstract We examined the production of interleukin (IL)-6 by human meningioma cells in vitro, and the effects of IL-1β and IL-4 on IL-6 production and meningioma cell growth. The histological classification of the tumours studied included transitional, syncytial, fibroblastic and atypical. All 10 meningiomas studied produced IL-6 (range 0.22–7.6ng/ml/10 6 cells/24 h). Separate addition of IL-1β or IL-4 to cultures increased IL-6 production up to ten fold, and two to three fold, respectively. Growth studies with IL-6 indicated that this cytokine significantly increased terminal cell density at a concentration greater than 1 ng/ml in 60% of the meningioma cultures studied. IL-1β caused a significant decrease in the terminal cell density in 25% of the meningioma cultures studied whereas IL-4 had a tendency to significantly inhibit growth in 16.6% of the cultures. These data suggest that IL-6 production by meningiomas can be modified by other cytokines and secondly, that IL-6, IL-1β and IL-4 can modify growth in vitro and may act as autocrine factors in vivo. By further determining the cytokine profiles within meningiomas and their effects, a better understanding of meningioma growth characteristics may be obtained.

Clinical biochemistry of hyperthermia

Heatstroke is the most severe form of heat-related disorders that include mild heat intolerance, heat exhaustion and heat stress. The incidence of heat-related disorders is increasing due to several factors that include climate change, co-morbidities and drug usage. Patients with heatstroke present with a core body temperature above 40°C, multiorgan dysfunction and central nervous system disorder. The pathogenesis of heatstroke is not fully understood; however, heat-shock proteins, inflammatory cytokines and their modulators have been implicated. The clinical biochemistry laboratory plays an important role in the management of patients with heatstroke. Biochemical findings in patients with heatstroke include elevated urea, creatinine, cardiac and skeletal muscle enzymes, myoglobin and troponin. There is also biochemical evidence of metabolic acidosis, respiratory alkalosis, hepatic injury with elevated enzyme levels as well as abnormal hematological and coagulation indices. This review article aims at increasing awareness of the biochemical changes seen in patients with heatstroke and their possible role in prognosis and in elucidating the pathogenesis of heatstroke.

Use of a highly sensitive assay for cardiac troponin T and N-terminal pro-brain natriuretic peptide to diagnose acute rejection in pediatric cardiac transplant recipients.

BACKGROUND Biomarkers have been proposed to augment or replace endomyocardial biopsy (EMB) to diagnose acute transplant rejection (AR). A new, highly sensitive assay for troponin T detects levels of cardiac troponin T (cTnT) 10- to 100-fold lower than standard assays but has not been investigated in transplant patients. N-terminal pro-brain natriuretic peptide (NT-proBNP) has not been evaluated in pediatric transplant patients. The purpose of this pilot study was to evaluate the association of cTnT and NT-proBNP with AR in pediatric cardiac transplant patients. METHODS Plasma was obtained at the time of EMB from pediatric patients ≥ 1 year old. N-terminal pro-brain natriuretic peptide was measured in fresh plasma at the time of biopsy, and cTnT was measured from frozen, stored samples using the highly sensitive assay for troponin T. Biomarker data were correlated with EMB results. Cellular AR was defined as an International Society for Heart and Lung Transplantation biopsy score of grade ≥ 2R. RESULTS Fifty-three blood samples were obtained from 42 patients (mean age 11 years). Seven episodes of AR occurred in 5 patients. Biopsies with vs without AR were associated with higher cTnT (median [interquartile range {IQR}] 66 [45-139] vs 7 [2-13] pg/mL, P = .001) and NT-proBNP (median [IQR] 11,169 [280-23,317] vs 334 [160-650] pg/mL, P < .01). After successful treatment of AR in 5 patients, cTnT fell markedly (median [IQR] 53.5 [44.8-66.5] to 10.7 [1.5-16.4], P = .05). CONCLUSION In this pilot study, we found marked elevation of cTnT and NT-proBNP among children with AR. Moreover, reduction in cTnT levels after treatment paralleled improvement in EMB results. If these findings are confirmed in larger prospective studies, monitoring with these biomarkers may obviate surveillance EMB.

Contractile protein synthesis rates in vivo in the rat jejunum: modulating role of adrenalectomy and thyroidectomy on ethanol-induced changes

Abstract Acute ethanol toxicity has many deleterious effects on the gastrointestinal tract and, in particular, inhibits small intestinal protein synthesis. The mechanism(s) of the ethanol‐induced inhibition of protein synthesis are unknown. This study was designed to investigate the role of adrenal and thyroid hormones on the ethanol‐induced inhibition of whole jejunal protein synthesis in adrenalectomised and thyroidectomised male Wistar rats. Acute ethanol dosage significantly reduced protein synthesis in all subcellular protein fractions of the whole jejunum, in sham‐thyroidectomized, thyroidectomized, sham‐ardrenalectomized and adrenalectomized rats. Synthesis rates relative to RNA and DNA were also highly significantly reduced in all treatment groups in ethanol‐dosed rats. However in most protein fractions the inhibition of protein synthesis was greater in thyroidectomized compared to sham‐thyroidectomized rats, whereas the reverse was true in adrenalectomized rats. Neither adrenalectomy or thyroidectomy completely abolished ethanol‐induced inhibition in protein synthesis, suggesting that ethanol or its metabolites, e.g. acetaldehyde, acts directly on the tissue. However, the ethanol‐induced inhibition of protein synthesis was greater in thyroidectomized rats demonstrating that contractile and non‐contractile proteins synthesis in the jejunum is under control of complex regulatory processes.

Association of Troponin T, Detected With Highly Sensitive Assay, and Outcomes in Infective Endocarditis

Troponin levels have been correlated with adverse outcomes in multiple disease processes, including congestive heart failure, acute coronary syndromes, sepsis, and, in a few small series, infective endocarditis. We hypothesized that a novel measurement of troponin using a highly sensitive assay would correlate with adverse outcomes when prospectively studied in patients with infective endocarditis. At a single center in the International Collaboration on Endocarditis, 42 patients met the inclusion criteria and underwent testing for cardiac troponin T (cTnT) using both a standard and a highly sensitive precommercial assay. The cTnT levels were associated with the prespecified primary composite outcome of death, central nervous system event, and cardiac abscess. Secondary outcomes included the individual components of the composite outcome and the need for cardiac surgery. A receiver operating characteristic curve was derived and used to identify the optimal cutpoint for cTnT using the highly sensitive assay. cTnT was detectable with the highly sensitive assay in 39 (93%) of 42 patients with infective endocarditis and with the standard assay in 25 (56%) of 42 (p <0.05). Of the 42 patients, 15 experienced the composite outcome, 4 died, 9 had a central nervous system event, and 5 had a cardiac abscess. With the hs-cTnT assay, the median cTnT was greater in the patients who experienced the primary outcome (0.12 vs 0.02 ng/ml, p <0.05). According to the receiver operating characteristic curve analysis (area under the curve of 0.74), cTnT levels of ≥0.08 ng/ml produced optimal specificity (78%) for the primary outcome. The patients with a cTnT level of ≥0.08 ng/ml were more likely to experience the primary outcome (odds ratio 7.0, 95% confidence interval 1.7 to 28.6, p <0.01) and a central nervous system event (odds ratio 9.3, 95% confidence interval 1.3 to 24.1, p = 0.02). In conclusion, cTnT is detectable in 93% of patients with infective endocarditis using a novel highly sensitive assay, with higher levels correlating with poor clinical outcomes.