Superior early diagnostic performance of a sensitive cardiac troponin assay as compared to a standard troponin test in the diagnosis of acute myocardial infarction

BACKGROUND

New generation cardiac troponin assays have sufficient precision to detect and quantify plasma troponin concentrations below the lower threshold of detection of the currently employed troponin tests. However, diagnostic performance of the newer generation assays in daily clinical practice is not well established.

AIM

To evaluate the diagnostic performance of a sensitive assay as compared to a standard assay in a single reading at admission in the diagnosis of acute myocardial infarction (AMI) in patients presenting to the Emergency Department with chest pain.

METHODS

The study comprised 187 consecutive patients admitted to the Institute of Cardiology in Warsaw in June and July 2010 with chest pain in whom the attending physician ordered troponin assay to rule AMI in or out. In all of these patients, in addition to the standard Dimension Flex Troponin I (Siemens Healthcare Diagnostics, Inc.) the sensitive Architect Stat Troponin I (Abbott Diagnostics) test was assayed. The triage of patients as well as all diagnostic and treatment decisions were left to the discretion of the attending physician who was blinded to the sensitive troponin test readings. The final diagnosis was adjudicated by a team of two cardiologists on the basis of all the available medical records except for sensitive troponin test results.

RESULTS

Mean age of the study cohort (n = 187) was 64.3 ± 13.9 years and 119 (63.6%) were males. The final diagnosis of AMI was adjudicated in 84 (44.9%) patients (mean age 67.5 ± 12.9 years; 119 [63.6%] males). Receiver operating characteristic (ROC) analysis showed greater area under the curve (AUC) for the sensitive cardiac troponin assay compared to the standard assay (AUC = 0.916, 95% CI = 0.866-0.951 vs AUC = 0.863, 95% CI = 0.806-0.909, respectively; p = 0.02) in a single reading at admission. Sensitive assay was characterised by higher sensitivity (87%), specificity (88%), positive (86%) and negative (89%) predictive values in the detection of AMI compared to the standard troponin test (82%, 81%, 78%, and 85% respectively).

CONCLUSIONS

The newer generation sensitive cardiac troponin assay presented superior diagnostic accuracy in the diagnosis of AMI compared to the standard troponin test in a single reading at admission with improved sensitivity and specificity. The sensitive troponin assay has the potential to improve early detection and/or exclusion of AMI.

The influence of low-power helium-neon laser irradiation on function of selected peripheral blood cells

The effects of low-level laser light irradiation are debatable and the mechanisms of its action are still unclear. This study was conducted to test the effects of low-level laser irradiation on human blood cells: erythrocytes, granulocytes, and lymphocytes. Whole blood obtained by phlebotomy was irradiated at 632.8 nm by using energy fluences 0.6 J/cm2. An analysis of blood gases revealed an increase in PO2 and SaO2 (P<0.001) in irradiated blood. No shifts in PCO2 and pH were recorded. Spontaneous synthesis of DNA in T and B blood lymphocytes decreased significantly after laser irradiation (P<0.02 and P<0.04, respectively). Phytohemagglutinin (PHA)-induced proliferation of T cells and SAC proliferation of B cells, expressed as a stimulation index, were statistically higher in the samples of irradiated than in non-irradiated blood (P<0.01). Chemiluminescence of fMLP-stimulated granulocytes from irradiated blood increased in comparison with non-irradiated samples (P<0.001). No changes of spontaneous and stimulated chemiluminescence kinetics in irradiated samples were observed. These results reveal the influence of photodynamic reactions on the ability of blood to transport oxygen and on immunomodulatory effects on leukocytes.

Kinetics of calcium ion concentration accompanying signal transduction in neutrophils from children with increased susceptibility to infections

Increased susceptibility to infections can be a consequence of altered function of immune cells including neutrophils. The goal of the study was to evaluate the process of neutrophil activation via Ca(2+)-mediated signal. The study was performed on isolated peripheral blood neutrophils obtained from 41 children with recurrent infections (21 girls, 20 boys) 3-10 years old with more than five episodes of respiratory tract infection (RI) per year and from a control group of 30 healthy children age and sex matched, free from allergic, immune and hematological disorders. Neutrophils were activated by bacterial peptide fMLP, opsonized zymosan (OZ), and phorbol myristat acetate (PMA). The kinetics of the intracellular Ca(2+) concentration i[Ca(2+) ] was assessed by flow cytometry (Coulter Epics XL) with the use of Fluo3 and Fura Red fluorescent dyes. Data were collected in histograms displaying Fluo3 fluorescence vs. time and Fura Red fluorescence vs. time and the mean channels of fluorescence intensity were used for calculations. fMLP and OZ-induced Ca(2+) mobilization lasted shorter in the RI group (P<0.05). The peak influx of free Ca(2+) and i[Ca(2+) ] in the resting state after stimulation with fMLP were lower in the patients (P<0.05). In the RI group stimulation with OZ was delayed compared with that in the control group (P<0.01). In response to PMA, i[Ca(2+) ] decreased faster. The kinetic slopes of i[Ca(2+) ] in both groups examined differed statistically at all points measured. A decrease in i[Ca(2+) ] after PMA stimulation was greater (P<0.01) and lasted longer in the RI group. We conclude that increased sensitivity to infections in RI children may be related to the disturbance in neutrophil activation that is mediated by changes in i[Ca(2+) ] with the subsequent production of free oxygen radicals. Such a disturbance may be inheritable or secondary to infection and antibiotic therapy.

[The activity of granulocytes in children with recurrent infections of respiratory tract]

Acute upper respiratory tract infection (URTI) is a common disease in young children. URTI contributes to approximately 20% of mortality in children younger than 5 years of age. Infections of the upper respiratory tract are the most common cause of viral morbidity in children. They represent the most frequent problem in general pediatric practice and are responsible for more than one third of school absences. On the other hand respiratory tract infections through MALT system play a positive role in maturation and development of immune system. Many different immunologic disturbances can occur during the development of respiratory infections. Disorders of granulocyte functions are the principal cause of inflammation in the upper respiratory tract. Chemiluminescence of granulocytes is a renowned method for the estimation their overall activity as measured by the production of reactive oxygen species. The goal of the study was to evaluate chemiluminescent activity of granulocytes from 41 children with recurrent infections of the respiratory tract compared to 30 healthy children. Chemiluminescent response to all the examined stimuli in children with recurrent infections was significantly lower compared to control. In the examined group of 41 children depressed response to at least 1 stimulus was detected in 32 (78%) cases. The use of both fMLP and opsonised zymosan allowed to detect defect of granulocyte function in 93,75% cases. This defect may be related to delayed maturation of the immune system in certain children or may be induced by intensive therapy with antibiotics.

[Familial occurrence of granulocyte disorders in two children with recurrent otitis media]

Releasing of oxygen reactive species in activated granulocytes play an important role in the intracellular killing of bacteria. The respiratory burst is accompanied by chemiluminescence (chl). In vitro, granulocyte chl can be stimulated by nFLMP (bacterial peptide) or opsonised zymosan (OZ) after their binding to chemotactic surface receptors or FcR and CR, respectively. Chl can be induced also by non receptor way by PMA. We have found that blood granulocytes taken from children with recurrent upper respiratory tract infections demonstrated significantly decreased ability to oxidative metabolism after stimulation by n-FMLP. Inability of granulocytes to respond to only one of three above mentioned stimulators can suggests deficit of this enzyme isoform which is necessary for intracellular signal transduction. THE AIM of this study was to assess the activity of peripheral blood granulocytes in two children from two families, suffering from recurrent otitis media.

MATERIALS AND METHODS

Study was performed in the 12 month old boy and 13 month old sick girl and in the children's parents. Chemiluminescence was measured in three blood samples, before and after n-FMLP, OZ and PMA stimulation. The light emission was measured in scintillation counter in presence of luminol. The study was performed after 2-3 weeks after treatment of otitis media.

RESULTS

Both children had reduced response with FMLP and PMA and additionally, the girl had decreased response after OZ. Both boy's parents had decreased response only with n-FMLP. The diseased girl's father demonstrated a lack of response after all three stimulators.

CONCLUSION

1. The study of chemiluminescence stimulated with the three known stimulators increased the chance of recognising disturbances in granulocyte function. 2. Recognising wrong function child's granulocytes should be an indication for parents' study.