RESUMEN
Myocardial infarction is a rarely reported complication of amphetamine use. We report the case of a healthy 31-year-old man who presented to our emergency department with no clinical evidence of an acute coronary event after intravenous injection of amphetamines. However, he subsequently experienced a non-Q-wave anterior wall myocardial infarction associated with the use of amphetamines.
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Trastornos Relacionados con Anfetaminas/complicaciones , Infarto del Miocardio/inducido químicamente , Adulto , Electrocardiografía , Humanos , Masculino , Infarto del Miocardio/diagnósticoRESUMEN
BACKGROUND: Cardiac troponin I (cTnI) results vary 100-fold among assays. As a step toward standardization, we examined the performance of 10 candidate reference materials (cRMs) in dilution studies with 13 cTnI measurement systems. METHODS: Solutions of 10 cTnI cRMs, each characterized by NIST, were shipped to the manufacturers of 13 cTnI measurement systems. Manufacturers used their respective diluents to prepare each cRM in cTnI concentrations of 1, 10, 25, and 50 microg/L. For the purpose of ranking the cRMs, the deviation of each cTnI measurement from the expected response was assessed after normalization with the 10 microg/L cTnI solution. Normalized deviations were examined in five formats. Parameters from linear regression analysis of the measured cTnI vs expected values were also used to rank performance of the cRMs. RESULTS: The three cRMs demonstrating the best overall rankings were complexes of troponins C, I, and T. The matrices for these three cRMs values differed; one was reconstituted directly from the lyophilized form submitted by the supplier; one was submitted in liquid form, lyophilized at NIST, and subsequently reconstituted; and the third was evaluated in the liquid form received from the supplier. The cRM demonstrating the fourth best performance was a binary complex of troponins C and I supplied in lyophilized form and reconstituted before distribution. CONCLUSIONS: The cRMs demonstrating the best performance characteristics in 13 cTnI analytical systems will be included in subsequent activities of the cTnI Standardization Committee of the AACC.
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Miocardio/química , Troponina I/normas , Algoritmos , Estándares de Referencia , Análisis de RegresiónRESUMEN
We studied the effects of the protein phosphatase (PP) inhibitor cantharidin (Cant) on time parameters and force of contraction (FOC) in isometrically contracting electrically driven guinea pig papillary muscles. We correlated the mechanical parameters of contractility with phosphorylation of the inhibitory subunit of troponin (TnI-P) and with the site-specific phosphorylation of phospholamban (PLB) at serine-16 (PLB-Ser-16) and threonine-17 (PLB-Thr-17). Cant (after 30 min) started to increase FOC (112 +/- 4% of control, n = 10) and TnI-P and PLB-Thr-17 (120 +/- 5 and 128 +/- 7% of control) without any alteration of relaxation time. Cant (10 microM) started to increase PLB-Ser-16, but the relaxation was shortened at only 100 microM (from 140 +/- 9 to 116 +/- 12 ms, n = 9). Moreover, 100 microM Cant, 3 min after application, started to increase PLB-Thr-17, TnI-P, and FOC. Cant (100 microM) began to increase PLB-Ser-16 after 20 min. This was accompanied by shortening of relaxation time. Differences in protein kinase activation or different substrate specificities of PP may explain the difference in Cant-induced site-specific phosphorylation of PLB in isometrically contracting papillary muscles. Moreover, PLB-Thr-17 may be important for inotropy, whereas PLB-Ser-16 could be a major determinant of relaxation time.
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Contracción Miocárdica/fisiología , Miocardio/enzimología , Fosfoproteínas Fosfatasas/metabolismo , Animales , Anticuerpos/farmacología , Calcio/análisis , Proteínas de Unión al Calcio/metabolismo , Cantaridina/farmacología , Relación Dosis-Respuesta a Droga , Inhibidores Enzimáticos/farmacología , Femenino , Cobayas , Técnicas In Vitro , Masculino , Fibras Musculares Esqueléticas/enzimología , Miocardio/citología , Músculos Papilares/citología , Músculos Papilares/enzimología , Perfusión , Fosfoproteínas Fosfatasas/antagonistas & inhibidores , Fosfoproteínas Fosfatasas/inmunología , Fosforilación , Ratas , Troponina/metabolismoRESUMEN
Compared with isolated electrically driven neonatal ventricular preparations, the total time of contraction, the time to peak tension, and the time of relaxation were decreased to approximately 50% in adult ventricular preparations. The expression of sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) was increased to 133% at the protein level and to 154% at the mRNA level in adult vs. neonatal ventricular preparations, whereas phospholamban was unchanged at both the protein and mRNA levels. Moreover, Ca2+ uptake was increased to 180% in adult vs. neonatal ventricular preparations. Phospholamban phosphorylation was enhanced in adult vs. neonatal ventricular preparations. In adult ventricular preparations, phosphatase activity was reduced to 53% of neonatal preparations, the protein levels of the immunologically detectable catalytic subunits of protein phosphatase types 1 and 2A were reduced to 28 and 61% of neonatal preparations, respectively, and the mRNA levels of type 1alpha, 1beta, 1gamma, 2Aalpha, and 2Abeta phosphatase isoforms were decreased to 69, 68, 54, 67, and 63%, respectively. We conclude that in the adult rat heart, the shortened time parameters of contraction can be explained by an elevated expression of SERCA. In addition, an increased phosphorylation state of phospholamban due to reduced phosphatase activity may be involved.
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Proteínas de Unión al Calcio/metabolismo , Calcio/metabolismo , Contracción Miocárdica/fisiología , Retículo Sarcoplasmático/metabolismo , Actinas/metabolismo , Factores de Edad , Animales , Animales Recién Nacidos , ATPasas Transportadoras de Calcio/metabolismo , Calsecuestrina/metabolismo , Diástole , Monoéster Fosfórico Hidrolasas/metabolismo , Fosforilación , ARN Mensajero/aislamiento & purificación , Ratas , Ratas Sprague-Dawley , Sístole , Troponina/metabolismo , Función VentricularRESUMEN
BACKGROUND: In the failing human heart myofibrillar calcium sensitivity of tension development is greater and maximal myofibrillar ATPase activity is less than in the normal heart. Phosphorylation of the cardiac troponin I (cTnI)-specific NH2-terminus decreases myofilament sensitivity to calcium, while phosphorylation of other cTnI sites decreases maximal myofibrillar ATPase activity. METHODS AND RESULTS: We examined cTnI phosphorylation in left ventricular myocardium collected from failing hearts at the time of transplant (n=20) and normal hearts from trauma victims (n=24). The relative amounts of actin, tropomyosin, and TnI did not differ between failing and normal myocardium. Using Western blot analysis with a monoclonal antibody (MAb) that recognizes the striated muscle TnI isoforms, we confirmed that the adult human heart expresses only cTnI. A cTnI-specific MAb recognized two bands of cTnI, designated cTnI1 and cTnI2, while a MAb whose epitope is located in the cTnI-specific NH2-terminus recognized only cTnI1. Alkaline phosphatase decreased the relative amount of cTnl1, while protein kinase A and protein kinase C increased cTnI1. The percentage of cTnI made up of cTnI1, the phosphorylated form of TnI, is greater in the normal than the failing human heart (P<.00). CONCLUSIONS: This phosphorylation difference could underlie the reported greater myofibrillar calcium sensitivity of failing myocardium. The functional consequence of this difference may be an adaptive or maladaptive response to the lower and longer calcium concentration transient of the failing heart, eg, enhancing force development or producing ventricular diastolic dysfunction.
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Gasto Cardíaco Bajo/metabolismo , Miocardio/metabolismo , Troponina I/metabolismo , Actinas/metabolismo , Adulto , Fosfatasa Alcalina/farmacología , Proteínas Quinasas Dependientes de AMP Cíclico/farmacología , Feto/metabolismo , Ventrículos Cardíacos , Humanos , Isomerismo , Fosforilación , Proteína Quinasa C/farmacología , Valores de Referencia , Tropomiosina/metabolismoRESUMEN
BACKGROUND: Throughout the 1980s, the number of laboratory tests performed in the United States grew at an annual rate of over 10%, and laboratory costs accounted for approximately 10% of overall health care expenditures. Recently, the influence of capitation, emphasis on cost-effectiveness, and changing roles among specialists and primary care physicians have begun to affect the growth of laboratory testing. We examined the impact of managed care on the economics of the clinical chemistry laboratory at Vanderbilt University Medical Center, Nashville, Tenn, to define the relative position of the clinical laboratory in the managed care environment of an academic medical center. METHODS: The following data were prospectively collected between fiscal years 1984/1985 and 1995/1996: number of inpatients and outpatients, average length of stay, number of laboratory tests, total laboratory revenue, direct costs (consisting of salary and consumable costs), and number of full-time-equivalent (FTE) personnel. Using these data, we derived the following parameters: revenue and direct cost per patient, and revenue and productivity per FTE. RESULTS: Between 1984/1985 and 1995/1996 the number of inpatients and outpatients increased 33% and 155%, respectively. Laboratory utilization, expressed as tests per patient, increased from 17 to 22 for inpatients between 1984/1985 and 1991/1992, and then sharply declined to 14.5 tests by 1995/1996, a 34% decrease compared with the 1991/1992 level. Laboratory utilization for outpatients increased from 0.23 in 1984/1985 to 0.45 tests in 1991/1992, decreased to 0.38 in 1993/1994, but then rose again to 0.43 in 1995/1996. Total revenue more than doubled between 1984/1985 and 1991/1992, mostly owing to increased inpatient revenue. Since 1992/1993, inpatient revenue has steadily declined, leading to a decrease in total revenue, which was partially offset by a continuous increase in outpatient revenue. In 1995/1996, outpatient revenue accounted for 32.1% of total revenue, compared with 7.7% in 1984/1985. Direct test cost per patient increased approximately 20% between 1984/1985 and 1991/1992, followed by a decline below the 1984/1985 level. The number of FTEs increased in parallel to the rising test volume through 1991/1992 and subsequently was reduced in response to the decrease in test volume and productivity. In 1995/1996, a 22.7% reduction in staff was imposed despite an upward trend in test volume, resulting in a sharp increase in revenue and productivity per FTE. The staff reduction did not decrease direct laboratory costs, which have remained constant since 1992/1993. CONCLUSIONS: After three decades of continued growth, managed care has caused a sharp reversal in the upward trend in the number of laboratory tests, the number of tests per inpatient, test costs per patient, laboratory revenue, and productivity. A recent staff reduction significantly increased revenue and productivity per FTE, but showed no effect on direct laboratory costs.
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Centros Médicos Académicos/economía , Laboratorios de Hospital/economía , Programas Controlados de Atención en Salud , Costos y Análisis de Costo , Eficiencia , Pacientes Internos/estadística & datos numéricos , Laboratorios de Hospital/estadística & datos numéricos , Tiempo de Internación/estadística & datos numéricos , Pacientes Ambulatorios/estadística & datos numéricos , TennesseeRESUMEN
Cardiac troponin T (cTnT), measurement of which has been recommended for diagnosing myocardial infarction, was initially believed to be specific for the heart. However, recent publications have reported cTnT in sera of patients without cardiac disease; therefore, we investigated whether cTnT could be found in human skeletal muscle tissues. Using immunohistochemistry, Western blot, and quantitative cTnT ELISA, we assayed human heart (n = 3), normal human skeletal muscle (n = 6), and diseased skeletal muscle samples from patients with polymyositis (PM, n = 13) and Duchenne muscular dystrophy (DMD, n = 6). All heart specimens contained cTnT, but the expression of cTnT in normal skeletal muscle samples varied widely, ranging from no expression (quadriceps femoris) to expression by up to 20% of the muscle fibers (diaphragm). Immunohistochemistry detected cTnT in skeletal muscle of 8 of the PM patients and all of the DMD patients. Mean myofibrillar cTnT concentrations (mg/g myofibrillar protein) were: cardiac = 10.0, normal skeletal = 0.8, PM skeletal = 0.7, and DMD skeletal = 4.37, confirming the results of immunohistochemistry. Western blot analysis also confirmed the expression of cTnT in muscle from DMD patients. These findings provide evidence that cTnT is not 100% cardiac-specific but also is expressed in regenerating (PM and DMD) as well as in normal (nonregenerating) skeletal muscle.
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Músculo Esquelético/metabolismo , Distrofias Musculares/metabolismo , Miocardio/metabolismo , Troponina/metabolismo , Especificidad de Anticuerpos , Biomarcadores/análisis , Western Blotting , Reacciones Cruzadas , Ensayo de Inmunoadsorción Enzimática , Humanos , Técnicas para Inmunoenzimas , Polimiositis/metabolismo , Regeneración/fisiología , Troponina/inmunología , Troponina TRESUMEN
Cardiac troponin-I (cTnI) is not found in sera of patients with skeletal muscle disease in the absence of myocardial injury. It is not known, however, whether trace amounts of cTnI are expressed in regenerating human skeletal muscle, as has been observed with creatine kinase MB. Using immunohistochemical and biochemical techniques, we investigated cTnI expression in various human muscle tissues: human heart tissue (n = 5), normal adult skeletal muscle (n = 3), and fetal heart (n = 3) and skeletal muscle (n = 3) obtained, respectively, during heart transplant, from autopsy, or from a tissue bank. Specimens from diagnostic tissue biopsies were used as diseased skeletal muscle: polymyositis (PM), n = 13; Duchenne muscular dystrophy (DMD), n = 6. Frozen sections 8 microns thick were stained immunohistochemically for either cTnI or TnI (cardiac or skeletal) by using monoclonal antibodies (MAb) 2B1.9 (cTnI specific) or 3C5.10 (reactive with all TnI isoforms), respectively. cTnI was measured in tissue homogenates by an immunofluorometric assay. Cardiac muscle was stained by both MAbs. Normal fetal and adult skeletal muscle, and samples from all of the PM and DMD patients, stained only with the nonspecific MAb (3C5.10), confirming the sole presence of skeletal TnI. No cTnI was detectable by immunoassay in any skeletal muscle sample. We conclude that cTnI is not expressed in human skeletal muscle during development or during regenerative muscle disease processes such as PM or DMD.
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Feto/química , Músculo Esquelético/química , Troponina/análisis , Adulto , Creatina Quinasa/análisis , Femenino , Humanos , Inmunohistoquímica , Distrofias Musculares/metabolismo , Miocardio/química , Polimiositis/metabolismo , EmbarazoRESUMEN
The influence of the adenosine derivative (--)-N6-phenylisopropyladenosine (R-PIA, 1 micron) and 5'N-ethylcarbox-amidoadenosine (NECA, 1 micron) on beta-adrenergic stimulated (isoproterenol, 10 nM) phosphorylation of sarcolemmal (15 kDa protein), sarcoplasmic reticular (phospholamban) and myofibrillar proteins (troponin I, C-protein) was studied in isolated 32P-labeled guinea-pig ventricles. The identification of the 15 kDa protein, phospholamban, troponin I and C-protein was based on their reaction with specific antibodies. Isoproterenol increased contractile parameters (developed tension, rate of tension development, rate of relaxation) and stimulated the phosphorylation state of a 15 kDa protein (now named phospholemman), of phospholamban, troponin I and C-protein (regarded as regulatory proteins). Isoproterenol concomitantly increased myocardial cyclic AMP levels. R-PIA and NECA attenuated the effects of isoproterenol on contractile parameters as well as on the phosphorylation of the regulatory proteins without affecting cyclic AMP levels. The effects of 1 microM R-PIA and 1 microM NECA on the isoproterenol-stimulated phosphorylation of regulatory proteins were blocked by the adenosine receptor antagonist 1.3-dipropyl-8-cyclopentylxanthine (DPCPX, 1 microM). Therefore, it is concluded that adenosine derivatives acting via adenosine receptors can reduce the isoproterenol-stimulated phosphorylation state of the following regulatory proteins: phospholemman, phospholamban, troponin I and C-protein.
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Adenosina/análogos & derivados , Agonistas Adrenérgicos beta/farmacología , Isoproterenol/farmacología , Miocardio/metabolismo , Fenilisopropiladenosina/farmacología , Fosfoproteínas/metabolismo , Agonistas del Receptor Purinérgico P1 , Adenosina/farmacología , Adenosina-5'-(N-etilcarboxamida) , Animales , Proteínas de Unión al Calcio/aislamiento & purificación , Proteínas de Unión al Calcio/metabolismo , Proteínas Portadoras/aislamiento & purificación , Proteínas Portadoras/metabolismo , Femenino , Cobayas , Ventrículos Cardíacos , Masculino , Contracción Miocárdica/efectos de los fármacos , Fosfoproteínas/aislamiento & purificación , Radioisótopos de Fósforo , Fosforilación , Sarcolema/metabolismo , Retículo Sarcoplasmático/metabolismo , Troponina/aislamiento & purificación , Troponina/metabolismo , Troponina IRESUMEN
In guinea-pig papillary muscles the positive inotropic effect of flosequinoxan (BTS) starting at 100 mumol/l amounted to 287.6 +/- 34.2% at 300 mumol/l without any effects on time to peak tension (103.9 +/- 2%) and relaxation time (107.1 +/- 6.7% of predrug value, respectively). 10 mumol/l carbachol attenuated the positive inotropic effect of 300 mumol/l to 166.5 +/- 11.6% (n = 10). The phosphorylation state of the inhibitory subunit of troponin (TnI) and phospholamban (PLB) in [32P]-labeled guinea-pig ventricular myocytes was increased starting at 100 mumol/l amounting to 142.5 +/- 12.6% and 130.9 +/- 2.2% at 300 mumol/l, respectively (n = 5). Furthermore, BTS (300 mumol/l) decreased phosphorylase phosphatase activity by 23.1%. It is concluded that the contractile effects of BTS are accompanied by enhanced phosphorylation of regulatory proteins which could in part be due to inhibition of phosphorylase phosphatase activity.
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Contracción Miocárdica/efectos de los fármacos , Quinolonas/farmacología , Adenosina Trifosfatasas/metabolismo , Animales , Autorradiografía , Proteínas de Unión al Calcio/metabolismo , Carbacol/farmacología , AMP Cíclico/metabolismo , Electroforesis en Gel de Poliacrilamida , Cobayas , Técnicas In Vitro , Proteínas Musculares/metabolismo , Miocardio/citología , Miocardio/enzimología , Músculos Papilares/efectos de los fármacos , Músculos Papilares/enzimología , Fosforilasa Fosfatasa/antagonistas & inhibidores , Fosforilación , Quinolonas/antagonistas & inhibidores , Troponina/metabolismoRESUMEN
In isolated 32P-labeled guinea pig ventricular cardiomyocytes phospholamban (PLB), myosin light chain 2 and the inhibitory subunit of troponin (Tnl) were identified by antibodies. In isolated 32P-labeled guinea pig ventricular cardiomyocytes isoproterenol (0.1 mumol/l) increased phosphorylation of PLB and of the inhibitory subunit of Tnl to 159 and 119% of control, respectively, without effect on the phosphorylation state of myosin light chain 2. Additionally applied carbachol or (-)-N6-phenylisopropyladenosine reduced phosphorylation of PLB and Tnl without reducing cyclic AMP content. After pretreatment of guinea pigs with pertussis toxin (18 micrograms/100 g b.wt.), carbachol or (-)-N6-phenylisopropyladenosine failed to reduce isoproterenol-stimulated phosphorylation of both PLB and Tnl. It is concluded that the reductions by carbachol and (-)-N6-phenylisopropyladenosine of isoproterenol-stimulated PLB phosphorylation and Tnl phosphorylation are pertussis toxin-sensitive.
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Proteínas de Unión al Calcio/metabolismo , Miosinas/metabolismo , Toxina del Pertussis , Receptores Muscarínicos/fisiología , Receptores Purinérgicos P1/fisiología , Troponina/metabolismo , Factores de Virulencia de Bordetella/farmacología , Animales , Carbacol/farmacología , Proteínas Quinasas Dependientes de AMP Cíclico/fisiología , Cobayas , Técnicas In Vitro , Fenilisopropiladenosina/farmacología , FosforilaciónRESUMEN
BACKGROUND: Perioperative myocardial infarction is the most common cause of morbidity and mortality in patients who have had noncardiac surgery, but its diagnosis can be difficult. The present study was designed to determine whether the measurement of serum levels of cardiac troponin I, a highly sensitive and specific marker for cardiac injury, would help establish the diagnosis of myocardial infarction. METHODS: We obtained preoperative measurements of MB creatine kinase, total creatine kinase, and cardiac troponin I, in addition to base-line electrocardiograms and two-dimensional echocardiograms, in 96 patients undergoing vascular surgery and 12 undergoing spinal surgery. Blood samples were obtained every 6 hours for at least the first 36 hours after surgery, and electrocardiograms were obtained daily; a second echocardiogram was obtained approximately three days after surgery. The appearance of a new abnormality in segmental-wall motion on the postoperative echocardiogram (that is, an abnormality that had not been seen on the preoperative echocardiogram) was considered to be indicative of perioperative infarction. RESULTS: Eight patients who underwent vascular surgery had new abnormalities in segmental-wall motion and received a diagnosis of perioperative infarction. All eight had elevations of cardiac troponin I, and six had elevations of MB creatine kinase. Of the 100 patients without perioperative infarction detected by echocardiography, 19 had elevations of MB creatine kinase, and 1 had a slight elevation of cardiac troponin I. CONCLUSIONS: The measurement of cardiac troponin I is a sensitive and specific method for the diagnosis of perioperative myocardial infarction. It avoids the high incidence of false diagnoses associated with the use of MB creatine kinase as a diagnostic marker.
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Infarto del Miocardio/diagnóstico , Complicaciones Posoperatorias/diagnóstico , Troponina/sangre , Creatina Quinasa/sangre , Reacciones Falso Positivas , Femenino , Humanos , Incidencia , Masculino , Persona de Mediana Edad , Infarto del Miocardio/sangre , Infarto del Miocardio/etiología , Complicaciones Posoperatorias/sangre , Factores de Riesgo , Sensibilidad y Especificidad , Troponina I , Procedimientos Quirúrgicos Vasculares/efectos adversosRESUMEN
BACKGROUND: Levels of MBCK can be increased in patients with skeletal muscle injury or renal failure in the absence of myocardial injury, causing diagnostic confusion. This study was designed to determine whether measurement of cardiac troponin I (cTnI), a myocardial regulatory protein with comparable sensitivity to MBCK, has sufficient specificity to clarify the etiology of MBCK elevations in patients with acute or chronic skeletal muscle disease or renal failure. METHODS AND RESULTS: Of the patients (n = 215) studied, 37 had acute skeletal muscle injury, 10 had chronic muscle disease, nine were marathon runners, and 159 were chronic dialysis patients. Patients were evaluated clinically, by ECG, and by two-dimensional echocardiography. Total creatine kinase (normal, < 170 IU/L) was determined spectrophotometrically, and cTnI (normal, < 3.1 ng/mL) and MBCK (normal, < 6.7 ng/mL) were determined with specific monoclonal antibodies. Values above the upper reference limit were considered "elevated." Elevations of total creatine kinase were common, and elevations of MBCK occurred in 59% of patients with acute muscle injury, 78% of patients with chronic muscle disease and marathon runners, and 3.8% of patients with chronic renal failure. Some of the patients were critically ill; five patients were found to have had myocardial infarctions and one had a myocardial contusion. cTnI was elevated only in these patients. CONCLUSIONS: Elevations of cTnI are highly specific for myocardial injury. Use of cTnI should facilitate distinguishing whether elevations of MBCK are due to myocardial or skeletal muscle injury.
Asunto(s)
Pruebas Enzimáticas Clínicas , Creatina Quinasa/sangre , Fallo Renal Crónico/diagnóstico , Enfermedades Musculares/diagnóstico , Infarto del Miocardio/diagnóstico , Troponina/sangre , Adulto , Biomarcadores/sangre , Diagnóstico Diferencial , Femenino , Humanos , Isoenzimas , Masculino , Persona de Mediana Edad , Músculos/lesiones , Carrera/lesiones , Sensibilidad y Especificidad , Troponina IRESUMEN
Measurement of glycohemoglobin has been recommended for the long-term assessment of glycemic control in diabetic patients. Because different analytical methods measure different glycohemoglobin species, it has been difficult to compare results between laboratories. Here we report 3 years of experience with calibration of an affinity chromatography method for measuring total glycohemoglobin (GHb). Calibration was achieved by including in each assay three hemolysate calibrators for which values for HbA1c and GHb had been determined by repeated analyses by high-performance liquid chromatography (HPLC) and affinity chromatography, respectively. Calibration improved interassay precision (CV = 3.20-7.90% and < 5.0% before and after the introduction of calibration, respectively) and eliminated lot-to-lot variability. In 91 samples, HbA1c was estimated by the calibrated affinity chromatography assay and measured by an ion-exchange HPLC method. Estimated and HPLC-measured HbA1c showed no clinically significant differences during 36 months. The high degree of long-term precision, the disappearance of lot-to-lot variability, and the excellent comparability between analytical methods measuring different species of glycated hemoglobins demonstrate the advantages of calibration.
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Cromatografía de Afinidad/normas , Hemoglobina Glucada/análisis , Laboratorios/normas , Cromatografía de Afinidad/estadística & datos numéricos , Humanos , Indicadores y Reactivos/normas , Control de Calidad , Valores de ReferenciaRESUMEN
To improve the specificity of biochemical markers of myocardial infarction (MI), we have developed a double monoclonal "sandwich" enzyme immunoassay to measure cardiac troponin-I (cTnI) in serum. We produced eight IgG monoclonal antibodies against human cardiac troponin-I (cTnI) and tested them against human and animal (canine, bovine, and rabbit) troponins. Five antibodies were cardiac-specific; none of the antibodies were species-specific. Two of the five cTnI-specific monoclonal antibodies were utilized in an immunoassay. Standards were made by adding purified human cTnI to affinity-stripped cTnI-free human sera to cover the range 0-100 micrograms/L for cTnI. The dose-response curve was nonlinear but reproducible. Total assay imprecision (CV) varied between 11% and 21%. The upper limit of the reference range (nonparametric 95% interval) was established as 3.1 micrograms/L by measuring cTnI concentration in sera of 159 hospitalized patients without evidence of cardiac disease. Purified human skeletal TnI up to 10,000 micrograms/L did not affect the assay (calculated cross-reactivity < 0.1%). Diagnostic sensitivities of creatine kinase MB isoenzyme (CK-MB) and cTnI were evaluated retrospectively in 49 consecutive patients with proven MI. In the 30 patients for whom sufficient information was available to establish an accurate time course, CK-MB was more sensitive during the first 4 h after the onset of chest pain, but thereafter the sensitivities were similar up to 48 h. However, cTnI is more cardiac-specific than is CK-MB and remains increased longer than does CK-MB.