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PubMed2002

Kinetics of the acidic and enzymatic hydrolysis of benazepril HCl studied by LC.

A reversed-phase high-performance liquid chromatographic (HPLC) method was developed and validated for the kinetic investigation of the chemical and enzymatic hydrolysis of benazepril hydrochloride. Kinetic studies on the acidic hydrolysis of benazepril hydrochloride were carried out in 0.1 M hydrochloric acid solution at 50, 53, 58 and 63 degrees C. Benazepril hydrochloride appeared stable in a pH 7.4 phosphate buffered solution at 37 degrees C and showed susceptibility to undergoing in vitro enzymatic hydrolysis with porcine liver esterase (PLE) in a pH 7.4 buffered solution at 37 degrees C. Benazeprilat appeared to be the major degradation product in both (chemical and enzymatic) studies of hydrolysis. Statistical evaluation of the proposed HPLC methods revealed their good linearity and reproducibility. Relative standard deviation (R.S.D.) was less than 4.76, while detection limits for benazepril hydrochloride and benazeprilat were 13.0 x 10(-7) and 9.0 x 10(-7) M, respectively. Treatment of the kinetic data of the acidic hydrolysis was carried out by non-linear regression analysis and k values were determined. The kinetic parameters of the enzymatic hydrolysis were determined by non-linear regression analysis of the data using the equation of Michaelis-Menten.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1995

Smooth pursuit performance in patients with affective disorders or schizophrenia and normal controls: analysis with specific oculomotor measures, RMS error and qualitative ratings.

Smooth pursuit performance in schizophrenia and affective disorders has generally been found to be abnormal using a variety of measures. The purpose of this study was to assess patients with these disorders and normal controls in order to compare the different measures across diagnoses. Smooth pursuit was assessed using quantitative specific measures (gain, catch-up saccade rate and amplitude, square-wave jerk rate, number of anticipatory saccades and total time scored), as well as two global measures: root mean-square error (RMS) and qualitative rating. As previously reported, patients with schizophrenia had low gain, increased catch-up saccade rate and spent less time engaged in scoreable smooth pursuit than normal controls. Patients with affective disorders were not statistically different from controls on any of these measures, and had significantly higher gain than patients with schizophrenia. RMS error and qualitative rating measures were highly correlated (r = 0.87). In linear regression analyses, the quantitative specific measures were highly significant predictors of both RMS error and qualitative ratings (P < 0.0001). Linear regression analyses and a modelling study indicated that one quantitative specific measure, the percent of time engaged in scoreable smooth pursuit (total time scored), was most related to global ratings. However, RMS error and qualitative ratings were less sensitive than total time scored to the difference between controls and patients with schizophrenia. These data indicate two smooth pursuit performance deficits in schizophrenia: patients spend less time engaged in scoreable smooth pursuit and have low gain (accompanied by increased compensatory saccades) when the smooth pursuit is engaged.

Adult↗
PubMed2002

Central corneal thickness, radius of the corneal curvature and intraocular pressure in normal subjects using non-contact techniques: Reykjavik Eye Study.

PURPOSE: To establish a population profile of central corneal thickness (CCT), radius of the corneal curvature (CC) and intraocular pressure (IOP) and the relationships between them using non-contact techniques. METHODS: We used a population-based random sample of 415 male and 510 female Caucasians aged 50 years and older. CCT and the radius of CC were measured with Scheimpflug anterior segment photography. IOP was measured with air-puff tonometry. RESULTS: The mean IOP of right eyes was 15.1 mmHg (SD 3.3) among men and 15.8 mmHg among women (SD 3.1), which is a statistically significant difference. The mean radius of CC for male right eyes was 7.78 (SD 0.60) and for females 7.62 (SD 0.58) which is also statistically significant. Mean CCT for male right eyes was 0.528 mm (SD 0.041) and for females 0.526 mm (SD 0.037), which is not a significant difference. Linear regression analysis shows no relationship between the radius of CC and IOP or between age and radius of CC. Linear regression analysis of the relationship between CCT and IOP suggests higher IOP measurements with thicker corneas. There was no significant correlation between age and CCT. CONCLUSION: IOP was found to be independent of age and significantly higher in females than in males. Radius of CC was found to be age-independent and significantly steeper in females than in males. CCT appears to be independent of age and gender. Greater CCT is associated with higher mean IOP.

Age Factors↗
PubMed1999

A longitudinal study of cycloplegic refraction in a cohort of 350 Japanese schoolchildren. Cycloplegic refraction.

We performed a 5 year longitudinal study of cycloplegic refraction in a cohort of 350 Japanese schoolchildren from 6 to 11 years of age in a rural area of southwestern Japan. The spherical refraction was measured under cycloplegia with an infrared autorefractometer. The grouped data from 350 right eyes showed leptokurtic frequency distributions, and the median was +0.91 D at age 6 yrs, shifted towards emmetropia with increasing age and reached +0.34 D at age 11 years. The prevalence of myopia of -1.0 D or more was 0.3%, 0.6%, 2.0%, 2.6%, 2.9%, and 4.9% from age 6 to 11 years, and the prevalence of myopia of more than -2.0 D was less than 1% at age 6-9 years and thereafter increased up to 6.0% at age 11 years. Linear regression analysis for the longitudinal refractive data revealed that 247 (70.6%) of the 350 eyes exhibited first-order linear decrease in hyperopia or increase in myopia with an average annual change of -0.15 D/year, 14 (4%) showed second-order curvilinear change, and 89 (25.4%) remained unchanged. In the eyes with linear change, there was a significant relationship between the refraction at age 6 years and the rate of subsequent change such that the less hyperopic or emmetropic at age 6 years, the larger the change. The refraction at birth was estimated by extrapolation of the linear regression analysis results, implying that 88% of newborns have hyperopia of +1.0 D or greater and myopia is rare. These results indicate the current state of refraction in Japanese schoolchildren of a rural area.

Child↗
PubMed2004

Presliding friction identification based upon the Maxwell Slip model structure.

The problem of presliding friction identification based upon the Maxwell Slip model structure, which is capable of accounting for the presliding hysteresis with nonlocal memory, is considered. The model structure's basic properties are examined, based upon which a priori identifiability is established, the role of initial conditions on identification is investigated, and the necessary and sufficient conditions for a posteriori identifiability are derived. Using them, guidelines for excitation signal design are also formulated. Building upon these results, two new methods, referred to as Dynamic Linear Regression (DLR) and NonLinear Regression (NLR), are postulated for presliding friction identification. Both may be thought of as different extensions of the conventional Linear Regression (LR) method that uses threshold preassignment: The DLR by introducing extra dynamics in the form of a vector finite impulse response filter, and the NLR by relaxing threshold preassignment through a special nonlinear regression procedure. The effectiveness of both methods is assessed via Monte Carlo experiments and identification based upon laboratory signals. The results indicate that both methods achieve significant improvements over the LR. The DLR offers the highest accuracy, with the NLR striking a very good balance between accuracy and parametric complexity.

Journal Article↗
PubMed1990

Approximation of various canine left ventricular end-systolic relations by a cylinder model.

Assuming a linear end-systolic force-length relation and a cylindrical geometry of the left ventricle (LV), we have developed a mathematical model (cylinder model) and derived formulas for LV end-systolic force-diameter (Fes-Des), stress-diameter (Ses-Des), pressure-diameter (Pes-Des), and pressure-cylinder volume (Pes-Ves) relations. To assess the validity of this model for the study of the intact LV, eight healthy beagles were instrumented with ultrasonic crystals to measure LV diameter and wall thickness and a micromanometer to measure LV pressures. Preload was altered by vena caval occlusion. Contractility was increased by addition of Ca2+. Fes-Des relation was nearly linear under control contractility, whereas after addition of Ca2+ this relation became concave toward the diameter axis. Linear approximation was more accurate for this relation than for the Pes-Des and Pes-Ves relations in control contractility. Predictions from the model formulas more accurately reproduced observed data in the Pes-Des (P less than 0.01) and Pes-Ves (P less than 0.001) relations than those from linear regression equations, whereas the model predictions for the Ses-Des relation were as accurate as those of a linear regression equation. Although the slope of the Fes-Des relation increased with inotropic stimulation, diameter intercepts of this relation did not change. Thus the present results obtained under control contractility were consistent with assumptions of the model. This cylinder model might provide reasonable approximations for various canine LV end-systolic relations.

Animals↗
PubMed1997

Effects of ambient ozone exposures during the spring and summer of 1994 on pulmonary function of schoolchildren.

To investigate the effect of natural exposure to ambient ozone over time, a follow-up study of school-aged children was performed in two small towns in southwestern Germany (Freudenstadt and Villingen) between March and October of 1994. Ozone half-hour mean concentrations were measured continuously and pulmonary function was tested in each child on four occasions (April, June, August, and September). To obtain an average short-term ozone effect, we first analyzed the data from the four time points separately and then constructed a model that included all information. During the study period the median (5th to 95th percentile) of all half-hour values of the ozone concentration was 101 micrograms/m3 or 50.6 ppb (45-179 micrograms/m3 or 22.5-89.8 ppb) in Freudenstadt and 64 micrograms/m3 or 32.1 ppb (1 to 140 micrograms/m3 or 0.5-70.1 ppb) in Villingen. To assess the effects of an individual ozone exposure we related the highest ozone concentration in the respective 24 hours before lung function testing to the results of the subconcentration in the respective 24 hours before lung function testing to the results of the subsequent pulmonary function tests. In the lung function test following the highest ozone exposure, the results of our cross-sectional linear regression analysis showed a significant negative correlation (P = 0.0181) between ozone exposure and forced vital capacity (FVC). In the longitudinal linear regression model we observed a negative statistical correlation between ozone exposure and lung function for the subpopulation living in the town with the high ozone levels (Freudenstadt). The association was more pronounced in boys than girls. For the children in Freudenstadt the decrement of FVC was -12.31 ml/10 micrograms/m3 ozone and the decrease in the forced expiratory volume in 1 second (FEV1) was -11.29 ml/10 micrograms/m3 ozone.

Air Pollutants↗
PubMed1996

Renal findings in patients with short-term type 2 diabetes.

Under semiambulatory conditions, 85 consecutive patients with the diagnosis of Type 2 diabetes of short duration (excluding patients with islet cell antibodies or maturity onset diabetes of the young) were admitted to a self-control training program and were examined in this study. A comprehensive renal assessment was performed, including evaluation of albumin excretion rate (AER), renal hemodynamics, blood pressure (BP) profile, and indicators of genetic risk. AER > or = 30 mg/24 h was found in 13 (15%) of patients; in two of these patients, AER was > or = 300 mg/24 h. By logistic regression, high HbA1, current smoking, and BP parameters were significantly correlated with an increased risk of microalbuminuria (MA). In a multiple linear regression model, accounting for 57% of total variance, HbA1, ERPF, and current smoking were significantly correlated with AER. Median GFR (Cin(inulin clearance) 136 mL/min per 1.73m2; range, 94 to 194) and ERPF (Cpah(para-aminohippuric acid clearance) 733; range, 451 to 1328) were significantly higher in patients than in control subjects (upper 95th percentile, 131 and 706 mL/min per 1.73m2, respectively). In a multiple linear regression model, explaining 27% of total variance, age, AER, gender, and fasting blood glucose were significantly correlated to GFR. According to the criteria of average daytime BP > or = 135/85 mm Hg or 24-h BP > or = 130/80 mm Hg, 60% of patients were hypertensive (HT). Sixty-one percent of all patients (including 50% of the untreated normotensive patients) were "nondippers", i.e., < 15% nighttime decrease of mean arterial pressure. Either HT or nondipping was found in 79% of all patients, so that only 21% had a completely normal blood pressure profile. Ninety-four percent of untreated hypertensive patients had no MA. First-degree relatives of patients with MA compared with patients without MA had more frequent cardiovascular events (69% versus 31%). The risk of MA in diabetic patients with positive family history was amplified by poor glycemic control. MA, but not hypertension, was marginally related to K(m) of Na+/Li+ countertransport. It was concluded that (1) microalbuminuria is found in 15% of patients newly presenting with Type 2 diabetes; (2) a high proportion of patients exhibit hyperfiltration; (3) according to ambulatory BP only, 21% of patients have a completely normal circadian BP profile; (4) a family history of cardiovascular events interacts with glycemic control to increase the risk of MA.

Adult↗
PubMed2001

Computer algorithms for the automated measurement of retinal arteriolar diameters.

AIMS: Quantification of retinal vascular change is difficult and manual measurements of vascular features are slow and subject to observer bias. These problems may be overcome using computer algorithms. Three automated methods and a manual method for measurement of arteriolar diameters from digitised red-free retinal photographs were compared. METHODS: 60 diameters (in pixels) measured by manual identification of vessel edges in red-free retinal images were compared with diameters measured by (1) fitting vessel intensity profiles to a double Gaussian function by non-linear regression, (2) a standard edge detection algorithm (Sobel), and (3) determination of points of maximum intensity variation by a sliding linear regression filter (SLRF). Method agreement was analysed using Bland-Altman plots and the repeatability of each method was assessed. RESULTS: Diameter estimations obtained using the SLRF method were the least scattered although diameters obtained were approximately 3 pixels greater than those measured manually. The SLRF method was the most repeatable and the Gaussian method less so. The Sobel method was the least consistent owing to frequent misinterpretation of the light reflex as the vessel edge. CONCLUSION: Of the three automated methods compared, the SLRF method was the most consistent (defined as the method producing diameter estimations with the least scatter) and the most repeatable in measurements of retinal arteriolar diameter. Application of automated methods of retinal vascular analysis may be useful in the assessment of cardiovascular and other diseases.

Adult↗
PubMed1994

Nutrient intake and progression of coronary artery disease.

The relation between nutrient intake and progression of coronary artery disease was examined in 50 men receiving a lipid-lowering diet or usual care in the St. Thomas' Atherosclerosis Regression Study. Nutrient intake was assessed by diet history. Changes in coronary angiograms were measured by quantitative image analysis. In univariate linear regression analysis progression of disease over 39 months, as measured by decrease in minimum absolute width of coronary segments, was directly related to dietary energy (p < 0.001) and to the absolute intakes of total fat (p < 0.001), saturated fat (p < 0.001), monounsaturated fat (p = 0.016) and cholesterol (p = 0.06). No significant associations were seen with polyunsaturated fat, carbohydrate, protein, fiber, alcohol or with the ratio of intakes of polyunsaturated fatty acids to saturated fatty acids. In multiple linear regression analysis the associations of change in minimum absolute width of coronary segments with total or saturated fat persisted when adjusted for plasma low-density lipoprotein cholesterol concentration, age, weight, blood pressure, smoking or treatment group assignment. The findings suggest that in middle-aged men, progression of CAD is strongly influenced by intake of saturated fatty acids, an effect mediated in part by mechanisms other than the influence of this nutrient on plasma cholesterol and low-density lipoprotein cholesterol.

Basal Metabolism↗
PubMed1993

Pooled time series regression analysis in longitudinal studies.

Many longitudinal studies attempt to examine changes in outcome measures over time in groups of patients. Applying conventional analytic techniques, such as a single classical linear regression model, to these data will often not result in minimum variance estimates, and may affect the results of tests of significance. Pooled time series regression analyses comprise a set of techniques that may be used in these instances to model changes in outcome measures over time. Pooling of time series data from many individuals may be done using two types of models: fixed effect models, which specify differences among individuals in separate intercept terms, and random effects models, which allow for differences among individuals by including an additional error component in the model. The choice between these alternative model specifications is guided by both theoretical and statistical considerations. This paper describes the use of pooled time series analysis, contrasts these methods with two classical linear regression approaches, and demonstrates these differences using two examples: a hypothetical study of serum glucose measurements in patients with diabetic ketoacidosis, and a longitudinal study of the development of functional disability in a cohort of patients with rheumatoid arthritis. These methods may be applicable to the study of outcomes in many chronic illnesses.

Humans↗
PubMed1993

Statistical considerations for cross-sectional data relating to tracheal reconstruction over time.

Complementary statistical analyses are performed on data concerning tracheal reconstruction in rats. The principal response criterion is vessel area as defined by the area of a graft onto the trachea covered by blood vessels. Postoperatively, this vessel area changes in a nonlinear fashion over time. Starting at 0% immediately postoperation, the vessel area increases to a peak and then sharply decreases to a certain level at which it remains. A total of 64 independently observed cross-sectional pairs (postop day, vessel area) are distributed among four treated groups. Analysis consists of two-way analysis of variance and piecewise linear regression under the usual assumptions of normality and variance homogeneity. Other analyses that relax these assumptions are also considered; treatment differences are established by nonparametric tests, and a quasi-likelihood analysis of the piecewise linear regression model is applied under the assumption of a binomial-like variance function. The resulting fit of the normal-theory-based piecewise linear model is compared to that of a nonlinear model whose shape is that of a gamma function integrand.

Analysis of Variance↗
PubMed1998

Pharmacokinetics of sparfloxacin in the serum and vitreous humor of rabbits: physicochemical properties that regulate penetration of quinolone antimicrobials.

We have used a recently described animal model to characterize the ocular pharmacokinetics of sparfloxacin in vitreous humor of uninfected albino rabbits following systemic administration and direct intraocular injection. The relationships of lipophilicity, protein binding, and molecular weight to the penetration and elimination of sparfloxacin were compared to those of ciprofloxacin, fleroxacin, and ofloxacin. To determine whether elimination was active, elimination rates following direct injection with and without probenecid or heat-killed bacteria were compared. Sparfloxacin concentrations were measured in the serum and vitreous humor by a biological assay. Protein binding and lipophilicity were determined, respectively, by ultrafiltration and oil-water partitioning. Pharmacokinetic parameters were characterized with RSTRIP, an iterative, nonlinear, weighted, least-squares-regression program. The relationship between each independent variable and mean quinolone concentration or elimination rate in the vitreous humor was determined by multiple linear regression. The mean concentration of sparfloxacin in the vitreous humor was 59.4% +/- 12.2% of that in serum. Penetration of sparfloxacin, ciprofloxacin, fleroxacin, and ofloxacin into, and elimination from, the vitreous humor correlated with lipophilicity (r2 > 0.999). The linear-regression equation describing this relationship was not improved by including the inverse of the square root of the molecular weight and/or the degree of protein binding. Elimination rates for each quinolone were decreased by the intraocular administration of probenecid. Heat-killed Staphylococcus epidermidis decreased the rate of elimination of fleroxacin. Penetration of sparfloxacin into the noninflamed vitreous humor was greater than that of any quinolone previously examined. There was an excellent correlation between lipophilicity and vitreous entry or elimination for sparfloxacin as well as ciprofloxacin, fleroxacin, and ofloxacin. There are two modes of quinolone translocation into and out of the vitreous humor: diffusion into the eye and both diffusion and carrier-mediated elimination out of the vitreous humor.

Animals↗
PubMed2004

Acute renal failure needing dialysis in the intensive care unit and prognostic scores.

BACKGROUND: Generic prognostic scores used in acute renal failure (ARF) give imprecise results; disease-specific indices applied to distinct populations or intensive care practices becomes inaccurate. The current study evaluates the adequacy of prognostic scores, in patients with severe ARF needing dialysis. METHODS: Known generic (APACHE II) and disease-specific (ATN-ISS) indices were applied to a cohort (n = 280) with ARF needing dialysis, under intensive care. Possible risk factors as causal factors, organ dysfunctions and clinical variables were examined, and a local index assembled by multivariate logistic regression analysis. Area under the receiver operating characteristics (ROC) curves evaluated the indices discriminating capacity. Goodness-of-fit testing and linear regression analysis appraised calibration. Validation was accomplished by the bootstrapping technique. The end-point was hospital mortality. RESULTS: Overall mortality was 85%. Female gender < 44 years (OR: 0.29; 95% CI: 0.10-0.84), liver/obstructive biliary disease (OR: 6.03; 95% CI: 1.65-22.08), being conscious (OR: 0.49; 95% CI: 0.21-1.14), use of vasoactive drug (OR: 3.13; 95% CI: 1.25-7.83), respiratory dysfunction (OR: 5.20; 95% CI: 1.25-7.83) or sepsis (OR: 2.62; 95% CI: 1.14-6.02) were associated with outcome. Areas under the ROC curve of 0.815, 0.652 and 0.814; Goodness-of-fit test P = 0.593, P < 0.001 and P = 0.002; and linear regression R2 = 0.973, R2 = 0.526 and R2 = 0.919 for the local index, APACHE II and ATN-ISS, respectively, indicate better performance by the local index. The local index median area under the ROC curve, by bootstrapping, was 0.820 (95% CI: 0.741-0.907). CONCLUSIONS: APACHE II score was inaccurate, and ATN-ISS poorly calibrated. When mortality or intensive care practices significantly deviate, local scores may better evaluate prognosis in severe ARF.

Acute Kidney Injury↗
PubMed2005

Clinical comparison of tympanic membrane displacement with invasive ICP measurements.

OBJECTIVE: Tympanic membrane displacement (TMD) measurements may be useful in the management of patients with hydrocephalus if they can be directly associated with measurements of ICP. We have compared TMD measurements using the Marchbanks Measurement System with invasive ICP monitoring. METHODS: Twenty-nine patients who were undergoing routine invasive monitoring using a Camino fibre optic ICP measurement system as part of their clinical management were studied. Simultaneous measurements of ICP and TMD in both sitting and supine positions were successfully made in thirteen patients. RESULTS: Thirty-nine pairs of readings were obtained. The invasive ICP readings varied from 1 to 36 mmHg in the supine position and from -12 to +35 mmHg sitting. Corresponding TMD values varied from 275 to +277 nL in the supine position and -133 to +466 nL sitting. Linear regression showed a significant negative relationship between the two measurements (r = -0.57, p = 0.0013). CONCLUSIONS: There is a strong negative linear association between mean TMD and invasively measured ICP and this relationship is highly significant. Nevertheless, TMD is a poor surrogate for ICP in clinical terms because the predictive limits of the linear regression are too wide. However, serial intra-patient measurements may be useful to determine changes in ICP with time.

Acoustic Impedance Tests↗
PubMed1989

Estimation of pA2 values at presynaptic alpha 2-autoreceptors in rabbit and rat brain cortex in the absence of autoinhibition.

An attempt was made to determine pA2 values of antagonists at the presynaptic, release-inhibiting alpha 2-autoreceptors of rabbit and rat brain cortex under conditions when there was very little released noradrenaline in the autoreceptor biophase and, hence, pA2 values were not distorted by endogenous autoinhibition. Cortex slices were preincubated with 3H-noradrenaline and then superfused and stimulated by trains of 4 pulses delivered at 100 Hz or, in a few cases, by trains of 36 pulses at 3 Hz. The alpha-adrenoceptor agonists clonidine, noradrenaline, and alpha-methylnoradrenaline concentration-dependently decreased the stimulation-evoked overflow of tritium. The alpha-adrenoceptor antagonists yohimbine, rauwolscine and idazoxan did not increase the overflow of tritium elicited by 4 pulses/100 Hz in rabbit brain slices and increased it only slightly in rat brain slices. In contrast, the antagonists increased markedly the overflow at 36 pulses/3 Hz. All antagonists caused parallel shifts to the right of the concentration-response curves of clonidine, noradrenaline, and alpha-methylnoradrenaline. pA2 values were calculated either from linear regression of log [agonist concentration ratio - 1] on log [antagonist concentration] or from sigmoid curve fitting. The slopes of the linear regression lines were close to unity, and the pA2 values calculated by the two methods agreed well. There was no consistent preferential antagonism of any antagonist to any agonist. pA2 values determined with stimulation by 4 pulses/100 Hz were by 0.53-0.80 log units higher than those determined with stimulation by 36 pulses/3 Hz.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Calibration and validation of linearity in chromatographic biopharmaceutical analysis.

Calibration in chromatographic biopharmaceutical analysis is a major determinate of method performance and many methods have been proposed to evaluate an appropriate calibration model, to determine the linear range and to evaluate the goodness of fit. Ten chromatographic bioanalytical methods have been evaluated in this work by observation of concentration-response curves, linearity plots, calculation of concentration residuals, correlation coefficients and lack of fit analysis. These methods were applied to univariant linear regression, weighted regression, polynomial regression and power fit models in order to determine the most appropriate way to establish and evaluate calibration functions. It was found that weighted linear regression provided the most appropriate calibration function for eight of the 10 methods studied, whereas unweighted regression and the power fit model proved appropriate for one each of the other two methods. The choice of calibration function was best accomplished through observation of calculated concentration residuals. Linearity and sensitivity plots were of little value for assessment of linearity through the selected calibration range if conventional (+/- 5%) tolerance limits are employed. Validation of the calibration model can be accomplished by demonstrating the concentration residuals and the slope of the log concentration-log response plots are within reasonable tolerance limits or by lack of fit analysis. Correlation coefficients were demonstrated to be of little value for this purpose and the quadratic approach to linearity validation was in disagreement with other methods in four of the 10 methods evaluated.

Calibration↗
PubMed2006

Usefulness of plasma brain natriuretic peptide concentration for predicting subsequent left ventricular remodeling after coronary angioplasty in patients with acute myocardial infarction.

To determine the relation between plasma brain natriuretic peptide (BNP) and remodeling in terms of infarct-related artery (IRA) patency, 106 patients with a first anterior wall acute myocardial infarction with a patent IRA at 1 month were studied. The IRA reoccluded at 6 months in 17 patients (reoccluded IRA) and was patent in 89 patients (patent IRA). The 2 groups did not differ with respect to clinical characteristics, hemodynamic variables, and left ventricular function at 1 month, except for left ventricular end-diastolic and systolic volumes, which were significantly greater in the reoccluded IRA group. Plasma BNP concentration in the reoccluded IRA group (336 +/- 288 pg/ml) was significantly higher than that in the patent IRA group (116 +/- 106 pg/ml) at 1 month. BNP concentration decreased significantly at 6 months in the 2 groups (reoccluded IRA vs patent IRA 152 +/- 162 vs 44 +/- 58 pg/ml, p <0.05). The increase in left ventricular volume from 1 to 6 months was significantly correlated with plasma BNP concentration at 1 month in the patent IRA group (r = 0.314, p < 0.01) and the reoccluded group (r = 0.634, p < 0.01). Linear regression analysis showed that the correlation between the 2 parameters in the 2 groups was similar. Based on stepwise multivariate linear regression analysis, only plasma BNP concentration was significantly correlated with the increase in left ventricular volume from 1 to 6 months in the 2 groups. In conclusion, these results suggest that plasma BNP concentration predicts left ventricular dilation independently of IRA patency.

Angioplasty, Balloon, Coronary↗