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PubMed2007

Brachial artery diameter and vasodilator response to nitroglycerine, but not flow-mediated dilatation, are associated with the presence and quantity of coronary artery calcium in asymptomatic adults.

In the present study, we investigated whether measures of brachial artery reactivity were associated with the presence and extent of subclinical coronary atherosclerosis in asymptomatic adults. Electron beam computed tomography was employed to assess the presence and quantity of CAC (coronary artery calcium) in 441 participants (mean age, 61 years; 49% men) without prior history of CHD (coronary heart disease) or stroke, and CAC score was calculated using the method described by Agatston and co-workers [(1990) J. Am. Coll. Cardiol. 15, 827-832] High-resolution ultrasound was employed to measure BAD (brachial artery diameter), FMD (flow-mediated dilatation) and NMD (nitroglycerine-mediated dilatation). CAC score and FMD were log-transformed after adding 1 to reduce skewness. Multivariable logistic and linear regression models based on generalized estimating equations were used to assess whether BAD, FMD and NMD were each independently associated with the presence and quantity of CAC after adjustment for CHD risk factors and use of statin and hypertension medication. CAC was detectable in 64% of participants. After adjustment for age and sex, FMD was not correlated (r=-0.06; P=0.27), BAD was positively correlated (r=0.16; P=0.004) and NMD was inversely correlated in a borderline significant manner (r=-0.10; P=0.084) with log(CAC+1). In multivariable logistic regression analyses, FMD was not associated, whereas higher BAD (P=0.021) and lower NMD (P=0.030) were independently associated with the presence of CAC. In multivariable linear regression analyses, higher BAD (P=0.004) and lower NMD (P=0.016), but not FMD, were independently associated with log(CAC+1). We conclude that greater diameter of the brachial artery and lower vasodilator response to nitroglycerine, but not FMD, are associated with subclinical coronary atherosclerosis.

Adult↗

PubMed2001

Relation between initial blood distribution volume and propofol induction dose requirement.

BACKGROUND: Propofol induction dose is variable and depends on many factors, including initial volume of distribution and early disposition. The authors hypothesized that preadministration blood distribution volumes, cardiac output (CO), and hepatic blood flow (HBF) could be examined to establish a propofol induction dose. METHODS: Propofol dose required to reach loss of consciousness, when infused at infusion rate per lean body mass (LBM) of 40 mg x kg(-1) x h(-1), was determined in 75 patients aged 11-85 yr. CO, blood volume (BV), central blood volume (CBV), and HBF were measured with indocyanine green pulse spectrophotometry. Univariate least squares linear regression analysis was used to individually analyze the relation between propofol induction dose and patient characteristics, including LBM, baseline distribution volumes, CO, and HBF. Stepwise multiple linear regression models were used to select important predictors of induction dose. RESULTS: Although there was a significant correlation between the induction dose and each of the eight variables of age, sex, LBM, hemoglobin, CO, BV, CBV, and HBF, only factors of age (partial r = -0.655), LBM (partial r = 0.325), CBV (partial r = 0.540), and HBF (partial r = 0.357) were independently associated with the induction dose (R2 = 0.85) when all variables were included in a multivariate model. CONCLUSIONS: At a constant propofol infusion rate of 40 mg x kg(-1) x h(-1) as a function of LBM in patients with American Society of Anesthesiologists physical status I or II, the induction dose can be determined from four variables: age, LBM, CBV, and HBF.

Adolescent↗

PubMed2001

Prediction of thoracic kyphosis using the Debrunner kyphometer.

The Debrunner kyphometer is an accepted tool for detecting and evaluating thoracic kyphosis. This prospective study was conducted to create a mathematical formula that provides, with high approximation, the roentgenographic angle of thoracic kyphosis (T4-T12) using only the kyphometer. Several clinical (kyphometer value, age, and sex) and radiographic (Cobb angle [T4-T12]) parameters from 90 consecutively screened adolescents (44 male and 46 female) were correlated using simple and multiple linear regression analyses. The reliability of measurement using the Debrunner kyphometer was high. The kyphometer value was strongly correlated with the roentgenographically measured thoracic Cobb angle (simple linear regression analysis; probability range, 0.0026 to 0.0002). There was no correlation between age or sex and thoracic kyphosis. The predicted kyphosis angle using the kyphometer and the mathematic formula was 44.66 degrees +/- 2.68 degrees, (range 27 to 62 degrees), and the real roentgenographic kyphosis angle was 47.5 degrees +/- 3.53 degrees, (range, 24 to 70 degrees). The kyphometer and formula were more reliable and accurate when kyphosis less than 50 degrees was measured. In this study, the authors constructed a mathematical formula that accurately provides the roentgenographic T4-T12 kyphosis angle in adolescents using only the Debrunner kyphometer with a deviation of less than 3 degrees. The authors recommend that all physicians engaged in kyphosis screening programs use the kyphometer combined with the recently constructed simple mathematic formula. This method will reduce the cost of school screening programs, overdiagnoses, and unnecessary exposure of adolescents to irradiation.

Adolescent↗

PubMed1985

Energy intake, norepinephrine excretion, and oxygen consumption in low birthweight infants.

Eleven healthy, appropriately grown low birthweight infants, ages 3-15 days and 28-33 weeks gestation, were the subjects of this study. Energy intake, urinary norepinephrine excretion, and metabolic rate as reflected in VO2 were examined concurrently. Energy intakes were recorded. Simultaneous collection of a timed urine for norepinephrine excretion and measurement of VO2 using indirect calorimetry were performed. A servo control device was used to maintain an abdominal skin temperature of 36.5 degrees C. The results demonstrated increases in energy intake, urinary norepinephrine, and VO2 with advancing postnatal age. Simple linear regression analysis revealed significant positive correlations between energy intake and VO2 (p less than 0.003), norepinephrine excretion and VO2 (p less than 0.003), postnatal age and VO2 (p less than 0.01), and postnatal age and energy intake (p less than 0.001). Multiple regression analysis revealed a strong positive correlation between urinary norepinephrine excretion and VO2, and energy intake and VO2. When postnatal age was added to the multiple linear regression analysis as a variable, energy intake was no longer strongly correlated with VO2. This implies postnatal age and energy intake are closely linked in this study, and further studies are needed to better define these relationships.

Birth Weight↗

PubMed2003

Accuracy of computer-aided measurements in endovascular stent-graft planning: an experimental study with two phantoms.

RATIONALE AND OBJECTIVES: The aim of this study was to evaluate the accuracy of the new measurement software, created for aortic stent-graft planning. The software finds semiautomatically the centerline of the vessel from computer tomographic angiography data and calculates semiautomatically diameters and lengths. MATERIALS AND METHODS: Two phantoms were constructed, scanned by CT and measured with the measurement software. Results were compared with the known dimensions of the phantoms and mean fractional errors were calculated. Linear regression analysis was also made between measured and known diameters. RESULTS: The mean fractional error (+/- SD) for all diameter measurements combined was 0.017 +/- 0.011. In the linear regression analysis, was 1.000. For length measurements, the mean fractional error (+/- SD) was 0.009 +/- 0.0006. CONCLUSIONS: The software enables accurate measurements perpendicular or parallel to the semiautomatically created centerline path.

Aortic Aneurysm, Abdominal↗

PubMed1998

Decreased sensitivity to the hypnotic effects of ethanol early in ontogeny.

Sensitivity to the hypnotic effects of ethanol was examined in Sprague-Dawley male and female rats at 16, 26, 36, 46, 56, or 96 days postnatally. Following administration of 3.5, 4.0, 4.5, or 5.0 g/kg of a 17% v/v ethanol solution, sleep times were recorded and blood alcohol levels (BALs) and brain alcohol levels (BrALs) were measured upon awakening. In addition to examining ethanol sleep time during ontogeny, data were used to estimate acute tolerance (indexed by the slope of the linear regressions of waking BALs and BrALs as a function of dose) and initial brain sensitivity to ethanol (indexed by calculating the y-intercept from the linear regression of BrALs as a function of sleep time). The results showed a marked increase in sensitivity to ethanol hypnosis during ontogeny, with young animals exhibiting shorter ethanol-induced sleep times and high waking BALs and BrALs. This ontogenetic increase in ethanol sensitivity was associated with a developmental decline in acute tolerance, with acute tolerance being most pronounced at postnatal day (P) 16 and evident only up to P36. Initial sensitivity conversely increased with age, with P16 pups showing lower initial brain sensitivity to ethanol than at all other ages. Gender differences emerged in adulthood, with males sleeping significantly longer than females at P56 and P96. These findings suggest that the marked insensitivity of young animals to the hypnotic effects of ethanol is related to both pronounced acute tolerance, as well as reduced initial brain sensitivity to ethanol early in life.

Age Factors↗

PubMed1980

The respiratory frequency response to carbon dioxide inhalation in conscious rabbits.

1. The respiratory responses to CO(2) inhalation were measured in New Zealand White rabbits. Prior to testing, the rabbits either received drinking water ad libitum (C), or were subjected to 72 hr water deprivation (WD). The rabbits were tested in a climatic chamber at either 20 degrees C, (C20, WD20) or 30 degrees C (C30, WD30).2. CO(2) exposure caused increases in both tidal volume (V(T)) and minute volume (V(E)). The direction and magnitude of changes in respiratory frequency (f), however, were dependent upon treatment.3. Linear regressions were drawn for f vs.% CO(2) in inhaled gas. Treatment C20 showed zero slope, treatment C30 a large negative slope, and treatments WD20 and WD30 a significant positive slope.4. The slopes of the regression lines obtained from plotting f vs.% CO(2) were plotted against their intercepts for each rabbit under each treatment condition. This yielded a highly significant linear regression from which it could be concluded that the frequency response to CO(2) exposure is dependent upon the initial frequency when the rabbits are breathing air.5. It is suggested that frequency is shifted during hypercapnia towards an optimal value which is dependent upon the existing% CO(2) in the inspired gas.6. Comparison of the results obtained for the rabbit with results reported for the conscious dog and sheep suggest that a similar relationship may hold for these species.

Animals↗

PubMed2000

Relationship between serum bactericidal activity and serogroup-specific immunoglobulin G concentration for adults, toddlers, and infants immunized with Neisseria meningitidis serogroup C vaccines.

A new meningococcal group C-CRM(197) conjugate vaccine (MnCC; Meningitec) has been evaluated in multiple clinical trials in the United States and most recently has been approved for routine administration in the United Kingdom. Meningococcal serogroup C (MnC)-specific immunoglobulin G (IgG) antibodies in pre- and postimmunization sera obtained from healthy U.S. adults, toddlers, and infants were quantitated by enzyme-linked immunosorbent assay (ELISA) and by an antibody-dependent, complement-mediated serum bactericidal assay (SBA). Serogroup-specific IgG antibody (micrograms per milliliter) in adults immunized either with the quadrivalent polysaccharide (A, C, Y, and W-135) vaccine or with MnCC showed a strong correlation (r = 0.848 and 0.934, respectively) by linear regression analysis with SBA. Sera from infants immunized with the MnCC (n = 30) and an age-matched unimmunized control group (n = 15) were also analyzed. Linear regression analysis of serum bactericidal and IgG ELISA data from sera obtained at 2 months of age (preimmunization) showed no correlation; however, a high degree of correlation was observed at time points after two (r = 0.877) and three (r = 0.951) immunizations, where significant rises in anti-MnC polysaccharide antibodies occurred relative to the age-matched control group. Infants previously primed with 3 doses of MnCC were given a booster dose of conjugate vaccine at 12 to 15 months of age. The correlation coefficient of ELISA to SBA for combined pre- and postbooster data was r = 0.836 (n = 48 pairs). In conclusion, increases in serum bactericidal activity in immunized adult, toddler, and infant populations were found to correlate very well with increases in serogroup-specific IgG concentrations, whereas the correlation between these two assays in nonimmunized 2-month-old infants was poor. Characterizing the relationship between these methods is important for understanding the significance of antigen-specific antibody concentrations relative to vaccine performance and protection from disease.

Adult↗

PubMed1998

Predictors of short-term changes in serum intact parathyroid hormone levels in hemodialysis patients: role of phosphorus, calcium, and gender.

Several factors have been identified as important in the pathogenesis of secondary hyperparathyroidism in end-stage renal disease, including serum calcium, phosphorus, and calcitriol. To examine the independent effects of key factors, we prospectively studied 52 new hemodialysis patients with mild secondary hyperparathyroidism (PTH, 110-670 pg/mL) treated with a standardized regimen of calcium supplements, phosphorus binders, and no vitamin D derivatives. We used simple and multivariable linear regression analysis to examine the relationship between changes in PTH (deltaPTH) levels observed over a 4-week period and various biochemical and demographic variables. By simple linear regression we found that changes in serum phosphorus (r2 = 0.31; beta = 41.6; P = 0.0001), initial phosphorus concentration (r2 = 0.15; beta = 33.4; P = 0.005), initial PTH level (r2 = 0.29; beta = 0.58; P = 0.0001), changes in serum calcium (r2 = 0.12; beta = -74.0; P = 0.01), and gender (r2 = 0.07; beta = 76.1; P = 0.05) were significantly associated with deltaPTH. However, upon multivariable regression analysis, only the changes in phosphorus (partial r2 = 0.31; beta = 37.0; P = 0.0001), initial PTH level (partial r2 = 0.23; beta = 0.50; P = 0.0001), and gender (partial r2 = 0.05; beta = 63.1; P = 0.02) remained significantly associated with deltaPTH. Neither the serum concentration of 1,25-dihydroxyvitamin D3, bicarbonate, aluminum, or albumin nor changes in the serum bicarbonate concentration, the presence of diabetes, KT/V, or age were significantly associated with the deltaPTH. Our findings are consistent with independent effects of phosphorus and gender on parathyroid gland function in patients with dialysis-dependent renal failure through mechanisms that remain to be defined.

Adult↗

PubMed2001

Motor and sensory conduction velocities and amplitude of nerve or muscle potentials in the normal rat according to age.

The relative changes in sensory and motor nerve conductions and SNAP and CMAP amplitudes were studied on the sural and tibial posterior nerves in anesthetized male rats, between the 1st and the 23rd month. Neural growth was controlled with the measure of the nerve path length on the skin, between stimulating and recording cathodes for the sural nerve and proximal and distal stimulating cathodes for the tibial posterior nerve. The sural SCV and SNAP amplitude are consistent with a more accurate method than the H-reflex one. Similar changes were observed in both parameters. During the maturation of the peripheral nervous system, between the 1st and the 5th month, parameters rapidly increased. Over 14 months old, parameters decrease: the diminution of SNAP and CMAP amplitudes is characteristic of aging. The results were analyzed through quadratic and linear regression and were similar to those in young and elderly human patients. Parabola curves fitted the best way to represent the evolution of parameters. Moreover, the linear regression permitted to divide the rat life in 3 parts and to distinguish a period between the 6th and 13th months during which studied parameters are considered as constant. SCV, MCV, SNAP and CMAP amplitudes from the 1st to the 5th, from 6th to 13th and over the 14th month, could be used as reference.

Action Potentials↗

PubMed1989

Bayesian forecasting of serum lithium concentrations. Comparison with traditional methods.

Twelve pharmacokinetic methods of estimating lithium maintenance dosage requirements were compared in 21 patients with bipolar illness. Methods which were compared included the single- and multiple-point methods of Perry, 4 non-linear regression and 6 Bayesian methods. The REVOL algorithm was employed for converging on to estimates of clearance and apparent volume of distribution for the non-linear regression and Bayesian methods. Data analysis was based on an evaluation of prediction error as a measure of bias, and absolute prediction error as a measure of precision. In a direct comparison, there were no statistically significant differences in bias or precision between any of the methods.

Adolescent↗

PubMed1996

Real-time determination of left ventricular ejection fraction by automatic boundary detection in patients with dilated cardiomyopathy: a comparison with radionuclide ventriculography.

Echocardiographic automatic boundary detection (ABD) is a new on-line technique which automatically outlines the left ventricular endocardial border and instantly calculates the left ventricular area and volume from two dimensional echocardiographic images. To determine if left ventricular ejection fraction (LVEF) can be derived using the ABD method, 25 consecutive patients with dilated cardiomyopathy, aged 52.1 +/- 15.2 (range 14 approximately 75), underwent complete echocardiographic examination with both the ABD method and radionuclide ventriculography (RVG). End-diastolic and end-systolic left ventricular areas were obtained on-line from the apical four chamber view. Left ventricular length was also measured from an apical view. Left ventricular volumes and ejection fraction were calculated using the single plane area-length method. ABD measurements could be obtained in all patients. Linear regression analysis compared ejection fraction derived by ABD and RVG. The mean radionuclide LVEF was 20.9 +/- 6.8% and mean ABD-derived LVEF was 22.7 +/- 5.8%. Linear regression analysis revealed that the ABD-derived LVEF is closely correlated with the RVG-derived LVEF (r = 0.87, p < 0.001). In conclusion, ABD echocardiography is a new on-line technique which may be used to accurately calculate LVEF in patients with dilated cardiomyopathy.

Adolescent↗

PubMed1982

Assay in mice for minute amounts of endotoxin by pre-administration of lead acetate.

The enhancing effect of pre-administration of lead acetate on the body-weight decrease due to endotoxin was studied in mice for the purpose of developing a method for determination of minute amounts of endotoxin. By adoption of the body-weight ratio on the first day after endotoxin administration (BWR1) as a response, the linear regression lines of the dose-response were demonstrated over a wide range of log doses of several different endotoxin preparations tested. By use of these linear regression equations experimentally obtained, the minimum detectable dose was calculated. The minimum detectable dose was defined as a dose of an endotoxin preparation producing a mean body-weight response statistically distinguishable from that of the control. The doses obtained were mostly in nanogram order. The magnitude of the enhancement brought about by the lead treatment was estimated at about 40 to 100 times.

Animals↗

PubMed1990

Medical house officers' knowledge, attitudes, and confidence regarding medical ethics.

As part of a trial of ethics education in a university-based, categorical, internal medicine training program, we surveyed all medical house officers at our institution regarding their knowledge of medical ethics, their attitudes and beliefs about selected issues in medical ethics, and their confidence in dealing with ethical problems. In a multivariate linear regression model, house officer knowledge scores were negatively correlated with postgraduate year, and positively correlated with age and with reporting a Jewish religious identity. A multivariate linear regression model predicting house officer confidence in dealing with ethical issues revealed a positive correlation with self-reported quality of ethics training in medical school and with being in the experimental group of house officers receiving ethics education. Attitudes and beliefs were largely uncorrelated with training or demographic characteristics. These results have implications for ethics education of both medical students and residents.

Attitude of Health Personnel↗

PubMed2006

The Anticholinergic Drug Scale as a measure of drug-related anticholinergic burden: associations with serum anticholinergic activity.

Anticholinergic Drug Scale (ADS) scores were previously associated with serum anticholinergic activity (SAA) in a pilot study. To replicate these results, the association between ADS scores and SAA was determined using simple linear regression in subjects from a study of delirium in 201 long-term care facility residents who were not included in the pilot study. Simple and multiple linear regression models were then used to determine whether the ADS could be modified to more effectively predict SAA in all 297 subjects. In the replication analysis, ADS scores were significantly associated with SAA (R2 = .0947, P < .0001). In the modification analysis, each model significantly predicted SAA, including ADS scores (R2 = .0741, P < .0001). The modifications examined did not appear useful in optimizing the ADS. This study replicated findings on the association of the ADS with SAA. Future work will determine whether the ADS is clinically useful for preventing anticholinergic adverse effects.

Aged↗

PubMed1995

Does regression analysis of lung function data obtained from occupational epidemiologic studies lead to misleading inferences regarding the true effect of smoking?

Exposure-response studies of the relationship between ventilatory function and dust exposure in workers are often quantified using linear regression methods. In coal miners, this technique has indicated that average effects of smoking and moderate dust exposure are roughly equivalent. However, the validity of direct comparison of the average effects of smoking and dust exposure has been questioned, the argument being that smoking causes severe effects in a minority, but leaves the remainder largely unaffected. This hypothesis was studied by examining distributions of FEV1 in a group of working coal miners where mean effects associated with both smoking and dust exposure have been detected. Overall, the results suggest that comparison of average effects of smoking and dust exposure derived from linear regression analysis is valid and not misleading.

Adult↗

PubMed1995

Social desirability bias in dietary self-report may compromise the validity of dietary intake measures.

BACKGROUND: Self-report of dietary intake could be biased by social desirability or social approval thus affecting risk estimates in epidemiological studies. These constructs produce response set biases, which are evident when testing in domains characterized by easily recognizable correct or desirable responses. Given the social and psychological value ascribed to diet, assessment methodologies used most commonly in epidemiological studies are particularly vulnerable to these biases. METHODS: Social desirability and social approval biases were tested by comparing nutrient scores derived from multiple 24-hour diet recalls (24HR) on seven randomly assigned days with those from two 7-day diet recalls (7DDR) (similar in some respects to commonly used food frequency questionnaires), one administered at the beginning of the test period (pre) and one at the end (post). Statistical analysis included correlation and multiple linear regression. RESULTS: Cross-sectionally, no relationships between social approval score and the nutritional variables existed. Social desirability score was negatively correlated with most nutritional variables. In linear regression analysis, social desirability score produced a large downward bias in nutrient estimation in the 7DDR relative to the 24HR. For total energy, this bias equalled about 50 kcal/point on the social desirability scale or about 450 kcal over its interquartile range. The bias was approximately twice as large for women as for men and only about half as large in the post measures. Individuals having the highest 24HR-derived fat and total energy intake scores had the largest downward bias due to social desirability. CONCLUSIONS: We observed a large downward bias in reporting food intake related to social desirability score. These results are consistent with the theoretical constructs on which the hypothesis is based. The effect of social desirability bias is discussed in terms of its influence on epidemiological estimates of effect. Suggestions are made for future work aimed at improving dietary assessment methodologies and adjusting risk estimates for this bias.

Bias↗

PubMedDate not supplied

Variable effects of psychosocial factors on the clinical course of schizophrenia.

BACKGROUND: Recent work suggests that psychosocial stress factors play a lesser role (qualitatively) in the progression of schizophrenic illness in male patients. The authors endeavored to determine if hospitalization in schizophrenic patients of both sexes is associated with less quantifiable psychosocial stress over time. METHODS: Male and female, schizophrenic inpatients from 2 urban centers in New York State (n = 31) were enrolled in this retrospective and cross-sectional study. Linear regression analysis was performed with illness duration as the independent variable and ln (1 + Paykel Life Events Schedule) score, associated with current hospitalization, as the dependent variable. RESULTS: Linear regression analysis revealed an inverse relationship (slope = -.086) that was statistically significant (p < .01). This result indicates an annual 92% reduction in the psychosocial stress load associated with hospitalization. The inverse relationship remained intact when males and females were analyzed separately. CONCLUSIONS: The data suggest that, over time, male and female patients with schizophrenia experience hospitalization and, likely, relapse as well in response to less of a total significance load of psychosocial stress.

Adult↗