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At least 649 records · Page 36Linked to original sources
PubMed2002

Impact of postimplant edema on V(100) and D(90) in prostate brachytherapy: can implant quality be predicted on day 0?

PURPOSE: To determine the effect of edema on the dosimetric parameters V(100) (percentage of prostate volume that received a dose equal to or greater than the prescribed dose) and D(90) (minimal dose delivered to 90% of prostate volume) in 125I prostate brachytherapy and to determine whether the edema can be used to predict implant quality on the day of the implant (Day 0). METHODS AND MATERIALS: Fifty consecutive patients treated with (125)I implants who had two postimplant CT scans were selected for this study. The mean interval between the studies was 46 +/- 23 days. The implants were preplanned to deliver 150 Gy to the prostate plus a 3-5-mm symmetric dose margin using peripherally loaded 0.4-0.6-mCi (NIST-99) (125)I seeds. A dose-volume histogram was compiled for each postimplant CT scan. The V(100) and D(90) from the first and second CT scans were compared to determine the effect of edema on these parameters. A multivariate regression analysis was performed to define the linear relationships for predicting the V(100) or D(90) at 30-60 days after implant from the magnitude of the edema and the values of V(100) and D(90) on Day 0. RESULTS: V(100) and D(90) increased by 5% +/- 6% and 15% +/- 17%, respectively, during the interval between the first and second postimplant CT scans. The mean edema was 1.53 +/- 0.20. The increases in V(100) and D(90) were found to be proportional to the edema and the values of V(100) and D(90) on Day 0. The increase in V(100) was also found to depend on the width of the preplan dose margin. Linear relationships were derived that predict the V(100) and D(90) at 30-60 days after implant with a standard error of +/-4% and +/-24 Gy, respectively. CONCLUSION: V(100) and D(90) increased by 5% +/- 6% and 15% +/- 17%, respectively, during the first 30-60 days after implant. The results of a multivariate linear regression analysis showed that the increases in V(100) and D(90) were proportional to both the magnitude of the edema and the values of these parameters on Day 0. The relationships derived by linear regression analysis predict V(100) and D(90) at 30-60 days after implant to within +/-4% and +/-24 Gy, respectively. However, predicting the 30-60-day V(100) and D(90) on Day 0 is a poor substitute for obtaining a 30-60-day CT scan, because the uncertainty in the predicted values is greater by a factor of > or =2. Nevertheless, on average, the predicted values should provide a more reliable estimate of the actual V(100) and D(90) than the Day 0 values that ignore the effect of edema altogether. The increase in V(100) was also found to depend on the width of the preplan dose margin; therefore, our results for V(100) are only valid for implants planned with a 3-5-mm margin.

Algorithms↗
PubMed2004

The effect of corneal thickness on intraocular pressure measurement in patients with corneal pathology.

BACKGROUND/AIM: To compare intraocular pressure (IOP) measurements taken by the Goldmann applanation tonometer, the Tono-Pen and the ocular blood flow pneumotonometer in eyes with varying central corneal thickness (CCT) due to penetrating keratoplasty (PK), keratoconus (KC), and Fuchs' endothelial dystrophy (FED). METHODS: IOP was measured with the Goldmann applanation tonometer, Tono-Pen XL, and OBF pneumotonometer in 127 eyes with the following corneal abnormalities. There were 56 eyes that had undergone PK, 37 eyes with KC, and 34 eyes with FED. CCT was measured using an ultrasound pachymeter after IOP determinations had been made. RESULTS: Mean IOP measurements in all three patient groups were significantly higher when measured by OBF pneumotonometer. Linear regression analysis showed that patients with FED had a significant increase in IOP with increasing CCT of 0.18 mm Hg/10 microm using the Goldmann tonometer, 0.15 mm Hg/10 microm with the Tono-Pen, and 0.26 mm Hg/10 microm with the OBF pneumotonometer. In patients with KC and after PK, linear regression analysis did not show a significant effect of CCT on IOP. A multivariate linear regression model controlling for age, sex, graft size, and patient group, showed that the effect of CCT on IOP for Tono-Pen (0.13 mm Hg/10 microm CCT) and Goldmann (0.14 mm Hg/10 microm CCT) were significantly lower than for the OBF pneumotonometer (0.26 mm Hg/10 microm CCT). CONCLUSIONS: This study found that mean IOP measurements using the OBF pneumotonometer were significantly higher than those made using the Goldmann applanation tonometer or Tono-Pen in eyes with a variety of cornel pathologies. The OBF pneumotonometer was found to be most affected by variation in CCT. For all three instruments, the relation between IOP and CCT depended on the corneal pathology and was greatest for FED.

Aged↗
PubMed2000

Consideration of endogenous backgrounds in pharmacokinetic analyses: a simulation study.

OBJECTIVE: The pharmacokinetic analysis of biologic compounds is frequently disturbed by the presence of endogenous levels, which cannot be discerned from exogenous levels. The frequently used method of subtracting baseline levels from subsequent measurements was compared to a fully adjusted regression model in a simulation study. METHODS: Simulations (5,000 each) were carried out for a standard one-compartment model with rich (n = 10) and poor (n = 6) postdose sampling, using unweighted as well as two-weighted types of non-linear regression. RESULTS: Whereas the fully adjusted model performed properly across various scenarios, the subtraction method showed a noteworthy bias (up to 14%) for area under the curve (AUC) and elimination half-life with weighted non-linear regression. For estimation of the Cmax parameter using any weighting scheme, and of any parameter using unweighted non-linear regression, the two methods performed equally well. As expected, poor in contrast to rich sampling resulted in larger coefficients of variation, but also in increasing failures (4.4%) of the regression algorithm (failure to converge, negative Cmax or half-life) for the subtraction method when it was combined with the weighting scheme giving highest weight to small concentrations. CONCLUSION: The risk of biased results may result from the subtraction method, which may also affect the analysis of dose linearity, bioequivalence and population kinetic studies with biologic compounds. When background endogenous levels are not negligible, a fully adjusted model is recommended.

Area Under Curve↗
PubMedDate not supplied

A method to estimate the depth of the sciatic nerve during subgluteal block by using thigh diameter as a guide.

BACKGROUND AND OBJECTIVE: The subgluteal approach is common for sciatic nerve block. Although the surface landmarks are clear, the depth of this nerve at this level is difficult to judge. The purpose of this study is to establish a method of estimating the sciatic nerve depth using the anteroposterior (AP) diameter of the thigh as a marker. METHODS: The study was undertaken in 2 phases. Phase 1 entailed review of 100 magnetic resonance images (MRIs) of the pelvis and proximal lower extremity of patients. Measurements were taken of the AP diameter of the thigh at the midpoint of the lesser trochanter and then compared with distances of the sciatic nerves from the skin of the posterior aspect of the thigh at the same level. Phase 2 involved enrolling 40 patients undergoing lower-extremity surgery for whom subgluteal sciatic nerve blocks were indicated. The AP diameters of the thighs were measured from the subgluteal groove to the inguinal groove with the patient in the supine position. Placing the patient in the lateral position, the subgluteal sciatic block was then performed by using a stimulating needle. The distances from the skin at which the sciatic nerves were actually found, as estimated by maximum motor response to stimulus, were noted. RESULTS: Phase 1 showed a mean AP diameter of 18.94 cm +/- 2.61 cm (mean +/- standard deviation [SD]), mean nerve depth of 6.51 cm +/- 1.46 cm (mean +/- SD), and a linear regression slope of 0.48. Phase 2 showed a mean AP diameter of 16.28 cm +/- 2.73 cm (mean +/- SD), a mean nerve depth of 6.99 cm +/- 1.39 cm (mean +/- SD), and a linear regression slope of 0.43. The thigh diameters differed (P < .001) between the groups, but there was no difference in the depth to the sciatic nerve between the 2 groups (P = .07). CONCLUSIONS: Comparing phase 1 and phase 2 datasets shows the slopes of linear regression lines are nearly parallel. The clinical data from phase 2 verify the anatomical data collected in phase 1 and show that the sciatic nerve depth to AP diameter ratio is 0.43 or the depth of the sciatic nerve is approximately 43% of thigh diameter if the patient is positioned in the lateral decubitus position.

Adult↗
PubMedDate not supplied

Regression models for calculating gas fluxes measured with a closed chamber.

Portable closed chambers provide a valuable tool for measuring crop photosynthesis and evapotranspiration. Typically, the rates of change of CO2 and water vapor concentration are assumed to be constant in the short time required to make the closed-chamber measurement, and a linear regression model is used to estimate the CO2 and H2O fluxes. However, due to the physical and physiological effects the measurement system has on the measured process, assuming a constant rate and using a linear model may underestimate the flux. Our objective was to provide a model that estimates the CO2 and H20 exchange rates at the time of chamber closure. We compared the linear regression model with a quadratic regression model using field measurements from two studies. Generally, 60 to 100% of all chamber measurement data sets were significantly nonlinear, causing the quadratic model to yield fluxes 10 to 40% greater than those calculated with the linear regression model. The frequency and degree of nonlinearity were related to the measured rate and chamber volume. Closed-chamber data should be tested for nonlinearity and an appropriate model used to calculate flux. The quadratic model provides users of well-mixed closed chambers an alternative to a simple linear model for data sets with significant nonlinearity.

Carbon Dioxide↗
PubMed1981

Nearwork and familial resemblances in ocular refraction: a population study in Newfoundland.

There is considerable epidemiological evidence that the nearwork associated with formal education can cause myopia. The potential for nearwork and education, as aspects of common familial environment, to inflate resemblances among nuclear family members in ocular refraction, was therefore investigated in a sample of 957 persons aged 5 years and over, comprising approximately 80% of the population above that age in three communities on the west coast of Newfoundland. Refraction was evaluated using standard optometric methods, nearwork measured in hours/day as reported by each subject, education measured as last completed school grade in years. The effects of nearwork and education on refraction resemblances were evaluated by adjusting refraction for age and sex, then comparing correlations or regressions among relatives before and after further linear regression adjustment of refraction for nearwork and education. Reductions in sib-sib correlations and offspring-parent regressions were achieved in this way, suggesting that these environmental factors inflate familial resemblances in refraction. Patterns of resemblances among relatives after adjustment suggest that the effects of nearwork and education on refraction resemblances were not completely removed by the linear regression adjustment used.

Adolescent↗
PubMed1991

Median nerve somatosensory evoked potentials: studies on latency variability as a function of subject height, limb length and nerve conduction velocity.

Report on the results of regression analysis studies concerning median nerve somatosensory evoked potentials (SEPs) latencies, as dependent variables, and subject height, limb length and nerve conduction velocity (NCV), as independent variables. The tests were performed on 23 normal volunteers. Absolute SEP latencies could be predicted by a linear regression model when the independent variable was arm length; when it was subject height, however, both exponential and polynomial models proved better, the latter showing the best coefficients of determination, R 2. Multiple linear regression with two independent variables (arm length and NCV) was found to be better than simple linear regression for predicting P/N13 latency. The regression line for EP-P/N13 latency on height was found to be a polynomial curve; although the regression was found to be significant by the "F" test (alpha = 1%), the model had a low R 2 value (0.41). The same applies to the P/N13-N19 interpeak latency regression curve, but the regression was significant for alpha = 5% in that case. Although interwave latencies are the most useful parameters for clinical interpretation of median SEPs, absolute latencies may occasionally be important, and should be corrected for body size. In unusually tall subjects, it might be useful to double-check EP-P/N13 interwave latency prolongation by estimating the maximum expected P/N13 latency, using a model that takes into account both limb length and NCV.

Body Constitution↗
PubMed2001

The relationship between disease activity, joint destruction, and functional capacity over the course of rheumatoid arthritis.

OBJECTIVE: To investigate the relationship between functional capacity, disease activity, and joint destruction over the course of rheumatoid arthritis (RA). METHODS: The followup data on 378 patients with early RA (duration <1 year), included in an open, prospective study since 1985 at the Department of Rheumatology of the University Medical Center Nijmegen, were used. Functional capacity, disease activity, and joint destruction were assessed using the Health Assessment Questionnaire disability index (HAQ DI), the Disease Activity Score (DAS), and a modification of the sharp radiographic damage score, respectively. Multiple linear regression was used to model the data collected at 0, 3, 6, and 9 years after study start, to investigate which variables influenced functional capacity during the disease course. A general linear mixed model for longitudinal data, which included the variables identified as significant in the multiple linear regression models and several interaction terms between the variables, was run. RESULTS: On average, the functional capacity of the patients, as measured by the HAQ DI, worsened over the course of the disease after an initial improvement. After an initial reduction in the extent of disease activity, the mean DAS remained more or less stable over the course of the disease. The mean modified sharp joint damage score worsened over the course of the disease, with a slower progression rate later in the disease. In the multiple linear regression at 0, 3, and 6 years after study start, disease activity was found to be an important factor influencing functional capacity, and at 6 and 9 years, joint damage had an important effect on functional capacity. Furthermore, at 6 and 9 years, there was an interaction effect of joint destruction with disease activity. In the general linear mixed model, disease activity, joint damage, and an interaction effect of disease activity and joint damage were the main factors explaining functional capacity. CONCLUSION: The effect of disease activity and joint destruction on functional capacity changes over the course of the disease. In early RA, functional capacity is most associated with disease activity, and in late disease, with joint damage.

Adult↗
PubMed1995

Use of a neural network and a multiple regression model to predict histologic grade of astrocytoma from MRI appearances.

Several MRI features of supratentorial astrocytomas are associated with high histologic grade by statistically significant p values. We sought to apply this information prospectively to a group of astrocytomas in the prediction of tumor grade. We used 10 MRI features of fibrillary astrocytomas from 52 patient studies to develop neural network and multiple linear regression models for practical use in predicting tumor grade. The models were tested prospectively on MR images from 29 patients studies. The performance of the models was compared against that of a radiologist. Neural network accuracy was 61% in distinguishing between low and high grade tumors. Multiple linear regression achieved an accuracy of 59%. Assessment of the images by a radiologist yielded 57% accuracy. We conclude that while certain MRI parameters may be statistically related to astrocytoma histologic grade, neural network and linear regression models cannot reliably use them to predict tumor grade.

Astrocytoma↗
PubMed2003

Atoms-in-molecules study of the genetically encoded amino acids. III. Bond and atomic properties and their correlations with experiment including mutation-induced changes in protein stability and genetic coding.

This article presents a study of the molecular charge distributions of the genetically encoded amino acids (AA), one that builds on the previous determination of their equilibrium geometries and the demonstrated transferability of their common geometrical parameters. The properties of the charge distributions are characterized and given quantitative expression in terms of the bond and atomic properties determined within the quantum theory of atoms-in-molecules (QTAIM) that defines atoms and bonds in terms of the observable charge density. The properties so defined are demonstrated to be remarkably transferable, a reflection of the underlying transferability of the charge distributions of the main chain and other groups common to the AA. The use of the atomic properties in obtaining an understanding of the biological functions of the AA, whether free or bound in a polypeptide, is demonstrated by the excellent statistical correlations they yield with experimental physicochemical properties. A property of the AA side chains of particular importance is the charge separation index (CSI), a quantity previously defined as the sum of the magnitudes of the atomic charges and which measures the degree of separation of positive and negative charges in the side chain of interest. The CSI values provide a correlation with the measured free energies of transfer of capped side chain analogues, from the vapor phase to aqueous solution, yielding a linear regression equation with r2 = 0.94. The atomic volume is defined by the van der Waals isodensity surface and it, together with the CSI, which accounts for the electrostriction of the solvent, yield a linear regression (r2 = 0.98) with the measured partial molar volumes of the AAs. The changes in free energies of transfer from octanol to water upon interchanging 153 pairs of AAs and from cyclohexane to water upon interchanging 190 pairs of AAs, were modeled using only three calculated parameters (representing electrostatic and volume contributions) yielding linear regressions with r2 values of 0.78 and 0.89, respectively. These results are a prelude to the single-site mutation-induced changes in the stabilities of two typical proteins: ubiquitin and staphylococcal nuclease. Strong quadratic correlations (r2 approximately 0.9) were obtained between DeltaCSI upon mutation and each of the two terms DeltaDeltaH and TDeltaDeltaS taken from recent and accurate differential scanning calorimetry experiments on ubiquitin. When the two terms are summed to yield DeltaDeltaG, the quadratic terms nearly cancel, and the result is a simple linear fit between DeltaDeltaG and DeltaCSI with r2 = 0.88. As another example, the change in the stability of staphylococcal nuclease upon mutation has been fitted linearly (r2 = 0.83) to the sum of a DeltaCSI term and a term representing the change in the van der Waals volume of the side chains upon mutation. The suggested correlation of the polarity of the side chain with the second letter of the AA triplet genetic codon is given concrete expression in a classification of the side chains in terms of their CSI values and their group dipole moments. For example, all amino acids with a pyrimidine base as their second letter in mRNA possess side-chain CSI < or = 2.8 (with the exception of Cys), whereas all those with CSI > 2.8 possess an purine base. The article concludes with two proposals for measuring and predicting molecular complementarity: van der Waals complementarity expressed in terms of the van der Waals isodensity surface and Lewis complementarity expressed in terms of the local charge concentrations and depletions defined by the topology of the Laplacian of the electron density. A display of the experimentally accessible Laplacian distribution for a folded protein would offer a clear picture of the operation of the "stereochemical code" proposed as the determinant in the folding process.

Amino Acids↗
PubMed1985

Multiple regression for physiological data analysis: the problem of multicollinearity.

Multiple linear regression, in which several predictor variables are related to a response variable, is a powerful statistical tool for gaining quantitative insight into complex in vivo physiological systems. For these insights to be correct, all predictor variables must be uncorrelated. However, in many physiological experiments the predictor variables cannot be precisely controlled and thus change in parallel (i.e., they are highly correlated). There is a redundancy of information about the response, a situation called multicollinearity, that leads to numerical problems in estimating the parameters in regression equations; the parameters are often of incorrect magnitude or sign or have large standard errors. Although multicollinearity can be avoided with good experimental design, not all interesting physiological questions can be studied without encountering multicollinearity. In these cases various ad hoc procedures have been proposed to mitigate multicollinearity. Although many of these procedures are controversial, they can be helpful in applying multiple linear regression to some physiological problems.

Animals↗
PubMed1993

Determinants of thiopental induction dose requirements.

Dose requirements for thiopental anesthetic induction have significant age- and gender-related variability. We studied the association of the patient characteristics age, gender, weight, lean body mass, and cardiac output with thiopental requirements. Doses of thiopental, infused at 150 mg/min, required to reach both a clinical end-point and an electroencephalographic (EEG) end-point were determined in 30 males and 30 females, aged 18-83 yr. Univariate least squares linear regression analysis revealed outliers in the relationships of age, weight, lean body mass, and cardiac output to thiopental dose at clinical and EEG endpoints. Differential weighting of data points minimized the effect of outliers in the construction of a robust multiple linear regression model of the relationship between several selected independent variables and the dependent variables thiopental dose at clinical and EEG endpoints. The multiple linear regression model for thiopental dose at the clinical end-point selecting the regressor variables age, weight, and gender (R2 = 0.76) was similar to that for age, lean body mass, and gender (R2 = 0.75). Thiopental dose at the EEG endpoint was better described by models selecting the variables age, weight, and cardiac output (R2 = 0.88) or age, lean body mass, and cardiac output (R2 = 0.87). Although cardiac output varied with age, age always remained a selected variable. Because weight and lean body mass differed with gender, their selection as variables in the model eliminated gender as a selected variable or minimized its importance.

Adult↗
PubMed2002

Nonrandom selection and the attributable cost of surgical-site infections.

OBJECTIVE: To study the extent to which selection bias poses problems for estimating the attributable cost of deep chest surgical-site infection (SSI) following coronary artery bypass graft (CABG) surgery. DESIGN: Reanalysis of a prospective case-control study. SETTING: A large, Midwestern community medical center. PATIENTS: Cases were all patients who had an SSI (N = 41) following CABG and CABG and valve surgery between April 1996 and March 1998. Controls were every tenth uninfected patient (N = 160). METHODS: Estimates of the attributable cost of deep chest SSI were computed using unmatched comparison, matched comparison, linear regression, and Heckman's two-stage approach. RESULTS: The attributable cost of deep chest SSI was estimated to be $20,012 by unmatched comparison, $19,579 by matched comparison, $20,103 by linear regression, and $14,211 by Heckman's two-stage method. Controlling for selection bias substantially reduced the cost estimate, but the coefficient capturing selection bias was not statistically significant. CONCLUSIONS: Deep chest SSI significantly increases the cost of care for patients who undergo CABG surgery. Unmatched comparison, matched comparison, and linear regression estimated the attributable cost to be approximately $20,000. Although controlling for selection bias with Heckman's two-stage method resulted in a substantially smaller estimate, the coefficient for selection bias was not statistically significant, suggesting that the estimates derived from the other models should be acceptable. However, the magnitude of the difference between the models shows that the effect of selection bias can be substantial. Some exploration for selection bias is recommended when estimating the attributable cost of SSIs.

Aged↗
PubMed1987

Echocardiographic assessment of aortic valve area in elderly patients with aortic stenosis and of changes in valve area after percutaneous balloon valvuloplasty.

Echocardiographic studies, adequate for analysis of aortic valve area using the continuity equation, were obtained in 31 patients aged greater than or equal to 60 years who were undergoing catheterization for assessment of suspected aortic stenosis. Catheterization-determined aortic valve area was 0.74 +/- 0.30 cm2 (mean +/- SD) and Doppler-determined aortic valve areas were 0.68 +/- 0.27 and 0.65 +/- 0.27 cm2, depending on whether peak or mean velocities, respectively, were entered into the continuity equation. There were significant correlations between both of the Doppler-derived and the catheterization-determined aortic valve areas (r = 0.86, p less than 0.001 for both the continuity equation employing peak velocities and the continuity equation employing mean velocities) which were demonstrated to be linear by F test (catheterization area = -0.03 + 1.13 X Doppler area determined using peak velocities, SEE = 0.163 cm2, p less than 0.001; and catheterization area = -0.02 + 1.16 X Doppler area determined using mean velocities, SEE = 0.165 cm2, p less than 0.001). Both sets of correlations had linear regression parameters meeting the conditions for identity. Significant linear correlations were also noted between the non-invasive measurements of aortic valve excursion, ventricular ejection time, time to one-half carotid upstroke, maximal Doppler velocity and maximal Doppler gradient and catheterization aortic valve area, but the correlations were less tight than those between valve areas determined by catheterization and by Doppler continuity equation. Ten of the patients underwent percutaneous balloon aortic valvuloplasty. There were significant linear correlations between aortic valve areas determined by Doppler and catheterization methods both before valvuloplasty (r = 0.77, p = 0.01; p less than 0.001 by F test, SEE = 0.134 cm2) and after valvuloplasty (r = 0.85, p less than 0.01; p = 0.0001 by F test, SEE = 0.161 cm2). Linear regression parameters met the conditions for identity. There was also a significant linear correlation between catheterization and Doppler measurements of absolute change in aortic valve area (r = 0.79, p less than 0.01; p less than 0.001 by F test, SEE = 0.11 cm2). Aortic valve area can be determined reliably by continuity equation in elderly patients. In addition, results of balloon valvuloplasty, measured by changes in catheterization-determined aortic valve area, are accurately reflected by changes in aortic valve area determined using the continuity equation.

Aged↗
PubMed2003

Genetic determinants of nonmodulating hypertension.

We sought to determine whether genes of the renin-angiotensin-aldosterone system can predict the nonmodulating intermediate phenotype in essential hypertension. Aldosterone responses to angiotensin II were assessed in 298 subjects with hypertension. Subjects were genotyped at the angiotensinogen M235T, angiotensin-converting enzyme I/D, aldosterone synthase C-344 T, renin, angiotensin II type 1 receptor, and adducin loci. The data were analyzed by Student t test, ANOVA, stepwise linear regression and general linear model or GENMOD regression techniques, and chi2 analysis odds ratios (ORs). Aldosterone response varied by genotype for angiotensin and aldosterone synthase but not for the other loci. The combination of angiotensinogen 235 TT and angiotensin-converting enzyme DD showed further reduction (P=0.0377) when compared with angiotensinogen 235 TT alone, an example of genetic epistasis. When the subject was required also to possess the CYP11B2 -344 TT genotype, there was a further substantial reduction. Of these 3 loci, only angiotensinogen 235 TT significantly increased the OR of predicting the nonmodulating hypertensive phenotype (OR, 2.00; 95% confidence interval, 1.152 to 3.51). However, when angiotensin-converting enzyme DD was combined with angiotensinogen 235 TT, the OR nearly doubled to 3.74, with a further increase to 5.36-fold when the subject possessed all 3 genotypes. Thus, the angiotensinogen, angiotensin-converting enzyme, and aldosterone synthase genotypes identified individuals with the nonmodulating phenotype with an increasing degree of fidelity. For this subclass of essential hypertension, it is likely that genotyping can be substituted for complex phenotyping for therapeutic and preventive decision making.

Age Factors↗
PubMedDate not supplied

Does the hemoglobin concentration in fetal blood interfere with the accuracy of fetal reflection pulse oximetry?

OBJECTIVE: Our goal was to investigate the influence of the fetal hemoglobin (Hb) concentration on the accuracy of reflection pulse oximetry. METHODS: 179 fetuses were monitored by a reflection pulse oximetry system (RPOX MK2). Pulse oximetry measurements (SO2POX) were compared with the oxygen saturation and pH of umbilical artery and vein (UA-, UV-SaO2) immediately after delivery. Correlation and linear regression analyses were performed. Because it is unknown whether low or high Hb concentrations might interfere with the SO2POX measurements, the influence of the Hb level on the correlations was evaluated by weighting the linear regression in both ways; by Hb concentrations as weighting factor and as an inverse weighting factor (1/Hb). RESULTS: There was a significant correlation between SO2POX and UV-SaO2 (for the last 10 min of delivery, r = 0.45, p < 0.0005) but not with pH or UA-SaO2. Linear regression analysis between SO2POX and UV-SaO2 showed a multiple R of 0.45. Hb concentration in fetal blood ranged from 9.2 to 20.5 mg/dl. The weighted regression indicated a multiple RHb of 0.49, which did not differ by the inverse weighting (multiple Rinverse Hb: 0.49). CONCLUSIONS: Pulse oximetry measurements seem to reflect oxygen saturation in fetal blood, however further improvement is necessary. The Hb concentration in fetal blood does not interfere with the accuracy of fetal pulse oximetry and need not be taken into consideration in calibration curves.

Female↗
PubMed2006

Effect of massive weight loss induced by bariatric surgery on serum levels of interleukin-18 and monocyte-chemoattractant-protein-1 in morbid obesity.

BACKGROUND: Morbid obesity is associated with insulin resistance (IR), chronic inflammation and premature atherosclerosis. Since vascular inflammation may contribute to the increased risk of cardiovascular morbidity and mortality of these patients, we studied circulating Interleukin-18 (L-18) and monocyte-chemoattractant-protein-1 (MCP-1) levels in 37 patients with morbid obesity before and after significant weight loss induced by bariatric surgery and their preoperative and postoperative associations with C-reactive protein (CRP) and IR-associated factors. METHODS: High sensitivity assays were used to measure concentrations of fasting CRP, IL-18 and MCP-1. Differences between patients before and after bariatric surgery were analyzed by Student's paired t-test. To investigate the associations of the observed reductions of values, delta of parameters were calculated and preoperative, postoperative and delta data were tested by univariate and multivariate linear regression. RESULTS: After a mean follow-up period of 26.5 months and a massive weight loss of 35 kg induced by bariatric surgery, circulating IL-18 levels decreased by 37% (P<0.001) and circulating MCP-1 levels by 47% (P<0.001). Multiple linear regression of delta values of IL-18 showed that only 2-hour glucose (P=0.008) remained independently and significantly associated with IL-18, whereas multiple linear regression analysis of delta values of MCP-1 revealed that only delta of HOMA-IR (P<0.001) remained independently and significantly associated with MCP-1, respectively. CONCLUSIONS: Because both biomarkers have been shown to play an important role in the development and progression of atherosclerosis, the observations presented in this study could be of clinical relevance for morbidly obese patients undergoing bariatric surgery.

Adult↗
PubMed1997

Analysis of a complex oligogenic disease.

Our analysis of GAW10 problem 2 data set consisted of linear regression analysis followed by linkage analysis. The linear regression analysis allowed some exploration of the relationships between the quantitative variables. Furthermore, it isolated some of the components of certain quantitative variables that were not due to a major locus and facilitated the linkage analysis that followed. For the linkage analysis, we used MAPMAKER/SIBS and the SIBPAL program from S.A.G.E. We found linkage of Q4 to chromosome 8. Analysis using the residuals of Q1 and Q3 showed linkage to chromosomes 5 and 4, respectively.

Female↗