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PubMedDate not supplied

A six-hour extrapolated sampling strategy for monitoring mycophenolic acid in renal transplant patients in the Indian subcontinent.

BACKGROUND: Therapeutic drug monitoring for mycophenolic acid (MPA) is increasingly being advocated. The present therapeutic range relates to the 12-hour area under the serum concentration time profile (AUC).However, this is a cumbersome, tedious, cost restricting procedure. Is it possible to reduce this sampling period? AIM: To compare the AUC from a reduced sampling strategy with the full 12-hour profile for MPA. SETTINGS AND DESIGN: Clinical Pharmacology Unit of a tertiary care hospital in South India. Retrospective, paired data. MATERIALS AND METHODS: Thirty-four 12-hour profiles from post-renal transplant patients on Cellcept were evaluated. Profiles were grouped according to steroid and immunosuppressant co-medication and the time after transplant. MPA was estimated by high performance liquid chromatography with UV detection. From the 12-hour profiles the AUC up to only six hours was calculated by the trapezoidal rule and a correction factor applied. These two AUCs were then compared. STATISTICAL ANALYSIS: Linear regression, intra-class correlations (ICC) and a two-tailed paired t-test were applied to the data. RESULTS: Comparing the 12-hour AUC with the paired 6-hour extrapolated AUC, the ICC and linear regression(r2) were very good for all three groups. No statistical difference was found by a two-tailed paired t-test. No bias was seen with a Bland Altman plot or by calculation. CONCLUSION: For patients on Cellcept with prednisolone +/- cyclosporine the 6-hour corrected is an accurate measure of the full 12-hour AUC.

Adolescent↗

PubMed1983

Epidemiology and genetics of endemic goiter. I. Epidemiological aspects.

This study dealt with approximately 2,000 children and their parents living in a hyperendemic goiter area in Central Brazil, which is bounded by the jungle to the north and by a large plain to the south. The determination of goiter was made according to the methods and classification adopted by WHO. Conspicuous forms of goiter were found in 41% of the children examined. Multiple linear regression analysis showed an increase with age in the frequency of goiter in both sexes. Although data from the literature show that Mulattoes and Negroes have statistically higher frequencies of goiter than do Whites, our multiple linear regression analysis revealed no evidence for an effect of race on the endemism. There was no significant association with socioeconomic level. The presence of goiter in parents was shown to be statistically associated with its occurrence in the children.

Adolescent↗

PubMed1981

Method for predicting when children with progressive renal disease may reach high serum creatinine levels.

Optimal planning of therapy for children with progressive renal failure requires accurate prediction of the age at which the serum creatinine (SC) level of the patient will be sufficiently high to warrant dialysis or renal transplantation. In a retrospective study of 29 children with progressive renal disease, linear regressions for each child were developed from the reciprocal of serum creatinine (1/SC) on time. It was found that in children, as in adults, the rate of deterioration of renal function expressed as 1/SC described a linear regression. From the regressions developed, it was determined that predictions using at least six 1/SC values on time would have given acceptable estimates of the age at which dialysis treatment became necessary. With the more precise measurement of SC now available it is likely that even more accurate predictions will be possible in the future.

Child↗

PubMed1997

An analysis of the determinants of urinary urea and creatinine clearance in patients on continuous peritoneal dialysis.

The relative contribution of urinary volume (UV) and urine-to-plasma concentration ratios for urea (U/PUr) and creatinine (U/PCr) to urinary Kt/V urea (Kt/VU) and urinary uncorrected creatinine clearance (CCrU), respectively, was studied by simple and multiple linear regression analysis in 236 urea kinetic studies and 233 creatinine kinetic studies performed in 135 patients on continuous peritoneal dialysis (CPD). The following simple regressions were obtained: Kt/VU = 0.09 + 0.72 (UV), r = 0.75; Kt/VU = -0.01 + 0.11 (U/PUr), r = 0.55; CCrU = 12.06 + 56.46 + 46.46 (UV), r = 0.62; CCrU = 3.51 + 3.40 (U/PCr), r = 0.58. All r values were significant (p < 0.001). According to these regressions, a loss of 0.2 L/24 hours in UV leads to a loss of 0.15 weekly in Kt/VU and 11.3 L/1.73 m2 weekly in corrected CCrU (approximately 8 L/1.73 m2 weekly in corrected CCrU). By multiple linear regression, (1) Kt/VU = -0.38 + 0.70 (UV) + 0.10 (U/PUr). Standardized coefficients were 0.72 for UV and 0.51 for U/PUr (2) CCrU = -33.36 + 59.83 (UV) + 3.63 (U/PCr). Standardized coefficients were 0.65 for UV and 0.61 for U/PCr. UV is the most important determinant of both urea and creatinine urinary clearances in CPD patients. The contribution of the U/P ratios to the urinary clearances is important, but less than that of UV. The primary dependence of urinary clearances on UV allows the use of UV, which can be easily monitored by patients, as a first approximation index of changing residual renal function in CPD.

Creatinine↗

PubMed2000

Relationship of surface epithelium concentrations of IL-1 alpha and IL-1 beta to clinical inflammation during experimental gingivitis.

Experimental evidence has clearly demonstrated that IL-1 cytokine levels increase in experimental gingivitis (EG) models in response to plaque accumulation following the cessation of oral hygiene. These changes in cytokine production are reported to occur prior to visible signs of clinical inflammation, and as such may represent early markers of gingival inflammation. This clinical study used a novel dermal sampling tape as a method to collect cytokines from gingival epithelium, as opposed to the more commonly sampled gingival crevicular fluid. The primary objective of the study was to examine the relationship between changes in cytokine levels and clinical inflammation. Ten subjects participated in a 14-day EG model, where 5 days following a dental prophylaxis subjects refrained from all oral hygiene measures for 14-days. Clinical measures including the Löe-Silness Gingival Index (GI), a bleeding index derived from the GI, and the inflammation index (II) were made at baseline prior to the initiation of the EG period and following 14 days of EG. Dermal tape samples were collected from the right posterior buccal quadrant of each subject at both baseline and day 14. The tapes were extracted and the extracts analyzed for both IL-1 alpha and IL-1 beta by ELISA. Results of this study indicate that over a 14-day EG period statistically significant (p < 0.05) increases in GI, gingival bleeding, II, and IL-1 alpha were observed (tested by matched-pairs t test and Wilcoxon signed ranks test). A directional increase in IL-1 beta was also observed. Linear regression analyses demonstrated a strong positive correlation between the number of gingival bleeding sites from the region of gingiva sampled with Sebutape and IL-1 alpha (r = 0.93), as well as IL-1 beta (r = 0.90). In addition, linear regression analyses also demonstrated a strong positive correlation between the mean II score from the region of gingiva sampled with Sebutape and IL-1 alpha (r = 0.93), as well as IL-1 beta (r = 0.86). Similar correlations were observed for whole mouth scores of the number of gingival bleeding sites and mean II with respect to IL-1 alpha and IL-1 beta levels. Collectively, these data confirm the utility of the dermal tape for sampling epithelium cytokine levels from the gingiva and demonstrate a strong positive correlation between IL-1 alpha and IL-1 beta concentrations and gingival inflammation.

Adult↗

PubMed1995

Dental health and treatment needs in institutionalized psychiatric patients in Italy.

The caries prevalence, oral hygiene status, periodontal health and the treatment needs were assessed in a group of institutionalized psychiatric patients in Catanzaro, Italy. Of the total sample of 297 subjects, 165 (55.6%) were males, the mean age was 55.1 yr, the great majority (90.6%) was able to care for themselves, on average they had been institutionalized for 12.9 yr, and almost two-thirds were schizophrenic (65%). They did not receive any assistance in daily oral hygiene procedures, only 7.4% had visited a dentist and exclusively for emergency care. A total of 33 (11.1%) patients were edentulous, and the multiple logistic regression analysis showed a highly significant increase of edentulousness with increasing age (P < 0.001). No caries-free subjects were found and among the dentate the DMFT and DMFS scores for all age groups were respectively 15.5 and 88.6. The stepwise linear regression analysis showed that the mean DMFT index increased with age (t = 6.86; P < 0.001), and in the partly or totally helpless patients it was significantly higher than in the self-sufficient patients (t = 2.78; P = 0.006). Of the 264 dentate subjects, only 25 (9.5%) had no need of dental treatment; 213 (80.7%) required extractions with a mean number per person of 6.3 and the need for conservative dental care was recorded in 154 (58.3%) patients with a mean need for patient of 2.8. Mean OHI-S score was 4.2 and the stepwise linear regression analysis showed that it increased with age (t = 5.73; P < 0.001) and with the length of institutionalization (t = 3.42; P < 0.001). Only 0.9% of the entire sample was found with healthy periodontal tissue; bleeding on probing or a higher score was found in 4.6% of examined sextants; calculus in 10.1%; shallow pockets and deep pockets in 19.6% and 64.8% of all sextants. The results of the multiple logistic regression analysis indicated that the number of subjects with deep pockets as highest score increased with increasing age (P<0.001), and with the increasing length of institutionalization (P=0.005). The findings of this study demonstrate high caries prevalence, poor oral hygiene and periodontal health, and extensive unmet needs for dental treatment. More coordinated efforts between the social and dental care sector must be maintained to serve adequately the need of this disadvantaged group.

Adult↗

PubMed2003

Intersite consistency as a measurement of programmatic evaluation in a medicine clerkship with multiple, geographically separated sites.

PURPOSE: This study introduces "intersite consistency" as a measurement of programmatic evaluation and demonstrates its feasibility and construct validity. METHOD: Student data in our multisite, geographically separated clerkship were collected prospectively over a ten-year period (1990-2000). We calculated mean scores for each clerkship measurement and analyzed these data on both a yearly and a 10-year cumulative basis. Analyses of variance (ANOVA) and linear regression were used for statistical analysis. RESULTS: Data for 1,632 (98%) students were included in our study. During this ten-year study period, we had 22 different on-site clerkship directors at seven clerkship sites. ANOVA and linear regression of year-to-year and cumulative data did not demonstrate an effect of site on student outcomes. CONCLUSIONS: Intersite consistency can be used as one measure of programmatic evaluation for multisite clerkships.

Analysis of Variance↗

PubMed2006

Dietary factors related to higher plasma fibrinogen levels of Japanese-americans in hawaii compared with Japanese in Japan.

OBJECTIVE: We investigated whether dietary factors explain higher plasma fibrinogen levels in Japanese emigrants living a Western lifestyle in Hawaii compared with Japanese in Japan. METHODS AND RESULTS: Plasma fibrinogen and nutrient intakes were examined by standardized methods in men and women 40 to 59 years of age from a Japanese-American sample in Hawaii (100 men and 106 women) and 4 population samples in Japan (569 men and 567 women). Multiple linear regression models were used to examine the relationship between dietary factors and the plasma fibrinogen difference between Hawaii and Japan. Average plasma fibrinogen was significantly higher in Hawaii compared with Japan (P<0.001 in both genders). In multiple linear regression analyses with each dietary variable considered separately, body mass index reduced the plasma fibrinogen difference between Hawaii and Japan by 20.4%; iron intake (mg/1000 kcal) and estimated total sugar intake (%kcal) reduced this difference by 30.0% and 14.4%, respectively. In a model that included body mass index, iron, estimated total sugars, and caffeine (also age and gender), this difference was reduced by 61.3% (from 42.2 to 16.3 mg/dL). CONCLUSIONS: Higher intake of iron, sugar, and caffeine, in addition to obesity, account largely for higher fibrinogen levels with Westernized lifestyle.

Adult↗

PubMed1990

[Use of linear logistic regression in classification of observations].

In the present paper the prediction method using the logistic regression is explained, and the range of problems for its use is deliminated. The example is presented of mentioned method's application on how to predict the dog survival in a radiolobiological experiment. The obtained results are compared with the prediction of outcome using the linear discriminant function. Both models are identic in a proportion of erroneously classified subjects. This method may be diagnostically supportive in ranging individuals to one of two groups delimitated previously.

Regression Analysis↗

PubMed1984

A comparison of methods for determining compartmental analysis parameters.

The traditional method for determining compartmental analysis parameters relies on a visual selection of data points to be used for regression of data from each cellular compartment. This method is appropriate when the compartments are kinetically discrete and are easily discernible. However, where treatment effects on compartment parameters are being evaluated, a more objective method for determining initial parameters is desirable.Three methods were examined for determining initial isotopic contents and half-times of (86)Rb elution from cellular compartments using theoretical data with known parameters. Experimental data from roots of Douglas fir (Pseudotsuga menziesii [Mirb.] Franco) and barley (Hordeum vulgare L.) intact seedlings were also used. The three methods were a visually assisted, linear regression on data of semilog plot of isotope elution versus time, a microcomputer-assisted, linear regression on semilog plot where maximization of the square of the correlation coefficient (r(2)) was the criterion to determine data points needed for each regression and a mainframe computer-assisted, direct nonlinear regression on elution data using a model of the sum of three exponential decay functions. The visual method resulted in the least accurate estimates of compartmental analysis parameters. The microcomputer-assisted and nonlinear regression methods calculated the parameters equally well.

Journal Article↗

PubMed2006

Radiation dose in abdominal computed tomography: the role of patient size and the selection of tube current.

OBJECTIVE: To develop an algorithm for selecting tube current for computed tomography (CT), based on patient weight, that produces abdominal CT images of consistent image quality. METHODS: We recorded body weight and radiation exposure parameters for 37 patients undergoing abdominal CT. Two radiologists blind to the CT technique independently graded 11 measures of image quality, using a 5-point (5 = excellent, 4 = good, 3 = acceptable, 2 = poor, and 1 = unacceptable) scale. These scores were averaged to generate an overall image quality score. Using linear regression, we found a target image noise level that corresponded to an overall image quality score of 4.5. We measured CT image noise in 9 uniformly attenuating regions of interest in the liver and abdominal aorta. We used linear regression to assess the relation between tube current and image noise. A prediction equation was developed to set the tube current in different-sized patients to produce images at the target noise level. Finally, we calculated the dose savings that would have resulted with this tube-current selection technique. RESULTS: Image noise was correlated with patient weight (r2 = 0.81). At an overall image quality score of 4.5, the noise was 16 HU. Using this target noise value, we determined the required tube current for each patient weight and found that the use of this technique would have reduced radiation exposure for all patients weighing less than 70 kg. The dose reduction for the smallest patient (35.4 kg) was 72%. CONCLUSION: To produce CT scans of similar quality, a simple prediction equation can be developed for any scanner to optimize radiation dose for patients of all body weights.

Adult↗

PubMed2005

Change in intraocular pressure measurements after LASIK the effect of the refractive correction and the lamellar flap.

OBJECTIVE: To study the relationship between intraocular pressure (IOP) readings after LASIK and the amount of refractive correction. DESIGN: Retrospective noninterventional case series. PARTICIPANTS: Patients receiving primary LASIK for myopia and myopic astigmatism. METHODS: A database of preoperative, intraoperative, and 3-month postoperative data for 8113 consecutive eyes that underwent primary myopic and myopic astigmatic LASIK was retrospectively reviewed. Linear regression analysis of measured IOP change as a function of refractive change was then performed. Age and preoperative keratometry were also reviewed by multiple regression. MAIN OUTCOME MEASURES: Best-fit curve relating change in measured IOP to refractive change. RESULTS: The mean spherical equivalent of the refractive change was -4.98+/-2.64 diopters (mean +/- standard deviation). The mean decrease in measured IOP was 2.0+/-3.3 mmHg. Linear regression analysis revealed a decrease of 0.12 mmHg of measured IOP per diopter of refractive change (95% confidence interval [CI], 0.09-0.15, R(2) = 0.009, P<0.001). Extrapolation of the data to a theoretical correction of zero diopters revealed a decrease of 1.36 mmHg (95% CI, 1.20-1.51, P<0.001), suggesting a component of measured IOP change that is independent of laser ablation. CONCLUSIONS: The reduction of IOP readings after corneal refractive surgery is a linear function of the amount of refractive correction, with an additional constant reduction that is probably related to the lamellar corneal flap. These data suggest that the lamellar corneal flap makes no contribution to the load-bearing characteristics of the post-LASIK cornea.

Adult↗

PubMed1991

Inheritance and regression toward the mean in heterogeneous cell populations.

Traits such as birth size and lifetime can vary widely even among non-mutated progeny of the same cell proliferating in the same environment. On the other hand, population parameters of these traits may remain stable over many generations, and there may be a distinct inheritance of these traits from mother to daughters. We have reconsidered the implication of mother-daughter correlations in light of linear regression analysis. It is proposed that a non-mutant cell whose phenotype deviates from the population mean produces progeny whose rate of regression toward the mean is proportional to 1-r, where r is the mother-daughter correlation coefficient of the trait under study. Theoretical support for this proposition is derived from linear regression analysis. Empirical support is found in pedigree analysis of cell growth constants among NIH3T3 mouse fibroblast cells, where the presence of an activated human ras oncogene is associated with a decreased r and an increased rate at which the growth constants of progeny regress toward the population mean.

Animals↗

PubMed1995

Correlations between familial refractive error and children's non-cycloplegic refractions.

We examined the spherical equivalent refractions of 237 subjects who had been seen four or more times in a longitudinal study of refractive development in normal children. We employed both photorefraction and autorefraction using a Canon R1 autorefractor. We performed an analysis of variance (F-test for Lack of Fit) to determine the significance of a linear regression in fitting these refractions against three different measures of familial refractive status. One measure included only the number of myopic parents, a second took into account the number of hyperopic parents, and a third included the refractive states of extended genetic relatives. We found no significant correlation between photorefractive data and familial refractions; however, we did find significant, albeit weak, correlations between all measures of familial refractive status and infrared autorefractions of their children. A linear relationship between autorefractive data and overall familial refractive state was found to be most significant. Linear regression of children's autorefractions against a measure of parental myopia and hyperopia was less significant, while a linear model fitting only a measure of parental myopia was least significant, in addition to showing other non-linear trends. We attribute the failure to find a significant correlation between parent and offspring refractions using children's photorefractive data to vignetting by the apparatus and to the short distance of the fixation target. We believe the significant correlation patterns found with the autorefractor reflect the inheritance patterns of parental and familial refractive states.

Adolescent↗

PubMed1982

Correlation between lipid partition coefficients and surface permeation in Schistosoma japonicum.

Comparison of transintegumental membrane permeability and partition coefficients of selected nonelectrolytes was attempted to correlate the parameters of lipid solubility, hydrophilicity, and membrane permeation in male and female schistosomes (parasites of the portal venous tributaries of man). Surface permeation (measured by the triple isotope technique) and octanol/water partition coefficients were determined for 17 compounds (acetamide, aminopyrine, antipyrine, benzyl alcohol, butanol, caffeine, ethanol, ethylene glycol, glycerol, inosine, mannitol, methanol, polyethylene glycol, propylene glycol, sucrose, thiourea, and urea). Linear regression analyses comparing the logarithm of the partition coefficient to transintegumental uptakes indicate a positive correlation in both sexes: R = 0.76 (P less than 0.001) for males, and R = 0.77 (P less than 0.001) for females. Similarly, linear regression analyses comparing hydrogen bond number with the logarithm of tissue uptake index demonstrate a high (negative) correlation in both males (R = 0.85, P less than 0.001) for females (R = -0.90, P less than 0.001). The male and female schistosomes showed no statistically significant differences in correlation of these parameters. Surface permeation was the same in male and female schistosomes, suggesting that male-female variations in integumental uptake rates previously observed may be restricted to metabolites which enter by way of a selective carrier system.

Alcohols↗

PubMed2006

Adiponectin and glucose levels in women with negative or false positive glucose challenge test.

OBJECTIVE: To determine whether there is a correlation between adiponectin levels and glucose levels in women screened for gestational diabetes mellitus by means of a 50-g oral glucose challenge test, and to examine the difference in adiponectin levels between women who tested negative, and those who tested false positive. We further calculated the correlations between adiponectin levels and glucose levels, body mass index, gestational age and maternal age. METHODS: A case control study included 171 mothers with negative or false positive results in the 1-h 50-g glucose challenge test at 24-28 gestational weeks. Serum adiponectin levels were determined by radioimmunoassay at the time of the glucose challenge test. RESULTS: There was a significant difference between women who tested negative at screening, and those who tested false positive with respect to age, prepregnancy body weight and body mass index, and adiponectin levels. Correlation analysis showed adiponectin levels to be negatively correlated to glucose levels (r=-0.193, P=0.011). To examine the association between glucose levels, adiponectin levels and demographic variables, multiple linear regression analysis was carried out. Prepregnancy body mass index and age accounted for 14.6% of the variance in the glucose challenge test. Adiponectin levels did not contribute independently to the variation in glucose levels. A further multiple linear regression analysis was undertaken to investigate the association between adiponectin levels and age, prepregnancy body mass index and glucose levels in the glucose challenge test. In this regression model, prepregnancy body mass index and age explained 12.1% of the variance in adiponectin levels. CONCLUSIONS: In conclusion, our study indicated a negative correlation between adiponectin and glucose levels in women screened for gestational diabetes mellitus by a glucose challenge test. We further found that maternal age and body mass index were independent risk factors for a false positive glucose challenge test. Reduced adiponectin levels in women who tested false positive on the glucose challenge test were dependent on advanced age and higher body mass index.

Adiponectin↗

PubMed2006

Aortic stenosis is associated with elevated plasma levels of asymmetric dimethylarginine (ADMA).

OBJECTIVES: We tested the hypothesis that the presence of aortic stenosis (AS) is associated with elevation of plasma levels of asymmetric dimethylarginine (ADMA), a physiological inhibitor of nitric oxide synthase, a mediator and marker of endothelial dysfunction and an indicator of incremental cardiovascular risk. BACKGROUND: The presence of aortic sclerosis (ASC), the precursor of AS is independently associated both with endothelial dysfunction, and with incremental coronary event risk. It remains uncertain whether elevations of ADMA levels might mediate endothelial dysfunction in these conditions. METHODS: Forty two consecutive patients referred for echocardiography for evaluation of AS, who had calculated aortic valve areas of <1.4 cm(2) (AS group) were evaluated together with 42 consecutive age-matched referred patients (non-AS group). Plasma ADMA levels were measured by high-performance liquid chromatography (HPLC). Determinants of elevation of plasma ADMA levels were identified via stepwise multiple linear regression analysis. RESULTS: Plasma ADMA levels were not statistically different between the AS and non-AS group (median 0.59 vs 0.54 micromol/L, p=0.13, Mann-Whitney test) on univariate analysis. However, in backward stepwise multiple linear regression, the presence of AS was a significant predictor of elevated ADMA levels (p=0.04, 95% CI=0.001, 0.072). In addition, elevated plasma ADMA levels were also associated with history of atrial fibrillation (p=0.009, 95% CI=0.015, 0.100), and negatively associated with creatinine clearance (p=0.01, 95% CI=-0.002, 0.000), and the use of statin therapy (p=0.01, 95% CI=-0.081, -0.011). CONCLUSIONS: AS is independently associated with elevation of ADMA levels, beyond that implied by "conventional" risk factors for endothelial dysfunction. The clinical status of AS as an incremental marker of cardiovascular risk may reflect ADMA-mediated endothelial dysfunction.

Aortic Valve Stenosis↗

PubMed2000

Prediction of retention indices. V. Influence of electronic effects and column polarity on retention index.

The retention index increment for addition of a methylene group to an analyte molecule is shown for 1-halo-n-alkanes to be different from 100 i.u., a value that is customarily assigned according to the current convention in retention index prediction. In temperature-programmed gas chromatography using linearly interpolated retention index I, a linear regression equation, I=AZ+(GRF), with the number of atoms (Z) in the molecule as variable can describe the retention of 16 homologous series of organic compounds on non-polar and polar columns with characteristic A (linear regression coefficient) and (GRF) (group retention factor) values. A molecular model of retention on the basis of electron density and electron density distribution relative to that of n-alkane is proposed. This model brings out the inter- and intramolecular electronic effects in the analyte molecule and its dipole-dipole interaction with the stationary liquid phases, as variations in the A value. The (GRF) value varies with the connectivity ability of a functional group for extended conjugation, substitution, etc., but is most influenced by hydrogen bonding (H-bonding) with the stationary liquid phase. One can estimate the sequence of elution of a mixture of organic compounds from any two of the three parameters on the right-hand side of the above equation or retrieve the retention indexes of an entire homologous series from its A and (GRF) values. The fact that each analyte molecule has its own A value on different columns makes column difference (deltaI) compound-specific rather than column-specific, a departure from previous assumptions.

Chromatography, Gas↗