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PubMed2006

Duloxetine compared with fluoxetine and venlafaxine: use of meta-regression analysis for indirect comparisons.

BACKGROUND: Data comparing duloxetine with existing antidepressant treatments is limited. A comparison of duloxetine with fluoxetine has been performed but no comparison with venlafaxine, the other antidepressant in the same therapeutic class with a significant market share, has been undertaken. In the absence of relevant data to assess the place that duloxetine should occupy in the therapeutic arsenal, indirect comparisons are the most rigorous way to go. We conducted a systematic review of the efficacy of duloxetine, fluoxetine and venlafaxine versus placebo in the treatment of Major Depressive Disorder (MDD), and performed indirect comparisons through meta-regressions. METHODS: The bibliography of the Agency for Health Care Policy and Research and the CENTRAL, Medline, and Embase databases were interrogated using advanced search strategies based on a combination of text and index terms. The search focused on randomized placebo-controlled clinical trials involving adult patients treated for acute phase Major Depressive Disorder. All outcomes were derived to take account for varying placebo responses throughout studies. Primary outcome was treatment efficacy as measured by Hedge's g effect size. Secondary outcomes were response and dropout rates as measured by log odds ratios. Meta-regressions were run to indirectly compare the drugs. Sensitivity analysis, assessing the influence of individual studies over the results, and the influence of patients' characteristics were run. RESULTS: 22 studies involving fluoxetine, 9 involving duloxetine and 8 involving venlafaxine were selected. Using indirect comparison methodology, estimated effect sizes for efficacy compared with duloxetine were 0.11 [-0.14;0.36] for fluoxetine and 0.22 [0.06;0.38] for venlafaxine. Response log odds ratios were -0.21 [-0.44;0.03], 0.70 [0.26;1.14]. Dropout log odds ratios were -0.02 [-0.33;0.29], 0.21 [-0.13;0.55]. Sensitivity analyses showed that results were consistent. CONCLUSION: Fluoxetine was not statistically different in either tolerability or efficacy when compared with duloxetine. Venlafaxine was significantly superior to duloxetine in all analyses except dropout rate. In the absence of relevant data from head-to-head comparison trials, results suggest that venlafaxine is superior compared with duloxetine and that duloxetine does not differentiate from fluoxetine.

Antidepressive Agents↗

PubMed2001

A population pharmacokinetic-pharmacodynamic and logistic regression analysis of lotrafiban in patients.

OBJECTIVE: Our objective was to assess the safety, tolerability, pharmacokinetics, and pharmacodynamics of lotrafiban, an oral glycoprotein IIb/IIIa inhibitor, in patients with a recent myocardial infarction, unstable angina, transient ischemic attack, or stroke. METHODS: A 12-week, double-blind, multi-center, placebo-controlled, parallel-group, phase II study of lotrafiban (the Anti-platelet Useful Dose Study) was conducted in patients. Lotrafiban or placebo was administered as a twice daily oral dose at four dose levels (5-100 mg) for 12 weeks with daily doses of aspirin (300-325 mg). The pharmacokinetics of lotrafiban were characterized with the use of a population approach and were described by a two-compartment model with first order absorption and first order elimination. The pharmacodynamic data, ex vivo platelet aggregation, were described with the use of a direct effect inhibitory sigmoidal model with a baseline. The relationship between the severity of bleeding episodes and predicted steady-state lotrafiban exposure was characterized by logistic regression. RESULTS: Pharmacokinetic analysis showed that increasing age and decreasing creatinine clearance resulted in increased exposure to lotrafiban. The concentration-effect relationship was steep, with near complete inhibition of platelet aggregation at lotrafiban concentrations in excess of 20 ng/mL. Logistic regression showed that at exposures that exceeded approximately 835 ng. h/mL, the severity of adverse bleeding events increased considerably; this suggested that dosing recommendations should be generated to minimize the likelihood of patients having an area under the plasma concentration-time curve from 0 to 24 hours in excess of this value. CONCLUSIONS: Patients whose age exceeded 65 years or whose creatinine clearance was less than 60 mL/min should be given a lower dose of lotrafiban than younger patients with good renal function.

Adult↗

PubMed2003

Trail impacts in Sagarmatha (Mt. Everest) National Park, Nepal: a logistic regression analysis.

A trail study was conducted in the Sagarmatha (Mt. Everest) National Park, Nepal, during 1997-1998. Based on that study, this paper examines the spatial variability of trail conditions and analyzes factors that influence trail conditions. Logistic regression (multinomial logit model) is applied to examine the influence of use and environmental factors on trail conditions. The assessment of trail conditions is based on a four-class rating system: (class I, very little damaged; class II, moderately damaged, class III, heavily damaged; and class IV, severely damaged). Wald statistics and a model classification table have been used for data interpretation. Results indicate that altitude, trail gradient, hazard potential, and vegetation type are positively associated with trail condition. Trails are more degraded at higher altitude, on steep gradients, in areas with natural hazard potential, and within shrub/grassland zones. Strong correlations between high levels of trail degradation and higher frequencies of visitors and lodges were found. A detailed analysis of environmental and use factors could provide valuable information to park managers in their decisions about trail design, layout and maintenance, and efficient and effective visitor management strategies. Comparable studies on high alpine environments are needed to predict precisely the effects of topographic and climatic extremes. More refined approaches and experimental methods are necessary to control the effects of environmental factors.

Climate↗

PubMed2004

Limitations of bi-linear regression analysis for the determination of receptor occupancy with positron emission tomography.

BACKGROUND AND OBJECTIVES: Linear/multilinear regression methods are widely used in quantitative neuroreceptor positron emission tomography. A reference tissue method based on a bi-linear operational equation, the bi-linear reference tissue method, has been introduced in order to overcome the need for arterial blood sampling. The aim of the present paper was to investigate the sensitivity of the bi-linear reference tissue method to statistical noise, with special regard to the assessment of receptor occupancy. In addition, improvement of the bi-linear reference tissue method by regularization using physiological constraints was evaluated. METHODS: Application of the bi-linear method to dynamic positron emission tomography using the serotonin transporter ligand C-(+)McN5652 was considered. Investigations were performed by computer simulations and analysis of 29 patient studies. RESULTS: The equilibrium specific-to-non-specific partition coefficient V"3 was significantly underestimated by the bi-linear reference tissue method. At realistic noise levels the extent of the underestimation ranged from 25% to 75% for partition coefficients ranging from 0.3 to 0.3, respectively. This caused a 15-60% underestimation of changes in receptor occupancy after simulated intervention. The noise dependence of the bias was confirmed in the patient studies. Regularization significantly reduced the underestimation of the occupancy. CONCLUSIONS: When receptor status or noise level vary substantially, as in receptor occupancy studies, the bias of the bi-linear reference tissue method should be taken into account.

Adult↗

PubMed2002

Multivariate regression analysis of epidural pressure in cattle.

OBJECTIVE: To evaluate the effects of growth, maturity, and pregnancy on epidural pressure in cattle. ANIMALS: 50 healthy Holstein cattle (18 heifers, 23 lactating cows, and 9 pregnant nonlactating cows). PROCEDURE: Each of the cattle was restrained in a standing position. Height of the second lumbar vertebra's transverse process (2LTP) and humeral tuberosity (HT) on the right side as well as abdominal girth (AG) were measured in each animal, and body condition score (BCS) was ascertained. Skin caudal to the first lumbar spinous process was aseptically prepared, and anesthetic was injected. After inserting a 16-gauge 120-mm Tuohy needle in the ligamentum flavum, a calibrated pressure transducer was connected to the needle. Then, the needle was introduced into the epidural space, and epidural pressure was recorded. RESULTS: Mean +/- SD residual epidural pressure of heifers (-9.3+/-3.3 mm Hg) was significantly higher than that of lactating (-174+/-5.5 mm Hg) or nonlactating (-14.5+/-2.4 mm Hg) cows. Stepwise regression of 5 variables revealed that only the difference in height between 2LTP and HT (2LTP - HT) in heifers and only BCS in lactating cows were significantly correlated with residual epidural pressure. For all cattle, the optimal equation (R2 = 0.47) describing the relationship was y = -12.7 + 6.3x, - 0.4x2 - 0.1x3, where y is epidural pressure, x1 is BCS, x2 is 2LTP - HT, and x3 is age. CONCLUSIONS AND CLINICAL RELEVANCE: Negative epidural pressure was detected in standing cattle. Growth, maturity, and pregnancy affect epidural pressure in cattle.

Animals↗

PubMed1983

A life table and Cox regression analysis of patients with combined proximal left anterior descending and proximal left circumflex coronary artery disease: non-left main equivalent lesions (CASS).

Combined proximal left anterior descending and proximal left circumflex artery stenoses greater than or equal to 70% have been referred to as "left main equivalent" lesions. We compared the survival rates of medically treated patients who have this type of coronary anatomic characteristics with the survival rates of patients who have left main coronary artery stenoses greater than or equal to 70% by use of a stratified life table approach and a Cox regression model. Comparison of the patients with left main coronary artery stenoses with those who have left main equivalent lesions by use of life table analysis and three different calculations of patient exposure time revealed a poorer prognosis for the patients who had left main coronary artery disease (p less than or equal to .04 for all three methods). The stepwise Cox analysis also determined that patients who had left main artery stenoses had a significantly poorer prognosis than patients who had left main equivalent coronary disease (p = .002), even after consideration of important baseline variables known to affect survival rates. We then compared the patients who had combined proximal left anterior descending and proximal left circumflex artery disease with patients who had combined stenoses greater than or equal to 70% in the nonproximal left anterior descending stenosis influenced survival rates. The 5 year to determine if location of the left anterior descending stenosis influenced survival rates. The 5 year survival rate was not as high for the patients who had proximal left anterior descending artery disease (55% vs 70%, p = .001). In conclusion, combined proximal left anterior descending and proximal left circumflex artery disease identifies a high-risk (as determined by angiography) patient subset.(ABSTRACT TRUNCATED AT 250 WORDS)

Actuarial Analysis↗

PubMed2005

A decade of trials of interferon-alpha for chronic hepatitis C. A meta-regression analysis.

The most relevant randomized controlled trials of interferon-alpha (IFN) for naive patients with chronic hepatitis C (CHC) published in a decade, just before appearance of pegylated IFN trials in 2000, were included in this paper. Its purpose is to review the relationship between sustained biochemical response in active versus control group versus usual clinical variables as IFN regimens, cirrhosis, genotype and versus less frequently addressed variables as funding, methodological quality or location of principal author. Meta-analysis estimates of global treatment effect varied according to trial design: group 1=IFN versus placebo/no treatment, 32 RCTs, 2499 pts, OR 9.5 (6.3-14.2); group 2a=comparison of IFN schedules, 43 RCTs, 7454 pts, OR 1.6 (1.4-1.9); group 2b=IFN+other drugs versus standard IFN, 30 RCTs, 4737 pts, OR 2.0 (1.6-2.6). Fixed effects (arm-level) meta-regression on the complete data set (171 arms, 10,580 pts) revealed that sustained response was most likely in experimental arms of IFN+ribavirin or other drugs (OR 2.4), arms using yearly schedule (OR 2.0), trial principal author from Asia (OR 1.7), trial sample size >200 (OR 1.4) and arms enrolling less than 50% of cirrhotics (OR 1.3). Moreover, focus was on some significant interactions too, as the effect of trial's quality interacting to the recorded funding (more benefit if no-profit, less if for-profit) and the effect of trial funding interacting to the location of first author (more benefit if from Asia). Three main effects (experimental arm, cirrhosis, funding) and one interaction (funding*location of principal author) explained 31% of between study variability in a random-effect meta-regression. In a subgroup analysis on a data set including available information on HCV genotype (93 arms, around 7000 pts), meta-regression revealed that genotype 1 or 4 less than 50% per arm and specialistic journal were significant predictors of either biochemical (transaminases) or virological (HCV-RNA) sustained response, in a model including the same main effects identified in the complete data set analysis. Finally, although mostly captured by different IFN regimens along time, heterogeneity of effect in a large set of (not-pegylated) IFN trials was also explained by HCV genotype and variables of quality and reporting, such as trial's principal author from Asia.

Hepatitis C, Chronic↗

PubMed1992

Collinearity diagnosis for a relative risk regression analysis: an application to assessment of diet-cancer relationship in epidemiological studies.

In epidemiologic studies, two forms of collinear relationships between the intake of major nutrients, high correlations, and the relative homogeneity of the diet, can yield unstable and not easily interpreted regression estimates for the effect of diet on disease risk. This paper presents tools for assessing the magnitude and source of the corresponding collinear relationships among the estimated coefficients for relative risk regression models. I show how to extend three tools (condition indices, variance decomposition proportions, and standard inflation factors) for diagnosing collinearity in standard regression models to likelihood and partial likelihood estimation for logistic and proportional hazards models. This extension is based on the analogue role of the information matrix in such analyses and the cross-product matrix in the standard linear model. I apply the methodology to relative risk models that relate crude intakes (on the log scale) and nutrient densities to breast cancer cases in the NHANES-I follow-up study. The three diagnostic tools provide complementary evidence of the existence of a strong collinearity in all models that is due largely to homogeneity of the population with respect to our risk scale for the crude intakes. The analysis suggests that the non-significant relative risks for the crude intakes in these models may be due to their involvement in collinear relationships, while the nonsignificant relative risks for the nutrient densities are far less affected by multicollinearity.

Adult↗

PubMed1991

Quantitative evaluation of the tumour-stroma border by exponential regression analysis.

The architecture of the tumour margin is an essential feature for the histological diagnosis of certain neoplasms. In a previous study we have shown by computer simulations, that the degree of tumour cell motility and proliferation influences qualitative morphological criteria of the tumour border. Here we propose a method for an objective, quantitative description of the tumour cell distribution at the tumour-stroma border. 100 morphological patterns generated by computer simulation with different preset degrees of motility and proliferation were evaluated. On a measuring path starting at the most peripheral cell and going towards the tumour centre, the density of tumour cells for each distance from the tumour margin was calculated from the number of cells within a 5 x 5 matrix around each measuring point. An exponential regression function was adapted to the measured density distribution. The parameters of the regression curve and 'the goodness of fit' were tested for correlation with the preset simulation parameters. It was found that the degree of motility and proliferation can be deduced from the quantitative descriptors of the tumour margin (linear regression of the preset values and of the values estimated from the morphological analysis: r = 0.903; t = 20.7; P less than 0.001). Besides the evaluation of computer-simulated morphological patterns, the same measuring procedure can also be applied to histological slides of melanocytic skin tumours using automated image analysis.

Cell Division↗

PubMedDate not supplied

Evaluation of susceptibility status of Culex quinquefasciatus larvae to few organophosphorus insecticides based on logistic regression analysis.

A laboratory trial was carried out at Pune to evaluate the effectiveness of five types of larvicides viz. Malathion, Temephos, Fenthion, Dichlorvos and Fenitrothion against Culex quinquesfasciatus larvae. The expected number of mortality at various dose levels for the five types of insecticides were estimated separately using logistic regression model. Based on the fitted model, the estimated dose level corresponding to the 90 percent mortality (LC90) was obtained for each insecticide. Approximate 95 percent confidence intervals for the LC90 dose, in each case, has been provided. The analysis revealed that out of all the five types of insecticides included in the study, fenthion was the most effective. The estimated value of LC90 in this case was the lowest and is equal to 0.007 mg/L. The effectiveness of temephos, dichlorvos and fenitrothion was found to be approximately same and malathion was the least effective. The results were found to be comparable with that obtained under probit method.

Animals↗

PubMed2005

Applying a data duplication technique in linear regression analysis of waiting time to pregnancy.

This analysis demonstrates the application of a data duplication technique in linear regression with censored observations of the waiting time to third pregnancy ending in two outcome types, using data from Malaysia. The linear model not only confirmed the results obtained by the Cox proportional hazards model, but also identified two additional significant factors. The method provides a useful alternative when Cox proportionality assumption of the hazards is violated.

Adult↗

PubMed2005

Penalized Cox regression analysis in the high-dimensional and low-sample size settings, with applications to microarray gene expression data.

MOTIVATION: An important application of microarray technology is to relate gene expression profiles to various clinical phenotypes of patients. Success has been demonstrated in molecular classification of cancer in which the gene expression data serve as predictors and different types of cancer serve as a categorical outcome variable. However, there has been less research in linking gene expression profiles to the censored survival data such as patients' overall survival time or time to cancer relapse. It would be desirable to have models with good prediction accuracy and parsimony property. RESULTS: We propose to use the L(1) penalized estimation for the Cox model to select genes that are relevant to patients' survival and to build a predictive model for future prediction. The computational difficulty associated with the estimation in the high-dimensional and low-sample size settings can be efficiently solved by using the recently developed least-angle regression (LARS) method. Our simulation studies and application to real datasets on predicting survival after chemotherapy for patients with diffuse large B-cell lymphoma demonstrate that the proposed procedure, which we call the LARS-Cox procedure, can be used for identifying important genes that are related to time to death due to cancer and for building a parsimonious model for predicting the survival of future patients. The LARS-Cox regression gives better predictive performance than the L(2) penalized regression and a few other dimension-reduction based methods. CONCLUSIONS: We conclude that the proposed LARS-Cox procedure can be very useful in identifying genes relevant to survival phenotypes and in building a parsimonious predictive model that can be used for classifying future patients into clinically relevant high- and low-risk groups based on the gene expression profile and survival times of previous patients.

Biomarkers, Tumor↗

PubMed1980

Rapid determination of minimum inhibitory concentrations of antimicrobial agents by regression analysis of light scattering data.

A novel, rapid, automated method for determining the minimum inhibitory concentrations of antimicrobial drugs within ranges acceptable for therapeutic application is described and validated in this report. By employing a simple modification of the Autobac photometer currently in use and in optically clear, modified Mueller-Hinton broth, the method utilizes forward light scattering data measured in the presence of two concentrations of the antimicrobial agent to compute the minimum inhibitory concentrations. Empirically derived regression equations which simultaneously use scattering data from two drug concentrations are employed in this computation, rather than simple breakpoint analysis in which the light scattering measured in the presence of each drug concentration is referred to a threshold level. The minimum inhibitory concentrations obtained with this new method were highly reproducible and, as shown by side by side comparisons were in excellent agreement with the minimum inhibitory cencentrations obtained with the International Collaborative Study broth dilution method.

Anti-Bacterial Agents↗

PubMed2004

Joinpoint regression analysis of lung cancer mortality, Andalusia 1975-2000.

BACKGROUND: Previous analyses of lung cancer mortality were based on models of death rates within one time period, assuming that rates increase or decrease with time at a constant rate. The aim of this work is to analyse recent changes in lung cancer mortality trends in Andalusia (Spain) during the period of 1975-2000 using joinpoint regression models. PATIENTS AND METHODS: Mortality data were obtained from the Death Registry of Andalusia. For each gender, age group-specific and standardised (overall and truncated) rates were calculated by the direct method (using the world standard population). The joinpoint analysis was used to identify the best-fitting points where a statistically significant change in the trend occurred. RESULTS: Lung cancer is the leading cause of cancer mortality in men, with an increasing trend up to 1994. After that year, rates began to decrease significantly (-1.8% yearly from 1994 to 2000). Standardised rates in women exhibited a downward trend until the early 1990s, after which they levelled off (overall standardised rates) or increased significantly (truncated rates 35-64 years). CONCLUSIONS: An increase in lung cancer mortality has been observed in young women. There seems to be a relationship with the prevalence in smoking in men and women.

Adult↗

PubMed1993

A nonlinear regression analysis of nonlinear, passive-deflation flow-volume plots.

When studying lung mechanics of intubated premature infants, by the passive-deflation technique we noted that in many flow-volume plots the descending limb was curvilinear with a convexity toward the volume axis. By conventional linear analysis lung mechanics of these patients did not change after the administration of terbutaline, but Mead's tangent-chord slope ratio method for quantifying the amount of curvature showed that the shape of the flow-volume plots did change. Because of the limitations of this method, we developed a microcomputer-based, reiterative regression algorithm which optimizes a nonlinear function for the best fit to any given set of data. We then studied six very low birth weight infants with clinical evidence of pulmonary gas trapping (weight at study, 1.22 +/- 0.29 kg; age, 26 +/- 16 days). We measured respiratory system resistance (Rrs), compliance (Crs), and expiratory time constants (TCrs) by the passive deflation technique before and after subcutaneous administration of 0.02 mg/kg of terbutaline. No effect of terbutaline in a dose sufficient to increase heart rate > 25 beats/min was observed. The same data analyzed using the nonlinear regression technique with a function based upon a two compartment model of parallel inhomogeneities revealed one compartment with relatively normal Rrs, Crs, and TCrs values, and a second compartment with a very high Rrs. The latter fell by 50% after terbutaline. These data suggest that abnormalities of airway resistance in ventilated preterm infants are not easily identifiable by classic linear analysis of lung mechanics.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Resistance↗

PubMed2006

Body size and composition and prostate cancer risk: systematic review and meta-regression analysis.

The evidence that measures of obesity and stature are associated with prostate cancer is weak and inconsistent. We performed a systematic review and meta-analysis of the relationship between body mass index (BMI), height, weight, waist circumference and waist-to-hips ratio (WHR) and the risk of prostate cancer. Study-specific dose-response slopes were obtained, and random effects rate ratios (RRs) were computed from linear meta-regression models. We included 55,521 cases identified among 2,818,767 men from 31 cohort studies, and 13,232 cases and 16,317 controls from 25 case-control studies. The overall RR for BMI was 1.05 per 5 kg/m2 increment, 95% CI 1.01-1.08. For studies that reported results by stage of disease, the RRs were stronger for advanced disease (RR 1.12 per 5 kg/m2 increment, 95% CI 1.01-1.23) compared with localized disease (RR 0.96 per 5 kg/m2 increment, 95% CI 0.89-1.03), p = 0.02. Height was also positively associated with risk (RR 1.05 per 10 cm increment, 95% CI 1.02-1.09), but the evidence was weak for weight (RR 1.01 per 10 kg increment, 95% CI 0.97-1.04), waist circumference (RR 1.03 per 10 cm increment, 95% CI 0.99-1.07), and WHR (RR 1.11 per 0.1 unit increment, 95% CI 0.95-1.30). Stronger associations were observed among cohort studies compared with case-control studies for BMI (p = 0.006), height (p < 0.001) and weight (p = 0.02). This meta-analysis indicates that obesity is weakly associated with an increased risk of prostate cancer (particularly advanced stage tumors). While increased stature may also increase risk, there is little evidence for an association with central obesity.

Body Composition↗

PubMed1998

Predisposing factors of life-threatening deep neck infection: logistic regression analysis of 214 cases.

OBJECTIVE: In the era of antibiotics, most deep neck infections can be cured by conservative treatment, but some still result in life-threatening complications. In this study, we discuss whether or not there are predisposing factors of complicated deep neck infection. DESIGN: A retrospective chart review of patients presenting between 1988 and 1996 was conducted. METHOD: Among 214 deep neck infection patients, 18 cases resulted in lethal complications. We used the "dummy" variable with logistic regression as the statistical analysis method. RESULTS: Patients with an underlying disease, neck swelling, and delay time had a positive correlation that was statistically significance (p < .05). Patients who were older, male, with complete blood count/differential count-positive finding and fever had positive correlation, but this was not statistically significant (p > .05). CONCLUSION: Although complicated deep neck infection is a rapidly progressive disease with a high mortality, we can not thoroughly predict the prognosis or avoid it happening completely. But, if we can detect and pay more attention to the high-risk group of patients with use of aggressive therapy, the incidence of complicated deep neck infection may be reduced.

Abscess↗

PubMedDate not supplied

Testing the harvesting hypothesis by time-domain regression analysis. I: baseline analysis.

Although the association between air pollution and daily mortality is well established, the mechanisms by which air pollution results in excess mortality are not yet well understood. In particular, there exists debate over whether air pollution has a direct effect on mortality in the general population or simply shortens the life span of frail individuals, a hypothesis referred to as "harvesting." The goal of this investigation is to test the harvesting hypothesis using the time-domain regression method of Dominici et al. (2003a). We conducted simulations based on a two-compartment model that divides the population into a larger group of healthy individuals and a frail subpopulation. Death from air pollution is assumed to take place in two steps, by first moving from healthy population to the frail pool, then death with probability related to the level of air pollution. Using time-domain analysis, we seek to identify data patterns that would be characteristic of harvesting under different scenarios. For a pure harvesting model, time-domain analysis indicates that mortality is associated with a short-term air pollution episode of less than 2 d if the mean residency time in the frail pool is short. If both entrants and deaths depend on the level of air pollution and the rates of entry to and exit from the frail pool are about the same, the log relative risk estimates are essentially unchanged at all time scales. If pollution affects mortality in the frail pool more than entrants, larger effects will occur at shorter time scales.

Air Pollution↗