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PubMedDate not supplied

Psychometrics for two short forms of the Center for Epidemiologic Studies-Depression Scale.

The Center for Epidemiologic Studies-Depression Scale (CES-D; L. S. Radloff, 1977) assesses the presence and severity of depressive symptoms occurring over the past week. Although it contains only 20 items, its length may preclude its use in a variety of clinical populations. This study evaluated psychometric properties of 2 shorter forms of the CES-D developed by F. J. Kohout, L. F. Berkman, D. A. Evans, and J. Cornoni-Huntley (1993): the Iowa form and the Boston form. Data were pooled from 832 women representing 6 populations. Internal consistency estimates, correlations with the original version of the CES-D, and omitted-included item correlations supported use of the Iowa form over the Boston form when a shortened version of the scale is desired. Regression statistics are provided for use in estimating scores on the original CES-D when either shortened form is used. Factor analytic results from two populations support a single-factor structure for the original CES-D as well as the short forms.

Adolescent↗
PubMed2005

Prostate cancer outcome: epidemiology and biostatistics.

Substantial gaps exist in our ability to accurately predict prognosis, and these gaps limit our understanding of the complex mechanisms that contribute to the greatest cancer epidemic of our time, prostate cancer. This review addresses contemporary epidemiologic and biostatistical issues in prostate cancer. It covers the science of outcome prediction and biomarker evaluation, recognition of the need to combine biomarkers to improve the accuracy of our outcome estimates and an analysis of current outcome assessment methods, including the TNM staging system and multivariate regression models. The simplicity and intuitive ease of the current TNM staging system must be balanced against its serious limitations in predictive accuracy and its loss of clinical utility. Statistical regression methods are required as we move to the new era of personalized medicine. We must implement statistical approaches that integrate the new molecular biomarkers with existing prognostic biomarkers to accurately predict which patients require treatment and to determine the optimal therapy.

Biomarkers, Tumor↗
PubMed1989

Pancreatic amylase measured in serum by use of a monoclonal antibody immunochemically immobilized to a solid phase.

We studied a method for measuring the pancreatic isoenzyme of amylase (EC 3.2.1.1) by use of a mouse monoclonal antibody against human salivary-type amylase (Clin Chem 1985;31:1283) coupled indirectly to particles of polyvinylidene fluoride via polyclonal goat anti-mouse immunoglobulin. These particles, in 200 microL of a suspension, could remove salivary amylase (activity 2200 U/L) from an equal volume of serum in 5 min. Measurement of amylase activity in the supernatant fluids from treated sera thus provided an assay of pancreatic amylase. Precision studies at three activity concentrations yielded within-run CVs of 1.6% to 1.7% (n = 25) and total CVs of 2.2% to 5.1% (20 days). Salivary amylase added to each of 10 sera was completely (99.8%, SD 1.6%) removed. The new method (y) showed the following regression statistics when compared with an electrophoretic method (x): slope = 0.989 (SD 0.019), intercept = -0.220% (SD 1.48%), SEE 4.0%, n = 51. Similar respective regression values were found for urine samples: slope = 0.934 (SD 0.053), intercept = 2.3 U/L (SD 3.2), SEE 8.4 U/L, n = 26. The following respective values were found when the new method (y) was compared with the previously described immunoprecipitation assay (x): slope = 1.02 (SD 0.02), intercept = 2.2% (SD 1.4%), SEE 3.3%, n = 23 sera. Reference intervals for pancreatic amylase activity in serum were established for three different substrates: maltotetraose, maltopentaose, and p-nitrophenylheptaoside.

Acute Disease↗
PubMed2001

An efficient and robust statistical modeling approach to discover differentially expressed genes using genomic expression profiles.

We have developed a statistical regression modeling approach to discover genes that are differentially expressed between two predefined sample groups in DNA microarray experiments. Our model is based on well-defined assumptions, uses rigorous and well-characterized statistical measures, and accounts for the heterogeneity and genomic complexity of the data. In contrast to cluster analysis, which attempts to define groups of genes and/or samples that share common overall expression profiles, our modeling approach uses known sample group membership to focus on expression profiles of individual genes in a sensitive and robust manner. Further, this approach can be used to test statistical hypotheses about gene expression. To demonstrate this methodology, we compared the expression profiles of 11 acute myeloid leukemia (AML) and 27 acute lymphoblastic leukemia (ALL) samples from a previous study (Golub et al. 1999) and found 141 genes differentially expressed between AML and ALL with a 1% significance at the genomic level. Using this modeling approach to compare different sample groups within the AML samples, we identified a group of genes whose expression profiles correlated with that of thrombopoietin and found that genes whose expression associated with AML treatment outcome lie in recurrent chromosomal locations. Our results are compared with those obtained using t-tests or Wilcoxon rank sum statistics.

Acute Disease↗
PubMed1998

Predicting lettuce canopy photosynthesis with statistical and neural network models.

An artificial neural network (NN) and a statistical regression model were developed to predict canopy photosynthetic rates (Pn) for 'Waldman's Green' leaf lettuce (Latuca sativa L.). All data used to develop and test the models were collected for crop stands grown hydroponically and under controlled-environment conditions. In the NN and regression models, canopy Pn was predicted as a function of three independent variables: shootzone CO2 concentration (600 to 1500 micromoles mol-1), photosynthetic photon flux (PPF) (600 to 1100 micromoles m-2 s-1), and canopy age (10 to 20 days after planting). The models were used to determine the combinations of CO2 and PPF setpoints required each day to maintain maximum canopy Pn. The statistical model (a third-order polynomial) predicted Pn more accurately than the simple NN (a three-layer, fully connected net). Over an 11-day validation period, average percent difference between predicted and actual Pn was 12.3% and 24.6% for the statistical and NN models, respectively. Both models lost considerable accuracy when used to determine relatively long-range Pn predictions (> or = 6 days into the future).

Carbon Dioxide↗
PubMed1999

A bench-scale investigation of land treatment of soil contaminated with diesel fuel.

A bench-scale investigation (soil pan testing) was conducted with the objective of studying degradation rates of diesel contaminated soil (2500 and 10,000 ppm by weight of total petroleum hydrocarbons (TPH) to dry weight of soil) under different treatment conditions over a 17 week testing period. The greatest degradation of the diesel contaminated soil was obtained with the addition of nutrients (Co = 10,000 ppm of TPH; k = 0.19 week-1). 'k' for soil not amended with nutrients was 0.07 week-1. The control cell (C0 = 2500 ppm TPH), with sodium azide (to suppress degradation) was compared with an experimental cell of 2500 ppm initial concentration of TPH without nutrient amendment. The control cell exhibited a relatively low uniform degradation (k = 0.08 week-1) of TPH over the duration of the experiment with reasonable first-order kinetic regression statistics.

Biodegradation, Environmental↗
PubMed1998

The critical power function is dependent on the duration of the predictive exercise tests chosen.

The linear relationship between work accomplished (W(lim)) and time to exhaustion (t(lim)) can be described by the equation: W(lim) = a + CP x t(lim). Critical power (CP) is the slope of this line and is thought to represent a maximum rate of ATP synthesis without exhaustion, presumably an inherent characteristic of the aerobic energy system. The present investigation determined whether the choice of predictive tests would elicit significant differences in the estimated CP. Ten female physical education students completed, in random order and on consecutive days, five all-out predictive tests at preselected constant-power outputs. Predictive tests were performed on an electrically-braked cycle ergometer and power loadings were individually chosen so as to induce fatigue within approximately 1-10 mins. CP was derived by fitting the linear W(lim)-t(lim) regression and calculated three ways: 1) using the first, third and fifth W(lim)-t(lim) coordinates (I135), 2) using coordinates from the three highest power outputs (I123; mean t(lim) = 68-193 s) and 3) using coordinates from the lowest power outputs (I345; mean t(lim) = 193-485 s). Repeated measures ANOVA revealed that CPI123 (201.0+/-37.9W) > CPI135 (176.1+/-27.6W) > CPI345 (164.0+/-22.8W) (P<0.05). When the three sets of data were used to fit the hyperbolic Power-t(lim) regression, statistically significant differences between each CP were also found (P<0.05). The shorter the predictive trials, the greater the slope of the W(lim)-t(lim) regression; possibly because of the greater influence of 'aerobic inertia' on these trials. This may explain why CP has failed to represent a maximal, sustainable work rate. The present findings suggest that if CP is to represent the highest power output that an individual can maintain "for a very long time without fatigue" then CP should be calculated over a range of predictive tests in which the influence of aerobic inertia is minimised.

Adenosine Triphosphate↗
PubMed1997

Predictors of long-term patient survival after in situ vein leg bypass.

PURPOSE: The objective was to determine the long-term survival rates of patients who undergo distal arterial bypass surgery and to identify the preoperative factors that are predictive of survival. METHODS: Three hundred fifty-eight consecutive in situ distal leg bypass procedures were performed between July 1986 and December 1995. The relationship between 13 preoperative variables and late survival were determined using both univariate (Kaplan-Meier) and multivariate (Cox regression) statistical techniques. RESULTS: The cumulative survival rates at 1, 3, 5, and 7 years were 86.6% +/- 2.0%, 63.2% +/- 3.0%, 46.9% +/- 3.4%, and 35.3% +/- 3.8%, respectively. Using Cox regression, four significant variables were found to be associated with lower late survival rates: male gender, diabetes, chronic renal insufficiency (patients with creatinine levels greater than or equal to 1.7 mg/dl or 150 SI units), and a history of cerebrovascular disease (p < 0.001 for model). When none of these four variables were present, the predicted 5-year survival rate was 71%, whereas the survival rate was reduced to 43% to 60% when one was present, 23% to 42% when two were present, 8% to 22% when three were present, and 2% when all four were present. CONCLUSIONS: This study defines the long-term survival rates in a cohort of patients after undergoing distal bypass surgery and demonstrates that certain preoperative factors are predictive of late survival. Knowledge of these factors may be useful to assist in individual operative decisions between aggressive attempts at distal revascularization versus primary amputation.

Aged↗
PubMed2006

Analysis and prediction of flow from local source in a river basin using a Neuro-fuzzy modeling tool.

Traditionally, the multiple linear regression technique has been one of the most widely used models in simulating hydrological time series. However, when the nonlinear phenomenon is significant, the multiple linear will fail to develop an appropriate predictive model. Recently, neuro-fuzzy systems have gained much popularity for calibrating the nonlinear relationships. This study evaluated the potential of a neuro-fuzzy system as an alternative to the traditional statistical regression technique for the purpose of predicting flow from a local source in a river basin. The effectiveness of the proposed identification technique was demonstrated through a simulation study of the river flow time series of the Citarum River in Indonesia. Furthermore, in order to provide the uncertainty associated with the estimation of river flow, a Monte Carlo simulation was performed. As a comparison, a multiple linear regression analysis that was being used by the Citarum River Authority was also examined using various statistical indices. The simulation results using 95% confidence intervals indicated that the neuro-fuzzy model consistently underestimated the magnitude of high flow while the low and medium flow magnitudes were estimated closer to the observed data. The comparison of the prediction accuracy of the neuro-fuzzy and linear regression methods indicated that the neuro-fuzzy approach was more accurate in predicting river flow dynamics. The neuro-fuzzy model was able to improve the root mean square error (RMSE) and mean absolute percentage error (MAPE) values of the multiple linear regression forecasts by about 13.52% and 10.73%, respectively. Considering its simplicity and efficiency, the neuro-fuzzy model is recommended as an alternative tool for modeling of flow dynamics in the study area.

Forecasting↗
PubMed2003

Leukoplakia and intraoral malignancies: female cases increase in Greece.

UNLABELLED: In the developed world, intraoral malignancies are more frequent in males than females. Recent observations from Greece suggest that the number of females is increasing. AIM: The present study investigates gender and age statistics among subjects with cancers of the mouth or leukoplakia. METHODS: Five hundred and twelve subjects of Greek origin participated in this analysis. Chi-square and logistic regression statistics were used to compare if there are differences in participants' gender and age, stratified by histological type. RESULTS: Epithelial cancers and leukoplakia exhibited equal distributions among men and women. Men were diagnosed at a much younger age than women. Our data also indicates a progression in the process of epithelial cancer development, as benign leukoplakia was diagnosed 2-4 years earlier than epithelial dysplasia and 8 years earlier than squamous cell carcinoma (SSC). The same age difference was observed in non-Hodgkin's lymphoma, although the male to female ratio was 3:1. In regards to anatomy, 47% of SSC appeared in the tongue. The most prevalent site for the development of non-Hodgkin's lymphoma was the gingival (50%), followed by the palate (40%). CONCLUSION: Although oral cancer occurs earlier in men than women, the risk of females tends to be similar to that of males.

Age Factors↗
PubMed1988

Regression analysis in biological research: sample size and statistical power.

Regression analysis is often used to demonstrate associations among variables believed to be biologically related. Failure to demonstrate a "significant" relationship may be due to two factors: 1) the variables are truly unrelated, or 2) a relationship exists but goes undetected due to inadequate statistical power. Investigators must consider the second possibility since failure to detect a statistically significant relationship is often taken as evidence for no biological relationship. These issues are addressed in the context of the interrelationship between four features common to all statistical methods: the size of effect or relationship worth detecting, the Type I (alpha) error, the sample size, and the Type II (beta) error. An example derived from published data relating morphological characteristics of muscle fiber type and isokinetic strength performance illustrates the practical significance of this dilemma.

Regression Analysis↗
PubMed1993

Prognosis of intracoronal bleaching with sodium perborate preparation in vitro: 1-year study.

Bleaching materials containing hydrogen peroxide have been used for treating discolored nonvital teeth but their use was occasionally associated with external root resorption. In a previous study it was found that the immediate results of bleaching teeth in vitro were equal for sodium perborate mixed with either water or hydrogen peroxide. The purpose of this study was to compare the bleaching prognosis of sodium perborate mixed with water or hydrogen peroxide over a 1-yr period. Extracted human teeth with intact crowns were discolored with human erythrocytes and bleached by sodium perborate mixed with either 30% hydrogen peroxide (group A), 3% hydrogen peroxide (group B), or water (group C). The bleaching materials were placed in the pulp chambers of the discolored teeth and sealed with IRM. They were replaced with fresh preparations after 3 and 7 days. After 14 days the coronal access cavities were sealed with composite resin and the teeth photographed with a color slide film under standardized conditions. The teeth were stored in artificial saliva for 1 yr and photographed after 3, 6, and 12 months. Two separate evaluators ranked the teeth by comparing them with the shades before and after bleaching. The bleaching success rates of the tested groups at each time interval were compared and analyzed statistically. It was found that after 1 yr all of the teeth in groups A and C maintained their shades. In 20% of the teeth in group B there was color regression. Statistically, these differences were not significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Borates↗
PubMed2005

Structural analysis of sterol distributions in the plasma membrane of living cells.

Although plasma membrane (PM) cholesterol-rich and -poor domains have been isolated by subcellular fractionation, the real-time arrangement of cholesterol in such domains in living cells is still unclear. Therefore, dehydroergosterol (DHE), a naturally occurring fluorescent sterol, was incorporated into cultured L-cell fibroblasts. Two PM markers, the enhanced cyan fluorescent protein (ECFP-Mem) and 3'-dioctadecyloxacarbocyanine perchlorate [DiOC(18)(3)], were used to distinguish DHE localized at the PM of living cells. Spatial enrichment of DHE in the PM of living cells was visualized in real time by multiphoton laser scanning microscopy (MPLSM). Quantitative models and image-processing techniques were developed for statistical analysis of the distribution of DHE within the PM. The PM was resolved from the cytoplasm in a two-step process, and a smooth trajectory reference of the PM was refined by statistical regression and moments-based techniques. Thus, DHE intensities over the PM were measured following the major DHE intensity distributions. Spatial distributions of DHE within the PM were examined by a statistical inference technique, complete spatial randomness (CSR). For PM regions densely populated with DHE, the distributions of DHE exhibited statistical arrangements that were not spatial random (i.e., homogeneous Poisson process) or regular but, instead, exhibited strong cluster patterns. In effect, real-time MPLSM imaging data for the first time demonstrated that sterol enrichment occurred in clustered regions in the PM, consistent with the existence of cholesterol-rich domains in the plasma membrane of living cells.

Animals↗
PubMed1999

[Mathematical coupling and "regression to the mean". A statistical case history].

"Regression to the mean" (RTM) is a statistical phenomenon originating from the random variation of variables rather than a true association between the variables. RTM is closely linked to mathematical coupling; unawareness of these phenomena may lead to misinterpretation of data. A study examining intracranial pressure before and after infusion of manitol is presented, in which mathematical coupling caused a highly significant (but spurious) correlation between the analysed data. The significance of RTM and mathematical coupling is demonstrated by analysis of a data set derived from random numbers.

Data Interpretation, Statistical↗
PubMed1999

A global goodness-of-fit statistic for Cox regression models.

In this paper, a global goodness-of-fit test statistic for a Cox regression model, which has an approximate chi-squared distribution when the model has been correctly specified, is proposed. Our goodness-of-fit statistic is global and has power to detect if interactions or higher order powers of covariates in the model are needed. The proposed statistic is similar to the Hosmer and Lemeshow (1980, Communications in Statistics A10, 1043-1069) goodness-of-fit statistic for binary data as well as Schoenfeld's (1980, Biometrika 67, 145-153) statistic for the Cox model. The methods are illustrated using data from a Mayo Clinic trial in primary billiary cirrhosis of the liver (Fleming and Harrington, 1991, Counting Processes and Survival Analysis), in which the outcome is the time until liver transplantation or death. The are 17 possible covariates. Two Cox proportional hazards models are fit to the data, and the proposed goodness-of-fit statistic is applied to the fitted models.

Biometry↗
PubMed1990

Estimating respiratory volumes from rib cage and abdominal displacements during ventilatory and speech activities.

This methodological study examined the predictive strength associated with modeling respiratory volumes from chest-wall movements during selected ventilatory and speech activities. A linearized magnetometry system transduced the anterior-posterior diameters of the rib cage and abdomen, supplying kinematic data that were used to estimate respiratory volumes. Kinematic and airflow measures were acquired during (a) tidal ventilation, (b) vital capacity maneuvers, (c) Rainbow Passage reading at customary loudness, (d) Rainbow Passage reading at twice-customary loudness, (e) extemporaneous speech, and (f) /a/ prolongation. Multiple-regression statistics were applied to the body surface and integrated airflow data to obtain (a) intercepts, (b) volume-motion coefficients for the rib cage and abdomen, and (c) coefficients of determination. Volumes estimated by applying regression-derived intercepts and volume-motion coefficients to the respiratory kinematic data were then compared to integrated airflow signals. Two magnetometer-based, volume-estimation strategies were contrasted for the speech tasks, one based on volume-motion coefficients derived from that particular speech activity and one based on volume-motion coefficients derived from tidal ventilation. Regression-derived intercepts and volume-motion coefficients for the abdomen varied significantly across subjects but not tasks. Volume-motion coefficients for the rib cage varied significantly across both subjects and tasks. Coefficients of determination for the magnetometer-based volume estimates were affected significantly by subjects and tasks but not by volume-estimation strategies. The calibration, use, and potential limitation of respiratory kinematic devices for speech research are discussed.

Abdomen↗
PubMed1997

Therapeutic efficacy of the topoisomerase I inhibitor 7-ethyl-10-(4-[1-piperidino]-1-piperidino)-carbonyloxy-camptothecin against pediatric and adult central nervous system tumor xenografts.

Therapy of patients with malignant central nervous system tumors is frequently unsuccessful, reflecting limitations of current surgical, radiotherapeutic, and pharmacotherapeutic treatments. The camptothecin derivative irinotecan (CPT-11) has been shown to possess antitumor activity in phase II trials for patients with carcinoma of the lung, cervix, ovary, colon, or rectum and for patients with non-Hodgkin's lymphoma. The current study was designed to test the efficacy of the drug against a panel of human tumor xenografts derived from adult and pediatric central nervous system malignancies. Tumors included childhood high-grade gliomas (D-212 MG, D-456 MG), adult high-grade gliomas (D-54 MG, D-245 MG), medulloblastomas (D341 Med, D487 Med), ependymomas (D528 EP, D612 EP), and a rhabdomyosarcoma (TE-671), as well as sublines with demonstrated resistance to busulfan (D-456 MG (BR)), cyclophosphamide (TE-671 CR), procarbazine (D-245 MG (PR)) or melphalan (TE-671 MR), growing subcutaneously and intracranially in athymic nude mice. In replicate experiments, CPT-11 was given at a dosage of 40 mg/kg per dose via intraperitoneal injection in 10% dimethylsulfoxide on days 1-5 and 8-12, which is the dosage lethal to 10% of treated animals. CPT-11 produced statistically significant (P < 0.001) growth delays in all subcutaneous xenografts tested, including those resistant to busulfan, cyclophosphamide, procarbazine, and melphalan, with growth delays ranging from 21.3 days in D487 Med to 90+ days in several tumor lines. Further, tumor regression was evident in every treated animal bearing a subcutaneous tumor, with some xenografts yielding complete tumor regression. Statistically significant (P < 0.001) increases in survival were demonstrated in the two intracranial xenografts-D341 EP (73.0% increase) and D-456 MG (114.2% increase)-treated with CPT-11. These studies demonstrate that, of over 40 drugs evaluated in this laboratory, CPT-11 is the most active against central nervous system xenografts and should be advanced to clinical trial as soon as possible.

Adult↗