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Results for “Statistics, Nonparametric”

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PubMed2005

Overlap coefficient for assessing the similarity of pharmacokinetic data between ethnically different populations.

We developed a method to assess the similarity of pharmacokinetic data between ethnically different populations. An evaluation of confidence intervals for the mean difference in pharmacokinetic parameters, such as area under the concentration-versus-time curve (AUC), between populations is often used. We propose the use of the overlap coefficient (OC), which represents the proportion of overlap between two probability distributions, as a measure of the similarity between distributions. We considered five OC estimators--two parametric ones and three nonparametric ones. Simulation studies were conducted to compare the performance of the five OC estimators and their bootstrap confidence intervals. Results showed that nonparametric estimators with fixed-bandwidth kernel density estimation had a smaller mean squared error in almost all situations, and their coverage probabilities were close to the nominal level. The proposed method was applied to pharmacokinetic data from a bridging study of a combination therapy for metastatic colorectal cancer patients in the USA and Japan. From the analyses of this study, it was suggested that the distributions of the logarithmically transformed AUC for leucovorin and 5-fluorouracil were similar between the two populations.

Clinical Trials as Topic↗

PubMed1998

Weighting for joint surface area improves the information provided by a reduced 28-joint articular index of swollen joints.

The objective of our study was to examine whether weighting for joint surface area or recording of simultaneously tender and swollen joints increases the association of a reduced 28-joint articular index with clinical and outcome parameters. In a cross-sectional study we examined 61 consecutive outpatients with RA fulfilling the American Rheumatism Association 1987 revised criteria. Tender, swollen, and simultaneously tender and swollen joints were recorded. The association of 28- and 68-joint articular indices with clinical and outcome parameters were estimated with nonparametric correlation analyses. Weighting for joint surface yielded consistently increased correlation of clinical and outcome parameters with swollen and tender and swollen but not with tender joint counts. The correlation of the 28-joint articular and 68-articular indices with these parameters were similar. In conclusion, weighting for joint surface notably improves the information provided by swollen joint counts, whereas it does not appear to improve the information provided by tender joint counts.

Adult↗

PubMed2004

Testing separability in spatial-temporal marked point processes.

Nonparametric tests for investigating the separability of a spatial-temporal marked point process are described and compared. It is shown that a Cramer-von Mises-type test is very powerful at detecting gradual departures from separability, and that a residual test based on randomly rescaling the process is powerful at detecting nonseparable clustering or inhibition of the marks. An application to Los Angeles County wildfire data is given, in which it is shown that the separability hypothesis is invalidated largely due to clustering of fires of similar sizes within periods of up to 3.9 years.

Biometry↗

PubMed1997

The regional production of cytokines and lactate in sepsis-related multiple organ failure.

In order to explore whether an organ-specific pattern in cytokine and lactate concentrations exists in patients with multiple organ failure (MOF), we measured the cytokines interleukin-1beta (IL-1beta), IL-6, and tumor necrosis factor-alpha (TNF-alpha), and lactate in blood taken from the hepatic vein, pulmonary capillaries, and peripheral veins of 10 patients with MOF with hepatic involvement (MOF-HI), eight patients with MOF and adult respiratory distress syndrome (MOF-ARDS), and five head-injured patients (controls). Ten additional patients participated in a study of arteriovenous pulmonary concentration gradients of these substances. For statistical analysis, nonparametric tests and analysis of variance (ANOVA) were used. The regional concentrations of these substances exhibited a different pattern in the two MOF groups. In the MOF-HI group, mean +/- SD cytokines IL-1beta and IL-6 (pg/ml) were respectively 216 +/- 100 and 461 +/- 343 in the hepatic sinusoidal blood; 149 +/- 52 and 293 +/- 204 in pulmonary capillary blood; and 148 +/- 105 and 234 +/- 162 in peripheral venous blood. In the MOF-ARDS group the corresponding levels were 180 +/- 103 and 235 +/- 124; 235 +/- 94 and 280 +/- 108; and 130 +/- 77 and 194 +/- 127. The TNF-alpha levels also exhibited the same pattern. The mean +/- SD corresponding levels (mmol/L) for lactate in the MOF-HI group were 3.1 +/- 1.8, 1.5 +/- 0.3, and 1.2 +/- 0.6, and in the MOF-ARDS group were 1.1 +/- 0.9, 1.8 +/- 1.1, and 1.0 +/- 0.2, respectively. The differences in the levels of all substances between the liver and lungs in the two MOF groups were statistically significant (p < 0.003). In the study of transpulmonary gradients it was shown that the levels of cytokine and lactate were lower in arterial blood than in mixed venous blood in MOF-HI patients, whereas the opposite was true in MOF-ARDS patients. In this study, we found that in MOF, cytokines and lactate are secreted from the most severely affected organs.

Aged↗

PubMed2001

Comparative context of Plio-Pleistocene hominin brain evolution.

One of the distinguishing features of Homo sapiens is its absolutely and relatively large brain. This feature is also seen in less extreme form in some fossil Homo species. However, are increases in brain size during the Plio-Pleistocene only seen in Homo, and is brain enlargement among Plio-Pleistocene primates confined to hominins? This study examines evidence for changes in brain size for species and lineage samples of three synchronic East African fossil primate groups, the two hominin genera Homo and Paranthropus, and the cercopithecoid genus Theropithecus. Hominin endocranial capacity data were taken from the literature, but it was necessary to develop an indirect method for estimating the endocranial volume of Theropithecus. Bivariate and multivariate regression equations relating measured endocranial volume to three external cranial dimensions were developed from a large (ca. 340) sample of modern African cercopithecoids. These equations were used to estimate the endocranial volumes of 20 Theropithecus specimens from the African Plio-Pleistocene. Spearman's rho and the Hubert nonparametric test were used to search for evidence of temporal trends in both the hominin and Theropithecus data. Endocranial volume apparently increased over time in both Homo and Paranthropus boisei, but there was no evidence for temporal trends in the endocranial volume of Theropithecus. Thus, hypotheses which suggest a mix of environmental, social, dietary, or other factors as catalysts for increasing brain in Plio-Pleistocene primates must accommodate evidence of brain enlargement in both Homo and Paranthropus, and explain why this phenomenon appears to be restricted to hominins.

Africa, Eastern↗

PubMed2006

Genotoxicity in primary human peripheral lymphocytes after exposure to regular and white mineral trioxide aggregate.

OBJECTIVE: Taking into consideration that DNA damage plays an important role in carcinogenesis, the purpose of this study was to evaluate whether regular and white mineral trioxide aggregate (MTA) are able to induce genetic damage in primary human cells. STUDY DESIGN: Human peripheral lymphocytes obtained from 10 healthy volunteers were exposed to 2 presentation forms of MTA at final concentrations ranging from 1 to 1000 microg/mL for 1 hour at 37 degrees C. The negative control group was treated with vehicle control (phosphate buffer solution, PBS) for 1 hour at 37 degrees C and the positive control group was treated with hydrogen peroxide (at 100 microM) for 5 minutes on ice. Results were analyzed by the Friedman nonparametric test. RESULTS: The results pointed out that either regular or white MTA in all concentrations tested did not induce DNA breakage in human peripheral lymphocytes as depicted by the mean tail moment. CONCLUSION: In summary, our results indicate that exposure to MTA may not be a factor that increases the level of DNA lesions in human peripheral lymphocytes as detected by single cell gel (comet) assay.

Adult↗

PubMed2005

Genetic linkage analysis of the X chromosome in autism, with emphasis on the fragile X region.

The higher prevalence of autism in males than in females suggests the possible involvement of the X chromosome. To test the hypothesis that there are mutations increasing susceptibility to autism on the X chromosome, and in particular the distal portion of the long arm that encompasses the FMRI and MECP2 loci, a genetic linkage study was performed. Twenty-two fragile X-negative families multiplex for autism and related disorders were used for the study. Linkage analysis, for markers in the Xq27-q28 region, using model-free likelihood-based analysis, produced a maximum MLOD of 1.7 for the narrowest diagnostic category of the typical autism/severe autism spectrum, and nonparametric analysis produced a maximum non-parametric lod (NPL) score of 2.1 for a broad phenotype diagnostic model. Thus, this study offers modest support for a susceptibility locus for autism within the Xq27-q28 region. Further genetic investigations of this region are warranted.

Autistic Disorder↗

PubMed2004

Genome-wide linkage analysis for hypospadias susceptibility genes.

PURPOSE: Hypospadias, when the urethra opens on the underside of the penis, is a common malformation that occurs in about 1/300 boys. The etiology of hypospadias is unknown but several lines of evidence indicate that it is caused by the combined influence of genetic and environmental factors. To identify chromosomal loci involved in the pathogenesis of hypospadias we performed genome-wide linkage analysis. MATERIALS AND METHODS: A total of 69 families with at least 2 members with hypospadias were genotyped with 360 microsatellite markers and analyzed with a nonparametric affected relative pair method. Of them 58 were of Swedish origin and 11 were from the Middle East. RESULTS: Suggestive linkage was found at the 4 chromosome regions 9q22 (in all families), 2p11, 10p15 and 10q21 (in Swedish families). CONCLUSIONS: These results provide a basis for outlining the genetic background of hypospadias.

Child↗

PubMed2003

The relationship between neuronal plasticity and serotonergic neurons in the brainstem of SIDS victims.

BACKGROUND: The sudden infant death syndrome (SIDS) is still the main cause of postneonatal infant death and its cause is still unknown. Recently, the medullary serotonergic network deficiency theory has been proposed and an association between SIDS and neuronal plasticity has also been suggested. The growth-associated phosphoprotein 43 (GAP43) is a marker of synaptic plasticity and is critical for normal development of the serotonergic innervation. Therefore, the characteristics of GAP43-positive elements and their association with serotonergic neurons were here investigated in the brainstem of SIDS victims. MATERIALS AND METHODS: The materials of this study included 26 cases of SIDS and 12 control cases. The brainstem material was collected and the immunohistochemistry of GAP43 and tryptophan hydroxylase (TrypH) carried out. The density of GAP43-positive neurons and dendrites and of TrypH-positive neurons were measured quantitatively. Nonparametric analyses of GAP43 between SIDS and non-SIDS and correlation analyses between GAP43 and TrypH were performed. RESULTS: No significant difference in GAP43-associated findings was found between SIDS and non-SIDS nor any significant correlation between GAP43-associated findings and TrypH-positive neurons. CONCLUSIONS: The results of this study were not in agreement with the association of GAP43 with SIDS and with serotonergic innervation in SIDS.

Brain Stem↗

PubMed1999

Perioperative rehydration in ambulatory anesthesia for dentoalveolar surgery.

OBJECTIVE: Patient recovery after anesthesia is dependent not only on the lingering pharmacologic effects of sedatives but also on the physiologic effects that patients experience after surgery. Preoperative fasting results in a perioperative dehydration that may contribute to these physiologic effects, resulting in complaints of headache, nausea, vomiting, fatigue, lightheadedness, dizziness, and thirst. The purpose of this study was to investigate the effects of perioperative hydration in the ambulatory oral and maxillofacial surgery patient who receives deep sedation or general anesthesia (nonintubated). STUDY DESIGN: This was a prospective, randomized, blinded study that administered either a high volume (16-17 mL/kg) or a low volume (1-2 mL/kg) of an isotonic solution to each of 77 patients who were scheduled to have their third molars extracted with deep sedation or general anesthesia. Each patient completed 3 postoperative questionnaires designed to evaluate potential adverse outcomes. RESULTS: Nonparametric analysis of the data demonstrated a more favorable outcome with respect to subjective feelings for the high volume hydration group; this was evident both during the immediate postoperative period and in the evening of the day of surgery, and it persisted into the first postoperative day. CONCLUSIONS: This study demonstrated that appropriate perioperative rehydration decreases postoperative adverse outcomes and improves the patient's perception of the postoperative period.

Ambulatory Surgical Procedures↗

PubMed2003

Predicting basal metabolic rate in the obese is difficult.

OBJECTIVE: To reassess the validity of the Schofield equations for predicting basal metabolic rate (BMR) in the obese. DATA: The data collection compiled from many studies by Schofield in 1985. METHODS: Nonparametric curve fitting and comparison of groups. RESULTS: BMR increases more slowly at heavier weights in men (above about 75 kg) and women (above about 65 kg), and to ignore this is to predict overestimates of BMR. Data obtained from studies of different populations show substantial differences, which are influential when data are combined. CONCLUSIONS: The Schofield equations are unsuitable for obese populations. Given that current Western populations exhibit prevalences of obesity many times greater than those in the Schofield database, this indicates the need for further study of suitable predictors for these individuals.

Adolescent↗

PubMed1999

Nonparametric analysis of covariance for hypothesis testing with logrank and Wilcoxon scores and survival-rate estimation in a randomized clinical trial.

Many clinical trials have time-to-event variables as principal response criteria. When adjustment for covariates is of some importance, the relative role of methods for such analysis may be of some concern. For the Wilcoxon and logrank tests, there is an issue of how covariance adjustment can be nonparametric in the sense of not involving any further assumptions beyond those of the logrank and Wilcoxon test. Also of particular interest in a clinical trial is the estimation of the difference between survival probabilities for the treatment groups at several points in time. As with the Wilcoxon and logrank tests, there is no well known nonparametric way to incorporate covariate adjustment into such estimation of treatment effects for survival rates. We propose a method that enables covariate adjustment for hypothesis testing with logrank or Wilcoxon scores. Related extensions for applying covariate adjustment to estimation of treatment effects are provided for differences in survival-rate counterparts to Kaplan-Meier survival rates. The results represent differences in population average survival rates with adjustment for random imbalance of covariates between treatment groups. The methods are illustrated with a clinical trial example.

Humans↗

PubMed2005

Predicting the insertion distance for placing gastric tubes.

Approximately 1 million enteral tubes are placed through the nose or mouth in adults and children in the United States annually. Previous studies found gastric tube placement errors to be common. A primary issue in ensuring safe and effective gastric feeding by tube is achieving optimal tube position on insertion. The purpose of this study is to use 24 variables to develop a clinical prediction rule for gastric tube insertion distance in adults, using the internal-nares-to-distal-lower esophageal-sphincter distance. A three-variable model using gender, weight, and nose-umbilicus-flat was selected. This new model, validated using nonparametric bootstrap cross-validation, correctly predicted gastric tube insertion distance 85.3% of the time. This new model is compared to two other methods, one evidence based and one commonly used in practice, and was found to be superior. Two nomograms, one for each gender, are drawn to make this new model easier to use.

Adolescent↗

PubMed2002

Microleakage and wall adaptation of conservative restorations.

PURPOSE: To evaluate the microleakage and wall adaptation of different restorative materials in sealed and unsealed conservative restorations after storage in an acid environment. MATERIALS AND METHODS: 100 conservative cavity preparations were prepared in the occlusal surface of 50 non-carious, extracted human permanent molar teeth. The teeth were divided into 5 groups and restored with either flowable compomer, compomer, amalgam, resin-based composite or non-bonded resin-based composite (control). One half of the restorations in each group was sealed with a light cured unfilled sealant material, while the other half was left unsealed. The teeth were placed in artificial saliva for 30 days, radiographed, thermocycled 500 times, placed in an artificial caries solution, immersed in dye, sectioned three times, and recorded at x60 magnification. Three independent examiners assessed each of the 300 recorded sections for leakage and assessed each radiograph for wall adaptation using a slide projector. Kruskal Wallis and Mann-Whitney nonparametric tests were used to analyze the results. RESULTS: Sealed restorations showed significantly less leakage than unsealed (P < 0.001). Of the sealed groups, amalgam showed less leakage than flowable compomer (P = 0.027). Of the unsealed groups, flowable compomer showed less leakage than both composite groups (P = 0.032 and P = 0.045). Radiographically, the two compomer groups and the amalgam group had fewer adaptation voids than both composite groups (P < 0.001).

Bisphenol A-Glycidyl Methacrylate↗

PubMed1999

Robust estimation of parasite component community richness.

The performance of 2 nonparametric estimators of species richness, the bootstrap (S(B)) and kth-order jackknife (S(Jk)), are compared using simulated parasite communities. The parameters of the simulation match those of an earlier comparison that favored S(B) as an estimator but did not include S(Jk). S(Jk) is the least biased of the 2 estimators. Whereas the bias of S(B) is significantly affected by true species richness and the proportion of rare species, the bias of S(Jk) is relatively insensitive to changes in these parameters, and is, therefore, recommended as a robust estimator of species richness.

Analysis of Variance↗

PubMedDate not supplied

Subjective recovery time after exhausting muscular activity in postpolio and control subjects.

The purpose of this study was to determine whether the time to subjectively fully recover after the performance of exhausting muscular exercise was greater in unstable postpolio as compared with stable postpolio or control subjects. Twenty-five unstable (those complaining of declining muscle strength) postpolio, 16 stable (those denying declining muscle strength) postpolio, and 25 control subjects performed an isometric contraction of the knee extensor (quadriceps femoris) musculature at 40% of maximal torque until they were no longer able to do so. Five-second maximal effort contractions were made every 30 s through 2 min after the time of failure was reached and then at 1-min intervals through 10 min after failure was reached. Subjects reported the duration of time required to subjectively fully recover from this activity. Choices of "less than 1 day," "1 day," "2 days," etc., up to "greater than 2 wk" were given to the subjects for their response. Analysis was by nonparametric ANOVA and appropriate post hoc comparison procedures. Unstable postpolio subjects reported a greater recovery time than either the stable postpolio or control subjects (mean +/- SD of 2.6 +/- 3.0 days, 0.6 +/- 1.0 days, and 0.7 +/- 1.1 days, respectively, P < 0.05). Thus, the reported recovery time from exhausting isometric muscular exercise was found to be greater in unstable postpolio subjects than stable postpolio or control subjects. The cause for this finding is unknown and requires further investigation.

Adult↗

PubMed2005

Spin-labeling coronary MR angiography with steady-state free precession and radial k-space sampling: initial results in healthy volunteers.

The purpose of this study was to prospectively compare free-breathing navigator-gated cardiac-triggered three-dimensional steady-state free precession (SSFP) spin-labeling coronary magnetic resonance (MR) angiography performed by using Cartesian k-space sampling with that performed by using radial k-space sampling. A new dedicated placement of the two-dimensional selective labeling pulse and an individually adjusted labeling delay time approved by the institutional review board were used. In 14 volunteers (eight men, six women; mean age, 28.8 years) who gave informed consent, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), vessel sharpness, vessel length, and subjective image quality were investigated. Differences between groups were analyzed with nonparametric tests (Wilcoxon, Pearson chi2). Radial imaging, as compared with Cartesian imaging, resulted in a significant reduction in the severity of motion artifacts, as well as an increase in SNR (26.9 vs 12.0, P < .05) in the coronary arteries and CNR (23.1 vs 8.8, P < .05) between the coronary arteries and the myocardium. A tendency toward improved vessel sharpness and vessel length was also found with radial imaging. Radial SSFP imaging is a promising technique for spin-labeling coronary MR angiography.

Adult↗

PubMed1998

A pilot study comparing the efficacy of hard and soft stabilizing appliances in treating patients with temporomandibular disorders.

STATEMENT OF PROBLEM: Soft and hard stabilizing appliances have been used to treat temporomandibular disorders. No data exist to suggest whether a hard or soft appliance is beneficial. PURPOSE: This study compared soft and hard acrylic resin stabilizing appliances in the reduction of masticatory muscle pain in patients with temporomandibular disorders. MATERIALS AND METHODS: Twenty-three patients with at least one clinical sign from the list of diagnostic subgroups of temporomandibular disorders were alternately assigned a hard or soft appliance for temporomandibular disorder treatment. No other temporomandibular disorder treatment (self-care, physical therapy, biofeedback, or muscle or joint injections) was rendered. Each patient was seen by two dentists at each visit. One dentist initially fabricated the appliance and adjusted the appliance on each visit and an examining dentist examined the patient each visit and recorded signs of temporomandibular disorders. The appliance material (soft or hard) was not disclosed to the examining dentist, only to the dentist who fabricated and adjusted the appliance. Patients were examined and appliances were adjusted every 2 to 3 weeks for a minimum of 10 weeks. Masticatory muscles were palpated and charted on each visit. Data were analyzed and subjected to nonparametric Mann-Whitney test. RESULTS: Eighteen of the initial 23 patients, 7 in the hard appliance group and 11 in the soft appliance group finished the study over 10- to 15-week period. Soft and hard appliances performed the same in reduction of masticatory muscle pain. CONCLUSION: This study suggests, based on the limited number of participants, that soft and hard stabilizing appliances may be equally useful in reducing masticatory muscle pain in short-term appliance therapy.

Acrylic Resins↗