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PubMed2002

Capping the inflamed pulp under different clinical conditions.

BACKGROUND: A great deal of controversy exists regarding the reliability of capping the inflamed pulp. In particular, the use of calcium hydroxide as a capping agent has come into question. In this study, hard tissue barrier formation after inflamed pulps were capped directly or after partial pulpotomy was compared with calcium hydroxide or bonded resin and with no additional seal or an IRM surface seal. Seventy teeth in five dogs were used. Ten untreated teeth were used as negative controls. In 60 teeth, pulpal inflammation was induced by preparing a cavity close to the pulp and sealing a cotton pellet soaked in plaque in it for 1 to 2 weeks. The cavities were then re-entered and extended to expose the pulps. MATERIALS AND METHODS: In half the teeth (n = 30) a partial pulpotomy was performed and in the other half (n = 30) pulpal treatment was performed on the superficial exposed pulp. Both pulpal treatment groups received the same restorative procedures: (1) calcium hydroxide + amalgam + IRM surface seal; (2) OptiBond Solo, Prodigy with IRM surface seal; or (3) OptiBond Solo, Prodigy without IRM surface seal. The presence, absence, and quality of a hard tissue barrier were evaluated histologically. RESULTS: The calcium hydroxide groups were statistically superior to all other groups. The IRM surface seal resulted in significantly better healing. Although there was no statistically significant difference between direct pulp capping and partial pulpotomy with the numbers in this study, power statistics indicated that in clinical practice a partial pulpotomy would be preferable. CLINICAL SIGNIFICANCE The results of this study suggest that a partial pulpotomy, calcium hydroxide medicament, and a bacteria-tight coronal restoration represent a viable technique for capping the inflamed pulp.

Animals↗
PubMed1999

Reflections on two decades of research on teen sexual behavior and pregnancy.

During the past 20 years, both researchers and program developers made great progress in their efforts to reduce adolescent unprotected sex and prevent teen pregnancy. Research studies are now more likely to employ experimental designs with random assignments, to have large sample sizes with adequate statistical power, to measure actual sexual and contraceptive behaviors, to measure longer term effects, to employ proper statistical methods, and to report results in an unbiased manner. As a result of this body of research, large advances have occurred in our understanding of: 1) the incidence of teen pregnancy, and its consequences; 2) the effects of improving adolescent knowledge, increasing access to contraception, and improving parent/child communication; and 3) the characteristics of effective programs. The on-going evaluation of sex and HIV education programs coupled with creativity and perseverance on the part of program developers led to two groups of effective programs--sex and HIV education programs that reduce sexual risk-taking behavior, and youth development programs that reduce teen-age pregnancy and childbearing.

Adolescent↗
PubMed2002

Advice on statistical analysis for Circulation Research.

Since the late 1970s when many journals published articles warning about the misuse of statistical methods in the analysis of data, researchers have become more careful about statistical analysis, but errors including low statistical power and inadequate analysis of repeated-measurement studies are still prevalent. In this review, several statistical methods are introduced that are not always familiar to basic and clinical cardiologists but may be useful for revealing the correct answer from the data. The aim of this review is not only to draw the attention of investigators to these tests but also to stress the conditions in which they are applicable. These methods are now generally available in statistical program packages. Researchers need not know how to calculate the statistics from the data but are required to select the correct method from the menu and interpret the statistical results accurately. With the choice of appropriate statistical programs, the issue is no longer how to do the test but when to do it.

Analysis of Variance↗
PubMed1999

Sample size considerations for superiority trials in systemic lupus erythematosus (SLE).

For reasons of efficiency and ethics, sample size calculations are an important part of the design of all clinical trials. This paper highlights the statistical issues inherent to the estimation of sample size requirements in superiority trials particular to SLE. Calculations based on statistical power for testing hypotheses have historically been the method of choice for sample size determination in clinical trials. The advantages of using confidence intervals (CI's) rather than P-values in reporting results of clinical trials is now well established. Since the design of a trial should match the analysis that will eventually be performed, sample size methods based on ensuring accurate estimation of important parameters via sufficiently narrow CI widths should be preferred to methods based on hypothesis testing. Methods and examples are given for sample size calculations for continuous and dichotomous outcomes from both a power and confidence interval width viewpoint. An understanding of sample size calculations in association with expert statistical consultation will result in better designed clinical trials that accurately estimate clinically relevant differences between treatment outcomes, thereby furthering the treatment of patients with SLE.

Confidence Intervals↗
PubMed2004

Statistical methods in G-protein-coupled receptor research.

In this chapter we provide an introduction to statistical methods appropriate in G-protein-coupled receptor research, including examples. Topics covered include the choice of appropriate averages and measures of dispersion to summarize data sets, and the choice of tests of significance, including t-tests and one- and two-way analysis of variance (ANOVA) plus posttests for normally distributed (Gaussian) data and their nonparametric equivalents. Techniques for transforming non-normally distributed data to more Gaussian distributions are discussed. Concepts of statistical power, errors, and the use of these in determining the optimal size of experiments are considered. Statistical aspects of linear and nonlinear regression are discussed, including tests for goodness-of-fit to the chosen model and methods for comparing fitted lines and curves.

Analysis of Variance↗
PubMed2004

Getting started in research: the research protocol.

To be efficient and precise, research needs a 'road map', called the 'research protocol', which follows a standard format. It includes an abstract, study description, ethical considerations, significance of the study, the budget and a description of the investigators. Study description spells out the study question, the rationale for the study, including previous studies on the subject, the objectives, hypotheses and aims, design and methods, project management, strengths and limitations and a list of references. The objectives, hypotheses and aims are developed by outlining a general research topic (the objective), developing a hypothesis from the broad objective, translating it into the null hypothesis and then listing the steps by which the null hypothesis will be refuted or accepted (the aims). The design and methods describe the type of study to be undertaken, the population in which the study is carried out, including the sample size and statistical power, the selection of subjects, the methods of data collection, and outline of data management and statistical analysis. The detail of the protocol ensures that the study will be carried out successfully and is essential for all health research.

Data Collection↗
PubMedDate not supplied

Isoniazid hepatitis among pregnant and postpartum Hispanic patients.

On request of local health officials, the authors investigated isoniazid (INH) hepatitis morbidity and mortality among patients attending an Hispanic prenatal clinic. Among 3,681 women treated with INH during and after pregnancy to prevent tuberculosis (TB), 5 developed INH hepatitis, and 2 of the 5 women died. Comparison with previously collected Public Health Service data concerning 3,948 nonpregnant women, using the Cox proportional hazards model, revealed a 2.5-fold increased risk of INH hepatitis in the prenatal clinic group. The mortality rate was four times higher in the prenatal clinic group. However, statistical power was low because of the small number of cases, and neither of these findings was statistically significant (P greater than 0.05). In the absence of controlled studies, the issue of INH safety during the perinatal period remains unresolved. Nevertheless, current American Thoracic Society-Centers for Disease Control recommendations regarding TB screening, implementation of INH chemoprophylaxis programs, and adequate monitoring of individuals on INH should be adhered to. The results of this investigation raise concern that deviations from existing policy may contribute to unnecessary morbidity and mortality.

Adolescent↗
PubMedDate not supplied

Reproducibility and variability of the rectal mucosal proliferation index using proliferating cell nuclear antigen immunohistochemistry.

Rectal mucosal proliferation has been shown to be increased in patients with neoplastic lesions of the large bowel and may serve as a marker of risk for colorectal malignancy. We conducted analyses to determine reliability and components of variability that might suggest optimal analysis strategies for studies of proliferation. Endoscopic pinch biopsies were obtained from 17 adult patients, labeled using proliferating cell nuclear antigen, scored using strict rules, and then rescored. Labeling index, defined as the proportion of labeled cells in a crypt, was calculated for each crypt, biopsy, subject, and group. There was excellent reproducibility. The technician was able to select previously scored crypts 95% of the time. The overall labeling index was identical on repeat. There was considerable variability in labeling index among crypts from a single biopsy and between biopsies of a single subject. Variance component estimates suggested that 20% of the variability of labeling index was due to subject, 30% due to the biopsy within a subject, and 50% due to crypts within a biopsy. There were substantial gains in statistical power by scoring two biopsies rather than one. There was less gain from further increases in biopsy number. There was little statistical advantage for counting more than 8 crypts/biopsy. Demonstrating a decrease of 25% in the mean labeling index with 90% power could require more than 100 subjects/group. We conclude that proliferating cell nuclear antigen is an extremely reproducible method to determine proliferation index. There is considerable variability among subjects, biopsies, and crypts.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2006

Meta-analysis based on control of false discovery rate: combining yeast ChIP-chip datasets.

MOTIVATION: High-throughput microarray technology can be used to examine thousands of features, such as all the genes of an organism, and measure their expression. Two important issues of microarray bioinformatics are first, how to combine the significance values for each feature across experiments with high statistical power, and second, how to control the proportion of false positives. Existing methods address these issues separately, in spite of their linked usage. RESULTS: We present a novel method (ESP) to address the two requirements in an interdependent way. It generalizes the truncated product method of Zaykin et al. to combine only those significance values which clear their respective experiment-specific false discovery restrictive thresholds, thus allowing us to control the false discovery rate (FDR) for the final combined result. Further, we introduce several concepts that together offer FDR control, high power, quality control and speed-up in meta-analysis as done by our algorithm. Computational and statistical methods of research synthesis like the one described here will be increasingly important as additional genome-wide datasets accumulate in databases. We apply our method to combine three well-known ChIP-chip transcription factor binding datasets for budding yeast to identify significant intergenic regulatory sequences for nine cell cycle regulating transcription factors, both with high power and controlled FDR.

Algorithms↗
PubMed2005

Sparse imaging and continuous event-related fMRI in the visual domain: a systematic comparison.

Continuous image acquisition as used in most functional magnetic resonance imaging (fMRI) designs may conflict with specific experimental settings due to attendant, noisy gradient switching. In sparse fMRI, single images are recorded with a delay that allows the registration of the predicted peak of an evoked hemodynamic response (HDR). The aim of this study was to assess validity and sensitivity of single-trial sparse imaging within the visual domain. Thirteen subjects were scanned twice. Either continuous or sparse image acquisition was applied while participants viewed single trains of flashlights. Sparse fMRI results were compared to continuous event-related fMRI results on single- and multisubject level regarding spatial extent, overlap, and intensity of activation. In continuously recorded data, the variability of the HDR peak latency was examined because this measure determined the timing of sparse image acquisition. In sparse fMRI, the sensitivity was analyzed considering different numbers of averaged trials. Sparse imaging detected the core activity revealed using continuous fMRI. The intensity of signal changes detected by continuous or sparse fMRI was comparable. The HDR peak latency was stable across sessions, but intersubject and regional variability might have affected the power of sparse fMRI. In sparse imaging, adding trials resulted in extension of activation and improvement in statistical power. The comparison with established continuous fMRI confirms the validity of sparse imaging. Conventional event-related data acquisition and analysis provided more comprehensive results. However, only sparse fMRI offers the opportunity to apply stimuli and record further biosignals free of scanner-related artifacts during intervals without image acquisition.

Adult↗
PubMed2006

Pixel-based statistical analysis by a 3D clustering approach: application to autoradiographic images.

Statistical analysis of medical images in experimental laboratories plays an important role in confirming scientific findings and in guiding potential clinical applications. In experimental neuroscience studies, autoradiographic images taken under differing physiological or pathological conditions from replicate animals are often compared in order to detect any significant change in glucose utilization or blood flow and to localize these changes. For these comparisons to be valid and informative, proper statistical procedures are in order. Conventional methods include statistic parametric mapping (SPM) analysis, non-parametric analysis and cluster-analysis. Each method of comparison has a specific purpose. This paper describes an approach that combines these conventional methods and presents a non-parametric statistical procedure based on cluster-analysis for localizing significant differences in autoradiographic data sets. By thresholding cluster sizes rather than pixel values to reject false positives, this approach enhances statistical power. By re-shuffling the data sets to produce the null distribution of a cluster size statistic, the test makes few assumptions as to the statistical properties of the SPM, and thus it is valid under a broad range of conditions. The designed method was tested on autoradiographic images of rats subjected to moderate traumatic brain injury (TBI). Different methods were also performed on the same data sets. Comparison among these methods shows that this method is suitable for the statistical analysis of autoradiographic images.

Animals↗
PubMed1991

Adult age differences in direct and indirect tests of memory.

Indirect tests of memory assess the influence of recent experience on task performance without requiring awareness of remembering. Evidence concerning whether there are reliable age differences on such indicators of implicit memory has been inconsistent. This inconsistency may be related either to the low power of previous studies, or the contamination of indirect measures by conscious memory retrieval strategies. In a statistically powerful test of this question, indirect and direct tests of memory were administered to 584 adults from three age groups (19-36 years, 55-69 years, 70-86 years). Significant age differences in favor of the young were found on the indirect test as well as direct tests, suggesting that there are small but reliable age differences in implicit memory. Correlational analyses examining the relationship of memory performance to other cognitive variables indicated that the indirect test was supported by different components than the direct tests.

Adult↗
PubMed2005

Genome scan meta-analysis of rheumatoid arthritis.

OBJECTIVE: Genome scans for rheumatoid arthritis (RA) have yielded inconsistent results. The absence of replication of linkage might be due to lack of power of individual studies. We performed a genome scan meta-analysis of published data to increase statistical power and to assess evidence for linkage of RA across genome scan studies. METHODS: Four RA whole-genome scans containing 767 families with 964 sibling pairs were included for the genome scan meta-analysis (GSMA). The GSMA method was applied to pool the results obtained from four genome scans. For each study, 120 genomic bins of approximately 30 centimorgans were defined and ranked according to maximum evidence for linkage within each bin. Bin ranks were weighted and summed across all studies. The summed rank for each bin was assessed empirically for significance using permutation methods. RESULTS: A total of nine bins lay above the 95% confidence level (P=0.05) and four bins were above the 99% confidence level (P=0.01) in the RA GSMA, suggesting that these bins contain RA-linked loci: bins 6.2, 6.4, 8.1, 18.3, 12.3, 12.2, 1.5, 6.3 and 16.2. The strongest evidence for linkage occurred on chromosome 6p22.3-6p21.1 (bin 6.2), containing the HLA region (P(sumrnk)=0.0000008). CONCLUSION: This RA GSMA confirmed the evidence for HLA loci as the greatest susceptibility factor to RA and showed evidence for linkage at non-HLA loci, such as chromosomes 1p, 6, 8p, 12, 16 and 18q, across studies. These data may provide a basis to carry out targeted linkage and candidate gene studies, particularly in the regions.

Arthritis, Rheumatoid↗
PubMed2001

Consensus evidence evaluation in resuscitation research: analysis of Type I and Type II errors.

OBJECTIVE: This paper addresses the following statistical question: 'if genuine improvements in cardiopulmonary resuscitation (CPR) were discovered that doubled the probability of resuscitation success in a series of randomized clinical trials, would they be recognized and incorporated into consensus guidelines?'. METHODS: Statistical powers for hypothetical individual clinical trials comparing experimental and control CPR were computed as a function of the study N when the true probabilities for immediate survival, 24 h survival, and discharge survival in the experimental group were twice those in the control group. Next, the binomial distributions describing the numbers of statistically significant studies in a series of equally powered trials of the same intervention were determined. These were compared with varying criteria for consensus among expert reviewers, expressed in terms of the number of 'positive' studies showing a statistically significant difference that reviewers would require before approving the experimental method. RESULTS: False-negative evaluations (i.e. failures to approve a technique that actually doubled survival) were extremely common under a wide range of realistic assumptions and consensus criteria, especially when simulated long-term survival data were considered. Similar methods showed that false-positive evaluations would be extremely rare, provided that at least two of the clinical trials in a series showed a statistically significant benefit of the experimental method. CONCLUSIONS: Optimization of evidence evaluation can and should be carried out to make better use of available data in creating resuscitation guidelines. One simple approach is the 'two and one quarter test': if at least two well-conducted studies in a series are significantly positive (P<0.05) comprising at least one-quarter of all studies in the series, a positive effect can be inferred with small Type I and Type II errors. In addition, greater reliance on modern, unbiased methods such as cumulative meta-analysis is needed to increase the sensitivity of evidence evaluation for detecting useful innovations in resuscitation.

Clinical Protocols↗
PubMed2001

The relative power of SNPs and haplotype as genetic markers for association tests.

Identifying the polymorphisms that contribute to disease predisposition and drug response is a major goal of the post-genome era. Single nucleotide polymorphisms (SNPs) in disease-related genes are often used as candidates in the search for causative variations. Association tests based on haplotypes have also been suggested and, at times, have provided greater statistical power than tests based on the underlying SNPs. Here we review the statistical model traditionally used to describe association studies for complex traits and derive novel results for the relative power of SNP-based and haplotype-based tests of association. In the model, a set of independent SNP-based variations, some of which contribute to a measured phenotype, may be used as markers directly or may be organised into haplotype markers. Provided that the marker set includes all the causative SNPs, we find a simple rule for the relative power of SNP and haplotype markers: SNP-based tests have greater power when the number of causative SNPs (a subset of the total set of SNPs) is smaller than the total number of haplotypes. Furthermore, we find that regression tests for the simple main effect of each haplotype are generally more powerful than ANOVA tests applied to haplotype pairs. A review of recent literature supports our findings.

Analysis of Variance↗
PubMed2002

Power and sample sizes for linkage with extreme sampling under an oligogenic model for quantitative traits.

Extreme sampling of sibling pairs has been shown to be efficient in terms of statistical power and sample sizes (in number of sibling pairs needed to genotype) to detect a quantitative trait locus (QTL) when the residual distribution is normal. In the present study, the efficiency of extreme sampling strategies to detect each locus under an oligogenic model is analytically explored with a test statistic based on identical-by-descent (IBD) statuses of independent sibling pairs. In the oligogenic model, the joint effect of oligogenes is the sum of the effects of each locus. Under this model, detecting each single locus will depend, in part, on the allele frequencies and magnitudes of effect of the other loci. Effects of two QTLs with different magnitudes of displacement and acting nonepistatically are considered. Three types of extreme sampling-that is, extreme concordant high (ECH), extreme concordant low (ECL), and extreme discordant (ED)-are primarily considered herein. Among these, ED sampling under the oligogenic model is shown to be most efficient in most situations considered here in terms of allele frequency and mode of inheritance. Differences in results between ECH and ECL sampling are purely arbitrary, brought up mostly by the directions of displacement effects. However, power to detect a locus with the lesser (in magnitude) displacement effect does not necessarily increase with extremity of sampling. Combinations of extreme discordant and extreme concordant sibling pairs are briefly discussed.

Alleles↗
PubMed2001

Transformation works for non-normality? On one-sample transformation trimmed t methods.

If the assumption of normality is not satisfied, there is no simple solution to this problem for the one-sample t test. The present study proposes Hall's or Johnson's transformation in conjunction with the trimmed mean to deal with the problem. Computer simulation is carried out to evaluate the small-sample behaviour of the proposed methods in terms of Type I error rate and statistical power. The proposed methods are compared with the conventional Student t, Yuen's trimmed t, Johnson's transformation untrimmed t, and Hall's transformation untrimmed t statistics for one-sided and two-sided tests. The simulation results indicate that the proposed methods can control Type I error well in very extreme conditions and are more powerful than the conventional methods.

Bias↗
PubMed1994

Surgical versus balloon therapy for aortic coarctation in infants < or = 3 months old.

OBJECTIVES: This study compared the efficacy and safety of balloon angioplasty with surgical correction of native aortic coarctation in infants < or = 3 months old. BACKGROUND: There is a controversy with regard to the role of balloon angioplasty in the treatment of aortic coarctation, especially in young infants. METHODS: Data from 29 infants < or = 3 months old undergoing therapy for aortic coarctation during the decade ending 1992 were analyzed. Fourteen infants underwent surgery, and 15 had balloon angioplasty. The sole criterion for allotment to the balloon group was the availability of an interventional cardiologist at the time of presentation of the infant. RESULTS: The surgical and balloon groups were comparable (p > 0.1) with regard to age (27 +/- 35 [mean +/- SD] vs. 29 +/- 27 days), weight (3.5 +/- 0.9 vs. 3.8 +/- 1.0 kg) and prevalence (7 of 14 vs. 8 of 15) and type of associated defects. Operative (1 of 14 vs. 1 of 15) and late (3 of 13 vs. 3 of 14) mortality, immediate gradient relief (36 +/- 25 to 10 +/- 9 mm Hg vs. 41 +/- 14 to 6 +/- 6 mm Hg) and follow-up gradient (27 +/- 27 vs. 24 +/- 19 mm Hg) were similar (p > 0.1). Infants with a gradient > 20 mm Hg at follow-up (6 of 13 vs. 7 of 14) and need for reintervention (6 of 13 vs. 7 of 14) were also similar (p > 0.1) in both groups. Duration of hospital stay during the first intervention was higher (p < 0.05) in the surgical (32 +/- 37 days) than the balloon (7 +/- 6 days) group. Similarly, duration of endotracheal intubation and mechanical ventilation was longer (p < 0.05) in the surgical (12 +/- 16 days) than the balloon (2 +/- 3 days) group. Complications after surgical intervention (0.86 events/patient) were higher (p < 0.01) than those seen after balloon angioplasty (0.27 events/patient). However, the lack of significant differences observed for mortality rates and residual gradients may be due to low statistical power to detect differences (16% to 49%), implying that this may be due to either actual lack of statistical difference or small sample size. CONCLUSIONS: The data indicate that the degree of relief from aortic coarctation and the frequency with which reintervention is needed are similar in both groups. However, the morbidity and complication rates are lower with balloon than with surgical therapy. These data suggest that balloon angioplasty may be an acceptable alternative to surgical correction in the treatment of symptomatic aortic coarctation in infants < or = 3 months old.

Analysis of Variance↗