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PubMed2003

Review of efforts to decrease costly leg wound complications in the medicare population following coronary revascularization.

BACKGROUND: Current trends show that patients referred for coronary artery bypass grafting (CABG) are significantly older, sicker, and at higher risk for complications than ever before. Eliminating leg wound complications would significantly benefit these patients and reduce the consumption of health care time and dollars. Endoscopic vein harvesting (EVH) decreases the risk of wound complications in patients following CABG and may decrease costly long-term wound-related problems. METHODS: In this retrospective study, the cases of 1909 Medicare patients who had undergone EVH or open vein harvesting (OVH) for CABG were reviewed. The risk factors of these patients were examined and compared with those of 1485 non- Medicare patients. Readmissions, home health care costs, and office lengths of service were reviewed and analyzed. RESULTS: The results of univariate analyses of the Medicare versus non-Medicare populations indicated significant differences for peripheral vascular disease (25.4% versus 17.2%; P <.0001), renal failure (6.0% versus 2.8%; P <.0001), hypertension (75.4% versus 71.5%; P =.011), female sex (31.1% versus 22.4%; P <.0001), mean age (69.8 years versus 57.1 years; P <.0001), and mortality risk (4.6% versus 2.2%; P <.0001). The wound rates in the Medicare group were 1.1% for EVH (n = 741) versus 2.8% for OVH (n = 1168), and this difference was significant (P =.0163) despite a higher frequency of morbid obesity in the EVH population (P <.0001). No significant differences were found in readmission frequency, home health care costs, or office length of service. CONCLUSION: EVH benefits Medicare patients. Although this study is the largest to date to use disposable instruments, there is a lack of statistical power in the analysis of cost comparisons due to the small sample size of wound complications. However, there appears to be a general trend toward a lower treatment cost per patient and less resource use with EVH.

Aged↗
PubMed2005

Dynamic assessment of a composite arterial Y-graft achieving complete myocardial revascularization: transthoracic echo-Doppler correlates with myocardial scintigraphy.

BACKGROUND: Composite arterial grafts are presently being used ever more frequently in coronary bypass surgery. We assessed the composite radial artery and in situ left internal thoracic artery Y-graft by means of transthoracic echo-Doppler and myocardial perfusion scintigraphy (MPS). METHODS: In 53 patients who underwent complete myocardial revascularization using only this composite arterial graft, good transthoracic echographic images and pulsed Doppler signals of the Y-graft main stem were obtained at rest and early after standard exercise; the echographic parameters were measured. Stress/rest MPS was the gold standard for residual myocardial ischemia. The patients with negative MPS were divided into groups according to the number of coronary vessels grafted and their history of preoperative myocardial infarction. RESULTS: The diastolic-to-systolic ratio of the peak velocities and velocity-time integrals both at rest and after stress, and the stress-to-rest ratio of the diastolic peak velocities and diastolic velocity-time integrals in the negative MPS patients were significantly greater than in the 6 positive MPS patients. However, the restricted number of positive MPS cases limits the power of this statistical analysis. The stress-to-rest ratio of the diastolic velocity-time integrals in the patients with three grafted coronary vessels (median 2.3) and in those without preoperative myocardial infarction (median 2.1) were respectively greater than in the patients with two vessels grafted (median 1.7, p < 0.0001) and those with preoperative myocardial infarction (median 1.8, p = 0.0048). CONCLUSIONS: Dynamic assessment with transthoracic echo-Doppler of a composite arterial graft including the in situ left internal thoracic artery correlates with MPS. In patients with negative MPS, transthoracic echo-Doppler correlates with the myocardial demand.

Aged↗
PubMed1995

Performance on the athletic training certification examination based on candidates' routes to eligibility.

The National Athletic Trainers' Association Board of Certification initiated a task force whose purpose is to evaluate the criteria that determine eligibility for the athletic training certification examination. Candidates may qualify to take the examination through one of two routes: an academic-based curriculum program or the practical education, work-experience-based internship route. The certification examination is comprised of three sections: a written examination, a written simulation, and a practical examination. We retrospectively examined certification examination scores during a 2-year period to determine whether a significant difference existed between the two groups of candidates. Test results for first-time candidates sitting for one of the nine examinations administered during 1992 and 1993 were extracted from the data base maintained by Columbia Assessment Services, Inc (Raleigh, NC) and grouped according to the candidates' route to eligibility. Curriculum candidates had significantly greater scores than did internship candidates on each of the three parts of the examination. Although the test analysis yields strong statistical power in interpreting these results, examination outcomes may also be influenced by the structure and content of the academic program followed, the quality of the clinical experience, the heterogeneity of each of the routes, and the psychosocial rigors of the examination process.

Journal Article↗
PubMed1986

The Vancouver Lymphadenopathy-AIDS Study: 5. Antecedent behavioural, clinical and laboratory findings in patients with AIDS and HIV-seropositive controls.

In a group of homosexual men in Vancouver studied prospectively since November 1982, 26 cases of acquired immune deficiency syndrome (AIDS) have arisen. To identify behavioural, clinical and laboratory findings that might predict the development of AIDS in people with antibody to human immunodeficiency virus (HIV), we compared data for 25 patients with AIDS with corresponding data for 80 controls serologically positive for HIV selected from the cohort. The clinical and laboratory data for the patients with AIDS preceded the diagnosis of the syndrome by a mean of 17.5 months. The controls had been both seropositive and AIDS-free for a mean of 16.7 months after acquisition of their data. We detected significant differences between the patients with AIDS and the controls in IgG and IgA levels, absolute number of helper T cells and ratio of helper to suppressor T cells but not in lifetime number of male sexual partners, frequency of receptive anal intercourse or receptive fisting, illicit drug use or history of infectious disease. We also detected an increased risk of AIDS among those who had an elevated number of sexual contacts in AIDS-endemic areas in the 5 years before enrollment. A history of increased early sexual contact in AIDS-endemic areas is likely to be associated with early infection and with an increased risk of AIDS among men with HIV infection of unknown duration. Thus, although our analysis had limited statistical power, we conclude that most lifestyle variables appear to act as exposure factors in HIV infection but not as cofactors in the development of AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Change-to-Open-Label Design. Proposal and discussion of a new design for clinical parallel-group double-masked trials.

The "Change-to-Open-Label Design" (COLA-design) is proposed to overcome some of the ethical and organizational problems of the usual double-masked design in certain situations while preserving its scientific rigor. Patients are randomized on a doubled-masked basis into treatment groups. During the trial the patient or the treating physician may ask for a change from the masked treatment to any open-label treatment of their choice (experimental or not), if the masked treatment is thought to be unsatisfactory. It seems to be easier to obtain a patient's informed consent to participate in placebo controlled double-masked trials especially for long term studies. The main outcome variable in COLA-design is the time until a patient demands for such a change. "Survival analysis" is a powerful statistical method to evaluate this outcome variable. Even patients lost from observation can be included in the evaluation: they still deliver censored outcome values. Evidently, in trials with a COLA-design the patient's personal impression of the therapy is the most important factor in its assessment. Therapeutical success is mingled with undesirable effects into the outcome measure; therefore this design is especially applicable to investigate treatments supposed to increase quality of life.

Double-Blind Method↗
PubMed1994

Field effectiveness of needle disinfection among injecting drug users.

To examine the putative protective effect of disinfectant use on HIV seroconversion among injecting drug users, we conducted a nested case-control study of black heterosexuals comparing 34 HIV seroconverters with 154 persistent seronegatives matched on gender, cocaine injection (yes/no), date of study entry, and duration of follow-up. Injecting drug users who reported using disinfectant all the time had an odds ratio of seroconversion of 0.87, as compared with those who reported no use of disinfectants; the corresponding odds ratio was 1.00 for those who used disinfectants less than all the time. We examined the effect of drug use and sex practice variables, and responses to a socially desirable responding scale as possible confounders for the effect of needle disinfection on HIV seroconversion; the adjusted odds ratios for disinfectant use and HIV seroconversion were unchanged in this analysis. Despite limited statistical power and the potential for residual confounding, these data suggest that disinfection of injection equipment is not a substitute for abstinence from drugs or use of sterile injection equipment.

1-Propanol↗
PubMed1996

Prevention of gastrointestinal cancer--the potential role of NSAIDs in colorectal cancer.

Gastrointestinal cancers are among the leading sites of cancer and leading causes of cancer-related deaths. Gastrointestinal cancers are often at an advanced stage at the time of diagnosis, and are highly resistant to non-surgical therapy. Thus early diagnosis and prevention are approaches that are under active investigation. Screening and surveillance are considered secondary prevention. Primary prevention is the use of dietary or environmental modification or chemopreventive agents. This written review will emphasize the potential role of acetylsalicylic acid and other non-steroidal anti-inflammatory drugs (NSAIDs) in the prevention of gastrointestinal cancer, and specifically colorectal cancer. Cell culture and animal studies have shown that NSAIDs possess anti-proliferative and anti-neoplastic effects. Recent epidemiologic surveys also suggest that individuals who regularly take NSAIDs, particularly acetylsalicylic acid, have about a 50% decrease in colorectal cancer incidence and mortality. However, in the only interventional trial of aspirin (and beta-carotene), a retrospective analysis had inadequate statistical power to demonstrate any protective effect against colorectal cancer. About a dozen small prospective intervention studies have been done in a total of about a hundred patients with familial adenomatous polyposis to test the efficacy of NSAIDs, particularly sulindac. All human trials have shown substantial partial and some complete regression of colorectal and perhaps also duodenal adenomatous polyps. But virtually all patients had regrowth of adenomatous polyps after sulindac was stopped. In addition, sulindac and other NSAIDs result in occasional adverse events such as gastrointestinal bleeding. Thus sulindac cannot be recommended for routine use outside of a study setting. One valid current approach to the prevention of gastrointestinal cancer, and colorectal cancer in particular, is the adoption of a healthy lifestyle and appropriate screening and surveillance. Screening and surveillance guidelines have been developed by several public agencies and their recommendations should be adopted. In addition, we should adopt a healthy lifestyle and diet, which consists of low fat ( < 30% to total calories), and high fiber (> 3 daily servings of fruits/vegetables), with the avoidance of red meats ( < 3 weekly servings) and alcohol ( < 2 drinks daily), and the absolute avoidance of tobacco smoking.

Adenomatous Polyposis Coli↗
PubMed1997

The effect of an absorbable collagen membrane on the subgingival microflora.

The purpose of this study was to determine the effect of use of an absorbable collagen membrane in guided tissue regeneration (GTR) therapy upon the subgingival microflora. The study group consisted of 12 systemically healthy patients with bilateral mandibular furcation defects with attachment loss > or = 6 mm; one site was randomly assigned for GTR treatment while the contralateral site received surgical flap debridement only. Subgingival plaque samples were collected by paper point on the day of surgery and at 2, 4 and 6 months post-surgery. Three sites were sampled in each patient: a collagen membrane site, a control surgical site, and an unoperated control site. Plaque samples were transported in a non-phosphated buffer solution and examined by phase-contrast microscopy. Cocci, rods, spirochetes, fusiforms, curved rods, and total bacteria were recorded per 10 high-power fields. Following statistical analysis utilizing the Bonferroni (Dunn) t test, no differences in total bacterial counts were found among the sites at any of the time intervals examined. Total bacterial counts were found lower at both the collagen membrane and control surgical sites post-surgery as compared to unoperated control sites, but these differences were not statistically significant (P > .05). In addition, no significant differences were detected in bacterial profiles between sites or individual time points. Results from this 6-month limited clinical trial suggest that the placement of an absorbable collagen membrane as part of a standard surgical regimen for GTR therapy does not alter the local microflora.

Absorption↗
PubMed2005

High resolution T association tests of complex diseases based on family data.

This paper proposes family based Hotelling's T(2) tests for high resolution linkage disequilibrium (LD) mapping or association studies of complex diseases. Assume that genotype data of multiple markers or haplotype blocks are available for a sample of nuclear families, in which some offspring are affected. Paired Hotelling's T(2) test statistics are proposed for a high resolution association study using parents as controls for affected offspring, based on two coding methods: haplotype/allele coding and genotype coding. The paired Hotelling's T(2) tests take not only the correlation between the haplotype blocks or markers into account, but also take the correlation within each parent-offspring pair into account. The method extends two sample Hotelling's T(2) test statistics for population case control association studies, which are not valid for family data due to correlation of genetic data among family members. The validity of the proposed method is justified by rigorous mathematical and statistical proof under the large sample theory. The non-centrality parameter approximations of the test statistics are calculated for power and sample size calculations. From power comparison and type I error calculations, it is shown that the test statistic based on haplotype/allele coding is advantageous over the test statistic of genotype coding. Analysis using multiple markers may provide higher power than single marker analysis. If only one marker is utilized the power of the test statistic based on haplotype/allele coding is nearly identical to that of 1-TDT. Moreover, a permutation procedure is provided for data analysis. The method is applied to data from a German asthma family study. The results based on the paired Hotelling's T(2) statistic tests confirm the previous findings. However, the paired Hotelling's T(2) tests produce much smaller P-values than those of the previous study. The permutation tests produce similar results to those of the previous study; moreover, additional marker combinations are shown to be significant by permutation tests. The proposed paired Hotelling's T(2) statistic tests are potentially powerful in mapping complex diseases. A SAS Macro, Hotel_fam.sas, has been written to implement the method for data analysis.

Asthma↗
PubMed2003

Novel nonparametric approach to canonical correlation analysis with applications to low CNR functional MRI data.

Detection of activation in functional MRI (fMRI) is often complicated by the low contrast-to-noise ratio (CNR) in the data. The primary source of the difficulty is the fact that for activities that are subtle the signal can be hidden inside the inherent noise in the data. Classical univariate methods based on t-test or F-test are susceptible to noise, as they fail to harness systematic correlations in evoked responses within neighboring voxels. Here the power of a multivariate statistical analysis tool known as canonical correlation analysis (CCA) in fMRI studies is demonstrated where the CNR is low. As a further illustration of the power of the method, a comparative study of CCA and ordinary correlation analysis using simulated data under various noise levels is also performed. A novel nonparametric approach is introduced to calculate the P-values from the distribution of the complicated test statistic. The circumstances under which CCA is a better performer as well as when it is not the case are discussed. As an example, this method is applied to detect hippocampal activation from memory-related tasks.

Adult↗
PubMed1997

Power vectors: an application of Fourier analysis to the description and statistical analysis of refractive error.

The description of sphero-cylinder lenses is approached from the viewpoint of Fourier analysis of the power profile. It is shown that the familiar sine-squared law leads naturally to a Fourier series representation with exactly three Fourier coefficients, representing the natural parameters of a thin lens. The constant term corresponds to the mean spherical equivalent (MSE) power, whereas the amplitude and phase of the harmonic correspond to the power and axis of a Jackson cross-cylinder (JCC) lens, respectively. Expressing the Fourier series in rectangular form leads to the representation of an arbitrary sphero-cylinder lens as the sum of a spherical lens and two cross-cylinders, one at axis 0 degree and the other at axis 45 degrees. The power of these three component lenses may be interpreted as (x,y,z) coordinates of a vector representation of the power profile. Advantages of this power vector representation of a sphero-cylinder lens for numerical and graphical analysis of optometric data are described for problems involving lens combinations, comparison of different lenses, and the statistical distribution of refractive errors.

Computer Graphics↗
PubMed2003

Statistical practices: the seven deadly sins.

This paper discusses selected problems in applied statistical analysis: (a) over-reliance on null hypothesis statistical testing, (b) failing to perform a power analysis prior to conducting the study, (c) using asymptotic statistical approximations with small samples, (d) ignoring missing data, (e) failing to deal with the multiplicity problem when performing multiple statistical comparisons, (f) using stepwise procedures to select variables in regression analysis, and (g) failing to perform or report model diagnostics. Suggestions and guidelines to address these issues in manuscripts concerning child neuropsychological research are offered.

Child↗
PubMed2002

Pesticide studies: replicability of micro/mesocosms.

The objective of this state-of-the-art review was to quantify the replicability of pesticide studies using micro/ mesocosms. Low interpretability of micro/mesocosm studies, and inconclusive and highly variable data, resulted in a discontinuation of the use of these studies for the registration of pesticides. Coefficients of variation, CV%, were calculated on the basis of data tables as a measure of statistical 'effectiveness' taken from the literature. The average CV in the investigated studies was 45%; larger out-door mesocosms averaged 51%, and smaller indoor micro/mesocosms averaged 32%. CVs on variables involving animals were higher than CVs on plant end-points, which in turn were higher than abiotic variables for all experiments. However, to enhance the interpretability and implementation of micro/mesocosm studies for pesticide registration, a number of context-dependent steps could be incorporated; 1) determine the appropriate experimental design and number of replicates by using power analysis, 2) Utilise advanced statistical analysis, such as probabilistic effect distribution and principal response curves, 4) report, preferably in quantitative terms using power analysis, the risk of Type II error. The author's primary conclusion is that the level of CVs is context dependent and, therefore, it is not possible to suggest a generally acceptable level of CVs for all experiments. This has been suggested both directly and indirectly in the literature. Moreover, the number of insignificant (p > 0.05) results is high, 88% of all test biotic variables had no statistical significance. The average number of replicates were 3-4, which theoretically should yield significant effects at least at the highest test-concentration, then resulting in 75-66% insignificant results.

Animals↗
PubMed2002

Selecting the best method to evaluate bronchodilation when analysing bronchodilator studies.

Changes in lung function (that is, FEV(1)) are commonly expressed as a percentage of the predicted value. The question is whether this parameter is best suited for statistical analysis. A total of 2199 bronchodilation tests were selected and pre- and post-dilator FEV(1), age, height and sex extracted. Predicted FEV(1) values, the difference between pre- and post-dilator FEV(1) and the change as percentage of predicted or baseline FEV(1) were calculated. The latter parameters were subjected to analysis of variance and pre- and post-dilator FEV(1) to analysis of covariance. The statistical power of these four approaches and the residual structure were used to select the best approach. Analysis of variance of the change as percentage of predicted and covariance analysis of pre- and post-dilator FEV(1) offers the best performance. The residuals of the analysis of variance showed a funnel shaped structure. The latter causes residual heterogeneity, resulting in a loss of power and deviations between the actual and nominal alpha-level. This is not taken into account when calculating sample sizes using the standard equations, which implicitly assume lack of these problems. Analysis of covariance does not suffer from these problems. The best way to evaluate bronchodilation in trials is to use analysis of covariance.

Age Factors↗
PubMed2000

Combined linkage and linkage disequilibrium mapping for genome screens.

Linkage analysis and association studies, two major approaches for genetic studies of human diseases, are useful for mapping genes that are highly penetrant, but both use only part of the information that is available for mapping disease genes. Therefore, they provide limited utility when used alone. In this report, we present combined linkage and linkage disequilibrium mapping that simultaneously utilizes linkage and linkage disequilibrium information for mapping human disease genes. Compared with the existing linkage analysis and association study methods, this method has several advantages: 1) it has high statistical power by a joint analysis of linkage and linkage disequilibrium for localizing disease susceptibility loci: 2) it unifies the theory of linkage analysis and linkage disequilibrium mapping, 3) it retains the general framework for linkage analysis and, hence, can be easily incorporated into the existing software for the linkage analysis. The proposed LLDM is applied to familial hemophagocytic lymphohistiocytosis (FHL) disease.

Chromosome Mapping↗
PubMed1988

Spirometry in healthy adult never-smokers.

Spirometry was performed in 277 female and 240 male subjects constituting a random, unbiased population sample representative for the population of Denmark. Equipment, calibration and measurement procedures conformed strictly with established standards. Statistical analysis showed that certain power transformations (cubic, quadratic or square root) of the data produced models that fitted the data statistically significantly better than linear models, where no transformations are applied, or logarithmic models where a logarithmic transformation is applied to the response variable. Differences between predictions obtained with the three models were, however, small and without practical significance. Neither rigid adherence to established, well documented standards nor elaborate statistical analysis reduced the inter-individual variance significantly in comparison to previous investigations. The results emphasize that it is important that reference values are appropriate for the methods and populations in question.

Adult↗
PubMed2005

Sibship T2 association tests of complex diseases for tightly linked markers.

For population case-control association studies, the false-positive rates can be high due to inappropriate controls, which can occur if there is population admixture or stratification. Moreover, it is not always clear how to choose appropriate controls. Alternatively, the parents or normal sibs can be used as controls of affected sibs. For late-onset complex diseases, parental data are not usually available. One way to study late-onset disorders is to perform sib-pair or sibship analyses. This paper proposes sibship-based Hotelling's T2 test statistics for high-resolution linkage disequilibrium mapping of complex diseases. For a sample of sibships, suppose that each sibship consists of at least one affected sib and at least one normal sib. Assume that genotype data of multiple tightly linked markers/haplotypes are available for each individual in the sample. Paired Hotelling's T2 test statistics are proposed for high-resolution association studies using normal sibs as controls for affected sibs, based on two coding methods: 'haplotype/allele coding' and 'genotype coding'. The paired Hotelling's T2 tests take into account not only the correlation among the markers, but also take the correlation within each sib-pair. The validity of the proposed method is justified by rigorous mathematical and statistical proofs under the large sample theory. The non-centrality parameter approximations of the test statistics are calculated for power and sample size calculations. By carrying out power and simulation studies, it was found that the non-centrality parameter approximations of the test statistics were accurate. By power and type I error analysis, the test statistics based on the 'haplotype/allele coding' method were found to be advantageous in comparison to the test statistics based on the 'genotype coding' method. The test statistics based on multiple markers can have higher power than those based on a single marker. The test statistics can be applied not only for bi-allelic markers, but also for multi-allelic markers. In addition, the test statistics can be applied to analyse the genetic data of multiple markers which contain double heterozygotes--that is, unknown linkage phase data. An SAS macro, Hotel_sibs.sas, is written to implement the method for data analysis.

Diabetes Mellitus↗
PubMed1999

Comparison of PET [15O]water studies with 6-minute and 10-minute interscan intervals: single-subject and group analyses.

The authors recently showed that [15O]water PET data obtained with a short interscan interval (6 minutes) produced similar results whether or not the residual background from the previous scan is subtracted. The purpose of the present study was to compare scans obtained during motor activation using a short (6-minute) interscan interval protocol with those obtained with a standard (10-minute) protocol in the same scanning session. Single-subject and group analyses were performed using Worsley's method, which uses a pooled variance estimate and statistical parametric mapping with a local variance estimate. High consistency in both the activation maps, i.e., the number of activated motor brain structures and the Talairach coordinates of peak intensities of the activated regions, was obtained in the 6- and 10-minute studies in both single-subject and group analyses. However, in comparison to the 6-minute studies, a larger cluster size of activated brain regions and an approximately 20% higher peak activation in these regions were observed in the 10-minute studies with the same number of replicates. Analysis of these results suggests that using a 6-minute interval with an increased number of replications, i.e., without changing the subject's total study duration, should produce comparable statistical power to that of the 10-minute interval for group analysis and increased statistical power for single-subject analyses that use a local variance estimate because of increased degrees of freedom. Alternatively, with a small increase in the number of scans and the use of a 6-minute interscan interval, a comparable level of statistical significance may be achieved for single-subject experiments that use a local variance estimate, with an overall shortening of the study duration.

Adult↗