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PubMed1994

Practical Bayesian guidelines for phase IIB clinical trials.

A Phase IIB clinical trial typically is a single-arm study aimed at deciding whether a new treatment E is sufficiently promising, relative to a standard therapy, S, to include in a large-scale randomized trial. Thus, Phase IIB trials are inherently comparative even though a standard therapy arm usually is not included. Uncertainty regarding the response rate theta s of S is rarely made explicit, either in planning the trial or interpreting its results. We propose practical Bayesian guidelines for deciding whether E is promising relative to S in settings where patient response is binary and the data are monitored continuously. The design requires specification of an informative prior for theta s, a targeted improvement for E, and bounds on the allowed sample size. No explicit specification of a loss function is required. Sampling continues until E is shown to be either promising or not promising relative to S with high posterior probability, or the maximum sample size is reached. The design provides decision boundaries, a probability distribution for the sample size at termination, and operating characteristics under fixed response probabilities with E.

Bayes Theorem↗
PubMed1996

[Profile of biostatistics utilization in three medical reviews. Implications for medical education].

OBJECTIVE: To identify the most commonly used biostatistical concepts and tests in three journals read by family physicians. DESIGN: Descriptive study of the biostatistical content of 12 issues of the Canadian Medical Association Journal (CMAJ), Canadian Family Physician (CFP), and the New England Journal of Medicine (NEJM). MAIN OUTCOME MEASURES: Frequency of citations of concepts and tests, and Spearman's correlation coefficients comparing the biostatistical profiles of the three journals. RESULTS: Biostatistical content of NEJM was diverse (on average, 39 concepts and 21 tests per issue). In CFP, we found 10 concepts and four tests per issue. In CMAJ, there were, on average, nine concepts and five tests per issue. CONCLUSIONS: The journals' profiles (order of importance of concepts and tests) were fairly similar.

Family Practice↗
PubMed1996

[Examples of pitfalls in statistical analysis--2. Parametric and nonparametric analyses].

When conducting statistical analysis, it is essential to use parametric and nonparametric analyses which properly accord with the attributions of data. What is often overlooked, however, is the need to select the most suitable method of spatistical analysis for the model of the studies. Parametric analysis certainly cannot be relied upon in all situations to yield the best resolutions, and even if we strictly distinguish between the use of parametric and that of nonparametric analyses, we still have done nothing to improve the resolutions themselves. In this article, I discuss several frequently asked questions by presenting an example in which I use parametric analysis on data that should be analyzed by nonparametric analysis.

Drug-Related Side Effects and Adverse Reactions↗
PubMedDate not supplied

Three-dimensional force measurements with mandibular overdentures connected to implants by ball-shaped retentive anchors. A clinical study.

The purpose of this in vivo study was to determine maximum and functional forces simultaneously in three dimensions on mandibular implants supporting overdentures. The anchorage system for overdenture connection was the ball-shaped retentive anchor. Five edentulous patients, each with two mandibular ITI implants, were selected as test subjects. A novel miniaturized piezo-electric force transducer was developed for specific use with ITI implants. Force magnitudes and directions were registered under various test conditions by means of electrostatic plotter records. The test modalities were maximum biting in centric occlusion, maximum biting on a bite plate, grinding, and chewing bread. Maximum forces measured in centric occlusion and on the ipsilateral implant when using a bite plate were slightly increased in vertical and backward-forward dimension (z-, y-axis) compared to the lateral-medial direction (x-axis). On the contralateral implant, equally low values were found in all three dimensions. This may be the effect of a nonsplinted anchorage device. With the use of a bite plate, force magnitudes on the ipsilateral implant were significantly higher on the z- and y-axis than mean maximum forces in centric occlusion (P < .001). Chewing and grinding resulted in lower forces compared to maximum biting, particularly in the vertical direction. The transverse force component in backward-forward direction, however, reached magnitudes that exceeded the vertical component by 100% to 300% during chewing function. This chewing pattern had not been observed in previous investigations with bars and telescopes, and therefore appears to be specific for retentive ball anchors. The prevalent or exclusive force direction registered on both implants in the vertical direction was downward under all test conditions. In the transverse direction during maximum biting the forward direction was more frequently registered, while no obvious prevalence of transverse force direction was observed during chewing and grinding.

Aged↗
PubMed1998

Dependence of vancomycin clearance on renal function via regression and bootstrap methods.

BACKGROUND: Frequently, the estimation of vancomycin on the basis of renal function is too rough because the unknown parameters of a regression function between the vancomycin clearance (CL) and the creatinine clearance (ClCR) are based on small sample sizes. OBJECTIVE: In this study we aim to compare linear and nonlinear regression, spline interpolation and nonlinear kernel estimation for defining the relationship between measured Cl and ClCR. METHOD: We used data from published papers and appropriate numerical methods. The variability and accuracy of the estimated regression functions were determined from bootstrap methods and kernel density estimators. Tests to prove the usually assumed linearity of the regression were carried out and the influence of patient age and weight on Cl was determined. RESULTS: A linear relationship reported by several authors earlier has been determined as ClVAN = 0.763 ClCR + 2.715, (ml/min) (Cl = 0.011 ClCR + 0.055, (ml/min/ kg)). CONCLUSION: Nonparametric regression analysis shows that a nonlinear approximately parabolic function could fit the relationship between Cl and ClCR in the present case somewhat better than a linear function.

Anti-Bacterial Agents↗
PubMedDate not supplied

Ototoxicity of topically applied gentamicin using a statistical analysis of electrophysiological measurement.

Ototoxicity of topically applied gentamicin was studied in guinea pigs. 0.3% gentamicin was instilled in one side of the middle ear cavity and Ringer's solution was instilled in the other side, and the difference in the cochlear microphonics measured with the round window electrode was analysed statistically. Instillation of Ringer's solution in the middle ear cavity for 1 day did not cause any significant sensorineural hearing loss, but on the 3rd day of instillation significantly reduced responses were observed, compared with the responses from non-treated ears, followed by a partial recovery starting on the 4th day. When gentamicin 0.3% was instilled into the middle ear cavity, significant deafness occurred 24 hours later, and highly significant deafness on the 2nd and 3rd day. The usage of gentamicin ear drops of the current formula should be discouraged until a better formula is provided.

Acoustic Stimulation↗