Biomedical subjects

B Iglewicz

Publications and source records attributed to B Iglewicz.

4 recordsLinked to original sources

PubMed1994

Robust and bootstrap testing procedures for bioequivalence.

A common problem encountered in bioequivalence studies is the presence of outliers. In this situation, the two one-sided t-tests proposed by Schuirmann fail to provide reasonable power for concluding bioequivalence. In contrast, our proposed 2 beta trimmed-t procedure has the following advantages: (1) it has higher efficiency for nonnormal symmetric distributions, (2) it is resistant to outliers, and (3) it is relatively easy to compute. Two bootstrap procedures introduced here provide further justification for the proposed trimmed t-test procedure. Results from Monte Carlo studies illustrate the power of the proposed procedures under various distributional assumptions for a 2 x 2 crossover trial.

Biological Availability↗

PubMed1986

The influence of uninterpretability on the assessment of diagnostic tests.

A frequent problem faced by physicians utilizing diagnostic tests is the occurrence of uninterpretable test results. Such results, if they occur commonly, can seriously impair the diagnostic performance of the test. Moreover, in assessing the characteristics of the test, i.e. sensitivity, specificity, etc. failure to consider the impact of uninterpretability will artificially inflate the test characteristics. In this paper we explore the implications of this issue. We observe that a relevant factor is the potential repeatability of the test, i.e. whether the cause of uninterpretability is a transient phenomenon or an inherent property of the subject. We distinguish uninterpretable results, in which no result is obtained, from indeterminate results, in which the result is equivocal, or for which predisposing concomitant factors limit the interpretability of the result. Our results demonstrate that the naive approach of ignoring uninterpretable results in test assessments may indeed be unbiased in certain circumstances. However, if the cause of uninterpretability is related to disease status or to the potentially observable test result, then this approach will lead to bias. In either case, the frequency of uninterpretability is an important consideration in the cost-effectiveness of the test.

Bayes Theorem↗

PubMed1984

Elevated levels of carbon monoxide in the patient compartment of ambulances.

Six hundred and ninety New Jersey ambulances were monitored for carbon monoxide (CO); 27 per cent had CO levels of 10 ppm or more greater than ambient air in the breathing zone of the patient. Twenty-nine of these ambulances had levels of at least 35 ppm greater than ambient air. Results indicate that a CO exposure problem exists in ambulances.

Air Pollutants↗

PubMed1980

A treatment allocation procedure for sequential clinical trials.

A dynamic treatment allocation procedure is proposed for clinical trials which require balancing across several prognostic factors. The treatment allocation decision is based on the minimization of a function which is an easily evaluated approximation to the variance of the treatment effect in a linear model relating the outcome variable to the chosen prognostic factors and selected interactions. By use of simulations, the procedure is shown to be superior to ad hoc procedures proposed by Pocock and Simon (1975, Biometrics 31, 103-115), over a variety of reasonable experimental situations. It is shown that it is feasible to evaluate the procedure by hand calculations and that it is extremely easy if a small programmable calculator is available. Practical problems relating to implementation of the procedure are discussed with special reference to multi-institutional clinical trials.

Clinical Trials as Topic↗