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Biomedical subjects

C B Mueller

Publications and source records attributed to C B Mueller.

At least 19 recordsLinked to original sources
PubMed1996

Introducing progress testing in McMaster University's problem-based medical curriculum: psychometric properties and effect on learning.

BACKGROUND: The progress test (or Quarterly Profile Examination), invented concurrently by the University of Missouri-Kansas City School of Medicine and the University of Limburg, is used to provide useful summative and formative judgments about students' knowledge without distorting learning. All students in all classes sit the same examination at regular intervals through the year, and their individual progress is noted. This paper reports on four years' experience with a progress test, the Personal Progress Index (PPI), at the McMaster University Faculty of Health Sciences. METHOD: The PPI, a 180-item multiple-choice test with items drawn from all disciplines of medicine, is administered to medical students in all three classes three times per year. Individual feedback is provided, and accumulated student performance is determined for summative purposes. This paper examines extensive evidence of reliability, validity, and effect on student learning, using samples from the entering classes of 1992-1995 (a total of 400 students). RESULTS: Reliabilities across test administrations (within classes) ranged from .46 to .63. The PPI demonstrated strong construct validity, with highly significant statistical tests of differences between classes and changes within classes on successive administrations. The predictive validity of the PPI, i.e., whether it could predict performance on the licensing examination of the Medical Council of Canada, increased monotonically from a correlation of .12 for the first test administration one month into medical school to a high of about .60 for the cumulative score across all administrations three months prior to the examination. CONCLUSION: The PPI seems to be performing as intended, with students showing growth in performance across the three years of the MD program. Additional benefits are that many more students now self-refer for remediation (based on low PPI scores) and that the consistent relative performances of individual students across test administrations allow for the identification of students who have severe and persistent problems.

Analysis of Variance↗
PubMed1995

Screening mammography and public health policy: the need for perspective.

The early trials of screening mammography, reporting 30% relative reduction in mortality from breast cancer in women over 50 years of age, led to strong professional and public demand for screening programmes. There has been little publicity about the subsequent trials showing no significant benefit in any age group, or about the harm and costs associated with screening mammography. For women under 50, there is a reluctant consensus that screening is not beneficial, but there is increasing pressure for publicly funded programmes for older women. When analysed in terms of population benefit, the randomised controlled prospective trials showed that the numbers of women screened to achieve one less death per year ranged from 7086 (Health Insurance Plan of New York), to 63,264 (Malmo), to infinity (Canadian National Breast Screening Study). About 5% of screening mammograms are positive or suspicious, and of these 80-93% are false positives that cause much unnecessary anxiety and further procedures including surgery. False reassurance by negative mammography occurs in 10-15% of women with breast cancer that will manifest clinically within a year. Our calculations confirm others that the mean annual cost per life "saved" is around $1-2 million (558,000 pounds). In the allocation of limited resources, public health policy on a proposed mass population intervention must be based on a critical analysis of benefits, harm, and cost. Since the benefit achieved is marginal, the harm caused is substantial, and the costs incurred are enormous, we suggest that public funding for breast cancer screening in any age group is not justifiable.

Adult↗
PubMed1994

Breast cancer: reporting results with inflationary arithmetic.

Numeric data are almost always generated as final measures in scientific experiments, but the publications of these "hard" data is rare. Reductions of the mass are always required and many techniques have been developed. Data reduction may take many forms and the selection of which form to present in a publication reflects an author's bias--it is inescapable since almost all forms are scientifically valid even though each carries its own subliminal message. This editorial reviews several of the means whereby data derived from breast cancer research or observation of outcomes may be presented. Unstated observations, the use of untested premises, selection of the denominator in establishing ratios, graphic display, the concept of "cure" and calculations of harm/benefit are discussed.

Breast Neoplasms↗
PubMed1993

Adjuvant chemotherapy in stage I breast cancer. More harm than benefit.

Clinical trials of adjuvant chemotherapy for breast cancer have shown a prolonged disease-free interval but no improvement in survival. This review of the evidence indicates that adjuvant therapy induces an antineoplastic drug resistance that makes "salvage" therapy less effective. The benefit that is seen only in group statistics, not in an individual, must be weighed against the harm an individual incurs from the chemotherapy.

Antineoplastic Agents↗
PubMed1992

Lymphatic and venous examination of the ulcerated leg: a preliminary report.

BACKGROUND: It has been widely accepted that deep venous thrombosis and venous incompetence initiate a series of events resulting in various ulcerations. The role of the lymphatic system in the progression of these events has not been extensively studied. METHODS: Twenty-three patients with nonarterial ulcerations of the legs were examined by phlebography and lymphangiography. All had recurrent ulcerations associated with nonpitting edema, brawny induration, and dermatitis characteristic of the postphlebitic syndrome. Arterial circulation was normal in all patients. RESULTS: Phlebographic abnormalities found were the presence of communicating vein incompetence in all 23 patients, varicose veins in six, and deep venous occlusion in one. Lymphatic abnormalities were also present in all patients. Extravasation in the area of the ulcer was seen in eight patients, dermal backflow in six, tortuosity and irregularity of the channels in four, and retention of contrast agent for more than 24 hours in seven. CONCLUSIONS: Significant abnormalities of the lymphatic system exist in patients with leg ulcers caused by the postthrombotic syndrome.

Humans↗
PubMed1991

NSABP trials of adjuvant chemotherapy for breast cancer. A further look at the evidence.

Two decades ago the National Surgical Adjuvant Breast Project (NSABP) began to test the hypothesis that adjuvant chemotherapy would influence favorably the postsurgical survival rates of women with breast cancer. Although the use of phenylalanine mustard (melphalan or (L-PAM) has been supplemented by other agents, the thrust to recommend adjuvant chemotherapy as standard treatment was created by an L-PAM series of five trials using L-PAM or L-PAM plus fluorouracil. Only the first trial, B-05, contained an untreated group. The main treated groups in these five trials are similar to each other in survival probabilities, and the main untreated group in B-05 is not different in survival than the combined results of these five trials. There were a total of nine comparison in each study-and in B-05 the subgroup of treated women 49 years or younger with one to three positive node was found to be different than the untreated group. Four subsequent subgroups of women who were 49 years or younger with one to three positive nodes are not similar in survival despite the fact that they were developed from similar main groups that had similar treatment. The initial treated subgroup in B-05 had a survival outcome that was never again achieved in the subsequent four studies. The untreated subgroup in B-05 was not different than three of the four subsequently treated subgroups. The NSABP now has evidence that denies the conclusion that adjuvant chemotherapy prolongs survival in premenopausal node-positive women. Recommendations that adjuvant chemotherapy become standard treatment for premenopausal node-positive women should be seriously reconsidered and probably withdrawn.

Adult↗
PubMed1991

The disease-free interval in breast cancer trials: scientific or spurious?

Reports that stem from the National Surgical Adjuvant Breast and Bowel Project clinical trials have had a major influence on the trend toward adjuvant chemotherapy. These reports use life-table analysis to report survival or disease-free survival (DFS). DFS is reported more frequently than survival, and most studies report an increase in DFS with adjuvant therapy but no difference in survival. This means a shorter time between recurrence (end of DFS) and death. A conceptual model is presented herein with five possible explanations for this observation: (1) Bias exists in randomizing (entrance); (2) bias is introduced by the examining physician (exit end point); (3) the spectrum of micrometastases is selectively affected; (4) the sites of systemic recurrence (macrometastases) are affected; (5) treatment after recurrence (salvage) is less effective in the previously treated group; probably because of the induction of resistance to antineoplastic therapy. Hypothesis 5 seems most probable, and if so, the benefit of chemotherapy should be reserved for those women who need it rather than rendering everyone less treatable. The disease-free interval, with its doctor-determined end point, is insufficiently reliable to be used for major decisions regarding adjuvant therapy.

Breast Neoplasms↗
PubMed1988

Stage II breast cancer is not simply a late stage I.

Conventional wisdom holds that stage II breast cancer (with positive axillary nodes) is a late stage I (with negative axillary nodes). The use of direct (e.g., 5-year) survival analysis, has led to the concept that these stages reflect a "delay" in diagnosis. Controlled clinical trials and demographic cancer registries, in which life table analysis of survival is used, provide data that require that this concept be reconsidered and perhaps discarded. Survival data published by NSABP B04 and the Connecticut Tumor Registry show that deaths in both stages start shortly after diagnosis but show different annual rates of dying. The anticipated "delay" (lead time bias) is not seen. These rates are permanently and consistently different. The local recurrence rates occurring in the two stages are different. The clinical response to tamoxifen citrate in postmenopausal women and chemotherapy in premenopausal women has been shown to be different between the two stages. Histopathologic examination of the primary tumor shows the two stages to be different with respect to size of tumor at time of diagnosis and the presence of lymphatic and vascular invasion. The conclusion must be reached that the two stages represent variants of breast cancer disease; stage II is not simply a late diagnosis of stage I.

Antineoplastic Agents↗