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Biomedical subjects

J R Beck

Publications and source records attributed to J R Beck.

At least 19 recordsLinked to original sources
PubMed1992

A decision analysis of traumatic splenic injuries.

We created a decision analysis model of the nonsurgical management of traumatic splenic injuries to clarify the risk of hospital survival, overwhelming postsplenectomy infection (OPSI) deaths, and transfusion-related deaths. We reviewed 72 cases of splenic injury at our institution to identify our transfusion requirements for successful observation (0.5 units), observation failure (1.0 units), and surgical splenic management (1.6 units). Using our model and baseline probabilities determined from the literature, we compared the nonsurgical management of splenic injuries with immediate laparotomy and found an increase in hospital survival with observation, but an over two-fold increase in the risk of transfusion-related death. The OPSI deaths were not markedly different between the two strategies. Overall, we found decision analysis useful in identifying important variables such as the probability of nontherapeutic laparotomy death or missed injury, and in clarifying the risk of the nonsurgical management of splenic injuries with regard to transfusion-related deaths and OPSI deaths.

Blood Transfusion↗
PubMed1992

Effect of the Clinical Laboratory Improvement Amendments of 1988 (CLIA '88) on the incidence of invasive cervical cancer.

The Clinical Laboratory Improvement Act of 1988 (CLIA '88) mandates strict, new quality-control measures for laboratories that interpret cervical cytology smears. Proposed regulations include proficiency testing of cytotechnologists and remediation for technologists and laboratories that fail to meet proposed proficiency standards. Proponents of the new regulations argue that these measures will reduce deaths from cervical cancer by reducing the false-negative rate of the Papanicolaou (Pap) test, but opponents argue that the regulations will increase the price of processing Pap tests and thereby reduce access to cervical cancer screening for high-risk, vulnerable populations. To examine these claims the authors used David Eddy's published simulation to model the natural history and detection of cervical neoplasia, and developed a new model to examine the health consequences of diminished access to Pap testing. The authors estimated the false-negative rate of the Pap test and the price elasticity of demand for preventive services on the basis of the published literature, and modeled the entire range of published or quoted predictions about the impact of CLIA '88 on accuracy and price. The results show that, if effects on access are ignored, reducing the false-negative rate from 15% to 5% would prevent 66 invasive cancers per 100,000 average risk women screened. However, under moderate assumptions regarding the effect of price on access, the regulations would prevent only 11 (instead of 66) cancers per 100,000 eligible women. The regulatory effect is very sensitive to the degree of improvement in the false-negative rate and increase in price that the regulations cause. Over the range of assumptions and predictions encountered in the literature and tested in our analysis, the proposed regulations could greatly reduce or greatly increase the incidence of invasive cancer, especially among high-risk and uninsured women. The implementation of the regulations should be delayed until new information regarding the actual false-negative rate of the Pap test allow a more precise estimate of the potential impact on the incidence of cervical cancer.

Clinical Competence↗
PubMed1991

Comparative cost-effectiveness analysis of quinidine, procainamide and mexiletine.

Quinidine and procainamide have the potential for major organ toxicity, whereas mexiletine has been reported to have little risk of organ toxicity, serious proarrhythmia or congestive heart failure, but a relatively high incidence of nuisance side effects. In light of the potential adverse effects of all antiarrhythmic agents as highlighted by the Cardiac Arrhythmia Suppression Trial, the relative cost-effectiveness of these 3 agents was assessed. Based on a review of greater than 1,000 published reports, studies included in the analysis examined greater than or equal to 1 of these agents in adults, with adequate efficacy or safety data, or both. The majority of studies assessed patients with symptomatic or malignant arrhythmias, or both. Data were analyzed using a decision analysis/cost-effectiveness model. Probabilities were averaged using techniques of meta-analysis. Costs were obtained from a university medical center cost-accounting system and from expected follow-up visits to university clinics. Thirty-seven separate side effects were included in the analysis. In terms of overall cost, 12 months of mexiletine would engender $875, quinidine $1,239 and procainamide $1,911 of expenses. Mexiletine dominates the older agents in terms of cost per successful drug response, a result that holds over a wide range of efficacy and safety data. Analyses demonstrated no increase in all-cause mortality for quinidine and mexiletine over placebo, but a trend toward higher mortality with procainamide. The results suggest that mexiletine is a cost-saving alternative therapy for ventricular arrhythmias when adverse reactions are considered in addition to pharmaceutical costs and treatment efficacy.

Ambulatory Care↗
PubMed1991

Recurrent renal cell carcinoma arising in Wilms' tumor.

A 19-month-old black girl had a radical nephrectomy for a Wilms' tumor that contained areas of epithelium indistinguishable from renal cell carcinoma. She was treated with chemotherapy but subsequently had pulmonary metastases develop and massive abdominal recurrence. The recurrent tumor was histologically renal cell carcinoma with no identifiable Wilms' tumor elements. The child died with recurrent and metastatic tumor 13 months after nephrectomy. Pathologic, immunoperoxidase, and flow cytometric studies of this unusual case are presented.

Carcinoma, Renal Cell↗
PubMed1991

Significant efficiency findings while controlling for the frequent confounders of CAI research in the PlanAlyzer project's computer-based, self-paced, case-based programs in anemia and chest pain diagnosis.

Richard E. Clark in his widely published comprehensive studies and meta-analyses of the literature on computer assisted instruction (CAI) has decried the lack of carefully controlled research, challenging almost every study which shows the computer-based intervention to result in significant post-test proficiency gains over a non-computer-based intervention. We report on a randomized study in a medical school setting where the usual confounders found by Clark to plague most research, were carefully controlled. PlanAlyzer is a microcomputer-based, self-paced, case-based, event-driven system for medical education which was developed and used in carefully controlled trials in a second year medical school curriculum to test the hypothesis that students with access to the interactive programs could integrate their didactic knowledge more effectively and/or efficiently than with access only to traditional textual "nonintelligent" materials. PlanAlyzer presents cases, elicits and critiques a student's approach to the diagnosis of two common medical disorders: anemias and chest pain. PlanAlyzer uses text, hypertext, images and critiquing theory. Students were randomized, one half becoming the experimental group who received the interactive PlanAlyzer cases in anemia, the other half becoming the controls who received the exact same content material in a text format. Later in each year there was a crossover, the controls becoming the experimentals for a similar intervention with the cardiology PlanAlyzer cases. Preliminary results at the end of the first two full trials shows that the programs have achieved most of the proposed instructional objectives, plus some significant efficiency and economy gains. 96 faculty hours of classroom time were saved by using PlanAlyzer in their place, while maintaining high student achievement. In terms of student proficiency and efficiency, the 328 students in the trials over two years were able to accomplish the project's instructional objectives, and the experimentals accomplished this in 43% less time than the controls, achieving the same level of mastery. However, in spite of these significant efficiency findings, there have been no significant proficiency differences (as measured by current factual and higher order multiple choice post-tests) between the experimental and control groups. Very careful controls were used to avoid what Clark has found to be the most common confounders of CAI research. Accordingly, this research proved Clark's rival hypothesis, that the computer, in itself, does not appear to contribute to proficiency gains, at least as measured by our limited post-testing. Clark's position is that the computer is primarily a vehicle--as is either a pill or a hypodermic needle for delivering a drug.(ABSTRACT TRUNCATED AT 400 WORDS)

Anemia↗
PubMed1991

Does the mediastinum of patients with non-small cell lung cancer require histologic staging? Future standards for computed tomography.

We asked whether noninvasive staging of the mediastinum is a reasonable alternative to invasive staging in patients with non-small cell lung cancer. Decision analysis was used to compare strategies relying upon mediastinoscopy, bronchoscopy with transbronchial needle aspiration, and/or thoracotomy for histologic or cytologic confirmation of mediastinal stage to two strategies primarily relying upon computed tomography for assessing the mediastinum. Life expectancy was the outcome of interest. Extensive sensitivity analysis showed that, if the specificity of computed tomography for mediastinal disease was above 0.90, a strategy primarily relying upon computed tomography to stage the mediastinum would provide a life expectancy within 1 month of that provided by invasive testing. The difference in life expectancy between the invasive and noninvasive staging strategies decreased further as the prior probability of unresectable disease increased. Surprisingly, the sensitivity of computed tomography for mediastinal disease was of little importance in determining overall life expectancy. These results suggest that noninvasive imaging techniques might reliably replace invasive mediastinal staging if their specificity exceeds 0.90.

Carcinoma, Non-Small-Cell Lung↗
PubMed1991

Flow cytometric analysis of granulosa cells from developing rat follicles.

Immature rats were treated with diethylstilboestrol (DES) or pregnant mares' serum gonadotropin (PMSG) and forward angle light-scatter (FALS) and 90 degrees light-scatter (90 degrees LS) signals were used to measure the size and the granularity (internal organization) of the granulosa cells, respectively. The results confirmed the presence of two major populations of granulosa cells in the ovaries of both groups of rats, with the same percentage of larger cells in both treatments (52.3% in DES, 49.5% in PMSG). Since DES treatment brings about granulosa cell growth while PMSG treatment causes growth and differentiation, it is evident that there is heterogeneity in granulosa cell sizes during different states of growth and differentiation. There was also heterogeneity in sizes of granulosa cells harvested from follicles of small (less than 210 microns), medium (210-420 microns) and large (greater than 420 microns) diameter. Quadrant analysis of granulosa cells in various fractions collected from Percoll gradients suggested an increase in granularity in the small and large granulosa cell populations. Cell cycle analysis of small and large granulosa cell populations collected from large follicles of rats treated with PMSG indicated that each population was distributed in G0/G1, S and G2/M phases. These results demonstrate that populations of small and large granulosa cells exist in rat ovarian follicles during various stages of growth and differentiation.

Animals↗
PubMed1991

A systems approach to planning biomedical information services.

A systems approach to planning was applied within the Biomedical Information Communication Center at Oregon Health Sciences University when its User Services division launched a strategic planning effort. By looking at the choice subsystem, the organizational structure, and the behavioral subsystem, those engaged in planning attempted to assure that desired change would permeate the entire system. The challenge of applying a theoretically ideal planning model within an environment averse to planning is delineated.

Information Centers↗
PubMed1991

Findings from an evaluation of PlanAlyzer's double cross-over trials of computer-based, self-paced, case-based programs in anemia and chest pain diagnosis.

We report on three years of research trials of the PlanAlyzer I Project--a carefully controlled research study using a microcomputer-based, self-paced, case-based, event-driven system for medical education. PlanAlyzer presents cases, elicits and critiques a second year student's approach to the diagnosis of anemias and chest pain. PlanAlyzer uses text, hypertext, images and critiquing theory. Students were randomized, one half becoming the experimental group who received the interactive PlanAlyzer cases in anemia, the other half becoming the controls who received the exact same content material in a text format. Later in each year there was a crossover, the controls becoming the experimentals for a similar intervention with the cardiology PlanAlyzer cases. Results at the end of the first two years of trials show that the programs have achieved some significant efficiency and economy gains. 96 faculty hours of classroom time were saved by using PlanAlyzer in their place, with no loss in student achievement. In terms of student proficiency and efficiency, combining the anemia and cardiology trials, the 328 students in the two years of full scale trials were able to accomplish the project's instructional objectives. The experimentals accomplished this in 43% less time than the controls. On the average, for both the anemia and chest pain programs, this amounted to students spending 7.5 hours longer on the 30 text cases than on the same 30 computer cases to achieve the same level of mastery. There have been no significant proficiency differences (as measured by current post-tests) between the experimental and control groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Anemia↗
PubMed1990

Light microscope immunolocation of Bacillus thuringiensis kurstaki delta-endotoxin in the midgut and Malpighian tubules of the tobacco budworm, Heliothis virescens.

Light microscope immunofluorescence was used to localize the membrane binding of Bacillus thuringiensis kurstaki 63-kDa delta-endotoxin in Heliothis virescens midgut and Malpighian tubules. Staining was observed along all exposed mucosal (apical microvillar) plasma membranes. Interpretation of the serosal (basal) plasma membrane staining was complicated because the basal lamina also stained. The results suggest that the toxin binds to all exposed plasma membranes without apparent specificity for particular membrane domains.

Animals↗
PubMed1990

The effect of decision analysis on clinical uncertainty at tumor board.

Decision analysis is a formal approach to clinical decision making in the setting of uncertainty. Computer assisted clinical decision analysis was used at tumor board to help examine difficult oncological cases. Patients were identified early in the week and the decisions, possible outcomes, and uncertainties of each decision were modeled. These models were then presented at tumor board where the calculated expected utilities of each decision could be discussed. A description of decision analysis and three representative cases are presented here. These exercises were valuable for at least two reasons. First, modeling the problems confronting practicing oncologists was instructive as such. Second, the mathematical treatment of the probabilities and the utilities of the various outcomes for each decision stimulated a lively debate among the board members, forcing them to quantify probabilities and outcomes that they had previously ascertained qualitatively.

Bayes Theorem↗
PubMed1990

The conjunction fallacy?

Tversky and Kahneman (1983) showed that when subjects are asked to rate the likelihood of several alternatives, including single and joint events, they often make a "conjunction fallacy." That is, they rate the conjunction of two events as being more likely than one of the constituent events. This, they claim, is a fallacy, since the conjunction of two events can never be more probable than either of the component events. In addition, they found that prior training in probability theory does not decrease the likelihood of making this fallacy. We argue that in some contexts, an alternative that contains the conjunction of two events can be more probable than an alternative that contains only one of the conjunction's constituent events. We carried out four experiments in which we manipulated this context. The frequency of making a conjunction fallacy was affected by the manipulation of context. Furthermore, when the context was clearly specified, prior training in statistics influenced the ratings.

Decision Making↗