Human trophoblast-lymphocyte cross-reactive (TLX) antigens define a new alloantigen system.

Antisera to human syncytiotrophoblast microvillous cell surface membranes from different placentas are cytotoxic for lymphocytes from some people but not others, demonstrating the presence of allotypic trophoblast-lymphocyte cross-reactive (TLX) antigens. Exploratory principal components factor analysis, performed on limited data consisting of 300 cytotoxic reactions produced by ten separate trophoblast antisera on a panel of lymphocytes from 30 random donors, suggested the presence of three distinct TLX antigen groupings. It is proposed that such TLX alloantigens are central in establishing maternal recognition and protection of the blastocyst, and that lack of recognition results in implantation failure and spontaneous abortion. These findings are compatible with contemporary results of immunotherapy to prevent recurrent spontaneous abortions, and their implications extend to other conditions of allogeneic coexistence, such as organ transplantation and the tumor-host relationship.

The electrocardiogram in obesity: statistical analysis of 1,029 patients.

The electrocardiogram in 1,029 obese subjects was correlated with the severity of obesity and with age, sex and blood pressure. The heart rate, PR interval, QRS duration, QTc interval and voltage (R + S or Q wave in leads I, II and III) increased, and the QRS vector shifted to the left with increasing obesity. These changes were independent of age, sex and blood pressure. Bradycardia was present in 19% of the patients, but tachycardia in only 0.5%. ST and T wave abnormalities were present in 11%, correlating better with increasing age and blood pressure than with severity of obesity. Conduction abnormalities were infrequent. Low voltage was present in only 3.9% of the patients and QTc prolongation was present in 28.3%. The heart rate and QRS voltage increase with increasing obesity. Conduction is slowed, and the QRS vector shifts toward the left as percent overweight increases. These changes must be considered when evaluating both baseline electrocardiographic studies in obese patients and the changes seen during weight reduction.

Similarity of obesity indices in clinical studies of obese adults: a factor analytic study.

The similarity of measurements obtained with six commonly used obesity indices was assessed with correlational and factor analyses performed on data for 951 obese adults participating in a weight reduction study. Intercorrelations among the indices were found to be very high, with a mean of 0.96. A factor analysis of the six indices resulted in a single factor which accounts for 97% of the aggregate variance in the six indices. A factor analysis of the six indices plus height and weight resulted in two factors. The six indices loaded nearly perfectly on one factor and not at all on the second. Height loaded perfectly on the second factor. The results of these analyses constitute strong empirical evidence that the obesity indices are measuring the same thing and that factor is independent of height. Although anthropological or other special studies may necessitate the use of a particular index, these results suggest that it should make little difference which of the six indices is used in a clinical study of obesity with obese adults.

Reassessment of body mass indices.

The accuracy of body mass indices (BMIs), such as Quetelet's index, for the definition of obesity was investigated in a large sample of healthy humans. Two hundred thirteen women and 150 men with a wide spectrum of weights, heights, and ages underwent densitometric analysis for the determination of percent body fat (%BF). %BF was then contrasted with various well-established BMIs. Although %BF was correlated with all the BMIs (r = 0.60-0.82), applying objective definitions of obesity based on BMIs or %BF by densitometry often produced conflicting results. It was also found that the 95% confidence intervals for predicting %BF by using Quetelet's index were very wide. Because of the wide variation for individuals between densitometrically determined body fat and body fat as estimated by BMIs, we conclude that BMIs should be used with caution as indicators of obesity.

A difference between front-loaded streptokinase and standard-dose recombinant tissue-type plasminogen activator in preserving left ventricular function after acute myocardial infarction (the Central Illinois Thrombolytic Therapy Study).

A blinded, randomized trial compared the effects of front-loaded streptokinase with those of the conventional dose of intravenous recombinant tissue-type plasminogen activator (rt-PA) on left ventricular (LV) function after acute myocardial infarction (AMI). Thrombolytic therapy was administered in the emergency departments of 30 community hospitals in central Illinois, and subsequent studies were performed at 1 tertiary referral center. Patients aged < or = 75 years with a first AMI who could be treated within 4 hours of the onset of chest pain were randomly assigned to receive either streptokinase (375,000 IU bolus, followed by 1,125,000 IU over 1 hour) or rt-PA (10 mg bolus, followed by 50 mg in the first hour, and 20 mg/hour for the next 2 hours). All patients were treated with aspirin (325 mg) and intravenous heparin. Patients were transferred for angiography within 24 hours. During the 30-month study, 253 patients were treated with intravenous thrombolytic therapy 2.4 +/- 1.0 hour after the onset of AMI. In patients with anterior wall AMI (n = 90), global LV ejection fraction measured by angiography within 24 hours was 45 +/- 12% with rt-PA, and 39 +/- 13% with streptokinase (p < 0.03). Convalescent radionuclide angiography documented a persistent beneficial effect of rt-PA on LV regional wall contractility, but not global ejection fraction. There were no differences between rt-PA and streptokinase in preserving global or regional LV function in patients with inferior wall AMI.

Diagnosis of secondary depression in schizophrenia.

Four diagnostic groups were studied to determine the relationship of depression secondary to schizophrenia to DSM-III major depression criteria and Hamilton Depression Rating Scale scores. The symptoms found in schizophrenic patients with major-type depressions differed qualitatively from those in primary depressives. Some of the criteria used to diagnose depression in schizophrenic patients (retardation and insomnia) probably arise from the schizophrenic syndrome. Since secondary depression in schizophrenia is associated with poor outcome, it is important that specific diagnostic criteria for distinguishing depressed from nondepressed schizophrenics be developed. Such criteria should not include symptoms that are part of the schizophrenic syndrome.

Cerebrospinal fluid acetylcholinesterase and choline measurements in Huntington's disease.

The caudate nucleus has the highest acetylcholinesterase (AChE) activity in the brain and it has been shown that autopsied brain tissue of patients with Huntington's disease (HD) have reduced levels of acetylcholine. Because of these findings, the cholinergic function in HD was studied by measuring cerebrospinal fluid (CSF) choline levels and AChE activity during a randomized, double-blind, cross-over, placebo-controlled clinical trial of isoniazid. While mean choline levels adjusted for age were lower compared with controls (P = 0.0007), AChE activity did not differ between HD patients and normal controls. Treatment with isoniazid had no significant effect on CSF choline levels or CSF AChE activity. CSF AChE activity showed a statistically significant increase with advancing age. The reduced level of choline in CSF of HD patients may reflect either a defect in choline transport into the brain or a decrease of choline-phospholipid output from the brain.

Effectiveness of problem-based learning curricula: research and theory.

PURPOSE: This article provides a critical overview of problem-based learning (PBL), its effectiveness for knowledge acquisition and clinical performance, and the underlying educational theory. The focus of the paper is on (1) the credibility of claims (both empirical and theoretical) about the ties between PBL and educational outcomes and (2) the magnitude of the effects. METHOD: The author reviewed the medical education literature, starting with three reviews published in 1993 and moving on to research published from 1992 through 1998 in the primary sources for research in medical education. For each study the author wrote a summary, which included study design, outcome measures, effect sizes, and any other information relevant to the research conclusion. RESULTS AND CONCLUSION: The review of the literature revealed no convincing evidence that PBL improves knowledge base and clinical performance, at least not of the magnitude that would be expected given the resources required for a PBL curriculum. The results were considered in light of the educational theory that underlies PBL and its basic research. The author concludes that the ties between educational theory and research (both basic and applied) are loose at best.

Effect of anonymous test grading on passing rates as related to gender and race.

BACKGROUND: Concerns about potential bias in the grading of medical students at the Southern Illinois University School of Medicine led to a major institutional policy change whereby students' identities were masked during the test-grading process. The present study assessed the effect of this anonymous test grading policy by comparing the performance of men and women students and of white and African American students prior to and after adoption of the policy change. METHOD: A test-passing rate was determined for each of 476 freshmen students in the comparison groups from the eight classes of 1988 through 1995. Mean test-passing rates for the four student cohorts prior to policy implementation (1988-1991) were compared with mean passing rates after the policy was implemented (1992-1995). RESULTS: The pre-post change in the mean test-passing rate of men was not significantly different from the pre-post change of women, and a nonsignificant effect was also found when the pre-post change in the mean test-passing rate of white students was compared with that of African American students. No significant pre-post change was found for white men, white women, African American men, or African American women. CONCLUSION: The results showed no effect of the anonymous test-grading policy, which suggests that there was no widespread gender or racial bias in the grading of freshman medical students before the change in institutional grading policy.

Technical issues: test application. AAMC.

Eighteen questions are posed that the authors believe address the major technical issues involved in the application of standardized patients (SPs). Following each question, selected empirical evidence and commentary are provided in response to the question and as background for further consideration of the issues. The authors conclude that the evidence from this large and systematic knowledge base about SP examinations is encouraging and should be cause for optimism. Moreover, it is noted that far less is known about the measurement properties of conventional procedures for clinical assessment in medical school courses and clerkships. The collective evidence from this extensive SP research base suggests that medical educators should move ahead to realize the benefits of the high-fidelity standardized approach provided by standardized-patient examinations.

Effects of student gender and standardized-patient gender in a single case using a male and a female standardized patient.

BACKGROUND: In previous studies assessing the effects of student gender, standardized-patient (SP) gender, and their interaction on multiple-station examinations of clinical competence, SP gender was confounded with cases, that is, male SPs were used for some cases and female SPs for others. The authors conducted two studies to investigate the effects of gender on a single case by using a male SP and a female SP for the same case. METHOD: Both studies involved one SP case in a comprehensive clinical evaluation used to assess fourth-year students at the end of a required ambulatory care clerkship at Saint Louis University School of Medicine in 1990-91 and 1991-92. In Study 1, 45 students in four rotations saw the same male SP; 42 students in three other rotations saw the same female SP. In Study 2, 69 students in six rotations were randomly assigned either the male SP (28) or the female SP (41) within the same rotation. For each study, to determine the interaction of student gender and SP gender as well as their main effects, analyses of variance were performed on the students' history-taking and physical examination scores and communication skills ratings. RESULTS: Neither study showed a significant interaction of student gender and SP gender on history taking, physical examinations, or communication skills. CONCLUSION: The findings of both studies suggest that the interaction between student gender and SP gender, unconfounded by case content, had no effect on the students' scores and ratings.

Screening test length for sequential testing with a standardized-patient examination: a receiver operating characteristic (ROC) analysis.

The feasibility of using sequential testing (i.e., using a screening test) to reduce the length and expense of a performance-based examination with standardized-patient cases was demonstrated previously. In the present study, quantitative criteria rather than practical considerations were used to determine optimal values for the length of the screening test (i.e., number of cases) and the location of the screening pass-fail cutoff (i.e., its relation to the mean of the pass levels for the different cases). Data were derived from five classes of senior students at the Southern Illinois University School of Medicine, 1987-1991. Specifically, receiver operating characteristic (ROC) curves were plotted for screening tests of varying lengths, with the points on each ROC curve corresponding to different pass-fail cutoffs on the screening test. The results showed that good accuracy can be attained with a screening test that is only one-third the length of the full examination and that the cutoff for this screen should be set slightly above the mean of the case pass levels to maximize sensitivity and specificity. The authors conclude that their study demonstrates the value of an ROC analysis in evaluating the psychometric properties of a screening test in sequential testing.

Using a standardized-patient examination to establish the predictive validity of the MCAT and undergraduate GPA as admissions criteria.

Performance of senior medical students on an objectively scored examination of clinical competence based on standardized-patient cases was used to assess the predictive validity of the two most commonly used admission measures, the Medical College Admissions Test and the undergraduate grade point average. The students were in the classes of 1986 and 1987 at Southern Illinois University School of Medicine. The correlations of the admissions measures with clinical performances were quite weak, and none of the admissions measures consistently showed a clear advantage as a predictor of clinical performance. Correlations of the admissions measures with scores on National Board of Medical Examiners (NBME) Part I and Part II examinations were small to moderate, although somewhat larger than the correlations with clinical performances. Correlations were corrected for attenuation due to differential unreliabilities of the clinical examination results and the scores on NBME examinations, and for restriction of range due to the stringent medical school selection process. Corrected correlations were small to moderate and showed the same pattern as the uncorrected ones. The study documents that traditional admissions measures are useful for selecting students who will perform effectively in clinical as well as basic science settings.

Effects of using two or more standardized patients to simulate the same case on case means and case failure rates.

The effects of using two or more standardized patients (multiple SPs) to simulate the same case in a performance-based examination were studied at the case level by comparing case means and case failure rates for multiple SPs simulating the same case, using data from the classes of 1988, 1989, and 1990 at the Southern Illinois University School of Medicine. For total scores and scores on the students' written answers, the effects on means and failure rates were negligible and could be explained as due to sampling error. For scores on the checklists completed by the SPs, there were more significant differences than would be expected by chance alone, even though the number of significant differences was relatively small. The results demonstrate a need for caution in the interpretation of scores obtained from a case checklist completed by multiple SPs, particularly in regard to making pass-fail decisions.

Station-length requirements for reliable performance-based examination scores.

PURPOSE: To directly compare the generalizability of medical students' performance scores under systematically varied station times in two surgery end-of-clerkship performance-based examinations. METHOD: The participants were 36 third-year students randomly assigned to the first two rotations of the core surgery clerkship during 1991-92 at Southern Illinois University School of Medicine. The students rotated through a 12-station examination that employed standardized patients (SPs). In the first rotation, the student took six five-minute stations and six ten-minute stations. In the second rotation, the time lengths were reversed for the same stations. The students' total scores were based on (1) subscores on checklists that were completed by the SPs and (2) subscores on the students' written responses to short questions about each station (these responses were provided at station couplets that were five minutes long, regardless of station length). Generalizability coefficients were computed from the pooled rotation results to provide reliabilities for scores from the two station lengths. RESULTS: Generalizability decreased in the ten-minute stations, mostly attributable to less variability among students' performances. The checklist subscores accounted for most of this variability, while couplet subscores remained stable between station lengths. CONCLUSION: The longer station length actually decreased the generalizability of the scores by decreasing the variability among students' performances; thus, allocating different times to stations can affect the score reliability, as well as impact on the overall testing time, of performance-based examinations.

Validating the standardized-patient assessment administered to medical students in the New York City Consortium.

PURPOSE: To test the criterion validity of existing standardized-patient (SP)-examination scores using global ratings by a panel of faculty-physician observers as the gold-standard criterion; to determine whether such ratings can provide a reliable gold-standard criterion to be used for validity-related research; and to encourage the use of these gold-standard ratings for validation research and examination development, including scoring and standard setting, and for enhancing understanding of the clinical competence construct. METHOD: Five faculty physicians independently observed and rated videotaped performances of 44 students from one medical school on the seven SP cases that make up the fourth-year assessment administered at The Morchand Center of Mount Sinai School of Medicine to students in the eight member schools in the new York City Consortium. RESULTS: The validity coefficients showed correlations between scores on the examination and the overall ratings ranging from .60 to .70. The reliability coefficients for ratings of overall examination performance reached the commonly recommended .80 level and were very close at the case level, with interrater reliabilities generally in the .70 to .80 range. CONCLUSION: The results are encouraging, with validity coefficients high enough to warrant optimism about the possibility of increasing them to the recommended .80 level, based on further studies to identify those measurable performance characteristics that most reflect the gold-standard ratings. The high interrater reliabilities indicate that faculty-physician ratings of performance on SP cases and examinations can or may be able to provide a reliable gold standard for validating and refining SP assessment.

Ventures in education: a pipeline to medical education for minority and economically disadvantaged students.

BACKGROUND: Ventures in Education is an independent, nonprofit educational organization established by the Josiah H. Macy, Jr. Foundation to improve the academic achievement of minority and economically disadvantaged students, particularly in science and mathematics. One specific objective has been to increase the number of students who enter schools of the health professions, in particular schools of medicine, which was the focus of this study. METHOD: A search was conducted of the Association of American Medical Colleges' (AAMC's) Student and Applicant Information Management System database, to determine whether any of the 981 graduates in the first five Venture classes (1985 to 1989) of the original five New York City high schools in the program had pursued medical education. RESULTS: The search located 160 of the 981 Ventures graduates, and, of those, 136 had taken the Medical College Admission Test (13.9%), 109 (11.1%) has applied to medical school, 75 (7.6%) had been accepted, and 72 (7.3%) had matriculated into medical school. All of these percentages were significantly higher than the corresponding percentages for the general population. CONCLUSION: The findings have important implications for the AAMC's Project 3000 by 2000, showing that a rigorous academic curriculum with resources for individualized attention can facilitate the entry of minority and economically disadvantage students into medical education, with at least 7.3% of the Ventures graduates entering medical school and nearly 70% of those applying subsequently being accepted.

Psychometric properties of a standardized-patient checklist and rating-scale form used to assess interpersonal and communication skills.

The results show that the SP checklist scores and the SP ratings of interpersonal and communication skills have comparable psychometric properties. The reliabilities of the five-item rating form (.76) and the single global rating of patient satisfaction (.70) were slightly higher than the reliability of the 17-item checklist (.65); this finding is of particular significance, given the greater length of the checklist. Also, the checklist scores and ratings appear to be measuring the same underlying dimension, with correlations of the checklist with the five ratings and with the single global rating being .82 and .81, respectively. Van der Vleuten and associates, in two excellent articles, noted a recent shift away from the use of subjective measures of clinical competence, such as rating scales, toward the use of presumably more objective measures, such as SP checklists. Their concern was that these objective measures may focus on somewhat trivial and easily measured aspects of the clinical encounter, and that more subtle but critical factors in clinical performance may be overlooked or ignored. They referred to such measurement as "objectified" rather than objective. The shift is based on the presumption that objective or objectified measurement is superior to subjective measurement, such as ratings, with respect to psychometric properties such as reliability. On the basis of a survey of several studies, though, the authors concluded that "objectified methods do not inherently provide more reliable scores" and "may even provide unwanted outcomes, such as negative effects on study behavior and triviality of the content being measured." The results of the present study support this conclusion, showing somewhat higher reliabilities for subjective ratings than for the objective (or perhaps objectified) checklist. Also, the high uncorrected correlations suggest that the more reliable ratings are measuring the same underlying dimension as are the checklist scores. The present study also illustrates the application of a recently proposed method for constructing a valid SP checklist, which would consist of items that best reflect global ratings of performance. In this study, the ratings were provided by the SPs themselves, but ratings could be obtained from faculty-physician experts who observe student performance on the SP case. Thus, performance on individual checklist items would be correlated with expert ratings, to identify the items that best predict the ratings. The checklist, then, would be constructed of just those items that best predict the ratings, and the checklist could be used for future testing without the need for further faculty ratings (yet the checklist scores would reflect the faculty ratings). With this approach, it would seem possible to construct checklists for history-taking and physical-examination skills, as well as for interpersonal and communication skills. Thus, the faculty ratings would provide a basis for case development and refinement, including scoring and standard setting, and scores on the checklist would serve as a proxy for the gold-standard faculty ratings. The study suggests that SP ratings may be more efficient and more reliable than SP checklists for assessing interpersonal and communication skills. The study also demonstrates that global ratings by SPs (or by expert physician observers) can provide a basis for SP-test construction.

Global ratings of videotaped performance versus global ratings of actions recorded on checklists: a criterion for performance assessment with standardized patients.

PURPOSE: To test whether global ratings of checklists are a viable alternative to global ratings of actual clinical performance for use as a criterion for standardized-patient (SP) assessment. METHOD: Five faculty physicians independently observed and rated videotaped performances of 44 medical students on the seven SP cases that comprise the fourth-year assessment administered at The Morchand Center of Mount Sinai School of Medicine to students in the eight member schools in the New York City Consortium. A year later, the same panel of raters reviewed and rated checklists for the same 44 students on five of the same SP cases. RESULTS: The mean global ratings of clinical competence were higher with videotapes than checklists, whereas the mean global ratings of interpersonal and communication skills were lower with videotapes. The correlations for global ratings of clinical competence showed only moderate agreement between the videotape and checklist ratings; and for interpersonal and communication skills, the correlations were somewhat weaker. CONCLUSION: The results raise serious questions about the viability of global ratings of checklists as an alternative to ratings of observed clinical performance as a criterion for SP assessment.

Relationship between clinical competence and interpersonal and communication skills in standardized-patient assessment.

PURPOSE: To evaluate the relationship between clinical competence and interpersonal and communication skills, in an attempt to clarify current thinking about these two dimensions as measured with standardized-patient (SP) examinations. METHOD: Simple Pearson correlations were computed between total examination scores for clinical competence and interpersonal and communication skills. Three sets of different types of data involving 15 separate examinations were used to explore the generality of the findings. To control for a within-case halo effect and measurement error, corrected cross-half correlations and corrected cross-case correlations were also computed. RESULTS: The simple correlations and the corrected cross-half and cross-case correlations showed moderate and above relationships between these two dimensions in the clinical context. The simple correlations centered around .50, and the corrected cross-half and cross-case correlations were slightly higher, centering around .65 and .70, respectively. CONCLUSION: The authors' thinking is that the moderate relationship between clinical competence and interpersonal and communication skills is not due to a flaw in the measurement of clinical competence, as has been suggested, but rather is a natural consequence of the clinical encounter, which exacts an interdependence of these two dimensions. At least, this possibility must be seriously considered so medical educators can think and act appropriately in the assessment of clinical performance.