Validity of simple approach to scoring and standard setting for standardized-patient cases in an examination of clinical competence.

The results are disappointing, providing little support for the validity of the case-passing decisions based on this simple approach to scoring and standard setting. The case-passing decisions predicted what the case author intended for about only 73% or 74% of the students on average and, with agreement expected by chance removed, predicted what the case author intended for about only 25% of the students. Even with the use of the optimal pass/fail cutoffs and the dropping of students with ambiguous borderline global ratings, the case-passing decisions failed to agree with the case authors' global ratings for 15% to 30% of the students. The findings might be dismissed as simply due to low reliabilities of passing decisions and global ratings based on a single case. Although this concern would apply to intercase reliabilities, which would be subject to case specificity, the appropriate reliabilities here would seem to be intracase (i.e., intrarater), which should be fairly high (if they could be computed). Nevertheless, it seems reasonable to expect much better agreement between results of case scoring and of standard setting developed by the case author and the case author's global ratings of performance on that case, given that the case author might recall the checklist, assign a weight to each item, and so forth. Also, case-passing decisions would possibly agree more with global ratings of live or videotaped performances than with ratings of written summaries of performance; however, that question remains a challenge for further research. In conclusion, the study provides only weak evidence, at best, for the validity of the scoring and standard setting commonly used with SP assessment. The results do not undermine claims about the realism of the SP approach, however, nor do they call into question the standardization afforded by this method of assessing clinical competence. The results do raise serious concerns about this simple approach to scoring and standard setting for SP-based assessments and suggest that we should focus more on the observation and evaluation of actual student performance on SP cases in the development of valid scoring and standard setting.

Localization of the lysosomal protease dipeptidyl peptidase II in the young normal rat lens: a correlative light and electron microscopic analysis.

This investigation was follow-up to an earlier biochemical and light microscopic histochemical study, in which the lysosomal protease dipeptidyl peptidase II (DPP II) was demonstrated in rodent lenses. In the present study, a method was employed that allowed a more precise histochemical localization of the enzyme, one that was suitable for ultrastructural as well as light microscopic analysis. Successful demonstration of the enzyme using either of two synthetic substrates, and the significant reduction of the enzyme reaction by phenylmethylsulphonyl fluoride (PMSF), a serine protease inhibitor, pointed to the sensitivity of the method. A flat-embedding technique allowed the correlative light and electron microscopic analysis of specific areas of the specimen. Examination of the epithelium and outer cortical regions of the lens revealed the compartmentalization of DPP II activity within lysosomal dense bodies that were concentrated primarily in the equatorial and sutural regions, and also an association of the reaction product with larger bodies that were confined to the sutural regions. The latter structures appeared to represent fiber cell fragments that were enwrapped with narrow extensions of the surrounding fiber cells. The location of enzyme activity within the sutural bodies and also within the intercellular spaces of the modified fiber cell extensions surrounding these bodies suggested that lysosomal proteases may play a role in the segregation and degradation of specific regions of normal lens fiber cells.

Changes in lens membrane major intrinsic polypeptide during cataractogenesis in aged Hannover Wistar rats.

Cataracts previously have been shown to occur spontaneously in aged Hannover Wistar rats. The morphology and time course of opacification of these cataracts are very similar to those appearing in the human lens, where it has been previously shown that the major intrinsic polypeptide (MIP26K) of the fiber cell membrane undergoes covalent modification during cataractogenesis. To ascertain possible biochemical similarities between the two cataract systems, antisera were made against synthetic peptides corresponding to the sequence of MIP26K to probe Western blots of lens proteins from transparent versus opaque lenses from normal aged rats. The results of this analysis showed that these antisera can detect the presence of covalent changes occurring in the MIP26K molecule during the development of cortical opacities in the normal aged rat.

A survey of medical school teachers to identify basic biomedical concepts medical students should understand.

Insights from the cognitive sciences indicate a continuing need for physicians to understand conceptual knowledge from the basic sciences, despite recent concerns regarding the increasing amount of information in medicine and the growing emphasis on performance skills. A 1987 survey of selected basic science and clinical teachers in North American medical schools was undertaken to identify basic biomedical concepts that are important in the practice of medicine and to specify how difficult these are for students to learn, apply, or both. Responses from faculty (nominated by their deans to answer the survey) from 82% of the medical schools indicated considerable agreement between the basic science teachers and clinical teachers on the relative importance of a set of biomedical concepts, and showed relatively minor levels of disagreement on how difficult these concepts are. The judgments of these teachers could prove extremely useful in (1) determining concepts that--because of their importance--should receive special attention in curriculum efforts, and (2) determining concepts that--because of their difficulty--need "special handling."