Multivariate matching and bias reduction in the surgical outcomes study.

BACKGROUND: Outcomes studies often need a level of detail that is not present in administrative data, therefore requiring abstraction of medical charts. Case-control methods may be used to improve statistical power and reduce abstraction costs, but limitations of exact matching often preclude the use of many covariates. Unlike exact matching, multivariate matching may allow cases to be matched simultaneously on hundreds of covariates. OBJECTIVES: To develop multivariate matched case-control pairs in a study of death after surgery in the Medicare population. RESEARCH DESIGN: Using 830 randomly selected index cases of patients who died within 60 days from admission, controls were found who did not die within that time period, matching on risk for death and other patient characteristics with up to 173 variables used simultaneously in the matching algorithms. SUBJECTS: General and orthopedic Medicare surgical cases in Pennsylvania from 1995 to 1996. Controls were either selected from across the entire state (108,765 possible subjects), or from within the same hospital as the case. MEASURES: Percent bias reduction and the average difference between cases and controls in units of standard deviations. RESULTS: Matched controls were far more similar to cases (deaths) upon admission to the hospital than typical patients, both in statewide and within hospital matches. Bias reduction was usually greater than 50% and often approached 100%. The difference between cases and matched controls for most variables was usually below 0.2 SD. CONCLUSIONS: Multivariate matching methods may aid in conducting studies with Medicare claims records by improving the quality of matches, thereby achieving a better understanding of the etiology of outcomes.

Multigenic control of Listeria monocytogenes susceptibility in mice.

We have used a novel quantitative trait locus model to study the genetics of survival of F2 progeny of susceptible BALB/cByJ and resistant C57BL/6ByJ mice that have been infected with Listeria monocytogenes. This allowed us to map modifiers of L. monocytogenes susceptibility to chromosomes 5 and 13.

Cytologic correlates of papillary immature metaplasia (immature condyloma) of the cervix.

Papillary immature metaplasia (PIM) of the cervix (immature condyloma) is a variant of low-grade squamous intraepithelial lesions (LSIL). It is frequently associated with human papillomavirus (HPV) types 6 and 11. The purpose of this study was to characterize the cytologic changes associated with this lesion. We analyzed 10 cases of PIM from our files and reviewed the Papanicolaou smears taken proximate to the time of the biopsy. Four cases had either reactive epithelial changes (2 cases) or cytologic findings typical of low-grade SIL, with koilocytosis (2 cases). Six cases displayed a spectrum of metaplastic cells with varying maturation that ranged from atypical reactive cells to atypical immature metaplastic cells. Binucleation was common. Some cells exhibited features characteristic of SIL, although the degree of nuclear atypia generally was less than that associated with high-grade SIL. Papanicolaou smears from all cases were interpreted as atypical (ASCUS) metaplasia or low-grade SIL. Follow-up biopsy in one case revealed a PIM in association with a high-grade SIL, the latter undiagnosed by smear alone. PIM is a distinct histologic entity that can present with a spectrum of cytologic findings. Its recognition histologically can resolve some cytologic/histologic discrepancies. Confusion with an immature HSIL or atypical immature metaplasia can occur in some instances and the diagnosis of PIM by cytology alone is not recommended, unless the diagnosis is qualified.

Physiological profiles of the Canadian Olympic Soccer Team.

Physiological profiles of elite athletes are becoming increasingly important both for the sport scientist and coach, primarily to effectively develop training programs and to use as a motivational tool in the pursuit of excellence. Descriptive profiles were developed on 16 aspirants of the Canadian Olympic Soccer team during their training program at U.B.C. Selected strength measures were obtained from a Cybex II isokinetic dynamometer at 30 degrees sec-1. Metabolic variables were derived utilizing a Beckman metabolic cart interfaced with a Hewlitt Packard 3052A data acquisition system. Protocols involved were the following: VO2max (initial velocity 8.05 km X h-1, greater than 0.805 km X min-1); Anaerobic speed test (AST) (20% grade, 12.8 km X h-1). the nonlinear increase in excess CO2 was utilized to determine the anaerobic threshold (AT). (Table: see text). Recommendations emphasized maintenance of low body fat, increasing maximal aerobic power by approximately 10% and creating a hams/quads ratio of 60%. Also, a nutritional survey and periodic evaluation of iron status is necessary for the athletes.

The development of a test of overarm throwing: an application of generalizability theory.

Although much effort has been directed toward an understanding of sequential progressions between and within motor skills, little evidence is available to indicate that teachers have incorporated this material into instructional practice. The fact that pupil progress has been evaluated primarily through movement achievement (distance, velocity), rather than through movement content (analysis of form), has been postulated as a reason for this non-use. It was thus the purpose of this study to develop a reliable, objective and practical method of measuring one particular manipulative skill--that of overarm throwing. As such, previously developed sequential progressions were analyzed and modified to produce a measure which did not require the use of a camera. A system of rating throwing performance was adopted which allows for separate rating of the three components: "foot placement", "body rotation", and "arm action". Each component depicts five hierarchically arranged levels, or "steps", and performance is rated on a scale ranging from 1-5. The throwing test was administered to 78 subjects by three trained observers. Reliability analyses, through the use of generalizability theory, showed high objectivity (r's of approximately .90) and good day-to-day reliability (r's of .75 to .93) for most testing conditions. It was concluded that this test is a reliable, valid and practical test for the analysis of overarm throwing in children.

Physical fitness of students in British Columbia: a criterion-referenced evaluation.

In 1979, the Ministry of Education completed a comprehensive study on the status of physical education in British Columbia. The purpose of this paper is to present the findings of this assessment, with respect to the physical fitness of public school children at the end of primary (grade 3), intermediate (grade 7), and secondary (grade 11) levels. Approximately 3000 students were tested on measures of cardiovascular endurance, static and dynamic muscular endurance, static and explosive strength and flexibility. Separate panels, one to determine "acceptable ranges of performance" and one to interpret the findings, were established by the provincial Ministry. Evaluation was of a criterion-referenced nature and ratings of "weak", "marginally satisfactory", "satisfactory", "very satisfactory", and "strong" were assigned. The results of the study indicate that fitness levels of both sexes, at the grade 3 and 7 levels, as well as the grade 11 females, were generally rated "weak" to "marginally satisfactory". "Satisfactory" ratings were recorded for the grade 11 males. Variables of particular concern were those of cardiovascular endurance and static muscle endurance. It was concluded that B.C. students, while comparing favourably with other provincial, national and international samples, fell well below the "acceptable ranges" set by the provincial evaluative panels.