Kinetic modeling of folate metabolism through use of chronic administration of deuterium-labeled folic acid in men.

This study was conducted as an initial investigation of in vivo folate kinetics in healthy men (n = 4) and made use of a chronic-administration protocol with stable-isotope labeling. Subjects were given 0.453 mumol (200 micrograms) total folic acid in aqueous solution daily throughout the 18-wk study while they consumed self-selected folate-adequate diets. After a 2-wk pretrial period with unlabeled folic acid, subjects were given 0.227 mumol (100 micrograms) pteroyl-L-[2H4]glutamic acid/d ([2H4]folic acid) combined with 0.227 mumol nonlabeled folic acid or [2H2]pteroylhexaglutamic acid/d for the next 8 wk; then for the next 8 wk the [2H4]folic acid was withdrawn and the subjects received only nonlabeled folic acid. Little unmetabolized folic acid was excreted in urine. Isotopic enrichment of urinary folate during [2H4]folic acid administration and withdrawal was consistent with a kinetic model having a rapid turnover pool and a slow turnover pool. In contrast with previous two-pool models, provisions were made for folate turnover by urinary folate excretion (as measured here) and by fecal excretion and catabolic processes. The precision of modeling will be improved in future studies by measurement of enrichment of additional pools. However, this study shows clearly the slow turnover of the whole-body folate pool (< or = 1% per day) and the feasibility of further long-term kinetic analysis.

The effects of an expectancy state on the fate of applications and psychotherapy in an outpatient setting.

This study describes an attempt to influence the outcome of outpatient psychotherapy by offering pretherapy information to application. The sample consisted of more than 1,300 applicants; the pretherapy information, in the form of a printed leaflet, was included with the application blank for alternate cases. The results suggest that the pretherapy information tended to discourage the completing of application blanks. Among those patients who eventually participated in psychotherapy, pretherapy information had no effect on the duration of treatment or on treatment outcomes as rated by the therapists. Incidentally, the data indicate that having health insurance has a strong, positive effect on the number of treatment interviews.

Use and costs under the Iowa capitation drug program.

This article evaluates changes in the use of drug services and the corresponding costs when the conventional fee-for-service system for reimbursement of pharmacists under medicaid is replaced by a capitation system. The fee-for-service system usually covers ingredient costs plus a fixed professional dispensing fee. The capitation system provided a cash payment (which varied by aid category and season of the year) per Medicaid eligible the first of each month. We examined drug use and costs in two experimental rural counties during a 1-year preperiod in which the fee-for-service form of reimbursement was employed, as well as a 2-year postperiod in which the capitation system was used. We compared the results with use and cost patients in two other rural counties which remained on the fee-for-service system during the same 3-year period. Drug use was similar among control and experimental counties with the exception of nursing home patients; use in this category decreased under capitation and increased under fee-for-service. Using three measures of drug cost: 1) average cost of a day's drug therapy; 2) average drug costs per recipient; and 3) average Medicaid expenditures for drug services per recipient, we observed significant savings under the capitation reimbursement system as compared to the fee-for-service system. We attributed savings under capitation to shifts in prescribing and dispensing behavior, as well as changes in use by nursing home patients. Based upon these findings, the total savings resulting from implementing capitation would be approximately 16 percent compared to fee-for-service reimbursement.

New developments in functional assessment: Probabilistic models for gold standards.

Advances in fundamental measurement have led to many exciting new developments in functional assessment. This paper presents fundamental measurement theory and method in summary form, and briefly describes its various applications to functional assessment, program evaluation, and outcomes analysis in physical medicine and rehabilitation. The implications of computerized medical records and longitudinal patient tracking in national or global computer networks for functional status and health status gold standards are briefly addressed.

Measurement-related problems in functional assessment.

Occupational therapists, like other rehabilitation professionals, have accepted ordinal raw scores as a sufficient basis for developing evaluation tools. This paper summarizes problems commonly found in evaluation methods based on summing ordinal raw item scores and demonstrates how Rasch measurement models provide a solution to the construction of calibrated (linear) measures. Rasch measurement models are contrasted with Steven's lax definition of measurement and Guttman's unreasonably rigid requirements. The simple Rasch model is a probabilistic formulation of the fundamental requirements for additive linear measurement. This formulation retains Guttman's concept of order, but construes it probabilistically, making it neither too lax (random) nor too rigid. When a measure is based on a theory of what counts as an observation of more or less of something, Rasch measurement models are useful for constructing valid measures.

Foundations for health status metrology: the stability of MOS SF-36 PF-10 calibrations across samples.

Interest in applying probabilistic conjoint measurement (PCM) models, such as those devised by the late Georg Rasch, to health status and quality of life data has grown significantly in the last few years. Applications have yet, however, to fully realize the opportunities for scientific generalization and practical convenience PCM offers. This article fleshes out the substance of some of these opportunities by comparing eight separate PCM calibrations of the SF-36 ten-item physical functioning scale (PF-10). The initial average correlation across the 28 pairs of calibrations is .84; after taking advantage of the PCM model's capacity to account for missing data by omitting from the comparisons items that vary due to sample idiosyncracies, the average correlation is .90. Opportunities for, and limitations on, generalization from PF-10 measures are explored.

A research program for accountable and patient-centered health outcome measures.

This article addresses the relevance of probabilistic conjoint (Rasch) measurement to five issues of accountability and patient-centeredness in health care. Goals for research, data quality standards, and standard metrics are proposed. The article is intended to begin to address concerns voiced by health care researchers, policy analysts, and the public about ways in which health care outcome measures can be improved.

Objectivity in psychosocial measurement: what, why, how.

This article raises and tries to answer questions concerning what objectivity in psychosocial measurement is, why it is important, and how it can be achieved. Following in the tradition of the Socratic art of maiuetics, objectivity is characterized by the separation of meaning from the geometric, metaphoric, or numeric figure carrying it, allowing an ideal and abstract entity to take on a life of its own. Examples of objective entities start from anything teachable and learnable, but for the purposes of measurement, the meter, gram, volt, and liter are paradigmatic because of their generalizability across observers, instruments, laboratories, samples, applications, etc. Objectivity is important because it is only through it that distinct conceptual entities are meaningfully distinguished. Seen from another angle, objectivity is important because it defines the conditions of the possibility of shared meaning and community. Full objectivity in psychosocial measurement can be achieved only by attending to both its methodological and its social aspects. The methodological aspect has recently achieved some notice in psychosocial measurement, especially in the form of Rasch's probabilistic conjoint models. Objectivity's social aspect has only recently been noticed by historians of science, and has not yet been systematically incorporated in any psychosocial science. An approach to achieving full objectivity in psychosocial measurement is adapted from the ASTM Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method (ASTM Committee E-11 on Statistical Methods, 1992).

Physical disability construct convergence across instruments: towards a universal metric.

OBJECTIVES: This study examines the stability of a physical disability construct across instruments and samples. The purpose is not to report a formal equating of instrument calibrations, but to indicate whether such an effort would be likely to succeed. Theory. The economics transforming health care from its orientation toward crisis-driven disease reactions to population- and evidence-based preventive health management and individualized disease management demand general scale-free measures of functional independence. METHODS: A new method, pseudo-common item equating, is demonstrated. Similar, but not identical items, from different instruments, calibrated on different samples, are compared. DATA: More than 30 articles presenting Rasch analyses of physical functioning scales were reviewed. Four instruments provided data from ten of these articles, for eleven different calibrations (two instruments are both included in one article). RESULTS: The final overall average correlation disattenuated for error is .93, with an average of 7 pseudo-common items, and an average p-value of .01, meaning that measures based on these calibrations should be linearly transformable versions of the same metric. Scientific importance. The quantitative stability of different areas of physical functional independence across instruments and samples suggests that the development and deployment of a universal metric is a realizable goal.

Equating the MOS SF36 and the LSU HSI Physical Functioning Scales.

This study equates the physical functioning subscales of the Medical Outcomes Study Short Form 36 (SF36) and the Louisiana State University Health Status Instruments (LSU HSI). Data from the SF36's 10-item physical functioning scale, the PF10, and the LSU HSI's 29-item Physical Functioning Scale (PFS), were fit to separate and mixed Rasch rating scale models. Data were provided by a convenience sample of 285 patients waiting for appointments in a public hospital general medicine clinic. Difficulty estimates for a subset of similar items from the two instruments were highly correlated (.95), indicating that the items from the two scales are working together to measure the same variable. The measures from the two equated instruments correlate .80 (.86 when disattenuated for error). Of the two instruments, the PFS's error is lower, model fit is better, and reliability coefficients are higher. Both instruments measure physical functioning, and can do so in a common unit of measurement. Conversion tables are provided for transforming raw scores from either instrument into the common metric.

A preimplementation assessment of a capitation reimbursement system using simulation.

Capitation is a system of reimbursement for services under which providers are paid a fixed amount per client served per time period. An experiment from April 1981 to December 1981 involved the use of a capitation system of reimbursement to pharmacies participating in the Iowa Medicaid drug program in 32 counties in Iowa. It was essential to demonstrate that cost savings were feasible and pharmacy reimbursement would be adequate before the capitation experiment was begun. An assessment of this issue was developed using simulation and data base management techniques. The positive results of this assessment gave evidence that cost savings due to capitation potentially could be realized by both the Medicaid drug program and pharmacists during the experiment.

Applying psychometric criteria to functional assessment in medical rehabilitation: I. Exploring unidimensionality.

While rehabilitation providers are facing increasing pressure to document treatment outcomes, critics have warned against the inappropriate use of ordinal functional assessment data in arithmetic operations. Two salient criticisms concern the combination of items representing multidimensional abilities into a single total score, and the indeterminate distances between hierarchical functional assessment scale categories. In this initial study, the factor structure of the Patient Evaluation and Conference System (PECS) was studied to assess the potential for unidimensional measurement. Factor analysis of a multidiagnostic dataset (n = 3,564) yielded eight factors accounting for 60% of the variance among 68 PECS items. The factors indicate that several unidimensional measures may underlie the PECS. These factors are delineated, and further studies of unidimensionality and additivity are recommended.

The effect of a group practice on rural health attitudes and behavior.

The opportunity to join a group practice has been identified as a successful inducement for physicians to locate in rural areas. Less is known of the effects of group practice on the health attitudes, behavior and status of the rural communities in which they are established. A random survey of households was conducted in 1972 in a rural Midwestern area, prior to the establishment of a community-sponsored multispecialty primary care group practice, and again on the same households in 1977, after establishment of this group practice (a total of 292 households representing 829 persons). Perceived access to health services before the establishment of the group practice did not significantly predict use of the group practice. Neither previous use of medical services nor health status measured by several indices was associated with eventual use of the group practice. The apparent impact on the community of the group practice was a significant improvement in access to physician services, shown by shorter average travel time to the place of primary care and a 62 per cent improvement in the ability to make a same-day appointment. Furthermore, a significant shift in the distribution of physician services was noted over the study period. The introduction of physician assistants significantly decreased the prior positive attitudes toward them. Despite improvement in access to care, no changes in population health status or receipt of preventive services were noted. Current users of the group practice appear similar to those utilizing conventional medical care sources in regard to access to services, use of services, as well as health status, attitudes and costs.

Does chiropractic utilization substitute for less available medical services?

In Muscatine, Iowa, a medically underserved rural area, a cohort study of health care utilization was made before and after a significant increase in medical manpower. There was a slight increase, rather than a decrease, in the use of chiropractic services associated with the growth in the physician manpower pool. The level of access to physician services was not a significant predictor of chiropractice utilization.

Rehabits: a common language of functional assessment.

Probabilistic measurement models offered by Rasch and others can be used to link different functional assessment instruments into a single measurement system. This study assessed 54 subjects (diagnoses: 8 brain injuries, 7 neuromuscular, 22 musculoskeletal, 7 spinal cord, 10 stroke) admitted to a free-standing rehabilitation hospital at admission and discharge using both the Functional Independence Measure (FIM) and the Patient Evaluation and Conference System (PECS). Thirteen FIM and 22 PECS motor skills items were scaled together into a 35-item instrument, providing scale values for all items in the same unit of measurement. Separate FIM and PECS measures produced for each subject correlate .94 and .91 (p < .0001), respectively, with the cocalibration measures, and 0.91 (p < .0001) with each other. Either instrument's ratings are easily and quickly converted into the other's using the common unit of measurement, the rehabit (rehabilitation measuring unit). This article argues that the stability of the PECS and FIM item difficulty estimates over thousands of subjects, dozens of hospitals, hundreds of raters, and years of assessment is convincing evidence in support of the widespread use of their cocalibrated, common scale values as a functionometric ruler.

Applying psychometric criteria to functional assessment in medical rehabilitation: II. Defining interval measures.

The use of functional assessment total scores in arithmetic operations has proliferated despite the lack of evidence supporting their use as interval measures of patient ability. Such evidence is minimally necessary to assure the validity of functional assessment total scores for clinical and management decision-making. Two requirements of interval measurement are explained and a set of Rasch analyses of 5,500 assessments using the Patient Evaluation and Conference System (PECS) are presented. The analyses were performed to determine the extent to which four item subsets identified in a previously reported factor analysis of the PECS comprise interval measures of functional independence status. Results indicate that the PECS scales meet these requirements to varying degrees. The analyses also identify areas in which measurement quality can be improved.

Capitation payment for pharmacy services: impact on generic substitution.

This article evaluates changes in the rate of generic substitution as well as the appropriateness of such changes in dispensing behavior when the conventional fee-for-service system for reimbursement of pharmacists is replaced by a capitation system. The fee-for-service system under Medicaid usually covers ingredient costs plus a fixed professional dispensing fee. The capitation system provides a cash payment per Medicaid eligible at the first of each month, which varies by aid category and season of the year. The dispensing behavior of pharmacists in two experimental rural counties is examined during a 1-year preperiod in which the fee-for-service form of reimbursement was employed, as well as a 2-year postperiod in which capitation was used in lieu of fee-for-service payments. The results are compared with pharmacist behavior patterns in two other rural counties which remained on the fee-for-service system over the same 3-year period. The data indicate highly significant increases in both the rate of generic substitution as well as the dollar savings per substitution in the experimental counties after the institution of capitation reimbursement. Using explicit criteria, no substantial differences in the appropriateness of generic substitution were noted between the two financing schemes.

Effects of capitation payment for pharmacy services on pharmacist-dispensing and physician-prescribing behavior: I. Prescription quantity and dose analysis.

This paper evaluates changes in quantities and appropriateness of dosages and quantities of prescription in capitation and control pharmacies. The data indicate that, under capitation, changes were made in the quantities of ingredients so that the quantities dispensed were significantly different from those prescribed. However, the number of such modifications to prescriptions was small, and the reader is cautioned against drawing broad conclusions. The analysis, then, considers changes in days' supply of prescription ingredients during the study period. There were significantly increases in the average day's supply of prescription ingredients for maintenance drugs dispensed under the capitation reimbursement scheme; however, no such differences were observed for non-maintenance drugs. Appropriateness of the dosages and quantities of prescriptions were then compared for capitation and fee-for-service pharmacies for the study period, and no significant differences were found. Thus, it is concluded that although capitation was associated with increases in the average days' supply of ingredients dispensed for maintenance prescriptions, such changes did not adversely affect the quality of drug therapy as measured by two sets of criteria.