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Biomedical subjects

J M Linacre

Publications and source records attributed to J M Linacre.

17 recordsLinked to original sources
PubMed2004

Capturing the true burden of dystonia on patients: the Cervical Dystonia Impact Profile (CDIP-58).

OBJECTIVES: To develop a new rating scale for measuring the health impact of cervical dystonia (CD) that includes patients' perceptions and complements existing observer dependent clinician rating scales. METHODS: Scale development was in three stages. In Stage 1, a large pool of items was generated from patient interviews (n = 25), expert opinion, and literature review. In Stage 2, these items were administered by postal survey to people with CD. The resulting data were analyzed using Rasch item analysis to construct, from the item pool, a rating scale that satisfied criteria for rigorous measurement. In Stage 3, the measurement properties of this rating scale were examined in an independent sample of people with CD. RESULTS: In Stage 1, 150 items concerning the health impact of CD were generated. In Stage 2, 556 people completed questionnaires (87% response rate) and a 58-item rating scale measuring the health impact of CD in eight areas was constructed (CD Impact Profile, CDIP-58). In Stage 3, CDIP-58 data from 391 people (87% response rate) were received. Analyses supported the measurement of eight unidimensional constructs (infit mean square range 0.62 to 1.50), item calibration (33.37 to 67.56), and patient separation statistics (2.59 to 3.38). Items demonstrated stable calibrations in subgroups of people with CD supporting the stability of the CDIP-58. CONCLUSIONS: The CDIP-58 is a reliable and valid patient-based rating scale measuring the health impact of CD in eight health dimensions.

Adult↗
PubMed2000

FIM levels as ordinal categories.

Data collected on rating scales have generally been analyzed without verifying that the scales have functioned as intended. The FIM levels are precisely conceptualized and meticulously defined. Their effective empirical functioning as ordinal categories merits continual monitoring. Ordinality implies that each succeeding level represents a higher level of functioning. Further, as a patient improves in functioning each ordinal level in turn is expected to be observed. Taking advantage of the clarity of Rasch theory, guidelines are suggested that prompt the analyst to investigate whether the rating categories are cooperating to produce observations on which useful measurement and prudent inference about patient status can be based.

Activities of Daily Living↗
PubMed1999

Investigating rating scale category utility.

Eight guidelines are suggested to aid the analyst in investigating whether rating scales categories are cooperating to produce observations on which valid measurement can be based. These guidelines are presented within the context of Rasch analysis. They address features of rating-scale-based data such as category frequency, ordering, rating-to-measure inferential coherence, and the quality of the scale from measurement and statistical perspectives. The manner in which the guidelines prompt recategorization or reconceptualization of the rating scale is indicated. Utilization of the guidelines is illustrated through their application to two published data sets.

Guidelines as Topic↗
PubMed1999

Understanding Rasch measurement: estimation methods for Rasch measures.

Rasch parameter estimation methods can be classified as non-interative and iterative. Non-iterative methods include the normal approximation algorithm (PROX) for complete dichotomous data. Iterative methods fall into 3 types. Datum-by-datum methods include Gaussian least-squares, minimum chi-square, and the pairwise (PAIR) method. Marginal methods without distributional assumptions include conditional maximum-likelihood estimation (CMLE), joint maximum-likelihood estimation (JMLE) and log-linear approaches. Marginal methods with distributional assumptions include marginal maximum-likelihood estimation (MMLE) and the normal approximation algorithm (PROX) for missing data. Estimates from all methods are characterized by standard errors and quality-control fit statistics. Standard errors can be local (defined relative to the measure of a particular item) or general (defined relative to the abstract origin of the scale). They can also be ideal (as though the data fit the model) or inflated by the misfit to the model present in the data. Five computer programs, implementing different estimation methods, produce statistically equivalent estimates. Nevertheless, comparing estimates from different programs requires care.

Algorithms↗
PubMed1998

Detecting multidimensionality: which residual data-type works best?

Factor analysis is a powerful technique for investigating multidimensionality in observational data, but it fails to construct interval measures. Rasch analysis constructs interval measures, but only indirectly flags the presence of multidimensional structures. Simulation studies indicate that, for responses to complete tests, construction of Rasch measures from the observational data, followed by principal components factor analysis of Rasch residuals, provides an effective means of identifying multidimensionality. The most diagnostically useful residual form was found to be the standardized residual. The multidimensional structure of the Functional Independence Measure (FIMSM) is confirmed by means of Rasch analysis followed by factor analysis of standardized residuals.

Factor Analysis, Statistical↗
PubMed1997

Relationships between disability measures and nursing effort during medical rehabilitation for patients with traumatic brain and spinal cord injury.

OBJECTIVE: The increasing use of disability measures requires that the validity of these instruments be adequately demonstrated. This study sought to evaluate the concurrent validity of one disability measure, the Functional Independence Measure (FIMSM) using minutes of care reported by nursing staff. STUDY DESIGN: Correlational, cohort design. SETTING: Eight inpatient medical rehabilitation hospitals that subscribe to the Uniform Data System for Medical Rehabilitation. PATIENTS OR OTHER PARTICIPANTS: 129 patients with traumatic brain injury (TBI) and 53 patients with traumatic spinal cord injury (SCI). INTERVENTIONS: Routine rehabilitation care. MAIN OUTCOME MEASURES: Patient-nurse contact times were recorded with a stop watch for a 24-hour period during the first and last weeks of inpatient rehabilitation. The FIM was also completed during the first and last weeks of rehabilitation. RESULTS: Contact times declined from the first to last weeks of rehabilitation, concurrent with improving scores on motor and cognitive measures derived from the FIM. Statistically significant correlations between contact times and FIM measures were observed for medication dispensing, treatment provision, and teaching/activities of daily living at admission and discharge. Smaller and usually nonsignificant correlations were observed in activities that did not involve direct patient contact. Contact times increased exponentially as disability increased. CONCLUSIONS: These results support the construct validity of the FIM by demonstrating strong relationships (r values in the range of .40 to .60) between burden of care and a measure of disability.

Adult↗
PubMed1997

FIM measurement properties and Rasch model details.

To summarize, we take issue with the criticisms of Dickson & Köhler for two main reasons: 1. Rasch analysis provides a model from which to approach the analysis of the FIM, an ordinal scale, as an interval scale. The existence of examples of items or individuals which do not fit the model does not disprove the overall efficacy of the model; and 2. the principal components analysis of FIM motor items as presented by Dickson & Köhler tends to undermine rather than support their argument. Their own analyses produce a single major factor explaining between 58.5 and 67.1% of the variance, depending upon the sample, with secondary factors explaining much less variance. Finally, analysis of item response, or latent trait, is a powerful method for understanding the meaning of a measure. However, it presumes that item scores are accurate. Another concern is that Dickson & Köhler do not address the issue of reliability of scoring the FIM items on which they report, a critical point in comparing results. The Uniform Data System for Medical Rehabilitation (UDSMRSM) expends extensive effort in the training of clinicians of subscribing facilities to score items accurately. This is followed up with a credentialing process. Phase 1 involves the testing of individual clinicians who are submitting data to determine if they have achieved mastery over the use of the FIM instrument. Phase 2 involves examining the data for outlying values. When Dickson & Köhler investigate more carefully the application of the Rasch model to their FIM data, they will discover that the results presented in their paper support rather than contradict their application of the Rasch model! This paper is typical of supposed refutations of Rasch model applications. Dickson & Köhler will find that idiosyncrasies in their data and misunderstandings of the Rasch model are the only basis for a claim to have disproven the relevance of the model to FIM data. The Rasch model is a mathematical theorem (like Pythagoras') and so cannot be disproven by empirical data once it has been deduced on theoretical grounds. Sometimes empirical data are not suitable for construction of a measure. When this happens, the routine fit statistics indicate the unsuitable segments of the data. Most FIM data do conform closely enough to the Rasch model to support generalizable linear measures. Science can advance!

Activities of Daily Living↗
PubMed1996

The structure of an instrument for assessing the effects of assistive devices and altered working methods in women with rheumatoid arthritis.

OBJECTIVE: To use Rasch analysis to transform the ordinal score from a newly developed instrument, the Evaluation of Daily Activities Questionnaire (EDAQ), in order to obtain unidimensional linear measures; to analyze whether items change in difficulty with interventions; and to follow changes in subjects' degree of ability. METHODS: Twenty-one women with rheumatoid arthritis rated their perceived difficulty without and with assistive devices or altered working methods using the EDAQ; the EDAQ consists of 102 items of daily activities, divided into 11 dimensions. RESULTS: All items in the EDAQ could be structured into an acceptable model from "hard" to "easy" with the subjects overall measures ranging from "more able" to "less able." Forty-one items showed a significant reduction of difficulty with interventions. For some items results indicated that easier initial difficulty led to greater effect of interventions. In general, difficulty without assistive devices could not predict difficulty with interventions. Twenty women demonstrated a significant increase in activities of daily living (ADL) ability after interventions. CONCLUSION: The EDAQ analyzed with the Rasch model, demonstrated a hierarchical order of difficulty in 102 items showing that it was possible to evaluate the effect of using assistive devices or altered working methods.

Activities of Daily Living↗
PubMed1996

Structure of a combination of Functional Independence Measure and Instrumental Activity Measure items in community-living persons: a study of individuals with cerebral palsy and spina bifida.

OBJECTIVE: To analyze the structure of a combination of physical items from the Functional Independence Measure (FIM) and seven instrumental activity items using ratings of dependence and perceived difficulty. DESIGN: Disability in terms of dependence and subject's perceived difficulty was studied in patients with cerebral palsy (CP) and spina bifida (SB). Rasch analysis was used to construct calibrated linear measure and to identify suitable models with respect to rating steps. SETTING: Interviews were performed at home with patients from an outpatient university rehabilitation unit for young disabled persons. PATIENTS: Fifty-three CP and 20 SB patients (including 5 with other early acquired spinal cord lesions), 20 to 39 years of age, participated and represented 62% and 80%, respectively, of available patients. All had fulfilled an elementary school program. RESULTS: The best scoring model using Rasch analysis was achieved using 5 levels for dependence and 4 levels for perceived difficulty. Hierarchic orders for all items are presented. The FIM items Bowel and Bladder showed different characteristics in the two groups of patients, especially for perceived difficulty, and were excluded in the joint calibrations. There was close overall agreement between the ratings of dependence and perceived difficulty. Person measure values from the Rasch analyses were separated between wheelchair users and walkers. CONCLUSION: The combination of physical items from FIM and instrumental activity measure (IAM) are useful for disability assessment in community-living persons and should be further studied in other impairment groups.

Activities of Daily Living↗
PubMed1995

Rasch analysis of Visual Analog Scale measurements before and after treatment of Patellofemoral Pain Syndrome in women.

The Visual Analog Scale (VAS) can be used to record subjectively experienced pain in different situations (items). By a mathematical method, the Rasch analysis, the original VAS recordings can be converted to an interval scale. Forty women with Patellofemoral Pain Syndrome (PFPS) reported their pain on the VAS from 12 different situations (items) before and after 12 weeks of rehabilitation. The items recorded pain during the last 3 months, during provocation tests, and during activities such as walking up stairs, jumping and strength testing. It was concluded that the items used for the patients with PFPS were hierarchically ordered in a statistically equivalent manner before and after rehabilitation. Subjectively reported pain after 12 weeks of rehabilitation was significantly alleviated for 23 (58%) of the 40 patients, compared with before rehabilitation. The patients with PFPS did not use the VAS as a linear scale over the full range. Rasch analysis of recordings made with the VAS gave a more detailed pain assessment.

Adolescent↗
PubMed1994

The structure and stability of the Functional Independence Measure.

The Functional Independence Measure (FIM) records the severity of disability of rehabilitation patients. The necessarily curvilinear relationship between the finite range of recorded FIM raw scores and the conceptually infinite range of additive disability measures is resolved through Rasch analysis. The analysis of admission and discharge FIM ratings of 14,799 patients shows that the 18 FIM items define two statistically and clinically different indicators. Thirteen items define disability in motor functions. Five items define disability in cognitive functions. Additive measures for each indicator have the same characteristics at admission and discharge, so that these measures can be used to assess change in patient status.

Activities of Daily Living↗
PubMed1994

Prediction of rehabilitation outcomes with disability measures.

This study evaluated the extent to which rehabilitation outcomes and resource use can be predicted by functional status measures. Linear measures of motor and cognitive function were derived from the Functional Independence Measure for a sample of 27,699 patients undergoing initial rehabilitation. Admission functional status was consistently related to discharge function and length of stay, though the strength of these associations varied with impairment. Motor function was a stronger predictor of length of stay than was cognitive function for all impairments. However, the unique contribution of cognitive function was apparent for specific impairment groups. The predicted variance at discharge in motor function averaged 55%, 70% in cognitive function, and 20% in length of stay. These results support the use of functional status measures in the development of rehabilitation resource use models. Recommendations for future research are proposed.

Activities of Daily Living↗
PubMed1993

Relationships between impairment and physical disability as measured by the functional independence measure.

This study was conducted to scale the Functional Independence Measure (FIM) with Rasch Analysis and to determine the similarity of scaled measures across impairment groups. The results show that the FIM contains two fundamental subsets of items: one measures motor and the second measures cognitive function. Rasch analysis of the Uniform Data System for Medical Rehabilitation patient sample yielded interval measures of motor and cognitive functions. The validity of the FIM was supported by the patterns of item difficulties across impairment groups. Adequate clinical precision of the FIM was demonstrated, though suggestions for improvement emerged. The frequency of misfit between patients and the performance scales varied across impairment groups, but was acceptable. The results of this project will enable clinicians and researchers to plan cost-effective treatment by providing a valid measure of disability.

Activities of Daily Living↗
PubMed1993

Performance profiles of the functional independence measure.

The functional independence measure (FIM) is used to determine the degree of disability that patients experience and the progress that they make through programs of medical rehabilitation. Rasch analysis is a statistical technique for constructing interval measures from ordinal data that was applied to derive FIM measures. The major factors that are taken into account to produce FIM measures are the relative difficulty in performance of FIM items and the ability of the persons tested. Our analyses showed the relative difficulties that patients experienced in performing items in the FIM. There were two dominant patterns of difficulty, one for motor FIM items and the other for cognitive FIM items. The patterns were consistent across impairment groups, although not identical. Of the motor items, eating and grooming were easiest whereas stair climbing, tub/shower transfers and locomotion were most difficult. Of the cognitive items, expression and comprehension were easiest and problem solving was the most difficult. The patterns of difficulty in performing FIM items are illustrated by analysis of the following impairment groups: for motor items, orthopedic conditions, stroke with left hemiparesis and spinal cord dysfunction; for cognitive items, orthopedic conditions, brain dysfunction, stroke with right hemiparesis and spinal cord dysfunction. By understanding patterns of difficulty in performing FIM items according to types of impairment and levels of function, clinicians may more precisely design treatment programs, use services and predict outcomes of medical rehabilitation.

Activities of Daily Living↗
PubMed1989

Observations are always ordinal; measurements, however, must be interval.

Quantitative observations are based on counting observed events or levels of performance. Meaningful measurement is based on the arithmetical properties of interval scales. The Rasch measurement model provides the necessary and sufficient means to transform ordinal counts into linear measures. Imperfect unidimensionality and other threats to linear measurement can be assessed by means of fit statistics. The Rasch model is being successfully applied to rating scales.

Humans↗
PubMedDate not supplied

Functional status and therapeutic intensity during inpatient rehabilitation.

The objective of this study was to describe the relationships between functional status at discharge and intensity of therapies received during inpatient medical rehabilitation. The sample was comprised of 140 patients with traumatic brain injury and 106 patients with spinal cord injury at eight hospitals that subscribe to the Uniform Data System for Medical Rehabilitation. Data included linear measures of motor and cognitive ability derived from the Functional Independence Measure at admission to and discharge from rehabilitation. Multiple regression was used to predict intensity of therapies, discharge motor and cognitive function, the extent to which potential functional gains were achieved, and the efficiency of gains. Intensities of occupational, physical, and speech therapies were not significant predictors of outcomes for either group, controlling linearly for admission function, psychology intensity, length of stay, onset to admission interval, age, and interrupted stays. Only intensity of psychology services seemed to have any relation to functional gain (in cognition for patients with traumatic brain injury). The apparent lack of benefit related to intensity of therapies may be due to factors such as spontaneous recovery, goals not measured by the Functional Independence Measure, limited modulation of therapy intensity according to likely patient responsiveness, or therapies focused on impairment or other goals rather than disability. We suggest that efficiently staged rehabilitation should vary the intensity and nature of services according to patients' functional status, impairments, comorbid conditions, and other clinical factors.

Adult↗