Biomedical subjects

Rebecca Holman

Publications and source records attributed to Rebecca Holman.

8 recordsLinked to original sources

PubMed2005

The Academic Medical Center Linear Disability Score (ALDS) item bank: item response theory analysis in a mixed patient population.

BACKGROUND: Currently, there is a lot of interest in the flexible framework offered by item banks for measuring patient relevant outcomes. However, there are few item banks, which have been developed to quantify functional status, as expressed by the ability to perform activities of daily life. This paper examines the measurement properties of the Academic Medical Center linear disability score item bank in a mixed population. METHODS: This paper uses item response theory to analyse data on 115 of 170 items from a total of 1002 respondents. These were: 551 (55%) residents of supported housing, residential care or nursing homes; 235 (23%) patients with chronic pain; 127 (13%) inpatients on a neurology ward following a stroke; and 89 (9%) patients suffering from Parkinson's disease. RESULTS: Of the 170 items, 115 were judged to be clinically relevant. Of these 115 items, 77 were retained in the item bank following the item response theory analysis. Of the 38 items that were excluded from the item bank, 24 had either been presented to fewer than 200 respondents or had fewer than 10% or more than 90% of responses in the category 'can carry out'. A further 11 items had different measurement properties for younger and older or for male and female respondents. Finally, 3 items were excluded because the item response theory model did not fit the data. CONCLUSION: The Academic Medical Center linear disability score item bank has promising measurement characteristics for the mixed patient population described in this paper. Further studies will be needed to examine the measurement properties of the item bank in other populations.

Academic Medical Centers↗

PubMed2005

Continuous monitoring of cerebrospinal fluid oxygen tension in relation to motor evoked potentials during spinal cord ischemia in pigs.

BACKGROUND: Perioperative assessment of spinal cord oxygenation might guide measures to prevent neurologic deficits secondary to ischemic or traumatic damage of the spinal cord. Although cerebrospinal fluid (CSF) partial pressure of oxygen (Po2) measurement has been used to detect spinal cord ischemia (SCI), the diagnostic value and the temporal resolution of CSF Po2 measurement compared with functional assessment of the spinal cord is unknown. This study compared CSF Po2 with transcranial motor evoked potentials (tcMEPs) for detection of experimental SCI. METHODS: The aorta and segmental arteries were exposed in 10 sufentanil-ketamine-anesthetized pigs (weight, 40-50 kg). Myogenic tcMEPs were recorded from the upper and lower limbs, and continuous assessment of CSF Po2 was provided by two Clark-type microcatheters inserted in the lumbar and thoracic intrathecal space. Graded lumbar SCI was produced by sequential clamping of segmental arteries. The relation between CSF Po2 and tcMEP during graded SCI was determined using linear regression. Diagnostic characteristics of CSF Po2 values for clinical SCI were determined using different cutoff points of CSF Po2. RESULTS: Lumbar CSF Po2 (baseline, 44 [interquartile range, 38-54] mmHg) decreased below 50% in all animals and was linearly related to loss of tcMEP amplitude in all animals. The median lumbar CSF Po2 during reduction of tcMEP to less than 25% of baseline was 11 (4-29) mmHg, whereas thoracic CSF Po2 remained constant (40 [28-50] mmHg). During absence of the tcMEP signal, lumbar CSF Po2 was less than 20 mmHg in 80% of the animals. Optimal sensitivity and predictive values of CSF Po2 measurement for SCI were in the range of 40-60% of baseline. CONCLUSIONS: The data indicate that intrathecal Po2 measurement is a sensitive monitoring technique to track real-time changes in local spinal cord oxygenation. Continuous monitoring of CSF Po2 might be applied for evaluation of patients who are at risk for direct or secondary SCI.

Animals↗

PubMed2005

Modelling non-ignorable missing-data mechanisms with item response theory models.

A model-based procedure for assessing the extent to which missing data can be ignored and handling non-ignorable missing data is presented. The procedure is based on item response theory modelling. As an example, the approach is worked out in detail in conjunction with item response data modelled using the partial credit and generalized partial credit models. Simulation studies are carried out to assess the extent to which the bias caused by ignoring the missing-data mechanism can be reduced. Finally, the feasibility of the procedure is demonstrated using data from a study to calibrate a medical disability scale.

Activities of Daily Living↗

PubMed2005

Implementation of participatory ergonomics intervention in construction companies.

OBJECTIVES: The effectiveness of the implementation of participatory ergonomics intervention to reduce physical work demands in construction work was studied. METHODS: In a cluster randomized controlled trial, 10 bricklaying companies were randomly assigned either to an intervention group (N = 5) or a control group (N = 5). The intervention strategy used a consultant-guided six-step approach in which company stakeholders participated. Bricklayers and bricklayers' assistants in the intervention group (N = 65) and the control group (N = 53) were followed for 6 months, and their use of four ergonomic measures (adjusting work height when picking up bricks and mortar, adjusting work height for bricklaying at a wall side, mechanizing brick transport, and mechanizing mortar transport) was compared. The use of the ergonomic measures was assessed from worksite observations and questionnaires at baseline and after 6 months. The workers' and employers' behavioral change phases were determined by questionnaires and interviews, respectively. Performance indicators were assessed for the intervention from the researchers' observations during the implementation process and through questionnaires completed by the workers. RESULTS The strategy had no statistically significant effect on the use of any of the four ergonomic measures, at either the cluster or the individual level. None of the companies in the intervention group passed through all six steps of the intervention. Process outcomes suggest that the ability to use ergonomic measures increased. In bricklaying, self-efficacy and skills to adapt the work height on the scaffolding improved significantly. CONCLUSIONS: The intervention did not lead to greater use of ergonomic measures in bricklaying or the transport of materials. Performance indicators of intervention and the corresponding behavioral change phases of stakeholders can help to detect essential elements of such intervention.

Construction Materials↗

PubMed2004

The AMC Linear Disability Score project in a population requiring residential care: psychometric properties.

BACKGROUND: Currently there is a lot of interest in the flexible framework offered by item banks for measuring patient relevant outcomes, including functional status. However, there are few item banks, which have been developed to quantify functional status, as expressed by the ability to perform activities of daily life. METHOD: This paper examines the psychometric properties of the AMC Linear Disability Score (ALDS) project item bank using an item response theory model and full information factor analysis. Data were collected from 555 respondents on a total of 160 items. RESULTS: Following the analysis, 79 items remained in the item bank. The remaining 81 items were excluded because of: difficulties in presentation (1 item); low levels of variation in response pattern (28 items); significant differences in measurement characteristics for males and females or for respondents under or over 85 years old (26 items); or lack of model fit to the data at item level (26 items). CONCLUSIONS: It is conceivable that the item bank will have different measurement characteristics for other patient or demographic populations. However, these results indicate that the ALDS item bank has sound psychometric properties for respondents in residential care settings and could form a stable base for measuring functional status in a range of situations, including the implementation of computerised adaptive testing of functional status.

Activities of Daily Living↗

PubMed2004

Practical methods for dealing with 'not applicable' item responses in the AMC Linear Disability Score project.

BACKGROUND: Whenever questionnaires are used to collect data on constructs, such as functional status or health related quality of life, it is unlikely that all respondents will respond to all items. This paper examines ways of dealing with responses in a 'not applicable' category to items included in the AMC Linear Disability Score (ALDS) project item bank. METHODS: The data examined in this paper come from the responses of 392 respondents to 32 items and form part of the calibration sample for the ALDS item bank. The data are analysed using the one-parameter logistic item response theory model. The four practical strategies for dealing with this type of response are: cold deck imputation; hot deck imputation; treating the missing responses as if these items had never been offered to those individual patients; and using a model which takes account of the 'tendency to respond to items'. RESULTS: The item and respondent population parameter estimates were very similar for the strategies involving hot deck imputation; treating the missing responses as if these items had never been offered to those individual patients; and using a model which takes account of the 'tendency to respond to items'. The estimates obtained using the cold deck imputation method were substantially different. CONCLUSIONS: The cold deck imputation method was not considered suitable for use in the ALDS item bank. The other three methods described can be usefully implemented in the ALDS item bank, depending on the purpose of the data analysis to be carried out. These three methods may be useful for other data sets examining similar constructs, when item response theory based methods are used.

Activities of Daily Living↗

PubMed2003

Power analysis in randomized clinical trials based on item response theory.

Patient relevant outcomes, measured using questionnaires, are becoming increasingly popular endpoints in randomized clinical trials (RCTs). Recently, interest in the use of item response theory (IRT) to analyze the responses to such questionnaires has increased. In this paper, we used a simulation study to examine the small sample behavior of a test statistic designed to examine the difference in average latent trait level between two groups when the two-parameter logistic IRT model for binary data is used. The simulation study was extended to examine the relationship between the number of patients required in each arm of an RCT, the number of items used to assess them, and the power to detect minimal, moderate, and substantial treatment effects. The results show that the number of patients required in each arm of an RCT varies with the number of items used to assess the patients. However, as long as at least 20 items are used, the number of items barely affects the number of patients required in each arm of an RCT to detect effect sizes of 0.5 and 0.8 with a power of 80%. In addition, the number of items used has more effect on the number of patients required to detect an effect size of 0.2 with a power of 80%. For instance, if only five randomly selected items are used, it is necessary to include 950 patients in each arm, but if 50 items are used, only 450 are required in each arm. These results indicate that if an RCT is to be designed to detect small effects, it is inadvisable to use very short instruments analyzed using IRT. Finally, the SF-36, SF-12, and SF-8 instruments were considered in the same framework. Since these instruments consist of items scored in more than two categories, slightly different results were obtained.

Health Status↗

PubMedDate not supplied

Clinical use of the Hamilton Depression Rating Scale: is increased efficiency possible? A post hoc comparison of Hamilton Depression Rating Scale, Maier and Bech subscales, Clinical Global Impression, and Symptom Checklist-90 scores.

BACKGROUND: The 17-item Hamilton Depression Rating Scale (HDRS) is used as a semi-gold standard in research. In treatment guidelines, the HDRS measurements serve to determine response and remission and guide clinical decision making for nonresponders. However, its use in clinical practice is limited, possibly because the HDRS is time consuming. In addition, the multidimensional HDRS is criticized for not measuring a unidimensional aspect as depression severity. The Maier and the Bech, two 6-item severity subscales extracted from the HDRS, are relatively unknown. This paper investigates whether the measurements obtained with these subscales are comparable with the original HDRS measurements. METHODS: Data from 2 randomized controlled trials in 482 male and female patients, diagnosed with a major depression (with or without dysthymia) according to Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition, of whom 219 participated in the trials, were reanalyzed. A standardized stepwise psychopharmacological treatment was compared with a combination of pharmacotherapy with Short Psychodynamic Supportive Psychotherapy in a psychiatric outpatient department. Outcome measures were internal consistency and concurrent validity of HDRS, Maier, Bech, Clinical Global Impression scales, and Symptom Checklist depression subscale. Effect sizes of HDRS, Maier, and Bech were used to compare measured treatment effects for the randomized subjects participating in the trials. Item Response Theory was used to obtain conversion tables for the HDRS, Maier, Bech, and Symptom Checklist depression subscale. RESULTS: We found moderate internal consistency (Cronbach alpha approximately 0.6-0.7) and high correlations of the Maier and Bech subscales with overall HDRS scores. Overall, there were no clinically relevant differences in effect sizes between Maier, Bech, and HDRS, although some differences were statistically significant. Receiver operating characteristic curves showed no difference between Maier and Bech to define remission but showed the Clinical Global Impression ratings to be unreliable. A cutoff < or =4 corresponded with an HDRS < or =7 criterion in both subscales. CONCLUSION: In clinical practice, both Maier and Bech scales can be used as equivalents of the HDRS, but will be more efficient.

Adult↗