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Biomedical subjects

Karon F Cook

Publications and source records attributed to Karon F Cook.

16 recordsLinked to original sources
PubMed2006

A 37-item shoulder functional status item pool had negligible differential item functioning.

OBJECTIVE: Measures of shoulder function may differ by dominance of affected shoulder, surgical history, gender, or race. We present a technique for determining whether observed differences in function between groups are due to biased test items or real differences in function. STUDY DESIGN AND SETTING: Four hundred patients who were receiving rehabilitation for a variety of shoulder impairments completed a survey of shoulder function. Thirty-seven items measuring shoulder function were analyzed for differential item functioning (DIF) related to demographic characteristics using an ordinal logistic regression (OLR) and item response theory (IRT) approach. When DIF was identified in an item, we modified the IRT analysis to calibrate item parameters separately in appropriate demographic groups. We compared adjusted and unadjusted patient ability measures in each demographic group. RESULTS: Several items were found to have a modest amount of DIF related to the different demographic characteristics, especially gender; however, adjusting measures for DIF had little impact on overall measures of shoulder function and made almost no difference in average shoulder function across demographic groups. CONCLUSION: In this pool of shoulder function items, adjustment for DIF made almost no difference in measures of function across demographic groups.

Activities of Daily Living↗
PubMed2006

The John Insall Award: Patient expectations affect satisfaction with total knee arthroplasty.

Satisfaction with the outcome of total knee arthroplasty is highly variable, with a small but significant percentage of patients reporting dissatisfaction with the procedure. The purpose of this study was to determine which factors contribute to patient satisfaction with total knee replacement (TKR), and their relative importance. At a minimum of 1 year post unilateral primary TKR, 253 patients completed a self-administered, validated "Knee Function Questionnaire," which examined each patient's participation in a broad range of activities involving the knee, their level of satisfaction, and the extent to which TKR had fulfilled their expectations. The association between function, expectation and satisfaction was examined using univariate and multivariate logistic regression. Seventy-five percent of patients were either "satisfied" or "very satisfied" with their knee replacement, while 14% were "dissatisfied" or "very dissatisfied." Satisfaction correlated significantly (p < 0.001) with age less than 60, absence of residual symptoms, fulfillment of expectations, and absence of functional impairment. Satisfaction with TKR is primarily determined by patients' expectations, and not their absolute level of function. Real improvements in the outcome of TKA must address prevention of residual pain, stiffness and swelling, and each patient's preoperative concept of the likely outcome of these procedures.

Adult↗
PubMed2005

Simulated computerized adaptive test for patients with shoulder impairments was efficient and produced valid measures of function.

BACKGROUND AND OBJECTIVE: To test unidimensionality and local independence of a set of shoulder functional status (SFS) items, develop a computerized adaptive test (CAT) of the items using a rating scale item response theory model (RSM), and compare discriminant validity of measures generated using all items (theta(IRT)) and measures generated using the simulated CAT (theta(CAT)). STUDY DESIGN AND SETTING: We performed a secondary analysis of data collected prospectively during rehabilitation of 400 patients with shoulder impairments who completed 60 SFS items. RESULTS: Factor analytic techniques supported that the 42 SFS items formed a unidimensional scale and were locally independent. Except for five items, which were deleted, the RSM fit the data well. The remaining 37 SFS items were used to generate the CAT. On average, 6 items were needed to estimate precise measures of function using the SFS CAT, compared with all 37 SFS items. The theta(IRT) and theta(CAT) measures were highly correlated (r = .96) and resulted in similar classifications of patients. CONCLUSION: The simulated SFS CAT was efficient and produced precise, clinically relevant measures of functional status with good discriminating ability.

Activities of Daily Living↗
PubMed2005

Proxy reports in Parkinson's disease: caregiver and patient self-reports of quality of life and physical activity.

We evaluated patient-proxy agreement in a population of veterans with Parkinson's disease and compared levels of agreement by patient subgroups. Patient and caregiver pairs completed questionnaires composed of standard measures and additional demographic and activity questions. Participants completed the Center for Epidemiologic Studies Depression Scale (CES-D), the PD Questionnaire 39 (PDQ-39), and three questions regarding physical activity. Caregivers completed proxy forms of the PDQ-39 and the physical activity questionnaire. The proxy forms asked caregivers to choose the answers that best described their "friend's/patient's situation." The results of our comparison of patient and proxy reports of quality of life were consistent with findings in other diseases. On average, proxies rated patient disability higher and quality of life lower than did patients. However, our comparison of patient and proxy reports of frequency of exercise diverged from previously published work. Less agreement was observed between patient and proxy reports of physical activity, even though this is a more objective variable than are the domains measured by the PDQ-39. Proxy reports may diverge appreciably from patient self-reports. These differences should be considered in research design and clinical decision making. Alternative approaches to the measurement of patient relevant outcomes could supplement traditional, retrospective self-reports.

Aged↗
PubMed2005

Measuring diagnoses: ICD code accuracy.

OBJECTIVE: To examine potential sources of errors at each step of the described inpatient International Classification of Diseases (ICD) coding process. DATA SOURCES/STUDY SETTING: The use of disease codes from the ICD has expanded from classifying morbidity and mortality information for statistical purposes to diverse sets of applications in research, health care policy, and health care finance. By describing a brief history of ICD coding, detailing the process for assigning codes, identifying where errors can be introduced into the process, and reviewing methods for examining code accuracy, we help code users more systematically evaluate code accuracy for their particular applications. STUDY DESIGN/METHODS: We summarize the inpatient ICD diagnostic coding process from patient admission to diagnostic code assignment. We examine potential sources of errors at each step and offer code users a tool for systematically evaluating code accuracy. PRINCIPLE FINDINGS: Main error sources along the "patient trajectory" include amount and quality of information at admission, communication among patients and providers, the clinician's knowledge and experience with the illness, and the clinician's attention to detail. Main error sources along the "paper trail" include variance in the electronic and written records, coder training and experience, facility quality-control efforts, and unintentional and intentional coder errors, such as misspecification, unbundling, and upcoding. CONCLUSIONS: By clearly specifying the code assignment process and heightening their awareness of potential error sources, code users can better evaluate the applicability and limitations of codes for their particular situations. ICD codes can then be used in the most appropriate ways.

Data Collection↗
PubMed2005

Dynamic assessment of health outcomes: time to let the CAT out of the bag?

BACKGROUND: The use of item response theory (IRT) to measure self-reported outcomes has burgeoned in recent years. Perhaps the most important application of IRT is computer-adaptive testing (CAT), a measurement approach in which the selection of items is tailored for each respondent. OBJECTIVE: To provide an introduction to the use of CAT in the measurement of health outcomes, describe several IRT models that can be used as the basis of CAT, and discuss practical issues associated with the use of adaptive scaling in research settings. PRINCIPAL POINTS: The development of a CAT requires several steps that are not required in the development of a traditional measure including identification of "starting" and "stopping" rules. CAT's most attractive advantage is its efficiency. Greater measurement precision can be achieved with fewer items. Disadvantages of CAT include the high cost and level of technical expertise required to develop a CAT. CONCLUSIONS: Researchers, clinicians, and patients benefit from the availability of psychometrically rigorous measures that are not burdensome. CAT outcome measures hold substantial promise in this regard, but their development is not without challenges.

Health Services Research↗
PubMed2005

Proxies and other external raters: methodological considerations.

OBJECTIVE: The purpose of this paper is to introduce researchers to the measurement and subsequent analysis considerations involved when using externally rated data. We will define and describe two categories of externally rated data, recommend methodological approaches for analyzing and interpreting data in these two categories, and explore factors affecting agreement between self-rated and externally rated reports. We conclude with a discussion of needs for future research. DATA SOURCES/STUDY SETTING: Data sources for this paper are previous published studies and reviews comparing self-rated with externally rated data. STUDY DESIGN/DATA COLLECTION/EXTRACTION METHODS: This is a psychometric conceptual paper. PRINCIPAL FINDINGS: We define two types of externally rated data: proxy data and other-rated data. Proxy data refer to those collected from someone who speaks for a patient who cannot, will not, or is unavailable to speak for him or herself, whereas we use the term other-rater data to refer to situations in which the researcher collects ratings from a person other than the patient to gain multiple perspectives on the assessed construct. These two types of data differ in the way the measurement model is defined, the definition of the gold standard against which the measurements are validated, the analysis strategies appropriately used, and how the analyses are interpreted. There are many factors affecting the discrepancies between self- and external ratings, including characteristics of the patient, the proxy, and of the rated construct. Several psychological theories can be helpful in predicting such discrepancies. CONCLUSIONS: Externally rated data have an important place in health services research, but use of such data requires careful consideration of the nature of the data and how it will be analyzed and interpreted.

Data Collection↗
PubMed2005

Prevalence and treatment of depression in Parkinson's disease.

Parkinson's disease (PD) is a progressive neurological condition with debilitating symptoms, and depression is a common comorbid condition of this disease. The authors review existing literature on the prevalence and treatment of depression in PD. Prevalence estimates of depression vary widely, ranging from 7%-76%. This variation is due to inconsistent methodology. Treatment options for depression in PD include medication therapy, electroconvulsive therapy (ECT), and psychotherapy. There are few randomized controlled trials of these treatment options. The authors argue for more systematic and controlled research examining both the prevalence and treatment of depression in PD.

Depression↗
PubMed2004

Outcome expectancies, functional outcomes, and expectancy fulfillment for patients with shoulder problems.

OBJECTIVES: This study was conducted to evaluate the relationship among patient outcome expectancies, perceived shoulder function changes, and perceptions of expectancy fulfillment. METHODS: Patients (n = 199) treated for shoulder problems at one orthopedic surgeon's office completed a baseline survey comprised of measures of outcome expectancies, shoulder function, health status, and demographics. At 1 month, 2 months, and 3 months, patients completed a mailed follow-up survey comprised of all baseline measures except demographic variables. At 3 months, a measure of expectancy fulfillment was added. A general linear modeling approach was used to assess the significance and effect size of 1) outcome expectancies on changes in shoulder function; and (2) outcome expectancies, shoulder function changes, and their interaction on perceptions of expectancy fulfillment. RESULTS: Outcome expectancies significantly predicted changes in shoulder function and accounted for 10% of the variance in functional improvement. The improvement difference between patients with high expectancies compared with those with low expectancies was clinically relevant (4.57 points), as it was greater than the minimal clinically important difference (3.02 points). Outcome expectancies and shoulder function changes significantly predicted patients' perceptions of fulfilled expectancies, but their interaction was not statistically significant. CONCLUSIONS: Results highlight the importance of patient expectancy in medical encounters. The findings suggest the need for interventions targeting patient expectancies such as including discussions about expectancy in patient-physician negotiations of therapeutic plans. Results also underscore the need for the development of better measures of outcome expectancies and expectancy fulfillment.

Adolescent↗
PubMed2003

Development and psychometric evaluation of the Flexilevel Scale of Shoulder Function.

BACKGROUND: Existing measures of self-reported shoulder function fail to measure effectively the full range of shoulder functioning. The classic approach for improving the reliability of a scale is adding items, but a scale with a substantial number of items imposes a large response burden on participants. A more efficient approach is to use modern psychometric methods to construct an adaptive scale in which patients respond only to items that are targeted at their level of shoulder function. METHODS: We developed a Flexilevel Scale of Shoulder Function (FLEX-SF). This scale includes three testlets that target low, medium, and high shoulder function. Scores on the testlets were equated to a common mathematical metric. DESIGN AND SUBJECTS: We developed an initial pool of 68 items. This pool was administered to 400 patients, and responses were calibrated using a rating scale model. Subsets of items were identified for an easy, medium difficulty, and hard testlet. Properties of the scale were evaluated in a 3-month longitudinal study of 200 shoulder patients. RESULTS: The FLEX-SF exhibited high reliability at both the scale level (intraclass correlation coefficient [3,1] = 0.90) and specific trait levels. The validity of the FLEX-SF was supported by its internal and external responsiveness (Guyatt responsiveness index = 1.12) and the pattern of its associations with other health status measures. CONCLUSIONS: The FLEX-SF can be used as a primary endpoint in clinical trials even when there are relatively few people in each treatment group. The scale also has excellent properties for use in clinical settings tracking individual changes over time.

Adult↗
PubMed2002

What functional activities are important to patients with knee replacements?

There is interest in quantifying the patient's function and mobility after joint replacement. The current study identified activities important to patients having total knee replacement and the prevalence of limitations to participation in these activities. A Total Knee Function Questionnaire consisting of 55 questions addressing the patient's participation in various activities was developed, validated, and mailed to 367 patients at least 1 year after knee replacement. Patients were asked the frequency with which they did each activity, the activity's importance to them, and the extent to which their participation was limited by their knee replacement. The questionnaire was returned by 176 patients, 40% men and 60% women, with an average age of 70.5 years. The most prevalent activities were stretching exercises (73%), leg strengthening exercises (70%), kneeling (58%), and gardening (57%). The activities most important to the patients were stretching exercises (56%), kneeling (52%), and gardening (50%); those most difficult were squatting (75%), kneeling (72%), and gardening (54%). The current study showed a high correlation between the importance of activities and frequency of patient participation confirming that knee replacement successfully restores a significant degree of function. However, after knee replacement, improvements in knee function still are needed to allow patients to do all activities that they consider important.

Activities of Daily Living↗
PubMed2002

A randomized controlled trial comparing 2 instructional approaches to home exercise instruction following arthroscopic full-thickness rotator cuff repair surgery.

STUDY DESIGN: A prospective unblinded randomized clinical trial. OBJECTIVES: To compare the effectiveness of 2 types of home program instruction, videotape versus personal instruction by a physical therapist, on subjective outcomes and exercise compliance following arthroscopic repair of a full-thickness rotator cuff tear. BACKGROUND: Advances in orthopedic surgery and rehabilitation have placed increased emphasis on home exercise programs. Therefore, assessing the effectiveness of different methods of home program instruction is important. METHODS AND MEASURES: Patients who consented to undergo surgical repair were randomly assigned to either a videotape or personal instruction group. A self-reported compliance log categorized subjects as fully compliant, partially compliant, or noncompliant. The Shoulder Pain and Disability Index and the University of Pennsylvania Shoulder Scale scores were obtained from subjects preoperatively and at 12, 24, and 52 weeks postoperatively. The null hypotheses that neither group would have better outcomes as measured by 2 shoulder outcome scales at any level of compliance over 4 levels of time, were assessed by 2 separate 2x3x4 multiple analyses of variances (MANOVAs), 1 for each outcome measure (alpha = 0.025). RESULTS: Neither MANOVA was significant and the null hypotheses were not rejected. The main effect of time (number of weeks postsurgery) was significant across all time intervals for both outcome measures (P < 0.0005). CONCLUSIONS: With a therapist available for questions, patients who utilized the videotape method for their home program instruction had self-reported outcomes equal to patients instructed in their home program personally by a physical therapist. Self-reported compliance with the rehabilitation program had little effect on the outcomes.

Adult↗
PubMed2002

Reliability by surgical status of self-reported outcomes in patients who have shoulder pathologies.

STUDY DESIGN: A test-retest design was used to evaluate the reliability of the self-report sections of 4 shoulder pain and disability scales. OBJECTIVE: The objective of the study was to compare interitem consistency and test-retest reliability by surgical status (postoperative versus nonoperative) and to evaluate the effect of surgical status in the prediction of retest scores. BACKGROUND: Patients and healthcare providers evaluate shoulder status based on self-evaluations of pain and disability. Shoulder outcome measures have been developed that include self-reports, but the properties of these measures have not been assessed by surgical status. METHODS AND MEASURES: A questionnaire containing self-report sections of 4 shoulder scales was administered to study participants twice with 1 week between administrations. The outcome measures examined were the: (1) University of California at Los Angeles (UCLA) Shoulder Score; (2) Constant-Murley Scale (CMS); (3) American Shoulder and Elbow Society (ASES) Shoulder Index; and (4) Shoulder Pain and Disability Index (SPADI). Intraclass correlation coefficients (ICC) were calculated to estimate the test-retest reliability of each of the scales and subscales. The interitem consistencies of the multi-item subscales were assessed using Cronbach's alpha. The effect of surgical status on shoulder outcome scale reliability was evaluated using a general linear models approach. RESULTS: The interitem consistency estimates for the multi-item scales were high with both operative and nonoperative participants (0.88 to 0.96). With the exception of the satisfaction subscale of the UCLA Shoulder Score for the nonsurgical group, the estimated intraclass coefficients ranged from 0.51 to 0.91. The prediction of UCLA-satisfaction and ASES-disability, pain, and total retest scores was improved with the addition of surgical status into a regression model. CONCLUSIONS: The examined scales exhibited good internal consistency across surgical status. The postsurgical sample's reproducibility estimates tended to be higher than those of the nonsurgical sample. Reliability of shoulder outcome scales can be affected by patient surgical status.

Adult↗
PubMedDate not supplied

The relationship among strength and mobility measures and self-report outcome scores in persons after rotator cuff repair surgery: impairment measures are not enough.

In the past, measures of active range of motion and strength testing were deemed sufficient to "prove" the efficacy of treatment interventions. In the current outcomes milieu, however, the focus has shifted to patient-centered assessment (ie, patients' ability to perform activities that are personally relevant). We report results from a study with patients in the private practice of a shoulder surgeon. In this study we evaluated the relationship between impairment measures and scores from several shoulder outcome scales. In addition, we examined transcripts of interviews with shoulder patients regarding the impact of shoulder problems on their lives. One hundred eight persons participated in a randomized trial of home exercise instruction after arthroscopic repair of rotator cuff tears. Two impairment measures were used-strength estimates obtained by use of a Nicholas electronic dynamometer and range of motion in the standing position. Self- reported outcomes were measured by use of the Shoulder Pain and Disability Index (SPADI) and the University of Pennsylvania (UPenn) Shoulder Scale. Pearson correlation coefficients were calculated to estimate the associations between scores on impairment measures and self-report measures. R 2 values were calculated to estimate the proportion of variance shared by impairment and self-report scores. We found that the linear relationship between impairment scores and patient-reported outcomes was quite low, explaining as little as 8% of the total variance. Qualitative analysis of patient interviews suggests that patients distinguish between their impairment and their status on personally relevant outcomes. Future research should evaluate the nature of patient judgments of shoulder health outcomes.

Exercise Therapy↗
PubMedDate not supplied

Development of a Flexilevel Scale for use with computer-adaptive testing for assessing shoulder function.

In a 5-year study, a self-report measure of shoulder function-the Flexilevel Scale of Shoulder Function (FLEX-SF)-was developed by use of item response theory. A large pool of candidate items (N = 68) was developed. A questionnaire that included the 68 items, another scale of shoulder function, and clinical and demographic questions were administered to 400 persons with shoulder complaints. Patients' responses to the 68 items were calibrated by use of Andrich's rating scale model. Thirty-three items were selected from the pool and subdivided into three overlapping testlets targeting low, medium, and high shoulder function. A table translates raw scores on testlets to a common mathematical metric. The validity and reliability of the FLEX-SF was evaluated in a longitudinal study of 199 patients. The FLEX-SF scores were highly reliable and exhibited excellent validity (including responsiveness). We report on a simulation of a computer-adaptive test of shoulder function. This simulation is based on the developmental items we tested for use in the FLEX-SF. The results indicate that greater measurement efficiency can be achieved with a computer-adaptive test format.

Computer Simulation↗