Toward the use of proxy reports for estimating long-term patient-reported outcomes in multiple sclerosis.

BACKGROUND: Assessment of disease impact in multiple sclerosis (MS) is usually driven by information obtained directly from patients using patient-reported outcomes. However, when patients' response in longitudinal studies is less reliable or missing, proxy respondents may be used. OBJECTIVE: The objective of this paper is to evaluate whether long-term patient scores can be reliably estimated using scores obtained from proxies. METHODS: Baseline, six-month and two-year data were collected from 155 patients and proxies on the physical scale of the Multiple Sclerosis Impact Scale (MSIS-29). Linear regression analyses were performed with the patient two-year scores as outcome, proxy two-year scores as predictor and other variables that could contribute to a better prediction of the patient follow-up score. RESULTS: The patient follow-up score could be predicted rather accurately (R(2) = 0.74) using the patient baseline score and the proxy follow-up score. The correlation between observed and predicted scores was 0.86. The model performed well in different follow-up durations and even better in an external cohort. CONCLUSION: A simple model of a constant value (intercept), the patient baseline score and the proxy follow-up score can predict patients' follow-up score on the physical impact of MS.

Do patient and proxy agree? Long-term changes in multiple sclerosis physical impact and walking ability on patient-reported outcome scales.

BACKGROUND: Patient-reported outcome scales (PROs) are useful in monitoring changes in multiple sclerosis (MS) over time. Although these scales are reliable and valid measures in longitudinal studies in MS patients, it is unknown what the impact is when obtaining longitudinal data from proxies. OBJECTIVE: The objective of this paper is to compare longitudinal changes in patient and proxy responses on PROs assessing physical impact of MS and walking ability. METHODS: In a prospective observational study, data on the Multiple Sclerosis Impact Scale (MSIS-29 physical) and Multiple Sclerosis Walking Scale (MSWS-12) were obtained from 137 patient-proxy couples at baseline and at two-year follow-up. Demographic and disease-related variables explaining agreement or disagreement between patients and proxies were investigated using linear regression analyses. RESULTS: Full agreement was found in 56% (MSIS) and 62% (MSWS) of the patient-proxy couples. Complete disagreement was very rare for both scales (2% MSIS, 5% MSWS). When patients were more positive than proxies, a higher age, longer disease duration, longer patient-proxy relationship and increased levels of depression, anxiety and caregiver burden in proxies were observed. CONCLUSION: In the majority of the patient-proxy couples there was agreement. Proxies can serve as a valuable source of information, but caution remains essential when using scores from proxies.

Analyzing differences between patient and proxy on Patient Reported Outcomes in multiple sclerosis.

BACKGROUND: Proxy respondents, partners of multiple sclerosis (MS) patients, can provide valuable information on the MS patients' disease. In an earlier publication we found relatively good agreement on patient reported outcomes (PROs) measuring physical impact and functioning, but we found large differences on (neuro)psychological scales. OBJECTIVE: We aim to identify patient and proxy related variables explaining differences between patients' and proxies' ratings on five PROs. METHODS: We report on data from 175 MS patients and proxy respondents. Regression analyses were performed, using as dependent variable the mean differences on five scales: Physical and Psychological scale of the Multiple Sclerosis Impact Scale (MSIS-29), the Multiple Sclerosis Walking Scale (MSWS), Guy's Neurological Disability Scale (GNDS) and the Multiple Sclerosis Neuropsychological Screening Questionnaire (MSNQ). The independent variables were patient, proxy and disease related variables. RESULTS: Caregiver strain was significantly related to differences between patient and proxy scores for all five PROs. A higher level of patient anxiety on the HADS was linked to larger differences on all PROs except the GNDS. In addition, cognitive functioning, proxy depression, walking ability, proxy gender and MS related disability were contributing to the discrepancies. CONCLUSION: We found several patient and proxy factors that may contribute to discrepancies between patient and proxy scores on MS PROs. The most important factor is caregiver burden.

Clinical scales in progressive MS: predicting long-term disability.

BACKGROUND: To determine which short-term changes on clinical scales including the Expanded Disability Status Scale (EDSS), Timed 25-Foot Walk (T25FW), 9-Hole Peg test (9HPT) and Guy's Neurological Disability Scale (GNDS) are most predictive of long-term outcome of disability as rated by the EDSS in progressive multiple sclerosis (MS). METHODS: From a longitudinal database, all progressive patients, both primary (PP) and secondary (SP), were selected on the basis of at least two complete examinations being available within a time interval of 1-2 years (short-term change). All patients who fulfilled the selection criteria were invited for a third visit after an interval of at least 3 years (long-term outcome). We used ordinal logistic regression to see which early changes were most predictive of the long-term EDSS. RESULTS: 181 patients fulfilled the selection criteria. Early change on EDSS and T25FW were the best predictors of long-term EDSS; both were significant predictors in a 'single predictor' model. Early EDSS change was a slightly stronger single predictor (R(2) 0.38, Wald χ(2) 42.65, p < 0.001) compared with early T25FW change (R(2) 0.27, Wald χ(2) 12.35, p < 0.001). Adding early T25FW change to early EDSS change in a 'combined predictor' model improved prediction (p = 0.036). CONCLUSION: Both early change on EDSS and T25FW predict long-term EDSS with comparable strength. Early change on T25FW adds significant independent information and improves the prediction model with early EDSS change only. Therefore we support the use of early T25FW examinations in future clinical trials in progressive MS.