Defining the Minimum Level of Detectable Change for the Roland-Morris Questionnaire

Defining the Minimum Level of Detectable Change for the RolandMorris Questionnaire self-administered disability measure in which greater levels of disability are reflected by higher numbers on a 24point scale. The RMQ has been shown to yield reliable measurements, which are valid for inferring the level of disability, and to be sensitive to change over time for groups of patients with low back pain. Little is known about the usefulness of this instrument in aiding decision making regarding individual patients. The purpose of this study was to determine the minimum level of detectable change when the RMQ is applied to individual patients. Subjects. The study sample consisted of 60 outpatients with low back pain. Methods. The RMQ was administered at the subjects' initial visit and again 4 to 6 weeks later. Conditional standard errors of measurement (CSEMs) were computed for initial and follow-up RMQ scores, and these values were used to estimate the minimum level of detectable change. Results. Minimum levels of detectable change at the 90% confidence level varied from 4 to 5 RMQ points. Conclusion and Discussion. The magnitude of CSEMs is sufficiently small to detect change in patients with initial scores in the central portion of the scale (4-20 RMQ points); however, the magnitude is too large to detect improvement in patients with scores of less than 4 and deterioration in patients who have scores greater than 20. [Stratford PW, Binkley J, Solomon P, et al. Defining the minimum level of detectable change for the Roland-Morris Questionnaire. Phys Ther. 1996;76:359-365.1 Key Words: Backache, Disability, Evaluation, Outcome. Paul W Straford Jill Binkley Patricia Solomon Elspeth Finch Caroline Gill Julie Moreland Physical Therapy . Volume 76 . Number 4 . April 1996 Background and Purpose. The Roland-Morris Questionnaire (RMQ is a The RMQ was selected because its measurement properties have been shown to be equal to or better than those of similar measures used to assess change in disability in patients with LBP.l-l5 In Table 1, we provide a brief summary of the more frequently used and researched measures. The RMQ is a self-administered questionnaire consisting of 24 items chosen from the Sickness Impact Profile (SIP).IfiItems were chosen to reflect a variety of activities of daily living. To improve the specificity of the response, Roland and Morris1 added the phrase "because of my back" to each item. An item receives a score of 1 if it is checked as applicable by the respondent and a score of 0 if it is not marked. Accordingly, total scores can vary from 0 (no disability) to 24 (severe disability). Research of the RMQ's measurement properties has provided consistent estimates of internal consistency, test-retest reliability (accounting for the interval between assessments), construct validity, and sensitivity-to-changecoefficients. The term "sensitivity to change" describes a measure's ability to assess change over time. One strategy for assessing and reporting change over time, reported in Table 1, is the receiver operating characteristic (ROC) curve.15 With this technique, sensitivity (y-axis) is plotted against l-specificity (x-axis). When assessing change over time, sensitivity is defined as the number of patients correctly identified (by a given questionnaire) as having undergone a clinically important change divided by all patients who truly underwent a clinically important change. Specijcity refers to the number of patients who were correctly identified (by a given questionnaire) as not undergoing a clinically important change divided by all patients who truly did not undergo a clinically important change. The greater the area under the curve, the greater a questionnaire's ability to distinguish patients who did and did not undergo a clinically important change. The area under the curve can be interpreted as the probability of correctly identifying a patient who has undergone a clinically important change from randomly selected pairs of patients who have and have not undergone an important change. PW Stratford, MSc, PT, is Assistant Professor, Faculty of Health Sciences, School of Rehabilitation Science, McMaster University, Bldg Tl6, 1280 Main St W, Hamilton, Ontario, Canada L8S 4K1 (stratforOmcmaster.ca). Address all correspondence to Mr Stratford. J Binkley, MClSc, PT, COMP, is Director of Research, Rehab Management Systems, D.ahlonega, G.4 30597. She was an orthopedic clinical specialist and Assistant Professor, Department of Physical Therapy, North Georgia College, Dahlonega, GA 30597, at the time of this study. P Solo~non,PhD, PT, is Assistant Professor, Faculty of Health Sciences, School of Rehabilitation Science, McMaster Univrrsity. E Finch, MHSc, PT, is Assistallt Professor, Faclllty of Health Sciences, School of Rehabilitation Science, McMaster Univrrsity. (: Gill, PT, is Senior Physiotherapist-Orthopaedics, StJoseph s Hospital, Hamilton, Ontario, Canada. J Morcland, MSc, ET, is Research Therapist, St Joseph's Hospital and St Peter's Hospital, and Assistant Clinical Professor, Faculty of Health Sciences, School of Rehabilitation Science, McMaster University. This study was approved by t l ~ rEthics Committee of' St Joseph's Hospital. 7x2s nrlztk runs \uhmztt~dF ~ h n ~ n9,9 1995, ond 7oar arrpptpd Novrmbui 28, 1995 360 . Stratford et al Physical Therapy . Volume 76 . Number 4 . April 1996 hysical therapists regularly use measurements (eg, of range of motion, pain, or disability) to determine whether a patient's status has changed over time. Often, when the results differ from one assessment to the next, therapists assume patients have undergone true change. Unfortunately, some or all of the difference between assessments can occur as a result of measurement error, including random fluctuation in patients who may or may not have truly changed. A patient who at the initial assessment scores 14 out of a possible 24 points on a particular disability questionnaire and 4 weeks later scores 10 points may appear to have undergone change. The 4point difference may represent true change, or it could fall within the limits of measurement error and inherent variability in a truly unchanged patient. The importance of this issue is underscored when the management options available to therapists are considered. For example, therapists who view the difference in scores as representing true change may elect to continue with an intervention. Therapists who consider the 4point change to be within the limits of measurement error, however, may choose to alter the intervention in hopes of selecting a treatment that is more effective. The goal of this report is to provide clinicians with guidelines for assessing change over time when they use the RolandMorris Questionnaire (RMQ '22 to assess disability in patients with low back pain (LBP). Table 1. Summary of Measurement Properties of Several Measures Used to Assess Patients With Low Back Paino Reliability I (...truncated)