Validity of the Neurology Quality-of-Life (Neuro-QoL) measurement system in adult epilepsy

Highlights

• We provide validation information on Neuro-QoL, a new health-related quality-of-life tool in epilepsy.

• We report on Neuro-QoL's internal consistency and test–retest reliability with a sample of adult patients diagnosed with epilepsy.

• We demonstrate Neuro-QoL's comparability to existing quality-of-life measures in adult epilepsy.

• We report on Neuro-QoL's ability to discern between known groups of seizure severity.

• We present information on the responsiveness of Neuro-QoL short forms over time.

Abstract

Epilepsy is a chronic neurological disorder that results in recurring seizures and can have a significant adverse effect on health-related quality of life (HRQL). The Neuro-QoL measurement initiative is an NINDS-funded system of patient-reported outcome measures for neurology clinical research, which was designed to provide a precise and standardized way to measure HRQL in epilepsy and other neurological disorders. Using mixed-method and item response theory-based approaches, we developed generic item banks and targeted scales for adults and children with major neurological disorders. This paper provides empirical results from a clinical validation study with a sample of adults diagnosed with epilepsy. One hundred twenty-one people diagnosed with epilepsy participated, the majority of which were male (62%) and Caucasian (95%), with a mean age of 47.3 (SD = 16.9). Baseline assessments included Neuro-QoL short forms and general and external validity measures. The Neuro-QoL short forms that are not typically found in other epilepsy-specific HRQL instruments include Stigma, Sleep Disturbance, Emotional and Behavioral Dyscontrol, and Positive Affect and Well-Being. Neurology Quality-of-Life short forms demonstrated adequate reliability (internal consistency range = .86–.96; test–retest range = .57–.89). Pearson correlations (p < .01) between Neuro-QoL forms of emotional distress (anxiety, depression, stigma) and the QOLIE-31 Emotional Well-Being subscale were in the moderate-to-strong range (r's = .66, .71 and .53, respectively), as were relations with the PROMIS Global Mental Health subscale (r's = .59, .74 and .52, respectively). Moderate correlations were observed between Neuro-QoL Social Role Performance and Satisfaction and the QOLIE-31 Social Function (r's = .58 and .52, respectively). In measuring aspects of physical function, the Neuro-QoL Mobility and Upper Extremity forms demonstrated moderate associations with the PROMIS Global Physical Function subscale (r's = .60 and .61, respectively). Neuro-QoL measures of perceived cognitive function (executive function and general concerns) produced moderate-to-strong correlations with the QOLIE-31 Cognition subscale (r's = .65 and .75, respectively) and moderate relations with the Liverpool Adverse Events Profile (r's = .51 and .69, respectively). Finally, the Neuro-QoL Fatigue measure demonstrated moderate associations with the QOLIE-31 Energy/Fatigue subscale (r = − .65), Liverpool Adverse Events Profile (r = .69), and the Liverpool Seizure Severity Scale (r = .50). Five Neuro-QoL short forms demonstrated statistically significant responsiveness to change at 5–7 months, including Fatigue, Sleep Disturbance, Depression, Positive Affect and Well-Being, and Emotional and Behavioral Dyscontrol. Overall, Neuro-QoL instruments showed good evidence for internal consistency, test–retest reliability, convergent validity, and responsiveness to change over several months. These results support the validity of Neuro-QoL to measure HRQL in adults with epilepsy.

Introduction

Epilepsy is a chronic neurological disorder that is characterized by recurrent, unprovoked seizures that are triggered by abnormal electrical discharges in the brain [1]. Once patients are diagnosed, they have several treatment options aimed at controlling seizures and reducing symptoms [2]. Although providing satisfactory seizure control is a primary goal, epilepsy's negative effect extends beyond the duration of individual seizures. Patients may also suffer from a host of cognitive, motor, and emotional changes that may result from the same brain disease that produces the seizures, which can significantly impact one's health-related quality of life (HRQL) [3], [4], [5], [6]. Additional issues facing persons with epilepsy include the risk of physical harm due to bone fracture, burns, drowning, and unexplained death, as well as risk from surgical intervention to control intractable seizure activity [5]. Medication side effects add to the challenges faced by patients and include sedation, nausea, double vision, tremor, and cognition and memory problems. Described as a social burden as well as a chronic illness, epilepsy also contributes to psychological concerns such as anxiety and fear of seizure occurrence and related social isolation as a result of stigmatization. Adults with epilepsy experience restricted driving privileges, higher rates of unemployment, and greater difficulty obtaining life or health insurance. Because of these long-term difficulties, HRQL assessment for persons with epilepsy requires attention to far more than the seizure event, medication side effects, or surgical intervention.

Instruments that were designed specifically to measure the HRQL of people that were diagnosed with epilepsy were not created until the 1980s [7]. Since then, there has been a growth in the development of HRQL measures that focus on epilepsy, its symptoms, and other aspects of treatment. One measure called the Performance, Subjective Evaluation and Socio-Demographic Data (PESOS) was created to measure epilepsy severity, HRQL, limitations in daily living, and psychosocial concerns. It is either self-administered or conducted through a face-to-face interview [8]. Another measure that is commonly used to measure HRQL of patients with epilepsy is the Quality of Life in Epilepsy (QOLIE-89) which has 31- and 10-item versions [9], [10]. It measures several domains including global HRQL, emotional well-being, energy–fatigue, seizure worry, medication effects, health status, and cognitive and social function. Other commonly used epilepsy-specific HRQL measures include the Well-Being Scale [11], the Liverpool Quality-of-Life Battery [12], the Quality-of-Life Assessment Schedule [13], and the Epilepsy Surgery Inventory [14].

The abundance of different generic and targeted HRQL measures that exist not only for epilepsy [15] but also for most major neurological diseases [16], [17], [18], [19], [20], [21], [22] has resulted in numerous clinical trials that lack the ability to be compared in a standardized manner. To address this, in 2005, the National Institute for Neurological Disorders and Stroke (NINDS) commissioned the creation of a new patient-reported outcomes measurement system for neurological disorders called “Neuro-QoL” [23]. Neurological Quality of Life was developed parallel to the NIH Patient-Reported Outcomes Measurement Information System (PROMIS) [24], [25], employing the same rigorous instrument-development guidelines and methodologies [26] and sharing common items with PROMIS item banks. Both PROMIS and Neuro-QoL employed item response theory (IRT) modeling [27] thereby enabling unique flexibility regarding item selection and use (e.g., use of Neuro-QoL-recommended short forms or the creation of trial-specific tailored forms), administration of items (use of static short forms or dynamic computerized adaptive tests), and deeper understanding of item information (e.g., ability to evaluate each item's information function, performance, and location along a given trait's severity continuum). The comprehensive development and initial calibration testing results of Neuro-QoL have been described previously [23], [28], [29], [30] and are beyond the scope of this clinical validation paper. The purpose of this paper is to report on the multisite validation testing results of Neuro-QoL short forms that have resulted from this work with a clinical sample of adult patients with epilepsy.