Balparda Kepa, Herrera-Chalarca Tatiana, Silva-Quintero Laura Andrea, Torres-Soto Sneider Alexander, Vanegas-Ramírez Claudia Marcela
Department of Cornea and Refractive Surgery, Black Mammoth Surgical, Medellín, Colombia.
Universidad de Valladolid, Valladolid, Spain.
Clin Ophthalmol. 2020 May 12;14:1287-1296. doi: 10.2147/OPTH.S254370. eCollection 2020.
Keratoconus is a disease characterized by progressive distortion of the corneal anatomy, coupled with a decrease in vision. Assessing quality of life (QoL) in keratoconus is essential. So far, no instrument in the world has been designed to evaluate both visual function and emotional distress in this population. The purpose of the following study is to develop and validate the "Keratoconus End-Points Assessment Questionnaire" (KEPAQ) in a population of ectatic patients, the very first disease-specific scale to measure emotional latent traits in keratoconus.
A last generation, Rasch analysis method was used for scale validation. First, a number of focus groups were carried out to create a pool of potential items. Then, a series of processes (such as "Content Validity Index") was carried out to develop a prior, 20-question version of the KEPAQ. Then, a study including 150 keratoconus patients was performed, followed by a careful Rasch analysis to validate and optimize both sub-scales (Emotional Compromise, KEPAQ-E, and Functional Compromise, KEPAQ-F).
Initially, 86 items were considered as potential elements. After test optimization, 20 items were retained. A total of 150 patients with a confirmed diagnosis of keratoconus were included for the Rasch analysis. The mean age was 29.84 ± 9.96 years. In 150 patients, 12.6% had a history of keratoplasty, 46.0% had corneal rings, and 31.3% had crosslinking. For both sub-scales, misfitting items were removed until no misfitting was determined by repetitive Rasch runs. For the final version of the KEPAQ-E sub-scale, variance explained by the model was 62.4% with a dimensional scale. Person Separation Index and Person Number of Strata were 2.43 and 3.57, respectively. For the final version of the KEPAQ-F sub-scale, variance explained by the model was 61.3% with a unidimensional scale. Person Separation Index and Person Number of Strata were 3.19 and 4.59, respectively. Both sub-scales showed excellent Person Reliability.
The KEPAQ is a robust scale, developed and validated through the latest theoretical models. It shows excellent psychometric properties, which render it extremely useful for both clinical and research use. To date, the KEPAQ is the only disease-specific scale worldwide to evaluate both functional and emotional compromise in keratoconus patients.
圆锥角膜是一种以角膜解剖结构逐渐变形并伴有视力下降为特征的疾病。评估圆锥角膜患者的生活质量（QoL）至关重要。到目前为止，世界上还没有一种工具被设计用于评估该人群的视觉功能和情绪困扰。以下研究的目的是在扩张性疾病患者群体中开发并验证“圆锥角膜终点评估问卷”（KEPAQ），这是首个用于测量圆锥角膜患者情绪潜在特征的疾病特异性量表。
采用最新一代的Rasch分析方法进行量表验证。首先，开展了多个焦点小组讨论以创建潜在项目池。然后，进行了一系列流程（如“内容效度指数”）来开发一个初步的、包含20个问题的KEPAQ版本。接着，开展了一项纳入150名圆锥角膜患者的研究，随后进行仔细的Rasch分析以验证和优化两个子量表（情绪妥协，KEPAQ-E，和功能妥协，KEPAQ-F）。
最初，86个项目被视为潜在元素。经过测试优化，保留了20个项目。总共150名确诊为圆锥角膜的患者被纳入Rasch分析。平均年龄为29.84±9.96岁。在150名患者中，12.6%有角膜移植史，46.0%有角膜环，31.3%有交联治疗史。对于两个子量表，不合适的项目都被剔除，直到通过重复的Rasch分析确定没有不合适的项目。对于KEPAQ-E子量表的最终版本，模型解释的方差为62.4%，具有维度量表。个人分离指数和个人分层数分别为2.43和3.57。对于KEPAQ-F子量表的最终版本，模型解释的方差为61.3%，具有单维度量表。个人分离指数和个人分层数分别为3.19和4.59。两个子量表均显示出出色的个人信度。
KEPAQ是一个强大的量表，通过最新的理论模型开发和验证。它显示出出色的心理测量特性，这使其在临床和研究应用中都极为有用。迄今为止，KEPAQ是全球唯一用于评估圆锥角膜患者功能和情绪妥协的疾病特异性量表。
