The researchers systematically and efficiently developed a novel instrument system for chronic diseases known as QLICDs. This system combines a general module with a specific module tailored for individual diseases, establishing the modular approach of Disease-Qol instruments. The general module QLICD-GM can be applied to a wide range of chronic diseases. This modular approach integrates disease-specific instruments and a general module into a single scale. For example, the general module QLICD-GM can capture the overall quality of life of patients with various diseases, such as SLE and chronic gastritis (CG), while the disease-specific module QLICD-SLE captures the quality of life facets specific to SLE.
The initial phases of the study led to the development of the general module QLICD-GM, which has subsequently demonstrated reliability, validity, and responsiveness [34]. In this study, the specific module of the quality of life assessment tool designed for patients with Systemic Lupus Erythematosus (SLE) was systematically formulated. This module was constructed with a focus on various dimensions (facets), including skin and mucosal symptoms (SMS), respiratory/circulation symptoms (RCS), urinary symptoms (URS), other symptoms (OTS), special mentation (SPM), and treatment side effects (TSE). Consequently, a novel and comprehensive quality of life scale tailored to SLE patients emerged, achieved by amalgamating this specific module with the pre-existing general module known as QLICD-GM.
QLICD-SLE is the first instrument developed for quality of life in patients with systemic lupus erythematosus in China. Unlike the WHOQOL and SF-36 of two general Qol instruments, the advantage of the QLICD-SLE is that it contains disease- specific items and domains, which will provide SLE-specific information regarding patients’ perceived health status.
Furthermore, QLICD-SLE distinguishes itself from existing SLE-specific instruments, such as SLE-Qol, L-Qol, and LupusQol. SLE-Qol primarily uses a 7-point Likert scale, whereas QLICD-SLE (2.0) uses a 5-point Likert scale. While SLEQOL focuses on assessing SLE-specific Health-Related Quality of Life (HRQOL), some of its domains provide a less comprehensive assessment, leaning more towards serving as health status indicators. L-QoL, utilizing the one-parameter Rasch model, is unidimensional with good item stability and minimal Differential Item Functioning (DIF), but it falls short in providing a comprehensive measurement of specific symptoms related to SLE and cannot be used for comparing various diseases [16].
All three instruments have been validated for English-speaking patients in various cultural contexts: SLEQOL for the Singaporean Chinese population, LupusQol for predominantly White British individuals, and L-QoL for populations primarily from Northern England and London. In contrast, QLICD-SLE (2.0) was primarily developed and validated for Chinese patients with systemic lupus erythematosus.
The content of QLICD-SLE is the result of specialist expertise and patient input. It consists of a moderate number of items with a clear hierarchy (item → facet → domain → overall), allowing for score analysis at different levels, including six facets, to detect detailed changes in patients. As a result, QLICD-SLE differs from existing lupus erythematosus quality of life instrument systems.
In terms of reliability, validity, and responsiveness, a practical clinical scale should exhibit high stability, accuracy, and sensitivity [35]. The present study adheres to the World Health Organization’s (WHO) definition of quality of life (WHO, 1995; WHOQOL Group, 1998) and employed pre-programmed decision-making procedures, focus group discussions, in-depth interviews, and pre-tests to construct the QLICD-SLE patient scale. These efforts effectively reduced the number of items in the final scale from an initial 65 in the universal module to 28, and from an initial 44 items in a specific module to 19, thereby preserving the scale’s content validity and the integrity of its conceptual structure.
Structural validity refers to the degree of correlation between the theoretical scale structure conceived by the researcher and the scale structure established by the survey results [36]. In this research, the structural validity of the scale was primarily evaluated through item-domain correlation analysis and exploratory factor analysis (EFA). The findings show that the inter-group correlation coefficient falls between 0.1 and 0.6, while the correlation coefficient between items and their respective domains and the total item score and total scale score range from 0.3 to 0.8, indicating good reliability and responsiveness [37].
The correlation analysis in this research reveals that items in each domain have a high correlation with their respective domains but a low correlation with different domains, indicating good structural validity. Additionally, EFA was used to further assess the structural validity of QLICD-SLE. The results indicate that nine and six principal components were extracted from the 28 items of QLICD-GM and 19 items of QLICD-SLE, respectively, consistent with previous studies [38, 39]. The nine principal components reflect the nine facets of QLICD-GM within the three domains, while the six principal components correspond to six facets of the specific domain of QLICD-SLE. Therefore, the EFA results suggest that QLICD-SLE has a well-structured design.
Reliability refers to the repeatability or consistency of item scores from one assessment to another [40]. In this research, reliability was primarily assessed using retest reliability (Pearson’s r), internal consistency reliability (Cronbach’s α coefficients), and ICC. In terms of retest reliability, if the health status of SLE patients remains relatively stable over a certain period, the difference in quality of life retest scores should not be statistically significant after analysis. The first measurement was conducted on the first day of admission, and the second on the second day of admission. The correlation coefficients between the two assessments for each domain reflected the consistency in the change trend of quality of life within each domain. Higher correlation coefficients indicated better retest reliability. In this research, the retest correlation coefficients (> 0.7) for all domains of the QLICD-SLE scale were high, indicating excellent retest reliability. As for internal consistency reliability, Cronbach’s α coefficient ranges from 0 to 1, with higher values indicating greater scale reliability. In this study, the Cronbach’s α coefficient (> 0.7) for all areas of the QLICD-SLE scale was high, signifying strong reliability.
The responsiveness of a scale refers to its ability to detect changes in patients’ quality of life over time due to treatments and other factors, which should be distinguished from the scale’s discriminative ability [41]. In this study, responsiveness was primarily assessed using the paired T-test for the first and second measurements (before and after treatment) across all areas of the scale, specific module facets, and the overall scale scores in SLE patients. The standardized response mean (SRM) was calculated to gauge the magnitude of effect, with values around 0.20, 0.50, and 0.80 representing small, moderate, and large responsiveness, respectively [42]. The paired T-test conducted using the QLICD-SLE scale before and after a treatment period revealed statistically significant differences in physical function, energy discomfort, social function, interpersonal communication, and urinary symptoms. This indicates a positive treatment response in these domains. However, the study found that the SRM for physiological, psychological, social function, and the specific module of the scale were all low (0.00 ~ 0.12). This may be attributed to several factors. As a chronic autoimmune disease, patients with SLE often have short hospital stays, during which they are unable to participate in regular social activities. Moreover, changes in specific modules before and after short-term treatments are not expected to be significant. Additionally, various factors can influence patients’ social function, making it challenging to observe substantial changes within a brief hospitalization period.
This tool stands out as a result of its focus on Systemic Lupus Erythematosus (SLE) research conducted among non-English-speaking patients in non-English-speaking countries. More significantly, QLICD-SLE takes into account the profound influence of Chinese culture on the treatment of systemic lupus erythematosus. Chinese culture places strong emphasis on family and kinship relationships, dietary practices, temperament, and spirituality. QLICD-SLE delves into various facets of this cultural heritage, including appetite, sleep, energy, and family support.
Several limitations are noteworthy in this study. Firstly, the subjects were exclusively selected from hospital inpatients, which potentially introduce selection bias. Secondly, while the QLICD-SLE(V2.0) scale has been developed and evaluated within the context of Chinese culture and population, further investigations are necessary to assess its applicability among outpatients in local clinics and patients from other East Asian countries. Lastly, it’s important to acknowledge that the assessment of the quality of life in SLE patients relied on conventional psychometric principles rather than clinimetric criteria [43], underscoring the imperative for future research dedicated to evaluating the clinimetric properties of this rating scale [44].
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