Illness Experiences of Chilean Women With Sjögren's Syndrome: The Patient Perspective

Researchers in rheumatology should avoid categorization of continuous predictor variables

BACKGROUND

Rheumatology researchers often categorize continuous predictor variables. We aimed to show how this practice may alter results from observational studies in rheumatology.

METHODS

We conducted and compared the results of two analyses of the association between our predictor variable (percentage change in body mass index [BMI] from baseline to four years) and two outcome variable domains of structure and pain in knee and hip osteoarthritis. These two outcome variable domains covered 26 different outcomes for knee and hip combined. In the first analysis (categorical analysis), percentage change in BMI was categorized as ≥ 5% decrease in BMI, < 5% change in BMI, and ≥ 5% increase in BMI, while in the second analysis (continuous analysis), it was left as a continuous variable. In both analyses (categorical and continuous), we used generalized estimating equations with a logistic link function to investigate the association between the percentage change in BMI and the outcomes.

RESULTS

For eight of the 26 investigated outcomes (31%), the results from the categorical analyses were different from the results from the continuous analyses. These differences were of three types: 1) for six of these eight outcomes, while the continuous analyses revealed associations in both directions (i.e., a decrease in BMI had one effect, while an increase in BMI had the opposite effect), the categorical analyses showed associations only in one direction of BMI change, not both; 2) for another one of these eight outcomes, the categorical analyses suggested an association with change in BMI, while this association was not shown in the continuous analyses (this is potentially a false positive association); 3) for the last of the eight outcomes, the continuous analyses suggested an association of change in BMI, while this association was not shown in the categorical analyses (this is potentially a false negative association).

CONCLUSIONS

Categorization of continuous predictor variables alters the results of analyses and could lead to different conclusions; therefore, researchers in rheumatology should avoid it.

Illness Experience and Quality of Life in Sjögren Syndrome Patients

Sjögren's syndrome (SS) is a disease with autoimmune features that affects mainly women and compromises the health-related quality of Life (HRQoL); it is important to evaluate illness experience for a better understanding of the life situation of the patient. The aim of the study was to summarize the individual life experiences and determine the impact of HRQoL and oral health-related quality of life (OHRQoL) and their correlation with health self-assessment in women with SS. The life experiences evaluation employed a concept mapping design to structure qualitative content obtained from semi-structured interviews. Hierarchical cluster analysis was used to analyze the patient's experiences. EQ-5D-5L and OHIP-14Sp were used. The correlation between appreciation of the general health status and OHIP-14 was evaluated. The experience classification by patients were analyzed and a dendrogram was obtained, identifying 10 clusters of disease experiences of SS, being limitations, pain and difficulties, coping and attitudes towards treatment the most common. Pain/discomfort in EQ-5D-5L and physical pain and psychological discomfort in OHIP-14 were the most affected dimensions in the patients. The results support the theoretical perspective that the experience of illness is relevant to describing the main difficulties of patients with SS and how it affects their quality of life.

The Experiences of Functioning and Health of Patients With Primary Sjögren's Syndrome: A Multicenter Qualitative European Study

Objective: To identify a spectrum of perspectives on functioning and health of patients with primary Sjögren's syndrome (pSS) from the five European countries in order to reveal commonalities and insights in their experiences.

Methods: A multicenter focus group study on the patients with pSS about their perspectives of functioning and health was performed. Focus groups were chaired by trained moderators based on an interview guide, audiotaped, and transcribed. After conducting a meaning condensation analysis of each focus group, we subsequently combined the extracted concepts from each country and mapped them to the International Classification of Functioning, Disability and Health (ICF).

Results: Fifty-one patients with pSS participated in 12 focus groups. We identified a total of 82 concepts meaningful to people with pSS. Of these, 55 (67%) were mentioned by the patients with pSS in at least four of five countries and 36 (44%) emerged in all the five countries. Most concepts were assigned to the ICF components activities and participation (n = 25, 30%), followed by 22 concepts (27%) that were considered to be not definable or not covered by the ICF; 15 concepts (18%) linked to body structures and functions. Participants reported several limitations in the daily life due to a mismatch between the capabilities of the person, the demands of the environment and the requirements of the activities.

Conclusion: Concepts that emerged in all the five non-English speaking countries may be used to guide the development and adaption of the patient-reported outcome measures and to enhance the provision of treatment options based on the aspects meaningful to patients with pSS in clinical routine.