Identification of symptom clusters in patients with ankylosing spondylitis

Symptom cluster refers to a group of 3 or more related symptoms that occur together. Our objectives were to: (1) investigate the frequency, severity and gender difference of symptoms in patients with ankylosing spondylitis (AS); and (2) identify symptom clusters in AS patients. A cross-sectional questionnaire-based survey was conducted using the Patient Health Questionnaire Symptoms Group combined with self-designed variables. Demographic and symptom variables between male and female patients in terms of C-reactive protein (CRP) and human leukocyte antigen (HLA)-B27 status were analyzed with 2-tailed independent t test for continuous variables and Chi-square or Fisher's exact test for categorical variables. Symptom clusters were extracted and analyzed by principal component analysis. There were 122 AS patients included in the study. The most severe symptoms included severe back pain, extremity or joint pain, difficulty in breathing, constipation, intestine discomfort and diarrhea. Stomachache was more prevalent in male patients in which odds ratio was 4.60 (CI 1.59-12.97) (P = .006). Patients with HLA-B27 negativity or a higher CRP value were more likely to have dry mouth. Four symptom clusters were classified, which explained 58.4% of the total variation. They were named as the gastrointestinal-cardiac cluster, the fatigue-sleep disturbance cluster, the headache-chest pain cluster, and the mouth-eye cluster. The symptoms appeared to cluster into 4 groups in AS patients, which should be noticed in clinical care.