Background: This integrative single-case study investigated the 12 h-to-12 h cause-effect relations between 55 kD soluble tumor necrosis factor receptor type 1 (sTNF-R55) and specific and unspecific symptoms in a 52-year-old Caucasian woman with mild systemic lupus erythematosus (SLE) disease activity.
Methods: The patient collected her entire urine for 56 days in 12 h-intervals to determine sTNF-R55/creatinine and protein/creatinine levels (ELISA, HPLC). Additionally, twice a day, she took notes on oral ulceration and facial rash; answered questionnaires (VAS) on fatigue, weakness, and joint pain; and measured body temperature orally. Time series analysis consisted of ARIMA modeling and cross-correlational analyses (significance level = p < 0.05).
Results: Time series analysis revealed both a circadian and a circasemiseptan rhythm in the urinary sTNF-R55 data. Moreover, several significant lagged correlations between urinary sTNF-R55 concentrations and SLE symptoms in both directions of effect were identified. Specifically, increased urinary sTNF-R55 concentrations preceded decreased urinary protein levels by 36-48 h (r = -0.213) and, in the opposite direction of effect, increased protein levels preceded increased sTNF-R55 concentrations by 24-36 h (r = +0.202). In addition, increased urinary sTNF-R55 levels preceded increased oral ulcers by 36-48 h (r = +0.277) and, conversely, increased oral ulceration preceded decreased sTNF-R55 levels by 36-48 h (r = -0.313). Moreover, increased urinary sTNF-R55 levels preceded decreased facial rash by 36-48 h (r = -0.223) and followed increased body temperature after 36-48 h (r = +0.209). Weakness, fatigue and joint pain were not significantly correlated with urinary sTNF-R55 levels.
Conclusions: This study gathered first evidence of real-life, long-term feedback loops between cytokines and SLE symptoms in mild SLE disease activity. Such insights into the potential role of sTNF-R55 in SLE would not have been possible had we applied a pre-post design group study. These findings require replication before firm conclusions can be drawn.