Expression of T-bet, a type 1 T-helper cell transcription factor, in the urinary sediment of lupus patients predicts disease flare

Background. Systemic lupus erythematosus (SLE) is characterized by the aberrant activation of T-lymphocytes. Since T-bet is the principal transcription factor for the differentiation of type-1 helper T-lymphocyte, we study the impact of urinary T-bet mRNA expression in clinically quiescent SLE patients on the risk of subsequent disease flare. Methods. We studied 60 quiescent SLE patients. Urinary mRNA expression of T-bet was studied by the real-time quantitative polymerase chain reaction. Patients were followed for 4 yrs for disease flare. Results. We studied 60 patients; 57 were female. The mean age was 38.8 +/- 11.2 yrs. Their baseline SLE disease activity index score was 1.63 +/- 1.64. During the follow-up, 28 patients (46.6%) developed lupus flare, of which 17 (28.3%) had severe flare. Receiver operating characteristic curves showed that urinary T-bet expression three times above the average level of healthy control had 64.3% sensitivity and 84.4% specificity of predicting all lupus flare. Using this cut-off, patients with a high urinary T-bet expression had a significantly higher risk of all lupus flare and severe flare than the patients with a low T-bet expression (log-rank test, P < 0.001 for both). With multivariate Cox proportional hazard model to adjust for potential confounding variables, urinary T-bet expression and patient's sex were the only independent predictors of all lupus flare and severe flare. It could be estimated that 1-fold increase in urinary T-bet expression would result in 8.4% excess risk of all lupus flare [95% confidence interval (CI), 4.1-13.0%, P < 0.001] and 12.9% excess risk of severe flare (95% CI 7.4-18.7%, P < 0.001). Conclusions. A high urinary T-bet expression was an independent predictor of lupus flare. Measurement of urinary T-bet may provide valuable information for the risk stratification of SLE patients.