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Biomarker studies
sIL7R concentrations in the serum reflect disease activity in the lupus kidney
  1. B R Lauwerys1,2,
  2. S Nieuwland Husson1,2,
  3. A L Maudoux1,
  4. V Badot3 and
  5. F A Houssiau1,2
  1. 1Pôle de pathologies rhumatismales, Institut de Recherche Expérimentale et Clinique, Université catholique de Louvain, Brussels, Belgium
  2. 2Service de Rhumatologie, Cliniques Universitaires Saint-Luc, Brussels, Belgium
  3. 3Service de Rhumatologie, Hôpital Erasme, Brussels, Belgium
  1. Correspondence to Professor B R Lauwerys; Bernard.Lauwerys{at}uclouvain.be

Abstract

Objectives Evaluation of disease activity in systemic lupus erythematosus (SLE) nephritis is a challenge, and repeated renal biopsies are usually needed in order to confirm a suspicion of flare. In a previous cross-sectional study, we reported that serum soluble form of the interleukin-7 receptor (sIL7R) levels is strongly associated with nephritis in SLE patients. In the present study, we wanted to confirm the association between changes in serum sIL7R concentrations and renal disease activity in a large longitudinal cohort of SLE nephritis patients.

Methods Sera were harvested longitudinally in 105 SLE nephritis patients. Serum sIL7R cut-off value for the detection of SLE nephritis activity was determined as the mean sIL7R concentration in non-nephritis SLE patients + 2 SDs using data collected in our previous study. Patients with glomerular filtration rate (GFR) <60 mL/min/1.73 m2 (n=17) were excluded from the study due to persistently elevated serum sIL7R values.

Results Serum sIL7R concentrations above the renal cut-off value were observed in 25 (out of 88) patients with a normal GFR. These patients had significantly higher serum double-stranded DNA (dsDNA) Ab and urinary protein to creatinine (UPC) ratio. Strikingly, 12 of them developed a renal British Isles Lupus Assessment Group index (BILAG) A within the next 3 months, while this was only the case in four out of the 63 other patients (p<0.0001). The test had 75.0% sensitivity and 81.9% specificity for the detection of a renal BILAG A. Combination of serum sIL7R with any of the classical tests (anti-dsDNA Ab titres, UPC ratio, serum C3) resulted in an increased specificity for the detection of a renal flare. Administration of immunosuppressive therapy resulted in a significant decrease in serum sIL7R concentrations.

Conclusions Serum sIL7R is a sensitive and specific marker of renal disease activity in SLE. Elevated serum sIL7R values in SLE patients are associated with or predict the occurrence of an SLE nephritis flare.

  • Lupus Nephritis
  • Systemic Lupus Erythematosus
  • Disease Activity

This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/

https://doi.org/10.1136/lupus-2014-000036

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