Antibodies to ribosomal P proteins in lupus nephritis: a surrogate marker for a better renal survival?

OBJECTIVE

To define if antibodies to ribosomal P proteins disclose a better lupus nephritis long-term survival.

METHODS

Sixty consecutive SLE patients with biopsy-proven nephritis (2004 ISN/RPS) were evaluated for renal survival parameters. Inclusion criteria were at least one serum sample at: renal flares, biopsy, and last follow-up until 2008. Anti-P was detected by ELISA/immunoblot and anti-dsDNA by indirect immunofluorescence/ELISA.

RESULTS

Eleven patients (18%) with anti-P+ (without anti-dsDNA) during renal flare were compared to 49 (82%) persistently negative for anti-P throughout the study. At the final follow-up post-biopsy (6.3±2.5 vs. 6.8±2.4 years, p=0.36), the comparison of anti-P+/anti-dsDNA- with anti-P- group revealed a trend to lower mean creatinine levels (0.9±0.3 vs. 2.3±2.1 mg/dl, p=0.07), lower frequency of dialysis (0% vs. 35%, p=0.025), and higher frequency of normal renal function (91% vs. 53%, p=0.037). The overall renal survival was significantly higher in anti-P+/anti-dsDNA- compared to anti-P- (11.0±4.5 vs. 9.2±4.5 years, p=0.033), anti-dsDNA+/anti-P- (vs. 8.7±4.7 years, p=0.017), and anti-P-/anti-dsDNA- (vs. 9.8±4.3 years, p=0.09) groups.

CONCLUSION

Our data supports the notion that anti-P antibody in the absence of anti-dsDNA during nephritis flares is a valuable marker to predict a better long-term renal outcome in lupus patients.