Efficacy of anti-ribosomal P protein antibody testing for diagnosis of systemic lupus erythematosus

Abstract

Objective. Anti-ribosomal P protein antibody (anti-P) is detected in a fraction of systemic lupus erythematosus (SLE) patients, especially with lupus psychosis, lupus nephritis, and lupus hepatitis. However, it has been unclear whether anti-P testing is specific for SLE. The current studies were designed to examine the efficacy of serum anti-P testing in diagnosis of SLE.

Method. Multicenter retrospective study was performed with 102 SLE patients, 102 patients with non-SLE rheumatic diseases, and 100 normal healthy subjects, who gave informed consents. The diagnosis of SLE was confirmed according to the 1982 ACR revised criteria. Serum IgG anti-P was determined by ELISA using the C-terminal 22 amino-acids of ribosomal P protein conjugated to human serum albumin. The specificity and sensitivity of anti-P were compared with those of anti-DNA, anti-Sm, and anti-cardiolipin (CL) antibodies.

Results. Serum anti-P was positive in 38 of 102 SLE patients (37.3%), in 4 of 102 patients with non-SLE rheumatic diseases (3.9%), and in none of 100 normal subjects. Receiver operating characteristic (ROC) curve analysis revealed that anti-P provided higher AUC (area under the curve) than anti-Sm or anti-CL. Consistently, the sensitivity of anti-P (37.3%) was superior to that of anti-Sm (27.5%) and anti-CL (24.5%), but inferior to that of anti-DNA (51.0%), whereas the specificity of anti-P (96.1%) was superior to that of anti-CL (86.3%) and comparable to that of anti-DNA (96.1%) and anti-Sm (96.1%).

Conclusion. These results indicate that serum anti-P testing might be an effective measure in diagnosing SLE, providing better diagnostic efficiency than anti-Sm and anti-CL.

Keywords:

• Anti-ribosomal P
• Anti-DNA
• Anti-Sm
• Anti-cardiolipin
• Diagnosis

Acknowledgments

The authors wish to thank Dr. Tamiko Yanagida, Department of Internal Medicine, Teikyo University School of Medicine, for her assistance in collecting samples from healthy individuals and Mr. Takashi Tsunoda and Mr. Hidekazu Nasu, SRL, Inc., for their assistance in collecting and analyzing the data. This work was supported by grants from SRL, Inc., Tokyo, Japan. These grants have no influences on the study design, the collection, analysis, and interpretation of data, the writing of the report, and in the decision to submit the paper for publication.

Conflict of interest

None.