Background/Purpose: The search for a marker of SLE disease activity has included inflammatory markers, chemokines and gene signatures.  We explored the ability of the BAFF gene expression to predict SLE disease activity in the subsequent year after measurement.

Methods: 292 patients (59% Caucasian, 34% African-American, 92% female, mean age 46 ±12 years) were enrolled in a prospective observational study.  At baseline, BAFF gene expression level was determined in peripheral blood RNA using Affymetrix chips.  Clinical associations, based on the same-day visit disease activity (using the Physician Global Assessment and SELENA SLEDAI) as well as activity over the ensuing year were then determined.  Results were determined with a generalized estimating equation to account for the repeated observations among the same patients. 

Results: The number of visits within a year after the measurement of BAFF gene expression varied from 1-9.  Six patients had 1 visit, 46 patients had 2-3 visits, 159 patients had 4 visits, and 81 patients had more than 4 visits.

Table 1.Percentage of visits with disease activity by BAFF gene expression

 

Variable	Low BAFF (<10.7) (%, N=387)	Med BAFF (10.7-11.4) (%, N=476)	High BAFF (>11.4) (%, N=347)	P-value	Adjusted P-value for Race
Physician global assessment >1	8%	21%	24%	.0003	.0041
SLEDAI ≥2	36%	57%	71%	<.0001	<.0001
Urine Protein/Creatinine Ratio (≥0.5)	3%	13%	13%	.0004	.0096
Anti-dsDNA ≥ 10	9%	21%	35%	<.0001	<.0001
C3 <79 mg/dL	4%	11%	21%	.0002	.0004
C4 <12 mg/dL	4%	11%	19%	.0004	.0005
ESR >20	35%	55%	63%	<.0001	.0005

We controlled for race, sex, baseline low complement and baseline anti-dsDNA.

Table 2.Average disease activity over a year of follow-up.

 

Variable	BAFF gene expression	Unadjusted Activity	Adjusted Mean Differences	P-values
PGA	Low (<10.7)	0.48	0  (Ref. Group)
	Med  (10.7-11.4)	0.70	0.14	.044
	High  (>11.4)	0.74	0.15	.045
SLEDAI	Low (<10.7)	1.08	0 (Ref. Group)
	Med (10.7-11.4)	2.10	0.39	.031
	High (>11.4)	2.98	0.72	.0029

Conclusion: We have previously shown that the BAFF gene expression correlates with same-day disease activity.  We now can prove that BAFF gene expression predicts disease activity over the ensuing year. This supports BAFF/BLyS as a target for clinical intervention.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/baffblys-gene-expression-predicts-disease-activity-in-systemic-lupus-erythematosis-over-one-year/