P223
Comparing anti-double stranded DNA Antibody assaysto monitor patients with
systemic lupus erythematosus (SLE)
Allyson Egan1, Joan Agama2, Panagiotis Pantelidis3, Phillippa Dodd1, Peter Kelleher3, Liz Lightstone1,
Marina Botto2.
Department of Renal Medicine1, Centre for Complement and Inflammation Research2, Department of
Infection and Inflammation3, Hammersmith Hospital, Imperial College London.
Introduction
SLE is characterised by the production of anti-double stranded (dsDNA) autoantibodies (Abs) directed against
nuclear self-antigens. The gold standard detection technique is the Chrithidia test, an immunofluorescent assay.
However, ELISA is the method most commonly employed to detect anti-dsDNA antibodies. This project aimed to
establish whether ELISA or a new bead based multiplex flow cytometry (Luminex) assay correlated better with the
gold standard Chrithidia test and which assay correlated best with disease activity assessed by the SLE disease
activity index (SLEDAI).
Methods
Anti-dsDNA antibody levels in 39 patients attending Lupus clinic were assessed by all three techniques, at two time
points (T1 and T2), four months apart. The notes were reviewed and SLEDAI scored. Chrithidia values were scored
as positive or negative. Patients were categorised according to their Chrithidia results T1 and T2 in 4 groups:
positive/positive (PP), positive/negative (PN), negative/ positive (NP),negative/negative (NN) (Fig B).
Results
Patients were between 21-63 years (mean age 37.61). 83% (n=35) were female and 6.8% (n=7) were male. The
median value for SLEDAI was 4 (T1 &T2). Fifteen patients had SLEDAI values greater or equal to 6 (T1 &T2).
Mean serum creatinine was 121 and 115 at T1&T2.
(B)
(A) Anti-ds DNA antibody levels
Assay (n=39)
Time 1
Time 2
ELISA (mean)
135.71
117.25
Luminex (mean)
250.2
361.15
Chrithidia (% positive)
64.1
69.2
(B) Diagram with the percentages of patients in the four group according to Chrithidia results.
The results obtained with Luminex correlated with ELISA data at both time points. In the PP group Luminex values
were higher than the ELISA values. In NN, patients had positive ELISA and Luminex titres in comparison to the
Chrithidia result. In NP and PN Luminex titres correlated better with the changes in Chrithidia results. SLEDAI
scores did not correlate with Luminex or ELISA data.
Conclusion
Luminex appears to be as reliable as ELISA in detecting anti-dsDNA antibody levels. The autoantibody values by
Luminex tend to be higher than those by ELISA. Luminex appears to mirror more closely the overall trend of
changes observed in Chrithidia results. However, both assays are variable and do not always correlate with each
other. The choice of assay should be made based upon practicality and cost of the test as their ability to correlate
with the disease activity is similar.