Disclosure(s): No financial relationships with ineligible companies to disclose
Background/Purpose: Antinuclear antibody (ANA) and SLE-related autoantibody testing are integral parts of SLE screening, diagnosis, and monitoring. However, these tests rely on access to phlebotomy for blood sample collection and a lab that can receive and perform these assays in a timely manner. This is a challenge for patients living in remote areas, including Indigenous populations and African countries, where SLE is likely underdiagnosed. Here, we investigated the performance of ANA and SLE-related autoantibody tests on dried blood spots (DBS) as a more resource-efficient and minimally invasive alternative for patients. Methods: Patients with SLE meeting the 2012 SLICC or 2019 ACR/EULAR criteria or rheumatoid arthritis (RA) meeting the 2010 ACR/EULAR criteria as disease controls were enrolled from a single tertiary care centre. Serum was collected by both venipuncture and DBS at the same visit. DBS cards were subsequently stored under four conditions: 1) 25°C (room temperature) for one week, 2) 25°C for 4 weeks, 3) 4°C for one week, and 4) 4°C for 4 weeks. For each condition, ANA was performed using an indirect immunofluorescence assay (IFA) on HEp-2 substrate (NovaLite,Werfen, CA). ANA patterns were classified according to the most recently updated International Consensus on ANA Patterns recommendations. Per manufacturers’ directions, a positive test was defined as a titer of >=1:80. SLE-related antibodies (anti-U1-RNP, -histone, Jo-1, -ribosomal P, -Sm, -Sm-RNP, -Scl70, -PmScl, -centromere B, -PCNA, -Ro52/TRIM21, -Ro60/SSA, and -La/SSB) were performed on Connective-13 profile (addressable laser bead immunoassay by Theradiag, positive >80 AU/mL) and anti-dsDNA by ELISA (Werfen, CA, positive >300 IU/mL). We compared the ANA (titres and patterns) and autoantibody titres between venipuncture vs. DBS under the different storage conditions. Results: 42 patients were enrolled (24 SLE, 18 RA). There was no statistical difference in the frequency of ANA positivity between venipuncture vs. DBS under all four storage conditions for SLE and RA controls (Fig1A). The ANA titres as indicated by intensity level measured using the automated digital IFA microscope (NovaView, Werfen) did not change significantly from week 1 to 4 at 25°C and 4°C. Most ANA patterns were the same between venipuncture and DBS after 1 week at both 25°C (79.5%) and 4°C (71.4%) (Fig2). There were more discrepancies in ANA pattern between venipuncture and DBS after 4 weeks for both 25°C (57.5%) and 4°C (52.5%). The correlation between venipuncture vs. DBS SLE-related autoantibodies was moderate to strong for most, except for anti-dsDNA, anti-histone, and anti-Scl70 antibodies (Table 1). Specifically, the correlation for anti-dsDNA was r=0.68 (p< 0.001).
Conclusion: In the study, we demonstrated that DBS performance is comparable to venipuncture for ANA and SLE-related autoantibody testing. Antibody titre did not vary significantly over time or with temperature variation. This highlights the sustainability of DBS as a potential screening test in under-resourced populations.
