This study developed a Flow Induced Dispersion Analysis (FIDA) assay to detect autoantibodies against double-stranded DNA (dsDNA), a key diagnostic marker for Systemic Lupus Erythematosus (SLE). FIDA was used to measure the change in apparent diffusivity of fluorescently labeled dsDNA probes: when patient autoantibodies bound the DNA, the probe's apparent size increased and its diffusivity dropped, signaling binding within minutes using only a few hundred nanoliters of sample. Analyzing plasma from six SLE patients with three different 32-base-pair DNA sequences, the researchers found autoantibodies bound different sequences with different affinities, revealing pronounced heterogeneity between patients. The assay worked directly in up to 85% plasma and flagged binding in samples scored negative by standard CLIFT and ELISA tests. The authors conclude FIDA is a promising approach for SLE diagnosis, patient stratification and disease monitoring.