Home-sampling of B cells using quantitative dried blood spots to enable tailored therapeutic re-dosing of anti-CD20 therapies.

Anti-CD20 monoclonal antibodies are commonly used to manage neuroinflammatory diseases. The rate of B-cell re-emergence after dosing of ocrelizumab or rituximab varies considerably between individuals, but most people remain completely B-cell depleted at 6 months. Tailoring the dosing according to B-cell re-emergence may improve the safety profile of anti-CD20s but poses logistical challenges such as the need for regular attendances for whole-blood sampling. Here we combined a quantitative dried blood spot sampling technique with a DNA methylation test, to provide a reliable means of remotely monitoring B-cell counts, with 100% sensitivity and specificity for reaching >10 × 106 cells/L.