Self-sampling of capillary blood for safety monitoring of DMARD therapy in patients with rheumatic disease: a feasibility and method-comparison study

Our study aimed to compare the quality of patient self-collected capillary samples with venous blood samples. Additionally, we assessed whether patients with rheumatic disease are both capable of and willing to perform capillary self-sampling through subjective and objective assessments. This research explores the future potential of at-home self-sampling. Patients with rheumatic diseases were asked to perform up to four supervised self-collected capillary blood samples, followed by a standard venous sample performed by study personnel. Anti-rheumatic drug treatment monitoring parameters, including biochemistry and hematology, were analyzed using Cobas 8000 and Sysmex XN-9000, respectively. The agreement was evaluated by Bland-Altman plots and compared to critical difference limits. Study personnel and patients answered a survey questionnaire after every visit to evaluate feasibility. In total, 21 patients completed 53 paired capillary and venous samples from November 2019 to December 2020. We found a strong correlation (<i>r</i> > 0.87) and good agreement for most parameters; platelets showed the poorest agreement. Patients experienced little pain, found self-sampling easy and reported no serious complications. Hemolysis affected 12/53 capillary biochemistry samples, and 5/53 capillary hematology samples coagulated. The good agreement for most parameters and excellent feasibility encourages the potential for capillary self-sampling of DMARD monitoring parameters, relevant limitations were hemolysis and aggregating platelets.