Capillary self-blood collection for centralized testing - a pan-European cross-sectional pilot study

Self-collection of capillary blood allows study participants to provide samples without in-person healthcare contact and to return them by mail to a central laboratory. We evaluated the feasibility and analytical agreement of internationally mailed self-collected capillary blood in a pan-European setting.

In this cross-sectional pilot study, adults attending the INFORM EU plenary meeting in Hannover, Germany provided two capillary blood samples: one sample was mailed from their country of residence (capillary mail-in sample, CMS); the other was analyzed within 24 h (capillary comparison sample, CCS). Thyroid-stimulating hormone (TSH), C-reactive protein (CRP), creatinine, and alanine aminotransferase (ALT) were measured. Agreement was assessed with correlation coefficients, Deming and Passing-Bablok regression, and Bland-Altman analysis.

Of 66 participants, 49 (74.2%) returned a mailed sample after a median transit of 8 days (Q25-Q75: 5-12). Analytically valid pairs were available for 17 (TSH), 16 (ALT), 16 (creatinine), and 19 (CRP) participants. Agreement was high for CRP (r and CCC = 1.00) and good for TSH (r = 0.90; CCC = 0.88). Creatinine showed a strong correlation but low concordance (r = 0.85; CCC = 0.19) with a proportional bias, and ALT showed the weakest agreement (r = 0.54; CCC = 0.21) and largest bias. Longer transit was associated with higher ALT differences (ρ = 0.57).

International postal return of self-collected capillary blood was achievable, and the main constraint was insufficient plasma volume rather than delivery. CRP, and to a lesser extent TSH, reached acceptable agreement, whereas ALT and creatinine did not. Given the small number of valid samples and healthy study population, these findings need further confirmation.

DRKS00033172 on January 30th, 2024.