Concordance of <scp>HbA1c</scp> , creatinine, <scp>LDL</scp> cholesterol, <scp>HDL</scp> cholesterol, and total cholesterol between venous and self‐collected capillary blood samples sent by mail

INTRODUCTION/AIMS: Self-collected capillary blood sampling with postal shipment may improve access to routine monitoring of HbA1c, creatinine, and lipid parameters, but evidence on concordance with venous samples under real-world transport conditions remains limited. This study evaluated the concordance of HbA1c, creatinine, and lipid parameters between self-collected mailed capillary samples, mailed venous samples, and courier-transported venous samples. MATERIAL AND METHODS: In this cross-sectional study, participants scheduled for a blood draw in a general practice office self-collected a capillary blood sample using the Tasso+ device and provided additional venous blood samples. One venous sample was sent by mail (VMS) with the capillary blood sample (CMS). The other venous sample was couriered directly to the laboratory (VCS). HbA1c, creatinine, LDL, HDL, and total cholesterol were measured. RESULTS: Samples of 105 participants were analyzed. High concordance was observed between CMS and VCS for HbA1c (absolute mean bias = 0.028%, relative mean bias = 0.463%, concordance correlation coefficient [CCC] = 0.999) and creatinine (absolute mean bias = 0.037 mg/dL, relative mean bias = 4.815%, CCC = 0.972). VMS showed high agreement with VCS for HbA1c (absolute mean bias = 0.028%, relative mean bias = 0.450%, CCC = 0.998) and creatinine (absolute mean bias = 0.026 mg/dL, relative mean bias = 3.320%, CCC = 0.990). Lipid parameters demonstrated good concordance for CMS and VMS compared to VCS, with relative bias values ranging from 3.0% to 5.7% and CCCs >0.95. CONCLUSIONS: Self-collected mailed capillary blood samples provide comparable HbA1c, creatinine, and lipid parameters to venous samples, even when sent by standard mail. Capillary self-sampling is a reliable method for remote monitoring of these parameters in diabetes management and screening.