Home monitoring of haemoglobin A_1c in diabetes: a systematic review and narrative synthesis on accuracy, reliability and patient acceptability

Aim: In the UK people with diabetes who do not attend annual review appointments often have higher haemoglobin A_1c (HbA_1c ) levels. We aim to determine the acceptability of self-collected posted capillary blood samples, and if they produce accurate and reliable HbA_1c results.

Methods: We include adult studies comparing capillary blood to venous blood for measuring HbA_1c . We exclude methods not suitable for postage. Electronic databases of MEDLINE, Embase, CINAHL, Web of Science, Google Scholar and OpenGrey were searched from inception to September 2021, as well as relevant conference abstracts. Two reviewers performed study selection, data extraction and risk of bias assessment independently. Narrative synthesis was performed.

Results: Our search retrieved 3747 records. Following de-duplication and screening 30 articles were included. The mean difference (MD) and limits of agreement (LoA) between capillary and venous HbA_1c were smaller and narrower respectively when micro/capillary tubes (micro/cap) were used for capillary blood storage compared to dried blood spots (capDBS) (micro/cap MD range -0.4 to 1.4 mmol/mol vs. capDBS MD range -4.3 to 7.2 mmol/mol, micro/cap LoA width 2.4 to 6 mmol/mol vs. capDBS LoA width 11.7 to 16.8 mmol/mol). After using self-collection kits, 83%-96% of participants reported satisfaction, 87%-99% found it easy and 69%-94% reported they would use it again.

Conclusion: Microtubes/capillary tubes look promising as a method of self-collecting and posting capillary blood samples for the measurement of HbA_1c based on the accuracy and reliability findings presented. DBS samples demonstrated comparatively poorer accuracy. Data on acceptability were limited and further research is needed.