Skin-prick blood samples are reliable for estimating Hb mass with the CO-dilution technique

Investigation of the impact of environmental stimuli such as altitude exposure on hemoglobin mass currently rely on invasive techniques that require venous blood sampling. This study assessed the feasibility of lancet skin pricks as an alternative to venepuncture to estimate hemoglobin mass with the carbon monoxide (CO) dilution technique, with the intent of making the technique accessible to technicians without phlebotomy training. Sixteen healthy volunteers rebreathed CO via a small-volume rebreathing apparatus. Blood was sampled simultaneously with a glass syringe (VEN) from a superficial forearm vein and with a capillary tube from either a lanced fingertip or earlobe (CAP). As a control, VEN blood was then aliquoted into capillary tubes (CONTROL-CAP). Samples were assayed for carboxy-hemoglobin (HbCO) using a diode-array spectrophotometer. Mean %HbCO was higher in CAP than VEN (bias 0.3+/-0.2%HbCO, p < 0.01), but VEN and CONTROL-CAP were not different (p = 0.55). Compared to VEN, Hb mass derived from CAP samples was overestimated by 1.7% (15+/-22 g Hb, p = 0.01). CAP samples to estimate Hb mass demonstrated a technical error of measurement of 2.7%, which is comparable to the 1.9% reported previously with VEN samples. We conclude that using CAP samples gives a reliable measure of %HbCO, and will make the estimation of Hb mass with the CO-technique accessible to technicians without phlebotomy training.