G6PD and G6PD deficiency: The diagnosis of G6PD deficiency in the field is usually performed with capillary blood (fresh or spotted on filter paper) using different methodologies (FST, Hirono, or WST8/1-methoxy PMS).4–6 Quantitative assessment of G6PD is, instead, more often performed on venous blood for several reasons, including volume requirement (the World Health Organization standard protocol) and ease of blood sampling and storage.12 The two sampling methods also often use different anticoagulants (EDTA for venous blood and heparin for capillary sampling).