If you draw a sodium citrate tube with a butterfly, do you use a discard tube first? The dead space can dilute the 9:1 ratio — roughly [redacted] in some sets — so we toss a small tube before the light blue; it always reminds me of baristas purging the line before an espresso shot. Curious who was taught a specific volume for the discard in your lab.
I treat the first tube as a true “purge the line” step only when the light blue is first with a butterfly — just a small nonadditive/waste to clear the tubing, then go straight to citrate so the 9:1 holds; if a serum tube is on the order, that’s my discard and I skip the extra. Small caveat: on fragile veins I switch to a pediatric citrate to avoid underfill; @OP do you do that when flow is borderline?