I just had it out with someone about this. There are many uses for blood. But in reality, this is a spectrum question, not a black or white one. I ask JW's
On a scale of 1-10 where
1 = Medical blood use is pagan midieval quackery.
5 = Medical blood use is sometimes necessary but never risk free and should be considered carefully with other medical options.
10 = Medical blood use is a miraculous panacea...
Where do people stand?
I think most JW's are between 1-3.
I think most doctors are between 5-7.
I think anyone between 3-8 could be reasonable moderates. I myself would probably be at about a 6. It's important to distinguish between emergency and surgical uses of blood.
You must consider how many people die from either no treatment or substitute treatment. Most such studies do not adequately address this, particularly emergency blood usage. This is because we don't just let someone almost bleed to death when we have the chance to use a - sometimes risky - solution.