The WT flipflopped on the use of blood components in 1961 when they published the pamphlet "Blood, Medicine and the Law of God". (Incidentally, 1961 was right about the time that Denton Cooley started doing cardiac surgery on JW patients using a heart and lung machine - a cell saver)
From the 1961 blood law book:
In view of the constant developments in the field of medical research, new treatments involving the use of blood and its component parts are constantly coming to the fore. But regardless of the method used to infuse it into the body and regardless of whether it is whole blood or a blood substance that is involved, God's law remains the same. If it is - blood and it is being used to nourish or to sustain life the divine law clearly applies.
and
Although Jehovah's witnesses will not eat blood as a food, nor in medical use consent to any kind of blood transfusion or, in place of it, an infusion of any blood fraction or blood substance, this does not rule out all medical treatment.
I think it was also in 1961 that taking a blood transfusion became a disfellowshipping offense (???).
1961 was a defining year in the blood phobia doctrine. The WT tightened up their rules on blood. Previously "allowed" fractions and serums became taboo.