Variability of the rate of coagulation of whole blood

1. 1. Variations in technic of obtaining the sample of blood and in measuring the rate of coagulation are only partly responsible for the variability of the whole blood clotting times. 2. 2. Some of the variability in whole blood clotting times is due to the in vivo effect of exogenous and endogenous factors affecting the circulating blood. 3. 3. With a standard technic which is fully described, the rate of clotting of whole blood is remarkably constant in the same individual on the same day or on different days if the individual is studied under conditions which keep the variability of endogenous and exogenous factors at a minimum. 4. 4. The basal state is the best condition in which to study the rate of clotting of whole blood because the variations in endogenous and exogenous factors are at a minimum. 5. 5. Ingested fat in the form of cream or butter accelerates the rate of coagulation of whole blood. The response is detectable in one-half hour after ingesting the fat and reaches a maximum in one hour. Thereafter, the effect progressively diminishes. This results in a constant and characteristic biphasic curve of response. 6. 6. The accumulation of thrombin on glass does not explain this phenomenon. 7. 7. The term “re-used” syringes is defined and evidence is presented that adequate washing in running water and saline permits the “re use” of a syringe without influencing the results. 8. 8. Sterilization of syringes, pipettes and test tubes which are used in measurements of the rate of blood coagulation is unnecessary.