Prothrombin and vitamin K: a review of this subject including a new simplified method of estimating prothrombin in capillary blood: written for the Gregor Prize for the Practice of Physic, 1941; Gunning Victoria Jubilee Prize in Medicine, 1941

In concluding this essay, one feels that it is desirable to indicate the part which the results of studies on prothrombin and vitamin K may be expected to play when viewed from the broad standpoint of clinical application and treatment value as a whole. The work on this subject, which has nearly all been done in the last few years, has yielded results of great value in the understanding and treatment of certain haemorrhagic states. In particular it has shown that the bleeding tendency in obstructive jaundice and in haemorrhagic disease of the newborn can be prevented and cured by administration of vitamin K. A similar bleeding diathesis in certain malabsorptive conditions has likewise been shown to be due to vitamin K deficiency and to be amenable to treatment with this substance. Estimation of the prothrombin content of the blood has cone to be recognised as an essential step in the investigation of a patient with a bleeding tendency, as providing the only real indication for vitamin K therapy, and as a possible test of liver function. Apart from these most important applications, however, the value of the prothrombin - vitamin K question would appear to be limited. In all new fields of research yielding spectacular results, there is a tendency for clinicians to fail to realise the limitations of the findings and to indulge in the irrational use of any new remedy described in many conditions outwith the scope of its applications. Thus it is felt that today many cases of haemorrhagic states are being given vitamin K therapy, just because of the bleeding tendency and quite without justification such as a demonstrable low blood prothrombin. It follows that in such circumstances the existence of a simple, rapid, test for prothrombin determination will be of much value in the investigation and treatment of these haemorrhagic conditions. It is hoped that the new simplified method for estimating prothrombin in capillary blood will help the subject of prothrombin and vitamin K to establish its real place amongst the advances in clinical science of our times