Prothrombin Time in Health and Disease. (According to Quick's Method)

Recent advances in physiology Dam (1934; 1935) observed that chicks on synthetic diets developed haemorrhages uncontrollable by vitamins A, C and D. He therefore attributed the bleeding tendency to lack of a specific food factor, vitamin K (coagulation vitamin). Dam and Schonheyder (1934) demonstrated that the delay in coagulation in chicks on diets deficient in vitamin K was not caused by a disturbance in the levels of fibrinogen, calcium or the cellular elements of the blood or the thrombokinase of the tissues. Dam, Schonheyder and Tage-Hansen (1936) subsequently showed the element deficient in the blood of these chicks to be prothrombin. Investigations along a different line have thrown new and valuable light on the significance of the above researches. Numerous studies relating to the coagulation defect in jaundice had revealed that bleeding in jaundice was not due to a disturbance in fibrinogen, calcium, or formed elements, or in any other easily studied component of clotting mechanism. Only one component in blood, prothrombin, remained to be still investigated. Quick (1935; 1937; 1938) devised a method, simple but specific, to determine blood prothrombin and also succeeded in demonstrating a prothrombin deficiency in jaundiced patients with haemorrhagic tendency. Warner, Brinkhous and Smith (1936) have developed a more accurate but somewhat complicated method. Recently, a third method has been employed and advocated by Dam and Glavind (1938; 1940). Two interesting findings are disclosed by the above studies. The first is that the prothrombin level is constant for each species. The second is that ordinarily the level of prothrombin is much in excess of the physiologic requirements, providing for large losses. Serious haemorrhages do not occur until 80 per cent of prothrombin is lost and the blood prothrombin sinks below 20 per cent. With the aid of these newer methods for the