It is now 24 years since the opening of New Tokyo International Airport. Nippon Medical School New Tokyo International Airport Clinic (Airport Clinic) was opened in December 1992 and is located in terminal 2 of the airport. We have treated 85,545 airport personnel (72.5%), 28,662 passengers (24.3%) and 3,746 other patients (3.2%), a total of 117,953 patients in its 8 years and 4 months of services so far. There were 8,485 non-Japanese patients (7.2%). There were 47 incidents of cardio-pulmonary arrest at the clinic of which 25 were suspected to be caused by pulmonary thromboembolism, otherwise known as the economy-class syndrome. Furthermore, out of the 75 severe and serious cases of pulmonary thromboembolism, there were 50 survivals and 25 fatalities. 14 of these cases were confirmed to be pulmonary thromboembolism while 61 cases were suspected of this disease. The age ranged from 21 to 95 with an average age of 59.1 years and the ratio of male to female patients was 31:44. The age range of the 14 confirmed cases were from 48 to 78 with an average age of 62.0 years and the male to female ratio was 1:13. There were 2 fatalities in the confirmed cases; both were women aged 66 and 69. The age of the 12 survival cases ranged from 48 to 78 with and average age of 61.0 years and the male to female ratio was 1:11. All these patients are now socially rehabilitated. The medical consultation rate was 1 in 4,000, the number of emergency medical care was 1 in 80,000 and the number of fatalities was 1 in 4 million passengers, roughly calculating from the figure of 26 million passengers a year at Narita Airport. The number of fatalities resulting from pulmonary thromboembolism was estimated at 1 in 7.5 million.

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A 66-year old Japanese woman developed gastrointestinal bleeding in July, 1994, after having been repeatedly transfused over a period of 11 years for aplastic anemia refractory to conventional treatments. Examination of her fundus oculi to screen diabetic retinopathy revealed left retinal bleeding due to left central retinal vein thrombosis. Coagulation tests gave positive results for lupus anticoagulant (LA), but, autoantibodies including antinuclear antibody and anticardiolipin antibody were not detected. Since autopsy revealed no apparent signs of sclerotic changes in the ocular vessels, hypercoagulability due to LA was considered the main cause of central retinal vein thrombosis. The thrombin generation inhibition assay showed that LA from the patient's plasma bound only to human prothrombin in the presence of anionic phospholipids and calcium ions, suggesting that her LA was induced by primary autoimmune response rather than secondary response to viral infections or blood transfusions.

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The antiphospholipid syndrome (APS) is one of the typical thrombosis-associated diseases and is diagnosed on the basis of clinical symptoms and laboratory data that indicate the presence of anti-cardiolipin antibody (aCL) and/or lupus anticoagulant (LA). Although criteria for the laboratory tests for the detection of aCL and LA had been proposed by the Scientific Standardization Committee of the International Society on Thrombosis and Haemostasis, these criteria have not necessarily been followed strictly. Thus, there are certain discrepancies among institutions in terms of accuracy of diagnosis and sensitivity to detect aCL and LA. In fact, we have recently experienced this sort of discrepancy between the data of tests conducted on a patient, in which the presence of LA was negative in a test performed by a commercially available blood test laboratory, whereas it was positive in the other conducted in our own hospital. Techniques employed in individual laboratories may differ : namely techniques for platelet deletion from plasma ; preparation of mixtures of normal and the patient's plasmas for the study of inhibitor (s) and the number of tests to be carried out for the detection of LA. These differences may well account for the discrepancy, and thus should be taken into consideration for the diagnosis of APS clinically.

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