Effect of N-acetylcysteine on the accuracy of the prothrombin time assay of plasma coagulation factor II+VII+X activity in subjects infused with the drug. Influence of time and temperature.

OBJECTIVES: The prothrombin time (PT) assay of factor II+VII+X activity is an important predictor of liver damage in paracetamol poisoned patients. It complicates interpretation of results that the antidote, acetylcysteine (NAC) depresses this activity. The aim was to investigate if NAC influences the accuracy of the plasma PT assay. MATERIALS AND METHODS: The accuracy of Nycotest PT was studied using plasma added NAC in vitro and plasma from subjects infused with NAC. The latter results were compared with those obtained by analysis of PT by CoaguChek S. RESULTS: Therapeutic NAC concentrations added to plasma in vitro decreased factor II+VII+X activity at 37 degrees C in a time-dependent manner. This effect was quenched at temperatures <24 degrees C. Activity lost at 37 degrees C could partly be recovered by subsequent incubation at 5 or 20 degrees C. Incubation at 37 degrees C prior to assay led to a significant additional depression of factor II+VII+X activity in plasma from subjects infused with NAC during the first 3h of infusion indicating that it contained reactive NAC. The risk that this NAC interfered with the accuracy of the PT assay was considered minimal with samples stored below 24 degrees C. This was supported by similarity of results obtained by analysis of appropriately stored plasma and simultaneously drawn blood by CoaguChek S. CONCLUSIONS: Residual reactive NAC does not interfere with the accuracy of the PT assay of plasma stored below 24 degrees C, but NAC-induced loss in activity at 37 degrees C may be partly recovered during subsequent storage below 24 degrees C.

[Serious bleeding in systemic lupus erythematosus complicated by lupus anticoagulant-hypoprothrombinaemia syndrome]. / Alvorlig blødning ved systemisk lupus erythematosus kompliceret med lupusantikoagulans-hypoprotrombinaemisyndromet.

Severe hemorrhagic diathesis due to lupus anticoagulant complicated by hypoprothrombinaemia resulting from prothrombin autoantibodies is a rare disorder and is often associated with systemic lupus erythematosus (SLE). We report a case in which a 15-year-old girl with SLE developed marked haemorrhagic manifestations due to menorrhagia and nosebleeds. The acute bleeding episode was treated with SAGM, tranexamic acid and recombinant factor VIIa. Lupus anticoagulant, cardiolipin antibodies and antiprothrombin antibodies were successfully depressed within weeks after corticosteroid therapy was begun.

[Pregnancy-related thrombocytosis]. / Svangerskabsrelateret trombocytose.

Pregnancy-related thrombocythaemia comprises myeloproliferative and inflammatory reactive subsets. In pregnant women treated for myeloproliferative disorders, especially polycythaemia vera and primary thrombocytosis, only 50-70 per cent are delivered successfully of a normal healthy baby. The maternal complications are cerebral, cardiac, and abdominal arterial thrombosis, and with deep venous thrombosis of the legs, whereas bleedings are mainly seen in the case of extreme thrombocythaemia, owing to absorption of factors by the platelets. The foetal complication are dominated by abruptio placentae, pre-eclampsia, placental insufficiency, and death. Reactive thrombocythaemia includes the physiological rise in platelets postpartum, believed to be part of the normal maternal haemostasis, which almost never causes thromboembolic complications, as far as is known today. In contrast, the inflammatory reactive thrombocythaemia, related to severe foetal and/or maternal necrosis, is generally related only to a moderate rise in the platelet count. As the blood-platelet count does not appear to be routine at general pregnancy check-ups, it is necessary to be aware of risk groups, consisting of women with otherwise unexplained abortions or stillbirths, unexplained foetal and placental malformations, and pre-eclampsia, even if the woman has never had any thromboembolic complications.

Frequent occurrence of anticardiolipin antibodies, Factor V Leiden mutation, and perturbed endothelial function in chronic myeloproliferative disorders.

Chronic myeloproliferative disorders (MPD) are characterized by a high incidence of thrombohaemorrhagic complications, possibly related to platelet abnormalities and disturbances of the coagulation system. In an attempt to define abnormalities in coagulation and fibrinolysis, we investigated risk markers for venous thromboembolism, fibrinolytic, and haemostatic system activation markers and antiphospholipid antibodies in blood samples from 50 MPD patients and 30 controls. Compared with controls median levels of protein S free and protein C were significantly decreased in the patients (0.27 vs. 0.38 arbitrary units; P < 0.001 and 0.86 vs. 0.99 arbitrary units; P < 0.001, respectively), and activated partial thromboplastin time was significantly prolonged in patients (33 vs. 27 sec; P < 0.001). No differences were observed in levels of antithrombin, thrombin-antithrombin complex, and fibrin D-dimer. In patients the median value of thrombomodulin was significantly increased indicating perturbed endothelial function. Anticardiolipin antibodies of IgM subtype (median 38 U/mL, 33-99) were detected in 11 patients (22%) and only in one control (3%) (P < 0.021; patients vs. controls). Seven patients were heterozygous for the Factor V Leiden, one patient was heterozygous for the prothrombin G20210A mutation, and one patient was homozygous for the Factor V Leiden mutation. Among controls, two were heterozygous for the Factor V Leiden mutation. Comparing the allele frequency of the Factor V Leiden mutation in patients with MPD and the background population disclosed a significantly increased allele prevalence of the Factor V Leiden mutation in the patients (9% vs. 3.4%; P = 0.003). Alterations in the level of anticoagulant proteins, disturbances of endothelial cell function, and the presence of cardiolipin antibodies and Factor V Leiden mutation may increase the cumulative thrombotic risk in MPD besides the risk imposed by platelet activation.