Antithrombin 3 depression and thrombin generation acceleration in women taking oral contraceptives

Markers of plasma coagulation and fibrinolysis after acute deep venous thrombosis

OBJECTIVE

Plasma markers of coagulation and fibrinolysis have proved sensitive in the initial diagnosis of acute deep venous thrombosis (DVT). The purpose of this study was to examine the evolution and utility of measuring D-dimer and prothrombin fragment 1+2 (F 1+2) levels after an acute DVT.

METHODS

Subjects with DVT confirmed by ultrasonography had quantitative plasma D-dimer and F 1+2 levels determined before anticoagulation. Ultrasound scan and coagulation studies were repeated at 3, 7, and 14 days; 1 month; and every 3 months for 1 year.

RESULTS

Sixty-one patients with a median initial thrombus score of 3 (interquartile range, 2-7) were followed up for 266 days (interquartile range, 91.5-364 days). Initial D-dimer levels were elevated in 92.7% of patients and were associated with thrombus extent (P =.003), whereas F 1+2 levels were increased in 94.5% of patients and were lower in patients with isolated calf vein thrombosis (P =.001). Initial D-dimer (P =.002) and F 1+2 levels (P =.009) were significantly higher in the 26 (43%) patients with recurrent thrombosis during follow-up. Initial D-dimer levels of 2000 ng/mL or greater were predictive of recurrent events after both proximal and isolated calf vein thrombosis. Although interval increases in these markers had little value in detecting recurrent thrombotic events, D-dimer levels of 1000 ng/mL or greater and 500 ng/mL or greater had respective sensitivities of 89.3% and 100% in detecting early and late recurrences. Corresponding specificities were 35.6% and 53.9%.

CONCLUSIONS

Initial D-dimer levels are determined by total thrombus load and remain elevated long after an acute DVT. F 1+2 levels are less sensitive to thrombus score and return to baseline more quickly. Initial levels of these markers may have some utility in predicting the risk of ultrasound scan-documented recurrences, whereas increased D-dimer levels are a sensitive but nonspecific marker of these events.

Hypercoagulability in cancer

The association of cancer with a hypercoagulable state is documented by numerous clinical, biochemical, pathologic, and pharmacologic studies. This association is manifested clinically by an increased incidence of intravascular thrombotic events in cancer patients and by fibrin deposition in and around tumor beds. Thromboembolic disease is a major cause of morbidity and mortality in patients with malignancy. This article discusses the complex pathogenesis of this problem and the associated laboratory and clinical syndromes with recommendations on diagnosis and treatment.

Early effects of continuous low-dosage all-norgestrel administered alone or with estrogen

Twenty-six postmenopausal women participated in a double-blind trial involving treatment according to a Latin square design with either (i) dl-norgestrel alone (0.075 mg/day) continuously for two cycles, (ii) estradiol-17 beta alone (1 mg on 25 of 28 days) for two cycles, or (iii) the combined hormones for six cycles. A placebo control cycle followed each hormonal treatment. Plasma triglycerides decreased by an average 22% during treatment with either dl-norgestrel alone (123 +/- 11 vs. 160 +/- 10 mg/dl, n = 25, P < 0.005) or combination therapy (126 +/- 11 vs. 162 +/- 11, n = 25, P < 0.005) as compared with control. Plasma total cholesterol fell by 5% during two cycles of treatment with either dl-norgestrel alone (229 +/- 11 vs. 242 +/- 10 mg/dl, n = 25, P < 0.02) or combination therapy (233 +/- 11 vs. 246 +/- 10, n = 25, P < 0.05) versus placebo. During the fifth and sixth cycles of combination therapy 94% of cycles were free of flushing (vs. 31% for control, P < 0.01), 64% of cycles were free of spotting not requiring protection (control 75%), 96% of cycles were free of vaginal bleeding (control 100%), endometrial biopsy showed inactive endometrium in nine of the 10 subjects re-biopsied, fasting blood pyruvate decreased by 20% (P < 0.05) and diastolic blood pressure fell by 4% compared with control (P < 0.05), whereas glucose tolerance was unchanged. There was a significant reduction in vasomotor flushing beginning with the third to fourth cycles of combination therapy.

Oral contraceptives and antithrombin III: variations by dosage and ABO blood group

A randomized clinical trial of oral contraceptives evaluated 67 women on a regimen of 50 micrograms ethinyl estradiol and 1.0 mg norethindrone, 61 women on a regimen of 35 micrograms ethinyl estradiol and 1.0 mg norethindrone, and 64 women on a regimen of 35 micrograms ethinyl estradiol and 0.5 mg norethindrone. ABO blood group type was determined in all women. At baseline and at 3, 6, and 9 months, plasma antithrombin III levels, by both an immunologic and an activity method, and selected plasma levels of the contraceptive steroids were measured. Antithrombin III levels for all oral contraceptive groups combined decreased from baseline by 19.7% and 28.8% for the immunologic and activity methods, respectively. Analysis of interrelationships among antithrombin III by activity method, oral contraceptive type, and ABO blood group showed larger declines in antithrombin III for type O women using the highest estrogen dose preparation (31.6%) and for non-type O women using the lowest progestin dose preparation (38.9%). Plasma levels of contraceptive steroids also were related to changes in the most extreme levels of antithrombin III.

Oral contraceptive therapy and the surgical management of ENT patients: a review of current clinical practice

The current policy of British Otolaryngologists with regard to the preoperative cessation of the oral contraceptive pill is reported. This is based on a confidential questionnaire sent to all members of the British Association of Otolaryngologists. The overall response rate was 66%, 91% of which were from practising otolaryngologists and forms the basis of this report, the remaining 9% being from respondents not engaged in active surgery. Although there is evidence to show an increased risk of developing thromboembolic complications after major abdominal, gynaecological and hip surgery in those patients taking the oestrogen-containing contraceptive pill, the risk following minor and intermediate surgery (which forms the bulk of the otolaryngologist's workload) is not known. Not surprisingly therefore the results of the survey show a varied policy across the country with 36.5% of respondents choosing to continue the pill and 25% always stopping the pill preoperatively. The remainder elect to stop the pill only in certain circumstances.

Effect of levonorgestrel contraceptive implants, Norplant, on blood coagulation

A longitudinal study of coagulation parameters was carried out on 47 women using the levonorgestrel subdermal implants, NORPLANT. The study comprised measurement of platelet count, prothrombin time, thrombin time, partial thromboplastin time with kaolin, clotting factors I, II, V and VI through XIII, plasminogen, antithrombin III (AT III), alpha 1 antitrypsin, alpha 2 macroglobulin and fibrinogen degradation products. The tests were done at admission and after one, three and six months of NORPLANT use. Parallel and similar studies were done on two groups of oral contraceptive users; the first group used a pill containing 1 mg norethisterone and 50 micrograms mestranol, and the second a pill consisting of 150 micrograms levonorgestrel and 30 micrograms ethinylestradiol. Results from this ongoing study have indicated that women using NORPLANT implants evidenced lack of effects on most of the parameters tested except for factor VII activity which was increased and AT III concentration which was decreased after six months of use. The combined pill users evidenced marked changes in the platelet count, the screening tests and in most of the coagulation-promoting factors; the changes were apparent after three months of use and became more pronounced after six months. The results demonstrate, with marked contrast, that the implants had less pronounced effects on the blood coagulation system than did the combined pills used in this study.

A comparison of antithrombin III procedures

Antithrombin III (AT III) is the most potent physiologic inactivator of thrombin and other serine proteases in the blood clotting mechanism. Hereditary deficiency of this protein is associated with recurrent deep-vein thrombosis that begins in late adolescence. Untreated, this disease may lead to early death from recurrent and massive pulmonary emboli. Attempts to identify groups of patients who are the most likely to develop thromboembolic disease because of an acquired deficiency of AT III have been frustrated by the lack of standardization of the assays and the inability to compare results of the different AT III assays. The functional assays and immunoelectrophoretic determinations do not measure the same component. In order to compare the ability of current AT III procedures to determine levels of AT III in various disease states, we used immunoelectrophoretic, chromogenic, and clottable assays to measure the AT III of patients with congenital AT III deficiency and of patients with possible acquired AT III deficiency.

Thrombin generation in normal plasma enriched with purified coagulation factors

During the intrinsic coagulation of normal platelet-rich plasma only 11% of the prothrombin is converted to thrombin. Complete conversion of prothrombin to thrombin occurs only via the extrinsic pathway (1). Addition of purified prothrombin to normal plasma to double or triple its concentration, doubled or tripled the amount of the generated thrombin as determined by the thrombin elution assay (1), so that the percentage of the proenzyme which was converted to thrombin remained the same. At the same time the activated partial thromboplastin time (APTT) was prolonged. Proportionality of the amount of the generated thrombin to the amount of prothrombin added and a delay in the appearance of thrombin activity was also observed with the thrombin generation test. Normalization of the APTT was observed when factor IX was added together with prothrombin. Addition of factor IX or X to normal plasma shortened the APTT but did not increase the amount of prothrombin which was converted to thrombin as determined by both the thrombin elution assay and the thrombin generation test. Further experiments indicated that (a) more factor X is activated per mg tissue factor than per mg of activated partial thromboplastin and (b) more thrombin is generated per unit of factor Xa in the presence of tissue factor than in the presence of activated partial thromboplastin. Thus, the two pathways differ not only by the mechanism of factor X activation but also by the extent to which prothrombin is activated by factor Xa.

Estrogen-induced deficiency and decrease in antithrombin III activity in patients with prostatic cancer

Plasma antithrombin III activity was studied in 22 patients with prostatic cancer who were on estrogen therapy. Normal plasma antithrombin III activity varies between 0.80 and 1.40 U. per ml. A loading dose of 15 mg. diethylstilbestrol daily resulted in a marked decrease in plasma antithrombin III activity (mean 0.24 U. per ml.). Patients with the lower end of normal range of pre-treatment plasma antithrombin III activity may suffer acquired antithrombin III deficiency and, thus, a concomitantly increased risk of thromboembolic complications as a result of estrogen treatment. Patients on maintenance therapy of approximately 1 mg. daily appear to have normal plasma antithrombin III levels. The results obtained suggest that plasma antithrombin III activity should be monitored before and during estrogen therapy in patients with prostatic cancer.

Oral contraceptives and venous thromboembolism

In 58 patients with phlebographically diagnosed deep vein thrombosis during oral contraception the extension and localization of the thrombotic process was analysed in relation to the coagulation and fibrinolytic system 6 months after thrombosis. Left-sided thrombi dominated and the thrombi were more extensive and proximal on the left side. This left-sided dominance was more apparent with higher oestrogen content in the pills. The right-sided thrombi more often were the source of pulmonary embolism. In 31% of the patients a defective fibrinolytic system was found; this defect was seen more often in patients with right-sided thrombi. Only very few defects were found in the coagulation system. No patients had an antithrombin III deficiency.

Oral contraceptives and blood coagulation: a critical review

Based on epidemiologic data, women who take oral contraceptives seem to have an increased risk of developing thromboembolic disease. In order to explain this association, some studies have been undertaken to find abnormalities in the hemostasis system. Many conflicting test results have been reported, probably reflecting in part the technical difficulties in use of reliable, reproducible, and specific assay systems. None of the data obtained seems to be specific for users of oral contraceptive drugs, and none was found uniformly in all takers of the drugs. Many findings are probably unimportant from the overall point of view of the physiology of hemostasis. Unfortunately, there seems to be no test procedure or even combination of tests that will reliably predict which patient might develop a thromboembolic episode in association with oral contraceptives or in association with any other condition recognized as being a risk factor. Even in most patients who do have a thrombosis, the test procedures fail to signal this event with reliability and predictability. At this time, it is not known whether oral contraceptives do or do not trigger the hemostasis system to develop a thrombosis or by which mechanism they could trigger the event. Fortunately, only a very small number of women develop thrombosis in association with oral contraceptives.

Menopausal status associated with increased inhibition of blood coagulation

Postmenopausal women receiving estrogen replacement therapy (ERT) are not as prone to inappropriate venous and arterial thrombosis as are younger women taking oral contraceptives. To establish whether menopausal status per se has any effect on the coagulation-fibrinolytic system normal premenopausal women (mean age 29 years) were compared with younger (mean age 23) and older (mean age 51) surgically menopausal women and a group of naturally postmenopausal women (mean age 53). The results show that in postmenopausal women, irrespective of age or type, the shift is away from clot formatiuon and toward clot inhibition and fibrinolysis as determined by static in vitro analysis. This was characterized by statistically significant increases in antithrombin III antigen, alpha 1-antitrypsin antigen, and plasminogen activity. These changes may help to explain in part why ERT does not appear to cause increased thrombosis in older women.

[Antithrombin III: reference values found with a chromogenic substrate (chromozym TH) (author's transl)]

A new kinetic assay for antithrombin III (heparin-cofactor) in plasma was used to determine reference values. Ranges of 10--15 IU/ml at 25 degrees C and 20--29 IU/ml at 37 degrees C were found for a reference population of 219 men and 204 women 15--93 years of age. There was no evidence that these values vary with age or sex, nor was there any difference between pre- and postprandial antithrombin activities, or between smokers' and non-smokers' values. None of the illnesses present in the reference population nor any related drug therapy affected the antithrombin III level, and there was no statistically significant difference between the values for women taking oral contraceptives and those who did not. However, this latter observation does not preclude the possibility of individual variation.

Development of large scale fractionation methods. VII. Preparation of antithrombin III concentrate

A large scale method for preparation of antithrombin III (AT III) concentrate from plasma or from Cohn fraction IV-1 (Fr. IV-1) has been described. It consists of the following steps: (a) partial purification by precipitation of impurities with 20% polyethylene glycol (PEG) 4000; (b) isolation of AT III from the PEG supernatant by batch adsorption and elution on heparin-Sepharose at a ratio corresponding to 45 vol of plasma or 80 vol of 10% Fr. IV-1 solution to 1 vol of gel; (c) concentration and desalting of the eluted AT III on a Pellicon ultrafiltration system; (d) pasteurization of AT III concentrate by heating for 10 h at 60 degrees C in the presence of 0.5 M sodium citrate at pH 7.5; (e) removal of excess citrate by gel filtration on Sephadex G-50; and (f) sterile filtration, filling and lyophilization. The recovery by activity was 32% from a 113-liter plasma batch and 16% from a 42-kg Fr. IV-1 batch. Both AT III concentrates, derived either from plasma or from Fr. IV-1, had similar specific activity and electrophoretic purity, were nonpyrogenic and met all other FDA requirements for biologic products. Pasteurization induced changes in disc gel and isotachophoretic patterns of AT III preparations.

The effects of quinestrol and bromocriptine on blood coagulation, serum prolactin and serum FSH levels in puerperal women

The effects of bromocriptine and quinestrol upon coagulation and fibrinolysis during the puerperium were studied. Quinestrol therapy was associated with increased levels of factors VII and IX and decreased antithrombin activity on the sixth postpartum day, and increased factor IX and plasminogen levels on the fourteenth postpartum day. Six weeks after delivery elevated levels of factors II and VII and of plasminogen were recorded in women given quinestrol. Bromocriptine therapy only caused an increase in the level of factor IX at six weeks after delivery. Compared to controls, patients given bromocriptine had lower prolactin and higher FSH levels during the puerperium whereas the patients given quinestrol had increased prolactin levels and a late fall in FSH levels.

[Blood coagulation and fibrinolysis in women receiving estrogen, gestagen and estrogen-gestagen-contraceptives (author's transl)]

Eight femal subjects received a contraceptive with a low estrogen content (Neogynon), the estrogen component (50 mug ethinylestradiol) and consecutively the gestagen component (250 mug D-Norgestrel) of the contraceptive. Each treatment cycle was followed by a control cycle. At various times of the control and therapy cycles several coagulation and fibrinolytic parameters were investigated. Statistical analyses were performed by multivariate two-factorial analysis of variance. Plasminogen exhibities a statistically significant increase during the treatment with ethinylestradiol and the combination of this steroid with D-norgestrel. No significant changes were found for all other parameters, including partial thromboplastin time, fibriogen, factors X, IX, VIII, factor VIII-related antigen, antithrombin III and fibrin(ogen)degradation products.

A study of blood coagulation parameters

The object of this study was to determine the presence or absence of abnormalities in a variety of blood coagulation parameters in women on contraceptive medication. A prospective double-blind study involving a control group with a total study enrollment of 211 women during a 29 month period was established. Although research has not proved that changes in coagulation parameters will cause abnormal clotting in normal patients, a pattern appears to be developing involving antithrombin III determinations. Corresponding patterns do not appear to be developing in the other blood coagulation parameters.

Conjugated estrogens and hypercoagulability

A group of 11 menopausal women receiving 1.25 mg. of conjugated estrogens daily had coagulation tests to determine the development of hypercoagulability after taking 5 and 21 tablets. There was no essential change in thrombin generation or fibrinolytic activity as measured by euglobin lysis time. There was a shift toward hypercoagulability in all three parameters of the thrombelastograms. The decrease of the antithrombin III activity was not as pronounced following the administration of conjugated estrogens as had been the change associated with oral contraceptives. Fibrin monomers were observed in some women during the first week of Premarin therapy.