Enhancement by factor V Leiden mutation of risk of deep-vein thrombosis associated with oral contraceptives containing a third-generation progestagen

Activated protein C resistance and deficiencies of antithrombin III, protein C or protein S and the risk of thromboembolic disease in users of oral contraceptives

The objective of this paper was to assess the risk of thrombosis in users of oral contraceptives. Furthermore, the sensitivity, specificity and predictive values of potential screening tests for the prediction of thromboembolic complications in users of oral contraceptives were calculated for the approximately six million German pill users. Despite high specificity, the predictive values of a positive family history, or evidence of either antithrombin III, protein C or protein S deficiency or resistance to activated protein C, are low due to the very low absolute risk of thrombosis among pill users. More than half of the 840 annual cases would pass the screening protocol undetected. A two-step screening protocol is suggested using family history as a selection criterion (thus reducing the need for laboratory screening by 85%) for laboratory investigation of activated protein C sensitivity and deficiencies of antithrombin III, protein C or protein S. Genotyping for factor V Leiden mutation is useful in cases with equivocal activated protein C sensitivities or to confirm a homozygous genotype.

Oral contraceptives and venous thrombosis: end of the debate?

During the more than 30-year history of oral contraceptives, clinicians have received several official warnings issued by regulating agencies on cardiovascular risks. These have affected not only gynecological practice, but also generated research activities resulting in the refined third-generation products marketed in the 1970s. The alert sent out by the UK Committee on Safety of Medicines (CSM), October 1995, on increased risk of deep venous thrombosis during use of these compounds was, therefore, very much unexpected. The statements were referring to unpublished data and, thus, indicated new and highly alarming findings. However, during the following months, although four epidemiological studies reported a 2-4 fold relative increase compared with the second-generation oral contraceptives. This relative increase means, looking at absolute risks, an excess of 1-2 cases of deep venous thrombosis per 10,000 oral contraceptive users per year. In the academic discussions following the primary publication of the four papers, the possibility of confounding factors and bias was strongly emphasized and follow-up studies together with re-analysis of the original studies have not generated evidence for the suspicion of the increased risk with third-generation oral contraceptives. In contrast, a decreasing tendency was demonstrated for more serious events such myocardial infarction. Also, the biological plausibility for increased risk of deep venous thrombosis with third-generation products is lacking, although one study has pointed to a change in the natural anticoagulatory mechanism. Obviously, the authorities have a right to react on suspicion, but the psychological and social effects of the abrupt stopping of oral contraceptive use should not be ignored, and the public understanding of scientific results is manipulated by the mass media. Following confirmed evidence from both epidemiological and biological studies, with full acknowledgement of the contraceptive and non-contraceptive benefits from oral contraceptives, an official statement should have been part of the communication strategy to prevent pill scare. A more appropriate reaction from the authorities would have been to await action until publication and scientific validation of several peer-reviewed articles and to include also absolute risks instead of relative findings.

Oral contraceptives and venous thromboembolism. A case-control study

To assess the influence of oral contraceptives (OC) on the risk for venous thromboembolism (VTE) in young women, a 5-year case-control study including all women 15-44 years old suffering a first deep venous thrombosis or a first pulmonary embolism from all Danish hospitals, along with 1200 control subjects during the period 1994-1995, was conducted. Of 586 patient and 1200 control subject questionnaires sent out, 523 patient (89.2%) and 1074 control (89.5%) questionnaires were returned with an agreement to participate. After exclusion of women with nonvalid diagnoses, women who were pregnant, and women with previous VTE or acute myocardial infarction (AMI), 375 patients and 1041 control subjects were available for analysis. Potential tested confounders included: body mass index, length of OC use, family history of VTE, AMI, or stroke, smoking habits, coagulopathies, diabetes, years of schooling, certainty of diagnosis, previous births, and treated hypertension during any pregnancy. A multivariate analysis was performed. Estrogen dose had no influence on the risk for VTE. The risk for VTE among current users of OC was primarily influenced by duration of use, with significantly decreasing odds ratios (OR) over time: < 1 year; 5.1 (3.1-8.5); 1-5 years; 2.5 (1.6-4.1); and > 5 years; 2.1 (1.5-3.1), all compared with those for nonusers of OC. This trend was still significant after adjustment for progestin types. Without adjustment for duration of use, current users of OC with second generation (levonorgestrel or norgestimate) and third generation (desogestrel or gestodene) progestins had OR of 1.8 (1.1-2.9) and 3.2 (2.3-4.4), respectively. After correction for duration of use, however, no significant differences were found between users of OC with different types of progestins. In conclusion, OC increase the risk for VTE significantly. The risk among current users of OC is primarily influenced by duration of use. No difference in risk was found according to estrogen dose, and the difference in risk between different types of progestins was not statistically significant after adjustment for duration of use.

Cerebral thrombosis and oral contraceptives. A case-control study

To assess the influence of oral contraceptives (OC) on the risk of cerebral thrombosis and transient cerebral ischemic attacks, a 5-year case-control study including all Danish hospitals was conducted. All women 15-44 years old who suffered a cerebral thromboembolic attack (CTA) during the period 1994-95 and 1200 age matched control subjects were included. Of 309 patients and 1200 control subjects questionnaires sent out, 271 patients (87.7%) and 1074 control subjects (89.5%) responded and agreed to participate. After exclusion of women with nonvalid diagnoses, previous thromboembolic diseases, or current pregnancy, 219 patients and 1041 control subjects were available for analysis. After confounder control and with nonusers as reference, current users of first generation OC (50 micrograms of ethinyl estradiol [EE] or estrans) had an odds ratio (OR) of CTA of 1.86 (95% confidence interval [CI] 0.88-3.92); users of second generation OC (levonorgestrel or norgestimate) had an OR of 2.37 (1.35-4.16); and users of third generation OC (desogestrel or gestodene) had an OR of 1.32 (0.78-2.22). Users of OC with 50, 30-40, or 20 micrograms EE had OR of 2.65 (1.11-6.34), 1.60 (1.05-2.43), and 1.59 (0.57-4.58), respectively. Odds ratios for specific progestin types were as follows: estrans 1.37 (0.60-3.13), levonorgestrel 2.43 (1.40-4.21), norgestimate 7.09 (1.87-26.8), desogestrel 1.62 (0.72-3.63), and gestodene 1.24 (0.67-2.30). Duration of use was without significant influence on the risk and the OR were constant across the age bands. Compared with women who had never used OC, former users had an OR of CTA of 0.95 (0.66-1.51). In conclusion, use of OC with 50 micrograms of EE and OC with second generation progestins increased the risk of CTA significantly. OC with third generation progestins did not have any significant influence on the risk of CTA. The risk of CTA among former users of OC was not increased.

Oral contraceptive use before and after the latest pill scare in The Netherlands. Changes in oral contraceptive use and how users change

In October 1995, a "pill scare" developed in Europe. In the Netherlands, the recommendations given were 1) to not alarm women without risk for deep vein thrombosis (DVT), and 2) to be reserved in prescribing third generation oral contraceptives (OC) for young women who were beginning OC use. To determine whether there is a change in the prescription of third generation OC after the latest pill scare, prescription data from 1/10/94 to 1/10/96, covering a population of +/- 120,000 persons, were studied with respect to OC use before and after the pill scare. Trend analyses revealed a significant decline in third generation compared with total OC prescribing only in the youngest age category (p = 0.0034). Further, switch behavior was studied. Switches from third to second generation OC were more prevalent after the pill scare than before (odds ratio = 2.63; 95% confidence interval 1.84-3.75) and switches from second to third generation OC were significantly less prevalent after the pill scare. This indicates that Dutch prescribers have reacted to the pill scare in the way that the government recommended.

[Estrogen therapy and venous thromboembolic disease]

A link between venous thromboembolism and oral contraceptive users is well established. This paper analyzes recent epidemiological studies affecting risk of venous thromboembolism with the use of oral contraceptive or with postmenopausal hormone replacement therapy. Four epidemiological studies showed a two-fold increase of venous thromboembolism with the use of oral contraceptives containing third generation progestins (gestodene and desogesterel, relative to second-generations product (levonorgestrel); relative risk 3.8 per 100,000 women years in non-user women, 16 per 100,000 women years in women using levonorgestrel containing oral contraceptive) and 29 per 100,000 women years in women using gestodene containing oral contraceptive). Third-generation oral contraceptives induce a resistance to the activated protein C of almost the same magnitude as the resistance induced by a mutation in coagulation factor V. Studies with postmenopausal estrogen-replacement therapy show a two-fold risk of venous thromboembolism with estrogen only as well as with combined estrogen-progestagen hormone replacement therapy. However venous thromboembolism risk is very small compared with the cardiovascular and other benefits.

[Hospitalization of young women after selected cardiovascular and thromboembolic incidents in Austria 1993 and 1994]

The aim of this study is to describe the hospitalization and regional distribution of selected cardiovascular and thrombo-embolic events (cardiac infarction, cerebral strokes, deep vein thromboses, pulmonary embolism) of young women in Austria in the years 1993 and 1994, and to collect basic epidemiologic data for the study of the side effects of oral contraceptives. The calculated hospitalization rates are based on the Austrian hospitals' discharge records of 1993 and 1994. The persons concerned are women aged between 15 and 44 who live in Austria. The results of the study reveal that--in 1993--of the above mentioned group 51 out of 100,000 inhabitants were hospitalized because of the selected cardiovascular and thromboembolic events: 4/100,000 had a cardiac infarction, 5/100,000 had a stroke, 17/100,000 had a pulmonary embolism, and 27/100,000 suffered a deep vein thrombosis. In 1994 the counted cases per 100,000 inhabitants were 48, out of which 4/100,000 where cardiac infarcts, 5/100,000 strokes, 16/100,000 pulmonary embolism, and 25/100,000 deep vein thromboses.

Hormonal contraception and risk of cardiovascular disease. An international perspective

The most frequent major adverse effect of hormonal contraception is an increased risk of cardiovascular disease. The effect on the risk of venous thromboembolism (VTE), ischemic and hemorrhagic stroke, and myocardial infarction (MI) differs and is strongly influenced by smoking and the presence of other cardiovascular risks factors, such as hypertension and diabetes mellitus. The incidence of each disease rises with age and there are differences in risk among hormonal contraceptive preparations. This article provides a framework within which to assess the balance of risks among types of hormonal contraceptives according to individual circumstances. Data on cardiovascular disease mortality rates in women of reproductive age in different countries of the world were compiled from nationally reported statistics and supplemented where possible with reported disease incidence rates. Risks associated with current use of hormonal contraception were compiled from the most recent publications on the cardiovascular effects of steroid hormone contraception. These were combined to estimate the total cardiovascular incidence and mortality according to baseline cardiovascular risk and individual characteristics. Mortality rates for cardiovascular diseases are very low in women of reproductive age. Myocardial infarction mortality rates rise from < 0.4 per 100,000 woman-years at age 15-24 years to the range 2 to 7 per 100,000 woman-years at age 35-44 years. Stroke mortality rates similarly rise steeply with age and are between 3 and 5 times higher than those for MI. VTE mortality rates rise less steeply with age and are approximately one-tenth the MI mortality rates at age 35-44 years. The adverse effect of oral contraceptives (OC) on the risk of VTE is the most important contributor to the total number of cardiovascular cases attributable to OC use. The increased risk of stroke and MI dominate the patterns of mortality in OC users and smokers. The additional risks attributable to smoking are greater than the additional risks attributable to OC use. The risk attributable to OC use in women < 35 years of age is small, even if they smoke, but there are substantially increased risks in older women who both smoke and use OC. The additional mortality attributable to OC use can be reduced by screening users, as this results in lower relative risks of ischemic stroke and MI. Differences between OC types in the relative risk of VTE contribute little to the total cardiovascular mortality associated with OC use, even though the total number of cardiovascular events is increased. A potential reduction in the risk of MI with desogestrel and gestodene compared with levonorgestrel-containing OC would have little difference on overall mortality rates in women in their 20s and 30s, but may result in a net reduction in OC-attributable mortality in women aged 40-44 years who smoke. An overall quantification of the risks for different types of oral contraceptive users is necessary for an informed choice of contraceptive method, and any assessment of the balance of cardiovascular risks is complex. The model provides a tool to assess, at the level of the individual, the risks associated with use of different OC according to personal circumstances. It is important to consider the user's age and smoking status when determining OC attributable risks.

Newer oral contraceptives and the risk of venous thromboembolism

Research on the relationship between venous thromboembolism and the progestagen content of combined oral contraceptives has pointed to an increase in risk associated with products containing desogestrel and gestodene. Although many biases must have been at play in these nonexperimental studies, the errors that have been suggested and examined are not of a sufficient magnitude to account for the observed results. The most plausible explanation of the available data is that combined oral contraceptives containing desogestrel and gestodene carry a very small risk of venous thromboembolism, which exceeds the even smaller risk carried by products containing levonorgestrel. The position of norgestimate is uncertain.

Blood coagulation and oral contraceptives. A critical review

The use of oral contraceptives is associated with altered plasma concentrations of many components of the coagulation and fibrinolysis system, increased plasma levels of markers indicating in vivo coagulation and fibrinolysis, and a modified response to challenge tests both in vivo and in vitro. None of these effects seems to be specific for users of oral contraceptives and none was found uniformly in all users. The predictive value of each of these effects, or even of certain combinations of tests, for the prediction of venous thrombosis is low. There is no established way to assess the "thrombogenicity" of particular pills. The individual susceptibility, however, to develop venous thrombosis varies considerably. Recently, several congenital abnormalities of the hemostatic system have been found that are associated with an increased risk of venous thrombosis in general. The risk associated with the use of oral contraceptives appears to act synergistically with some of these thrombophilic conditions. Although the prevalence of these congenital predispositions varies among different populations, screening for these conditions is not feasible: negative results would not exclude the occurrence of about two-thirds of oral contraceptives-associated thromboses and positive results are likely to be disregarded because of their poor predictive value. Future research has to evaluate the role of a more targeted screening strategy aiming at women with risk factors such as a positive personal or family history of venous thromboembolism.

The risks of venous thromboembolic disease among German women using oral contraceptives: a database study

This study investigated the risk of venous thromboembolic disease (VTE) between second and third generation combined oral contraceptives, using the German MediPlus database of patient records. Women studied included 42 patients between the ages of 18 and 49 years, with a diagnosis of VTE treated with an anticoagulant, who were exposed to an oral contraceptive (OC). Four controls per patient (168), matched by year of birth and exposure to an OC on the even day, were identified. More women were users of second generation than third generation OC, and none were using progestogen-only pills. There was no significant difference between patients and control subjects with respect to the type of OC used on the event day (unadjusted odds ratio for third versus second generation users was 0.77; 95% confidence interval [CI] 0.38-1.57). There was no significant age difference between second and third generation users among patients or control subjects. Between January 1 and the event date, there was no significant difference between the patients and control subjects in terms of the number of oral contraceptive prescriptions, number of consultations for psychotherapeutic complaints, or mixed physical and psychotherapeutic consultations; however, patients did demonstrate significantly more consultations for purely physical complaints compared with control subjects (p < 0.0001). There were no significant consultation differences between patients with pulmonary emboli (n = 6) and other VTE patients (n = 36). No significant differences with respect to VTE risk between users of second and third generation oral contraceptives were found in this study. Consultations (physical) for patients were higher than for control subjects before the VTE event. If consultation rate relates to the general health status of a person, this might indicate that VTE risk is higher among women of poorer health, but that this is not related to the type of progestogen in the oral contraceptive that they use.

Risk of acute cerebrovascular events related to low oestrogen oral contraceptive treatment

To establish if an association exists between use of oral contraceptives (OC) and the occurrence of cerebral arterial thromboembolism, cerebral venous thrombosis and retinal vein/artery thrombosis, we identified all women aged 15-44 years resident in the province of Parma, Italy, who were hospitalized because of a documented cerebral or retinal thromboembolic event during the period 1989-1993. The numbers of users and nonusers of OC were estimated from drug sale data and demographic statistics for the province. There were 21 cases of cerebral arterial thromboembolism during the study period: 10 in OC users and 11 in nonusers, for an estimated incidence rate of 1.70 and 0.35 per 10,000 woman-years OC of use and nonuse, respectively (RR=4.8, 95% CI = 1.8-9.0). Eight cases of cerebral venous thrombosis were observed: 6 in OC users and 2 in nonusers (both in puerperium), for an incidence rate of 1.00 and 0.06 per 10,000 woman-years, respectively (RR=16.7, 95% CI = 3.3-81.4). Finally, 13 cases of retinal vein/artery thrombosis were found: 1 in OC users and 12 in nonusers, for an incidence rate of 0.17 and 0.37 per 10,000 woman-years, respectively (RR=0.46, 95% CI = 0.06-3.7). In our population study the use of low oestrogen OC was associated with an increased risk of cerebral venous thrombosis and ischemic stroke, but not of retinal vein/artery thrombosis.

The pediatrician and the sexually active adolescent. Sexual activity and contraception

Sexuality and its resultant consequences continue to be major issues for adolescents and for those who provide their health care. This article discusses current sexual behavior in adolescents and describes the various forms of hormonal contraception that sexually active adolescents should use.

Mortality from venous thromboembolism among young women in Europe: no evidence for any effect of third generation oral contraceptives

STUDY OBJECTIVE

To investigate whether there has been an increase of venous thromboembolism (VTE) mortality in European countries, concurrent with the replacement of second generation by third generation combined oral contraceptives (COCs). Such an increase has been predicted, and reportedly detected, because published studies have detected an increased incidence of VTE associated with third generation rather than second generation COC use.

DESIGN

Data were collected on population and annual VTE mortality in women 15-34 and 35-49 years old, and on second and third generation COC sales, from 1981 to 1994 in 13 European countries. Data from the seven most populous countries were analysed by linear regression of annual VTE mortality, in the 15-34 and 15-49 age groups, with respect to calculated total and third generation COC use rates, and the regression coefficients used to estimate mortality differences between second generation users and non-users and between third and second generation users, respectively.

MAIN RESULTS

The estimated mortality differences in all seven countries had confidence intervals wide enough to contain both zero and the excess mortalities expected from the results of published studies. This was true both for the mortality difference between third and second generation COC users and for that between second generation users and COC non-users.

CONCLUSIONS

Mortality differences of the size expected from the published studies cannot be measured using annual national VTE mortality and COC sales data alone, because of residual interannual variation in VTE mortality, and possibly confounding between rising third generation market share and total COC use.

Molecular Genetics of Factor V Leiden: Genetic Origins and Modern DNA-Based Detection Strategies

It has been acknowledged that a prothrombotic tendency may result from a specific genetic defect. Resistance to activated protein C (APC) (factor V Leiden) is now recognized as the most prevalent cause of increased thrombogenicity, being found in 2% to 5% of the world population. The APC-resistant phenotype arises from a well-characterized transitional mutation, resulting in an arginine(R)-506-glutamine(Q) amino acid substitution. Much remains to be uncovered concerning the importance of this mutation and how it relates to other conditions on a broader basis. Relevant and accurate detection methods that quickly identify the genetic lesion will play a major part in this strategy. This article details recent advances in identifying the factor V Leiden mutation by modern molecular techniques.

Third-generation oral contraceptive and deep venous thrombosis: from epidemiologic controversy to new insight in coagulation

Four epidemiologic studies showed a twofold increase in risk of deep venous thrombosis with the use of oral contraceptives containing third-generation progestins, relative to second-generation products. These findings have been strongly debated ever since, and new studies have been added. In the current article we examine whether the findings can be explained by potential biases or other shortcomings of the epidemiologic studies. We conclude that complete certainty cannot exist but that the most rational conclusion from the epidemiologic findings and their discussion is that an increased risk of deep venous thrombosis with third-generation contraceptives is likely, especially in first-time and young users. The controversy has recently led to new insights in coagulation: Women who use third-generation contraceptives acquire a resistance to the blood's own anticoagulation system, similar to the activated protein C resistance that is seen in persons who carry the factor V Leiden mutation but different from that in women using second-generation contraceptives.

Modern oral contraceptives and cardiovascular disease

We reviewed evidence that bears on the cardiovascular safety of combined oral contraceptives containing second- and third-generation progestogens and < 50 micrograms of estrogen. Recent epidemiologic studies indicate that current use of these formulations is associated with a smaller increase in the incidence of venous thromboembolism than earlier formulations. In some studies the increase for third-generation formulations containing desogestrel or gestodene was about 1.5 to 2 times that for second-generation formulations, but there is evidence that differences between users in underlying risk and likelihood of being diagnosed contributed to this result. Recent studies of myocardial infarction suggest a smaller increase in risk associated with modern formulations than with earlier ones; one study suggests a threefold increase for second-generation formulations and no increase for third-generation formulations, but the finding requires confirmation. Recent studies of stroke indicate little or no increase in risk for modern formulations among women without risk factors. We conclude that modern combined oral contraceptives are safer than earlier formulations with respect to cardiovascular disease, which occurs rarely in young women.

The pill and thrombosis: epidemiological considerations

The oral contraceptive is one of the most widely taken medications in the healthy population. The clinically important side-effects are venous and arterial thrombosis. Accurate estimates of incidence of these side-effects have proven to be difficult. Diagnostic modalities for thrombosis are sub-optimal and the problems of study methodology, primarily a reliance on non-experimental studies, have limited the ability to define the attributable risk of thrombosis from oral contraception. Pharmacological attempts to further decrease venous thrombotic side-effects by the use of third-generation oral contraceptives have failed. This places a greater emphasis on the selection of patients to help avoid giving medication to those patients with underlying thrombotic risk factors. An example of this approach has been the clear confirmation of the adverse effects of cigarette smoking and arterial thrombosis in oral contraceptive users. At the biochemical level, hypercoagulability testing may be useful. Screening for high-frequency prothrombotic abnormalities, such as the Factor V Leiden genotype, represents an important addition to the process by which patients are selected, and may be prototypic of further advances.

First-time use of newer oral contraceptives and the risk of venous thromboembolism

Recent epidemiologic studies reported that the risk of venous thromboembolism (VTE) was higher with the use of the newer third generation oral contraceptives than with second generation agents. Although the overall findings of these studies are similar, the results, as they relate to patterns and duration of oral contraceptive use particularly among first-time users, are inconsistent. We reanalyzed data from the Transnational case-control study to assess the risk of VTE associated with first-time use of oral contraceptives as a function of its duration of use. Over the period 1993 to 1995, 471 cases of venous thromboembolism were identified in Germany and the United Kingdom. For each case, up to four controls were obtained, for a total of 1772 controls. Data on oral contraceptive use and confounding variables, including data on sociodemographic, lifestyle, medical history, and family history of disease, were obtained by interview. Data analysis was based on the 105 cases and 422 controls who were first-time users of second or third generation agents, or never users of oral contraception. Rate ratios, adjusted for confounders and approximated by odds ratios, were estimated as a continuous function of duration of oral contraceptive use by logistic regression and quadratic spline models. We found, for first-time users, that the adjusted rate ratio of VTE as a function of the duration of oral contraceptive use is essentially identical for second and third generation pills relative to never users. This rate ratio increases to around 10 in the first year of use and decreases to around two after 2 years of use, remaining at this risk level thereafter for both second and third generation agents. We conclude that second and third generation agents are associated with identical risks of venous thromboembolism when they are prescribed to women who are using oral contraceptives for the first time ever.

Estrogen and progestin components of oral contraceptives: relationship to vascular disease

Recently, new information has been published about: a) the relationship between combination oral contraceptives (OCs), estrogen dose, cigarette smoking, and the risk of myocardial infarction (MI) and stroke; and b) the effect of different progestins on the risk of venous thromboembolism (VTE). We review the epidemiologic data. Regardless of age, in the absence of smoking, use of sub-50 micrograms OCs is not associated with any meaningful increase in risk of MI or stroke. If the small, statistically nonsignificant elevations in risk for these diseases are assumed (for the sake of argument) to be causal, then the incidence of MI and stroke associated with use of OCs containing less than 50 micrograms ethinyl estradiol (EE) would be approximately 2 per 100,000 per year. For women less than 35 years of age who do not smoke or do not have a history of hypertension, the risk would be even lower. Any woman over the age of 35 who smokes should be advised to use a non-estrogen or nonhormonal contraceptive. There are now two reports, from jick et al. and Lewis et al., that demonstrate that the relative risk of MI is certainly no greater for users of OCs containing desogestrel or gestodene than for users of OCs containing older progestins. In fact, both show reduced relative risks for the newer progestins compared to the older ones. With respect to progestins, four recent epidemiologic studies have indicated a twofold increased risk of nonfatal VTE with use of OCs containing desogestrel or gestodene compared with levonorgestrel. A fifth report, which showed an increased relative risk for norgestimate, is based on use among only 19 cases and 31 controls and is not statistically significant. As the authors themselves caution and as subsequent follow-up analyses and editorials conclude, these studies do not provide evidence for a cause-and-effect relationship between OCs containing desogestrel or gestodene, and VTE. The recommendation with respect to desogestrel- and gestodene-containing OCs is that no change in prescribing practices is warranted for either current or new-start patients. There is a growing body of evidence demonstrating that OCs containing 30 or 35 micrograms of EE have lower risks of MI, stroke, and VTE than higher dose OCs. However, there is no epidemiologic study that demonstrates a greater risk of vascular events among women using OCs containing 30 or 35 micrograms EE compared with preparations containing 20 micrograms EE. Users of sub-50 micrograms OCs of any age have no clinically meaningful increase in incidence of MI or stroke compared with non-OC users. This is also true for smokers under the age of 35 years who use OCs. However, smokers over the age of 35 years who use OCs still have an unacceptably high incidence rate of MI and stroke and should not use combination OCs. Sub-50 micrograms OCs of all types are associated with a small excess risk of VTE, about 15 per 100,000 events per year. Until there is biologic explanation of the twofold greater risk of VTE in users of OCs containing desogestrel or gestodene compared with users of those containing older progestins, this association should not be accepted as one of cause and effect.

Modeled estimates of myocardial infarction and venous thromboembolic disease in users of second and third generation oral contraceptives

Consistent reports from several recent studies suggest that users of third generation oral contraceptives (OCs) containing gestodene and desogestrel may be at increased risk of venous thromboembolic disease (VTE). Paradoxically, other reports indicate that these users may be at decreased risk of acute myocardial infarction (MI) compared with users of second generation OCs. To determine whether the potentially increased risk of VTE would outweigh the potentially reduced risk of MI in users of third generation OCs, we conducted an analysis to quantify the trade-offs providers and users may be faced to make between these formulations. The baseline rates of VTE and MI among non-users were calculated using US data on incidence and mortality of these conditions and estimates of the proportion of women exposed to these formulations in the US. These were multiplied by relative risks published in recent studies on third generation progestins to produce age- and formulation-specific risks. Results indicate that there would be small differences in disease burden between users of second and third generation OCs under the model assumptions at younger ages. However, among women 35-44 years of age, modeling results indicate that the potentially decreased incidence of MI among users of third generation OCs more than offsets the potentially increased risk of VTE at this age.

Medroxyprogesterone interferes with ovarian steroid protection against coronary vasospasm

Cardiovascular disease, the major cause of death in post-menopausal women, can be reduced by replacement of ovarian steroid hormones. To compare medroxyprogesterone with progesterone as the progestin in hormone replacement therapy from the standpoint of coronary artery vasospasm, we treated ovariectomized rhesus monkeys with physiological levels of estradiol-17 beta in combination with medroxyprogesterone or progesterone for four weeks. Coronary vasospasm in response to pathophysiological stimulation without injury showed that progesterone plus estradiol protected but medroxyprogesterone plus estradiol failed to protect, allowing vasospasm. We conclude that medroxyprogesterone in contrast to progesterone increases the risk of coronary vasospasm.

The factor V Leiden mutation: spectrum of thrombotic events and laboratory evaluation

PURPOSE

This study aims to describe the spectrum of clinical thrombotic events and to compare the methods of laboratory evaluation for the newly described prothrombotic factor V Leiden mutation.

METHODS

Specimens from 1376 patients with thrombotic events or their relatives were tested for the factor V Leiden mutation by polymerase chain reaction plus restriction digest from Jan. 1, 1995, to Mar. 31, 1996. Activated protein C (APC) resistance test data was available for 554 of these patients. Clinical information was available for 166 patients with the mutation.

RESULTS

Of 1376 patients tested for factor V Leiden mutation, 270 (19.6%) were positive, with 12 homozygotes and 258 heterozygotes. Of 554 patients for whom APC resistance data was available, 221 (39.9%) had low APC resistance ratios (< or = 2.4); of these only 97 (43.9%) were factor V Leiden-positive. Among 333 samples with normal or elevated APC resistance ratios, 19 (5.7%) were later identified with the factor V Leiden mutation, despite the normal screening test. One hundred fourteen of 166 patients (68.7%) with the mutation had at least one thrombotic event, most commonly deep venous thrombosis and pulmonary embolus. Arterial cerebrovascular thrombotic events occurred in 11 patients (10%), and myocardial infarctions in eight (7%). The mean age of all patients with arterial thrombotic events was 45.4 years.

CONCLUSIONS

The factor V mutation is a common cause of venous thromboses but may also be associated with the early presentation of arterial thrombotic events. The APC resistance test is a sensitive screening assay but has limitations of its specificity in clinical practice.

Population-based study of risk of venous thromboembolism associated with various oral contraceptives

BACKGROUND

Four studies published since December, 1995, reported that the incidence of venous thromboembolism (VTE) was higher in women who used oral contraceptives (OCs) containing the third-generation progestagens gestodene or desogestrel than in users of OCs containing second-generation progestagens. However, confounding and bias in the design of these studies may have affected the findings. The aim of our study was to re-examine the association between risk of VTE and OC use with a different study design and analysis to avoid some of the bias and confounding of the earlier studies.

METHODS

We used computer records of patients from 143 general practices in the UK. The study was based on the medical records of about 540,000 women born between 1941 and 1981. All women who had a recorded diagnosis of deep-vein thrombosis, venous thrombosis not otherwise specified, or pulmonary embolus during the study period, and who had been treated with an anticoagulant were identified as potential cases of VTE. We did a cohort analysis to estimate and compare incidence of VTE in users of the main OC preparations, and a nested case-control study to calculate the odds ratios of VTE associated with use of different types of OC, after adjustment for potential confounding factors. In the case-control study, we matched cases to controls by exact year of birth, practice, and current use of OCs. We used a multiple logistic regression model that included body-mass index, number of cycles, change in type of OC prescribed within 3 months of the event, previous pregnancy, and concurrent disease.

FINDINGS

85 women met the inclusion criteria for VTE, two of whom were users of progestagen-only OCs. Of the 83 cases of VTE associated with use of combined OCs, 43 were recorded as deep-vein thrombosis, 35 as pulmonary thrombosis, and five as venous thrombosis not otherwise specified. The crude rate of VTE per 10,000 woman-years was 4.10 in current users of any OC, 3.10 in users of second-generation OCs, and 4.96 in users of third-generation preparations. After adjustment for age, the rate ratio of VTE in users of third-generation relative to second-generation OCs was 1.68 (95% CI 1.04-2.75). Logistic regression showed no significant difference in the risk of VTE between users of third-generation and second-generation OCs. Among users of third-generation progestagens, the risk of VTE was higher in users of desogestrel with 20 g ethinyloestradiol than in users of gestodene or desogestrel with 30 g ethinyloestradiol. With all second-generation OCs as the reference, the odds ratios for VTE were 3.49 (1.21-10.12) for desogestrel plus 20 g ethinyloestradiol and 1.18 (0.66-2.17) for the other third-generation progestagens.

INTERPRETATION

The previously reported increase in odds ratio associated with third-generation OCs when compared with second-generation products is likely to have been the result of residual confounding by age. The increased odds ratio associated with products containing 20 micrograms ethinyloestradiol and desogestrel compared with the 30 micrograms product is biologically implausible, and is likely to be the result of preferential prescribing and, thus, confounding.

Increased number of induced abortions in Norway after media coverage of adverse vascular events from the use of third-generation oral contraceptives

After the press release in Lancet (October 18, 1995) of increased risks for adverse vascular events in users of pills containing desogestrel and gestodene the total sales of oral contraceptives dropped over a two-month period by 17%, while sales of the only desogestrel brand available (Marvelon) dropped by over 70% in Norway. From sales, we can estimate that more than 45,000 women either changed from Marvelon to a second or first-generation brand or stopped using OCs. In total, more than 25,000 women discontinued OC use in Norway during November and December of 1995. Abortion data from one Norwegian county, representing 6-7% of the Norwegian population, show no statistically significant changes in the total number of induced abortions from the first quarter of 1996 as compared with that of the first quarter in preceding years. However, abortion rates that had been steadily decreasing from 1992 through 1995 in women 24 years old or younger, were promptly interrupted by a significant 36% increase during the first quarter of 1996. Most of the additional cases were found among single, childless students. The observed increased abortion rate among younger women is most probably linked to changes in contraceptive use during the pill scare of the late October through December of 1995, during which time these women conceived.

Activated protein C resistance due to a common factor V gene mutation is a major risk factor for venous thrombosis

Inherited resistance to activated protein C (APC) was recently discovered to be a cause of familial thrombophilia and is now known to be the most common genetic risk factor for venous thrombosis. It is caused by a single point mutation in the gene for factor V, which predicts substitution or arginine (R) at position 506 with a glutamine (Q). Accordingly, the activated form of mutated factor V (FVa:Q506) is more slowly degraded by activated protein C than normal FVa (FVa:R506) is, resulting in hypercoagulability and a lifelong 5- to 10-fold increased risk of venous thrombosis. Previously known inherited hypercoagulable states, i.e. deficiencies of the anticoagulant proteins antithrombin III, protein S, and protein C, are found fewer than 10-15% of thrombosis patients in western countries, whereas inherited APC resistance is present in 20-60% of such patients. The FV mutation is common in populations of Caucasian origin, with prevalences ranging from 1-15%, whereas it is not found in certain other ethnic groups such as Japanese and Chinese. The high prevalence of APC resistance, in combination with the availability of simple laboratory tests, will have a profound influence on the development of therapeutic and prophylactic regimens for thrombosis and will, it is hoped, result in a decreased incidence of thromboembolic events.

Factor V Leiden: should we screen oral contraceptive users and pregnant women?

The factor V Leiden mutation is the most common genetic risk factor for deep vein thrombosis: it is present in about 5% of the white population. The risk of deep vein thrombosis among women who use oral contraceptives is greatly increased by the presence of the mutation. The same seems to be true of the risk of postpartum thrombosis. Several authors have called for all women to be screened before prescription of oral contraceptives and during pregnancy. Such a policy might deny effective contraception to a substantial number of women while preventing only a small number of deaths due to pulmonary emboli. Moreover, in pregnancy the ensuing use of oral anticoagulation prophylaxis might carry a penalty of fatal bleeding that is equal to or exceeds the risk of death due to postpartum thrombosis. It might pay, however, to take a personal and family history of deep vein thrombosis when prescribing oral contraceptives or at a first antenatal visit to detect women from families with a tendency to multiple thrombosis.

Prospective study of exogenous hormones and risk of pulmonary embolism in women

BACKGROUND

Current use of oral contraceptives (OCs) is a well-recognised risk factor for venous thrombosis and consequent pulmonary embolism (PE). Little is known about residual effects of past OC use. Furthermore, few epidemiological studies have assessed the relation between postmenopausal use of hormones and thrombotic disease.

METHODS

In this prospective study information was obtained through questionnaires sent every 2 years (1976-92) to 1125,93 women aged 30-55 in 1976. We excluded women with previously diagnosed cardiovascular disease or cancer in 1976 and at the beginning of each subsequent 2-year follow-up period.

FINDINGS

From self-reports and medical records, we documented 123 cases of primary PE (no identified antecedent cancer, trauma, surgery, or immobilisation). Current users of postmenopausal hormones had an increased risk of primary PE (relative risk adjusted for multiple risk factors 2.1 [95% CI 1.2-3.8]). However, past use showed no relation to PE (1.3 [0.7-2.4]). In current users of OCs the risk of primary PE was about twice that in non-users (2.2 [0.8-5.9]), but this finding was based on only five cases who were current OC users. Users of OCs in the past had no increase in risk of PE (0.8 [0.5-1.2]). These relations were consistent irrespective of cigarette-smoking status.

INTERPRETATION

Primary PE was uncommon in this cohort. The risk was increased by current though not past use of postmenopausal hormones or OCs.

Resistance to activated protein C, associated with oral contraceptives use; effect of formulations, duration of assumption, and doses of oestro-progestins

Resistance to activated protein C (APC-R) is at present considered the most frequent laboratory abnormality in patients with deep vein thrombosis. An increased risk for venous thrombosis is associated with the use of oral contraceptives (OCs). We recently described a statistically significant association between APC-R status and oral contraceptives use in a healthy group of women. We re-evaluated 50 healthy women taking low-dose combination OCs in order to consider a possible correlation between the APC sensitivity ratio (APC-SR) and different oral contraceptive formulations. Seven women showed an APC ratio < or = 2 (APC-resistant). Only one of the seven women was found to be heterozygous for Leiden factor V mutation. We observed no significant differences between normally sensitive and APC-resistant women in terms of duration of OC use, amount of estrogenic or progestogenic dose, or type of formulation. We conclude that APC-resistance associated with oral contraceptives use seems to occur only in predisposed subjects (in our results, about 12% of the healthy population).

The increased risk of venous thromboembolism and the use of third generation progestagens: role of bias in observational research. The Transnational Research Group on Oral Contraceptives and the Health of Young Women

A matched case-control study was undertaken in 10 centers in Germany and the United Kingdom to explore the association of current use of major combination oral contraceptives with the occurrence of venous thromboembolism. The cases recruited were 505 women aged 16-44 years with venous thromboembolism, controls were 1877 women (at least 3 controls per case) matched for 5-year age group and region without VTE. The main outcome measures were odds ratios derived by comparing current use of a specific oral contraceptive or group of OC against current use of other groups or against no current use of OC. The odds ratios (95% confidence intervals) for venous thromboembolism were: for third generation products (low dose ethinyloestradiol, gestodene and desogestrel) versus second generation products (low dose ethinyloestradiol, no gestodene and desogestrel, 1.5 (1.1 to 2.0), for third versus second generation products with norgestimate included in third generation, 1.6 (1.2 to 2.2). The odds ratios for current use for women aged 16-44 of specific progestagens versus levonorgestrel-containing compounds were 1.7 (1.1 to 2.6) for gestodene, 1.8 (1.2 to 2.6) for desogestrel, 1.9 (1.0 to 3.6) for norgestimate and 1.3 (0.7 to 2.5) for progestagen-only pills. For women aged 25 to 44 likely to be exposed to any of these progestagens, odds ratios for the comparison of progestagens versus levonorgestrel showed a successive increase by market introduction ranging from 1.5 (0.9 to 2.5) for desogestrel with 30 micrograms oestrogen content (introduced 1981) to 2.8 (1.3 to 6.5) for desogestrel with 20 micrograms oestrogen content (introduced 1992) significant in linear trend analysis (p = 0.00012). The influence of norgestimate classification as third or second generation product does not significantly alter the results regarding the association of third generation products and venous thromboembolism. A direct comparison of current use of norgestimate (which is primarily metabolized to levonorgestrel) versus levonorgestrel shows an increased odds ratio. The trend of increasing risk of progestagens by recency of market introduction when compared with levonorgestrel is strongly indicative of the existence of external bias due to attrition of susceptibles.

Oral contraceptives and venous thromboembolism

In October, 1995, the United Kingdom Committee on Safety of Medicines recommended that women should use oral contraceptives containing desogestrel or gestodene only if prepared to accept an increased risk of thromboembolism. This action was based on observational studies that indicated a 2-3-fold increase in the risk of thromboembolism when desogestrel and gestodene-containing contraceptives were compared to products with levonorgestrel. The fact that these studies point in the same direction is concerning, but it is possible that these observational studies, somewhat similar in design, are influenced by the same unrecognized biases. Furthermore, the case numbers are relatively small (20-40 cases), and, for example, preferential prescribing to women at greater risk could affect the results. It is difficult to reconcile the conclusions with the strong belief supported by good evidence that thrombosis is an estrogen dose-related complication, and that progestational agents have no impact on clotting parameters. In my view, these equivocal reports are not of sufficient strength to escape biases and to change our prescribing of oral contraceptives.