A resonant sextuplet of sub-Neptunes transiting the bright star HD 110067.

Planets with radii between that of the Earth and Neptune (hereafter referred to as 'sub-Neptunes') are found in close-in orbits around more than half of all Sun-like stars1,2. However, their composition, formation and evolution remain poorly understood3. The study of multiplanetary systems offers an opportunity to investigate the outcomes of planet formation and evolution while controlling for initial conditions and environment. Those in resonance (with their orbital periods related by a ratio of small integers) are particularly valuable because they imply a system architecture practically unchanged since its birth. Here we present the observations of six transiting planets around the bright nearby star HD 110067. We find that the planets follow a chain of resonant orbits. A dynamical study of the innermost planet triplet allowed the prediction and later confirmation of the orbits of the rest of the planets in the system. The six planets are found to be sub-Neptunes with radii ranging from 1.94R⊕ to 2.85R⊕. Three of the planets have measured masses, yielding low bulk densities that suggest the presence of large hydrogen-dominated atmospheres.

Nitrogen removal from coke making wastewater through a pre-denitrification activated sludge process.

Under the Industrial Emissions Directive (IED), coke production wastewater must be treated to produce an effluent characterised by a total nitrogen (TN) <50 mg/L. An anoxic-aerobic activated sludge pilot-plant (1 m3) fed with coke production wastewater was used to investigate the optimal operational requirements to achieve such an effluent. The loading rates applied to the pilot-plant varied between 0.198-0.418 kg COD/m3.day and 0.029-0.081 kg TN/m3.day, respectively. The ammonia (NH4+-N) removals were maintained at 96%, after alkalinity addition. Under all conditions, phenol and SCN- remained stable at 96% and 100%, respectively with both being utilised as carbon sources during denitrification. The obtained results showed that influent soluble chemical oxygen demand (sCOD) to TN ratio of should be maintained at >5.7 to produce an effluent TN <50 mg/L. Furthermore, nitrite accumulation was observed under all conditions indicating a disturbance to the denitrification pathway. Overall, the anoxic-aerobic activated sludge process was shown to be a robust and reliable technology to treat coke making wastewater and achieve the IED requirements. Nevertheless, the influent to the anoxic tank should be monitored to ensure a sCOD:TN ratio >5.7 or, alternately, the addition of an external carbon source should be considered.

Helium in the eroding atmosphere of an exoplanet.

Helium is the second-most abundant element in the Universe after hydrogen and is one of the main constituents of gas-giant planets in our Solar System. Early theoretical models predicted helium to be among the most readily detectable species in the atmospheres of exoplanets, especially in extended and escaping atmospheres 1 . Searches for helium, however, have hitherto been unsuccessful 2 . Here we report observations of helium on an exoplanet, at a confidence level of 4.5 standard deviations. We measured the near-infrared transmission spectrum of the warm gas giant 3 WASP-107b and identified the narrow absorption feature of excited metastable helium at 10,833 angstroms. The amplitude of the feature, in transit depth, is 0.049 ± 0.011 per cent in a bandpass of 98 angstroms, which is more than five times greater than what could be caused by nominal stellar chromospheric activity. This large absorption signal suggests that WASP-107b has an extended atmosphere that is eroding at a total rate of 1010 to 3 × 1011 grams per second (0.1-4 per cent of its total mass per billion years), and may have a comet-like tail of gas shaped by radiation pressure.

Characterization of priority substances in effluents from an integrated steelworks in the United Kingdom.

In the Water Framework Directive, a list of priority substances that are deemed to be persistent, toxic, and liable to bioaccumulate have been identified. Within this list, a range of polycyclic aromatic hydrocarbons (PAHs) and certain trace metals are relevant to the steel industry. This study summarizes work carried out by Tata Steel Europe (Rotherham, U.K.) to characterize the emissions of PAHs and trace metals from wastewater streams at one of its main integrated steelworks in the United Kingdom over a 3-year period (2010 to 2012). The emissions inventory revealed that PAH emissions to water were almost entirely attributable to the cokemaking process, with emissions factors ranging from 20 to 55 mg/tonne of coke. Furthermore, analysis of the PAH distribution in coke oven effluents revealed that medium- and high-molecular-weight PAHs were associated with the suspended solids (particle-bound). Regarding trace metals, both ironmaking and steelmaking processes were the most important emission sources.

Inflammation markers and their trajectories after deep vein thrombosis in relation to risk of post-thrombotic syndrome.

BACKGROUND: Post-thrombotic syndrome (PTS) is a frequent chronic complication of deep vein thrombosis (DVT). OBJECTIVE: In the BioSOX study, we investigated whether inflammation markers predict the risk of PTS after DVT. METHODS: We measured C-reactive protein (CRP), ICAM-1, interleukin (IL)-6, and IL-10, at baseline, and 1 month and 6 months after a first proximal DVT, among 803 participants in the SOX trial. Participants were prospectively followed for 24 months for development of PTS. RESULTS: Median CRP levels at 1 month, ICAM-1 levels at baseline, 1 month and 6 months, IL-6 levels at 1 month and 6 months and IL-10 levels at 6 months were higher in patients who developed PTS than in those who did not. Multivariable regression with the median as a cutoff showed risk ratios (RRs) for PTS of 1.23 (95% confidence interval [CI] 1.05-1.45) and 1.25 (95% CI 1.05-1.48) for ICAM-1 at 1 month and 6 months, respectively, and 1.27 (95% CI 1.07-1.51) for IL-10 at 6 months. Quartile-based analysis demonstrated a dose-response association between ICAM-1 and PTS. ICAM-1 and IL-10 were also associated with PTS severity. Analysis of biomarker trajectories after DVT demonstrated an association between the highest-trajectory group of ICAM-1 and PTS. CONCLUSIONS: In this prospective study, ICAM-1 over time was most consistently associated with the risk of PTS. Further study is required to confirm these findings and assess their potential clinical relevance.

P values are only an index to evidence: 20th- vs. 21st-century statistical science.

Early statistical methods focused on pre-data probability statements (i.e., data as random variables) such as P values; these are not really inferences nor are P values evidential. Statistical science clung to these principles throughout much of the 20th century as a wide variety of methods were developed for special cases. Looking back, it is clear that the underlying paradigm (i.e., testing and P values) was weak. As Kuhn (1970) suggests, new paradigms have taken the place of earlier ones: this is a goal of good science. New methods have been developed and older methods extended and these allow proper measures of strength of evidence and multimodel inference. It is time to move forward with sound theory and practice for the difficult practical problems that lie ahead. Given data the useful foundation shifts to post-data probability statements such as model probabilities (Akaike weights) or related quantities such as odds ratios and likelihood intervals. These new methods allow formal inference from multiple models in the a prior set. These quantities are properly evidential. The past century was aimed at finding the "best" model and making inferences from it. The goal in the 21st century is to base inference on all the models weighted by their model probabilities (model averaging). Estimates of precision can include model selection uncertainty leading to variances conditional on the model set. The 21st century will be about the quantification of information, proper measures of evidence, and multi-model inference. Nelder (1999:261) concludes, "The most important task before us in developing statistical science is to demolish the P-value culture, which has taken root to a frightening extent in many areas of both pure and applied science and technology".

Exclusion of deep vein thrombosis using the Wells rule in clinically important subgroups: individual patient data meta-analysis.

OBJECTIVE: To assess the accuracy of the Wells rule for excluding deep vein thrombosis and whether this accuracy applies to different subgroups of patients. DESIGN: Meta-analysis of individual patient data. DATA SOURCES: Authors of 13 studies (n = 10,002) provided their datasets, and these individual patient data were merged into one dataset. ELIGIBILITY CRITERIA: Studies were eligible if they enrolled consecutive outpatients with suspected deep vein thrombosis, scored all variables of the Wells rule, and performed an appropriate reference standard. MAIN OUTCOME MEASURES: Multilevel logistic regression models, including an interaction term for each subgroup, were used to estimate differences in predicted probabilities of deep vein thrombosis by the Wells rule. In addition, D-dimer testing was added to assess differences in the ability to exclude deep vein thrombosis using an unlikely score on the Wells rule combined with a negative D-dimer test result. RESULTS: Overall, increasing scores on the Wells rule were associated with an increasing probability of having deep vein thrombosis. Estimated probabilities were almost twofold higher in patients with cancer, in patients with suspected recurrent events, and (to a lesser extent) in males. An unlikely score on the Wells rule (≤ 1) combined with a negative D-dimer test result was associated with an extremely low probability of deep vein thrombosis (1.2%, 95% confidence interval 0.7% to 1.8%). This combination occurred in 29% (95% confidence interval 20% to 40%) of patients. These findings were consistent in subgroups defined by type of D-dimer assay (quantitative or qualitative), sex, and care setting (primary or hospital care). For patients with cancer, the combination of an unlikely score on the Wells rule and a negative D-dimer test result occurred in only 9% of patients and was associated with a 2.2% probability of deep vein thrombosis being present. In patients with suspected recurrent events, only the modified Wells rule (adding one point for the previous event) is safe. CONCLUSION: Combined with a negative D-dimer test result (both quantitative and qualitative), deep vein thrombosis can be excluded in patients with an unlikely score on the Wells rule. This finding is true for both sexes, as well as for patients presenting in primary and hospital care. In patients with cancer, the combination is neither safe nor efficient. For patients with suspected recurrent disease, one extra point should be added to the rule to enable a safe exclusion.

Predictors of post-thrombotic syndrome in a population with a first deep vein thrombosis and no primary venous insufficiency.

BACKGROUND: Post-thrombotic syndrome (PTS) is the most frequent complication of deep vein thrombosis (DVT). Its diagnosis is based on clinical characteristics. However, symptoms and signs of PTS are non-specific, and could result from concomitant primary venous insufficiency (PVI) rather than DVT. This could bias evaluation of PTS. METHODS: Using data from the REVERSE multicenter study, we assessed risk factors for PTS in patients with a first unprovoked unilateral proximal DVT 5-7 months earlier who were free of clinically significant PVI (defined as absence of moderate or severe venous ectasia in the contralateral leg). RESULTS: Among the 328 patients considered, the prevalence of PTS was 27.1%. Obesity (odds ratio [OR] 2.6 [95% confidence interval (CI) 1.5-4.7]), mild contralateral venous ectasia (OR 2.2 [95% CI 1.1-4.3]), poor International Normalized Ratio (INR) control (OR per additional 1% of time with INR < 2 during anticoagulant treatment of 1.018 [95% CI 1.003-1.034]) and the presence of residual venous obstruction on ultrasound (OR 2.1 [95% CI 1.1-3.7]) significantly increased the risk for PTS in multivariable analyses. When we restricted our analysis to patients without any signs, even mild, of contralateral venous insufficiency (n = 244), the prevalence of PTS decreased slightly to 24.6%. Only obesity remained an independent predictor of PTS (OR 2.6 [95% CI 1.3-5.0]). Poor INR control and residual venous obstruction also increased the risk, but the results were no longer statistically significant (OR 1.017 [95% CI 0.999-1.035] and OR 1.7 [95% CI 0.9-3.3], respectively). CONCLUSIONS: After a first unprovoked proximal DVT, obese patients and patients with even mild PVI constitute a group at increased risk of developing PTS for whom particular attention should be paid with respect to PTS prevention. Careful monitoring of anticoagulant treatment may prevent PTS.

Risk of post-thrombotic syndrome after subtherapeutic warfarin anticoagulation for a first unprovoked deep vein thrombosis: results from the REVERSE study.

BACKGROUND: Risk factors for post-thrombotic syndrome (PTS) remain poorly understood. OBJECTIVES: In this multinational multicenter study, we evaluated whether subtherapeutic warfarin anticoagulation was associated with the development of PTS. METHODS: Patients with a first unprovoked deep venous thrombosis (DVT) received standard anticoagulation for 5-7 months and were then assessed for PTS. The time in the therapeutic range was calculated from the international normalized ratio (INR) data. An INR below 2, more than 20% of the time, was considered as subtherapeutic anticoagulation. RESULTS: Of the 349 patients enrolled, 97 (28%) developed PTS. The overall frequency of PTS in patients with subtherapeutic anticoagulation was 33.5%, compared with 21.6% in those with an INR below two for ≤ 20% of the time (P = 0.01). During the first 3 months of therapy, the odds ratio (OR) for developing PTS if a patient had subtherapeutic anticoagulation was 1.78 (95% confidence interval [CI] 1.10-2.87). After adjusting for confounding variables, the OR was 1.84 (95% CI 1.13-3.01). Corresponding ORs for the full period of anticoagulation were 1.83 (95% CI 1.14-3.00) [crude] and 1.88 (95% CI 1.15-3.07) [adjusted]. CONCLUSION: Subtherapeutic warfarin anticoagulation after a first unprovoked DVT was significantly associated with the development of PTS.

Comparison of the Villalta post-thrombotic syndrome score in the ipsilateral vs. contralateral leg after a first unprovoked deep vein thrombosis.

BACKGROUND: Post-thrombotic syndrome (PTS) is the most frequent complication of a deep vein thrombosis (DVT). International guidelines recommend assessing PTS with the Villalta scale, a clinical measure that incorporates venous symptoms and signs in the leg ipsilateral to a DVT. However, these signs and symptoms are not specific for PTS and their prevalence and relevance in the contralateral leg have not previously been studied. METHODS: Using data from the REVERSE prospective multicentre cohort study, we compared the Villalta total score and prevalence of venous signs and symptoms in the ipsilateral vs. contralateral leg in patients with a first, unilateral DVT 5 to 7 months previously. RESULTS: Among the 367 patients analyzed, the mean Villalta score was higher in the ipsilateral than in the contralateral leg (mean ± standard deviation [SD] 3.7 [3.4] vs. 1.9 [2.5], respectively; P<0.0001). Villalta scores in the ipsilateral and contralateral legs were strongly correlated (r=0.68; P<0.0001). Ipsilateral PTS (defined by a Villalta total score >4) was present in 31.6% (n=116) of patients. Among these, 39.7% (n=46) of patients had a Villalta score >4 in the contralateral leg, and the distribution of Villalta symptoms and signs components was similar between the legs. CONCLUSIONS: Villalta scores in the ipsilateral and contralateral legs are strongly correlated. Almost half of cases considered to be PTS might reflect pre-existing symptomatic chronic venous disease. Alternatively, patients with pre-existing chronic venous disease might be more prone to developing PTS after a DVT. Performing a bilateral assessment of Villalta scores at the acute phase of DVT could be of clinical interest from a diagnostic, prognostic and therapeutic point of view.

The evidence for the use of recombinant factor VIIa in massive bleeding: revision of the transfusion policy framework.

In 2006, the Canadian National Advisory Committee on Blood and Blood Products (NAC) developed a transfusion policy framework for the use of off-label recombinant factor VIIa (rFVIIa) in massive bleeding. Because the number of randomised controlled trials has doubled, the NAC undertook a review of the policy framework in 2011. On the basis of the review of 29 randomised controlled trials, there remains little evidence to support the routine use of rFVIIa in massive bleeding. Mortality benefits have not been demonstrated. Contrarily, an increase in arterial thromboembolic events has been observed with the use of off-label rFVIIa. Given the absence of evidence of benefit and with evidence of the risk of harm, the NAC recommends that recombinant VIIa no longer be used for the off-label indications of prevention and treatment of bleeding in patients without haemophilia.

Direct and indirect costs of management of long-term warfarin therapy in Canada.

BACKGROUND: Comparisons of overall costs and resource utilization associated with anticoagulation management are important as new alternatives to warfarin are introduced. The aim of the present study was to assess total costs of warfarin-based anticoagulation in different health care models. METHODS: Physician- or pharmacist-managed hospital- or community-based anticoagulation clinics in five Canadian provinces were asked to provide itemized information on costs for staff, laboratory, hardware and overheads associated with warfarin management. At each site, cohorts of patients were provided with diaries and participants prospectively entered all costs for warfarin medication and associated health professional contacts, travel to the laboratory, required assistance and time lost from work by patient or caregiver over 3months. All costs were calculated for a 3-month period. RESULTS: Data from 429 patients at 15 sites were evaluated. The cost from the Ministry of Health perspective ranged from $108 to $199 per 3months in the different settings, the patient costs were $40-$80 and the total societal costs ranged from $188-$244. Sensitivity analyses with typical blood test intervals, the most prescribed strength of warfarin and dispensing fee from another province increased these estimates to $230-$302. When reimbursement for unemployed caregivers was also entered the total cost was $308-$503 per 3months. CONCLUSIONS: The total cost for warfarin-based anticoagulation amounted to at least 10 times the lowest cost for the drug. The costs provided should be useful for comparisons with newer drugs without requirement for routine laboratory monitoring and dose adjustments.

Subsegmental pulmonary embolism diagnosed by computed tomography: incidence and clinical implications. A systematic review and meta-analysis of the management outcome studies.

BACKGROUND: Multiple-detectors computed tomographic pulmonary angiography (CTPA) has a higher sensitivity for pulmonary embolism (PE) within the subsegmental pulmonary arteries as compared with single-detector CTPA. Multiple-detectors CTPA might increase the rate of subsegmental PE diagnosis. The clinical significance of subsegmental PE is unknown. We sought to summarize the proportion of subsegmental PE diagnosed with single- and multiple-detectors CTPA and assess the safety of diagnostic strategies based on single- or multiple-detectors CTPA to exclude PE. PATIENTS AND METHODS: A systematic literature search strategy was conducted using MEDLINE, EMBASE and the Cochrane Register of Controlled Trials. We selected 22 articles (20 prospective cohort studies and two randomized controlled trials) that included patients with suspected PE who underwent a CTPA and reported the rate of subsegmental PE. Two reviewers independently extracted data onto standardized forms. RESULTS: The rate of subsegmental PE diagnosis was 4.7% [95% confidence interval (CI): 2.5-7.6] and 9.4 (95% CI: 5.5-14.2) in patients that underwent a single- and multiple-detectors CTPA, respectively. The 3-month thromboembolic risks in patients with suspected PE and who were left untreated based on a diagnostic algorithm including a negative CTPA was 0.9% (95% CI: 0.4-1.4) and 1.1% (95% CI: 0.7-1.4) for single- and multiple-detectors CTPA, respectively. CONCLUSION: Multiple-detectors CTPA seems to increase the proportion of patients diagnosed with subsegmental PE without lowering the 3-month risk of thromboembolism suggesting that subsegmental PE may not be clinically relevant.

Linking structure and function in glaucoma.

The glaucomas are a group of relatively common optic neuropathies, in which the pathological loss of retinal ganglion cells causes a progressive loss of sight and associated alterations in the retinal nerve fiber layer and optic nerve head. The diagnosis and management of glaucoma are often dependent on methods of clinical testing that either, 1) identify and quantify patterns of functional visual abnormality, or 2) quantify structural abnormality in the retinal nerve fiber layer, both of which are caused by loss of retinal ganglion cells. Although it is evident that the abnormalities in structure and function should be correlated, propositions to link losses in structure and function in glaucoma have been formulated only recently. The present report describes an attempt to build a model of these linking propositions using data from investigations of the relationships between losses of visual sensitivity and thinning of retinal nerve fiber layer over progressive stages of glaucoma severity. A foundation for the model was laid through the pointwise relationships between visual sensitivities (behavioral perimetry in monkeys with experimental glaucoma) and histological analyses of retinal ganglion cell densities in corresponding retinal locations. The subsequent blocks of the model were constructed from clinical studies of aging in normal human subjects and of clinical glaucoma in patients to provide a direct comparison of the results from standard clinical perimetry and optical coherence tomography. The final formulation is a nonlinear structure-function model that was evaluated by the accuracy and precision of translating visual sensitivities in a region of the visual field to produce a predicted thickness of the retinal nerve fiber layer in the peripapillary sector that corresponded to the region of reduced visual sensitivity. The model was tested on two independent patient populations, with results that confirmed the predictive relationship between the retinal nerve fiber layer thickness and visual sensitivities from clinical perimetry. Thus, the proposed model for linking structure and function in glaucoma has provided information that is important in understanding the results of standard clinical testing and the neuronal losses caused by glaucoma, which may have clinical application for inter-test comparisons of the stage of disease.

An orbital period of 0.94 days for the hot-Jupiter planet WASP-18b.

The 'hot Jupiters' that abound in lists of known extrasolar planets are thought to have formed far from their host stars, but migrate inwards through interactions with the proto-planetary disk from which they were born, or by an alternative mechanism such as planet-planet scattering. The hot Jupiters closest to their parent stars, at orbital distances of only approximately 0.02 astronomical units, have strong tidal interactions, and systems such as OGLE-TR-56 have been suggested as tests of tidal dissipation theory. Here we report the discovery of planet WASP-18b with an orbital period of 0.94 days and a mass of ten Jupiter masses (10 M(Jup)), resulting in a tidal interaction an order of magnitude stronger than that of planet OGLE-TR-56b. Under the assumption that the tidal-dissipation parameter Q of the host star is of the order of 10(6), as measured for Solar System bodies and binary stars and as often applied to extrasolar planets, WASP-18b will be spiralling inwards on a timescale less than a thousandth that of the lifetime of its host star. Therefore either WASP-18 is in a rare, exceptionally short-lived state, or the tidal dissipation in this system (and possibly other hot-Jupiter systems) must be much weaker than in the Solar System.

D-dimer testing is useful to exclude deep vein thrombosis in elderly outpatients.

BACKGROUND: Deep vein thrombosis (DVT) can be safely and reliably excluded in patients with a low clinical probability and a negative D-dimer result but the accuracy and utility of such a strategy is unclear in elderly patients. OBJECTIVES: We sought to compare the performance of the Wells pretest probability (PTP) model and D-dimer testing between patients of different age groups and to examine the utility of the two PTP model classification schemes (low/moderate/high vs. unlikely/likely) in excluding DVT in elderly outpatients. PATIENTS/METHODS: Pooled analysis of databases from three prospective diagnostic studies evaluating consecutive outpatients with suspected DVT. RESULTS: A total of 2696 patients were evaluated. DVT was diagnosed in 400 (15%) patients overall and in 50 out of 325 (15.5%) patients > or = 60 years old. The PTP distribution and the prevalence of DVT in each PTP category were similar among the different age groups. The negative predictive values of a low or unlikely PTP score in combination with a negative D-dimer result were 99% for all groups. A negative D-dimer in combination with a low or unlikely PTP excluded 21.7% and 31% of patients > or = 80 years old, respectively. CONCLUSIONS: The combination of a low or unlikely PTP with a negative D-dimer result can effectively and safely exclude DVT in a significant proportion of elderly outpatients. However, this clinical prediction rule needs to be prospectively validated with different D-dimer assays in this specific population.

A pilot study of central venous catheter survival in cancer patients using low-molecular-weight heparin (dalteparin) and warfarin without catheter removal for the treatment of upper extremity deep vein thrombosis (The Catheter Study).

BACKGROUND: Central venous catheters in patients with cancer are associated with development of deep vein thrombosis (DVT); however, there is no accepted standard treatment. OBJECTIVES: To assess the safety and effectiveness of a management strategy for central venous catheter-related DVT in cancer patients consisting of dalteparin and warfarin without the need for line removal. PATIENTS/METHODS: Patients older than 18 years of age with an active malignancy and who had symptomatic, acute, objectively documented UEDVT were eligible. Patients were treated with dalteparin 200 IU kg(-1) per day for 5-7 days and warfarin with a target International Normalized Ratio of 2.0-3.0. Patients were followed for 3 months for recurrent venous thromboembolism, major hemorrhage and survival of the central venous catheter. RESULTS: There were 74 patients (48 males). The average age was 58 years. There were no episodes of recurrent venous thromboembolism and three (4%) major bleeds. No lines were removed because of infusion failure or recurrence/extension of DVT. CONCLUSION: Treatment of UEDVTs secondary to central catheters in cancer patients with standard dalteparin/warfarin can allow the central line to remain in situ with little risk of line failure or recurrence/extension of the DVT.

Does the type of hormone replacement therapy influence the risk of deep vein thrombosis? A prospective case-control study.

BACKGROUND: Although hormone replacement therapy (HRT) is associated with an increased risk of deep vein thrombosis (DVT), it is not clear if the risk differs in users of combined estrogen-progestin HRT and estrogen-only HRT. METHODS: We prospectively studied postmenopausal women with suspected DVT in whom HRT use status was ascertained and who subsequently had objective diagnostic testing to confirm or exclude DVT. Cases were patients with idiopathic DVT, in whom there were no DVT risk factors, and controls were patients without DVT, in whom there were also no DVT risk factors. The risk of DVT was determined in users of estrogen-progestin HRT and estrogen-only HRT by comparing the prevalence of current HRT use in cases with idiopathic DVT and controls without DVT (reference group). Multivariable regression analysis was done to adjust for factors that might confound an association between HRT use and the risk of DVT. RESULTS: One thousand one hundred and sixty-eight postmenopausal women with suspected DVT were assessed, from whom 95 cases of idiopathic DVT and 610 controls without DVT and no DVT risk factors were identified. Estrogen-only HRT was associated with an increased risk for DVT that was not statistically significant [odds ratio (OR) = 1.22; 95% confidence interval (CI) 0.57, 2.61]. Estrogen-progestin HRT was associated with a greater than 2-fold increased risk for DVT (OR = 2.70; 95% CI 1.44, 5.07). CONCLUSION: The risk of developing DVT may be higher in users of combined estrogen-progestin HRT than in users of estrogen-only HRT.