Combination Of Wells Research Articles

Sedimentary Reservoir Characteristics of Fuyu Oil Formation in the Middle of Fuxin Uplift, Southern Songliao Basin

Currently, the Fuyu reservoir in the middle of the Fuxin uplift, located in the southern Songliao Basin, is in a high water cut development stage. The understanding of this reservoir is limited, and the distribution of favorable reservoirs remains unclear, necessitating detailed reservoir characterization. This study employs a combination of well and seismic technologies to accurately depict the sedimentary and reservoir characteristics of the Fuyu oil reservoir. By conducting detailed correlations of oil zones, a regional high-resolution isochronous stratigraphic framework is established. The division of sedimentary microfacies enables fine characterization of single sand bodies, identifying channel boundaries, clarifying lateral connectivity, and detailing the vertical contact relationships of sand bodies across different deposition periods. The results demonstrate that root-mean-square amplitude and total energy metrics effectively correspond to sand bodies in the study area and can be used to analyze sand body distribution. Provenance is primarily from the southwest to the northeast, with shallow deltas predominantly developed. Delta plain subfacies are found in zones 4-12, while delta front subfacies are in zones 1-3. Microfacies types mainly include the main distributary channel, distributary channel sides, crevasse splay, overbank sand, and underwater distributary channels. The main distributary channel reservoirs exhibit the best physical properties, with porosity ranging from 20-25%, while sand bodies at the sides of distributary channels reach 15-20%. Predicted favorable areas are mainly located at the intersections of distributary channels and structural highs, where drilling is likely to yield high oil flow.

AIRPORT PLANNING: APPROACHES TO DETERMINING THE PLANNING HORIZON

Airport planning is a challenging task that requires knowledge of many standards and recommended practices, bylaws and procedures. Besides, it is possible that politicians would try to intervene in the planning process, which always exceeds the election period of one government. Therefore, the article provides in-depth theoretical analysis of the problem and summarizes the results of research that focused on comparing the approach to the airport planning issues in the Slovakia and Croatia. The primary goal was to develop a methodology for determining the airport planning horizon, to assess the significance of individual planning phases and to evaluate results. The research was carried out using a combination of several methods. The main challenge was to determine the length of the planning horizon. In 2 panels, 32 experts from Slovakia and Croatia were interviewed and 224 different responses were received and processed by the fuzzy Delphi method. The advantage of this approach relies on combination of well – developed theory and practical solutions in cooperation with experts from the industry. Despite the different legal frameworks and similar standards for airport planning in both countries, the results of the research proved that the values of the optimal planning horizons are comparable. As a result, the methodology can therefore be used in other countries with similar conditions. However, planning procedures and practices depend on the specifics of states or even regions. Eventually, the experience from the research provides relevant and robust material to support teaching. Besides, it is transferable to other fields of transport infrastructure planning. Additionally, the research results were provided to the state planning authorities.

A New Combination of Surgical Techniques for the Treatment of 1st Carpometacarpal Joint Arthritis

Up till now, many different techniques have been used for the treatmentof 1st carpometacarpal (cmc) joint arthritis. Here we present a new combination of well- known techniques and surgical approaches that gave excellent results in a five year follow up.

Simulation and optimization coupling model for soil salinization and waterlogging control in the Urad irrigation area, North China

How to rationally optimize the allocation of surface water and groundwater resources in saline-alkali areas is a difficult problem in current model optimization. Based on an interval two-stage stochastic programming (ITSP) method, this paper considers the system risk involved in saline-alkali land treatment, follows a robust optimization method, and constructs an interval two-stage data-driven subrobust optimization (ITDRO) model, which can optimize the distribution of groundwater and surface water for different crops and realize the combination of wells and canals through the joint dispatch of surface water and groundwater. This paper takes the Urad Irrigation Area as the research object, and the obtained results provide water distribution objectives under situations of multiple sources of water, multiple crops, and different robust coefficients. After the successful calibration and verification of the SaltMod model, the water distribution target is taken as the main input parameter and substituted into the simulation model based on the principle of water and salt balance. The output includes soil salinity, drainage salinity, groundwater salinity (GWS), groundwater table (GWT) depth, and drainage. The results show that the integrated ITDRO and SaltMod model can control the groundwater level below the critical depth under the premise of satisfying crop irrigation, reducing the groundwater level by approximately 0.75 m and the GWS in the irrigation area by approximately 0.68 g/L, which can provide a reference for the prevention and control of soil salinization and waterlogging. This approach is suitable for arid and semiarid regions that face similar problems.

Full-Field Optimization of Offshore Squeeze Campaigns in Total Gulf of Guinea Fields

SummaryScale inhibitor (SI) squeeze treatments are one of the most common techniques to prevent downhole scale formation. In this paper, we present the optimization of treatment design for multiple wells included in offshore campaigns. Two offshore fields with 8 and 12 production wells in west Africa were considered that are separately treated via yearly squeeze campaigns. The wells included in each campaign are treated in a single trip of the supply vessel. Based on the storage capacity of the vessel, the available volume of SI onboard should be optimally allocated to each of the wells (having different properties and water production rates), so that they are all protected from scaling for 1 year until the next campaign is carried out. A hybrid optimization methodology was applied to optimize the squeeze campaign design.The gradient descent (GD) algorithm was first applied to derive the squeeze “isolifetime proxies” related to each well. Each proxy includes all the possible squeeze designs that result in 365 days of squeeze lifetime in the well. Using these proxies, any combination of wells’ squeeze designs could be nominated as the campaign design, because that would result in treating all wells until the next campaign. The multiobjective particle swarm optimization (MOPSO) technique was implemented to optimize the campaign design by simultaneously minimizing the total SI volume and the total injection time for the whole campaign. Minimizing the total pumping time would consequently minimize the deferred oil volume and the total cost of squeezes in the field.Finally, the Pareto Front was identified for each field, showing the most optimum campaign designs. The Pareto Front was shown to be a valuable tool for the operator to make a trade-off between the size of the vessel and the injection time; that is, to use a bigger vessel to transport more inhibitor to the wells or to use a smaller one but for a longer time to inject more water during the squeeze treatments in the field. A cost analysis was performed to identify the most optimum deployment plan providing the most optimum inhibitor allocation strategy, including the optimum inhibitor volume and the optimum injection time for each campaign.

Predicting Venous Thromboembolic Events in Patients with Coronavirus Disease 2019 Requiring Hospitalization: an Observational Retrospective Study by the COVIDIC Initiative in a Swiss University Hospital.

Background Coronavirus disease 2019 (COVID-19) can result in profound changes in blood coagulation. The aim of the study was to determine the incidence and predictors of venous thromboembolic events (VTE) among patients with COVID-19 requiring hospital admission. Subjects and Methods. We performed a retrospective study at the Lausanne University Hospital with patients admitted because of COVID-19 from February 28 to April 30, 2020. Results Among 443 patients with COVID-19, VTE was diagnosed in 41 patients (9.3%; 27 pulmonary embolisms, 12 deep vein thrombosis, one pulmonary embolism and deep vein thrombosis, one portal vein thrombosis). VTE was diagnosed already upon admission in 14 (34.1%) patients and 27 (65.9%) during hospital stay (18 in ICU and nine in wards outside the ICU). Multivariate analysis revealed D-dimer value > 3,120 ng/ml (P < 0.001; OR 15.8, 95% CI 4.7-52.9) and duration of 8 days or more from COVID-19 symptoms onset to presentation (P 0.020; OR 4.8, 95% CI 1.3-18.3) to be independently associated with VTE upon admission. D-dimer value ≥ 3,000 ng/l combined with a Wells score for PE ≥ 2 was highly specific (sensitivity 57.1%, specificity 91.6%) in detecting VTE upon admission. Development of VTE during hospitalization was independently associated with D-dimer value > 5,611 ng/ml (P < 0.001; OR 6.3, 95% CI 2.4-16.2) and mechanical ventilation (P < 0.001; OR 5.9, 95% CI 2.3-15.1). Conclusions VTE seems to be a common COVID-19 complication upon admission and during hospitalization, especially in ICU. The combination of Wells ≥ 2 score and D − dimer ≥ 3,000 ng/l is a good predictor of VTE at admission.

Inferring interwell connectivity in a reservoir from bottomhole pressure fluctuations of hydraulically fractured vertical wells, horizontal wells, and mixed wellbore conditions

A technique using interwell connectivity is proposed to characterise complex reservoir systems and provide highly detailed information about permeability trends, channels, and barriers in a reservoir. The technique, which uses constrained multivariate linear regression analysis and pseudosteady state solutions of pressure distribution in a closed system, requires a system of signal (or active) wells and response (or observation) wells. Signal wells and response wells can be either producers or injectors. The response well can also be either flowing or shut in. In this study, for consistency, waterflood systems are used where the signal wells are injectors, and the response wells are producers. Different borehole conditions, such as hydraulically fractured vertical wells, horizontal wells, and mixed borehole conditions, are considered in this paper. Multivariate linear regression analysis was used to determine interwell connectivity coefficients from bottomhole pressure data. Pseudosteady state solutions for a vertical well, a well with fully penetrating vertical fractures, and a horizontal well in a closed rectangular reservoir were used to calculate the relative interwell permeability. The results were then used to obtain information on reservoir anisotropy, high-permeability channels, and transmissibility barriers. The cases of hydraulically fractured wells with different fracture half-lengths, horizontal wells with different lateral section lengths, and different lateral directions are also considered. Different synthetic reservoir simulation models are analysed, including homogeneous reservoirs, anisotropic reservoirs, high-permeability-channel reservoirs, partially sealing barriers, and sealing barriers.The main conclusions drawn from this study include: (a) The interwell connectivity determination technique using bottomhole pressure fluctuations can be applied to waterflooded reservoirs that are being depleted by a combination of wells (e.g. hydraulically fractured vertical wells and horizontal wells); (b) Wellbore conditions at the observations wells do not affect interwell connectivity results; and (c) The complex pressure distribution caused by a horizontal well or a hydraulically fractured vertical well can be diagnosed using the pseudosteady state solution and, thus, its connectivity with other wells can be interpreted.

PP-NFR: an improved hybrid learning approach for porosity prediction from seismic attributes using non-linear feature reduction

Seismic attributes are being increasingly utilized in both reservoir characterization and exploration. In the Reservoir characterization, one might be interested in modeling different reservoir properties like water saturation, permeability, and porosity. The direct estimation of these reservoir properties from the seismic data is a challenging and time-consuming task. Therefore, it is desirable to build a model that uses seismic attributes to measure the different lithological properties of need. In recent decades, various advancements have been done to estimate porosity from seismic attributes and well-logs effectively. However, the modeling of nonlinear porosity patterns is still underdeveloped for robust solutions as the existing methods implement linear or functional network based reduction techniques to estimate petrophysical properties. Therefore, in this study, we propose a nonlinear hybrid approach that integrates Generative Topographic Map with Machine Learning prediction models (ML) to estimate the property porosity. The approach initiates by extracting relevant attributes based on the two different feature selection strategies. Subsequently, the Radial Basis Function (RBF) and Random Forest regressors are used to build the training model for the target well property porosity using extracted attributes. The different combinations of wells are formed to show the variations in model training and testing error. To demonstrate the effectiveness of proposed PP-NFR approach, the prediction results of the proposed hybrid approach are compared with the linear prediction technique. Furthermore, the performance of PP-NFR approach is also evaluated by comparing the prediction results with the state-of-the-art prediction models (ANN and SVM). The prediction results revealed that the proposed non-linear hybrid approach outperforms other state-of-the-art prediction models by providing an average prediction error of 0.124 as compared to 0.15 and 0.159 generated by SVM and ANN models respectively.

On Demand Release and Retrieval of Bacteria from Microwell Arrays Using Photodegradable Hydrogel Membranes.

Microwell arrays are important tools for studying single cell behavior and cell-cell interactions, both in microbial and mammalian systems. However, retrieval of cells from microwell arrays with high spatial precision remains a major technical hurdle that prevents follow-up genetic and phenotypic characterization of cells within observed microwells. This work describes a new, material-based approach to grow and retrieve live bacterial cells from small (≥20 μm diameter) microwells in an array using the plant pathogen Agrobacterium tumefaciens as a model bacterium. Our approach uses a light-responsive, step-polymerized poly(ethylene glycol) hydrogel interface as a membrane that confines motile cells within microwells while allowing nutrient exchange and cell growth. The key design feature is the photodegradability of the membrane, as it enables individual wells of interest to be opened using patterned UV light for selective release and retrieval of cells. Extraction can occur in parallel from any number and combination of wells defined by the user. These advancements represent a new use for light-responsive hydrogels and the ability to retrieve cells from microwells with high spatial precision enables several applications that require the isolation and characterization of cells with rare phenotypes from heterogeneous populations.

Research on Constrained Sedimentary Facies Reservoir by Well-seismic Inversion

The combination of well and seismic is a geophysical method to describe sedimentary microfacies. Seismic inversion is mainly used to predict the continuity of cross-well sand bodies, the geometric shape of sand bodies and the boundary of cross-well sand bodies, to make up for the lack of cross-well information. Combining logging information, reasonable combination and prediction are made according to certain sedimentary model, and the distribution of different sedimentary microfacies sand bodies is described.

Research and Application on Sedimentary Characteristics of Reservoir

The oil field enters the extremely high water cut period, the fine reservoir description work is aimed to deepen the reservoir understanding and clear the potential distribution. In this paper, the favorable conditions of dense well net north region west, combining with coring data, using the combination of well and seismic fine reservoir description method, in-depth and detailed study of the reservoir in the study area, the deepening of the I, 2, 3 class reservoir sedimentary characteristics of the understanding, established 9 kinds of sedimentary reservoir the corresponding relation model, depositional model and sedimentary environment, analyzes the different deposition patterns and the distribution of remaining oil, the development of effective guidance adjustment and tapping the potential of remaining oil.

Histopathological Features of Lymph Nodes of Tuberculous Lymphadenitis Patients: Experience of 50 cases in Bangladesh

Background: Tuberculous lymphadenitis is common manifestation of extra-pulmonary tuberculosis in Bangladesh. Objective: The purpose of the present study was to see the histopathological features of tuberculous lymphadenitis patients. Methodology: This cross sectional study was done at the Department of Pathology at Banghabandhu Sheikh Mujib Medical University (BSMMU), Dhaka from January 2009 to March 2011 for a period of nearly two years. All the patients irrespective of age and sex with the clinical features suggestive of tuberculous lymphadenitis and later on proved to be the same histologically were selected for the study purposively. Relevant information was recorded in a prescribed data sheet and histomorphological findings were recorded accordingly. In cases where fresh specimen was available, caseous portion of lymph node was sent for culture. FiteFaraco staining was also done on lymph node sections in all cases. Result: A total number of 50 tuberculous lymphadenitis patients were recruited for this study of which well formed granuloma was detected in 34(68.0%) cases followed by ill defined and combination of well and ill defined which were 8(16.0%) cases in each. Among 34 well defined cases coalescing and discrete were found in 6(17.6%) cases in each. However, both types were found in 22(64.7%) cases.Conclusion: In conclusion well formed granuloma is most commonly found in tuberculous lymphadenitis with combined variety of coalescing and discrete histopathologic featuresBangladesh Journal of Infectious Diseases 2016;3(2):40-42

Experimental basis for the design of horizontal subsurface-flow treatment wetlands in naturally aerated channels with an anti-clogging stone layout

An innovative design is presented of horizontal subsurface-flow treatment wetlands with high operational reliability against clogging; traceable metre by metre for modelling purposes. For two years, urban wastewater was treated in a full-scale wetland whose construction was based on conclusions drawn from laboratory tests. No clogging was observed. In contrast to existing designs, channel configuration is used for the plug-flow circulation of water, the bed has a longitudinal diagonal design of angular stones of decreasing size, and a circuit of forced natural ventilation is formed by the combination of wells and chimneys connected within an air chamber over the water surface. The cross-section values of influent load were four times higher than those traditionally employed. The stone diagonal splits the wetland into an upper region of aerated reactor and a lower region conveying water over a bed which works as an anaerobic digester, thereby demonstrating the importance of the circuit of aeration and of the gradient of hydraulic conductivity of the bed that adapts itself to the variation in the quality of the water along its course. Overloads and isolated halts fail to alter the oxidation-reduction potential since these biological systems present high inertia when faced with changes in feed supply.

Three-dimensional geostatistical inversion of synthetic tomographic pumping and heat-tracer tests in a nested-cell setup

A main purpose of groundwater inverse modeling lies in estimating the hydraulic conductivity field of an aquifer. Traditionally, hydraulic head measurements, possibly obtained in tomographic setups, are used as data. Because the groundwater flow equation is diffusive, many pumping and observation wells would be necessary to obtain a high resolution of hydraulic conductivity, which is typically not possible. We suggest performing heat tracer tests using the same already installed pumping wells and thermometers in observation planes to amend the hydraulic head data set by the arrival times of the heat signals. For each tomographic combinations of wells, we recommend installing an outer pair of pumping wells, generating artificial ambient flow, and an inner well pair in which the tests are performed. We jointly invert heads and thermal arrival times in 3-D by the quasi-linear geostatistical approach using an efficiently parallelized code running on a mid-range cluster. In the present study, we evaluate the value of heat tracer versus head data in a synthetic test case, where the estimated fields can be compared to the synthetic truth. Because the sensitivity patterns of the thermal arrival times differ from those of head measurements, the resolved variance in the estimated field is 6 to 10 times higher in the joint inversion in comparison to inverting head data only. Also, in contrast to head measurements, reversing the flow field and repeating the heat-tracer test improves the estimate in terms of reducing the estimation variance of the estimate. Based on the synthetic test case, we recommend performing the tests in four principal directions, requiring in total eight pumping wells and four intersecting observation planes for heads and temperature in each direction.

Structural properties of fluids interacting via piece-wise constant potentials with a hard core

The structural properties of fluids whose molecules interact via potentials with a hard core plus two piece-wise constant sections of different widths and heights are presented. These follow from the more general development previously introduced for potentials with a hard core plus n piece-wise constant sections [A. Santos, S. B. Yuste, and M. Lopez de Haro, Condens. Matter Phys. 15, 23602 (2012)] in which use was made of a semi-analytic rational-function approximation method. The results of illustrative cases comprising eight different combinations of wells and shoulders are compared both with simulation data and with those that follow from the numerical solution of the Percus-Yevick and hypernetted-chain integral equations. It is found that the rational-function approximation generally predicts a more accurate radial distribution function than the Percus-Yevick theory and is comparable or even superior to the hypernetted-chain theory. This superiority over both integral equation theories is lost, however, at high densities, especially as the widths of the wells and/or the barriers increase.

Effect of charge, hydrophobicity, and sequence of nucleoporins on the translocation of model particles through the nuclear pore complex.

The molecular structure of the yeast nuclear pore complex (NPC) and the translocation of model particles have been studied with a molecular theory that accounts for the geometry of the pore and the sequence and anchoring position of the unfolded domains of the nucleoporin proteins (the FG-Nups), which control selective transport through the pore. The theory explicitly models the electrostatic, hydrophobic, steric, conformational, and acid-base properties of the FG-Nups. The electrostatic potential within the pore, which arises from the specific charge distribution of the FG-Nups, is predicted to be negative close to pore walls and positive along the pore axis. The positive electrostatic potential facilitates the translocation of negatively charged particles, and the free energy barrier for translocation decreases for increasing particle hydrophobicity. These results agree with the experimental observation that transport receptors that form complexes with hydrophilic/neutral or positively charged proteins to transport them through the NPC are both hydrophobic and strongly negatively charged. The molecular theory shows that the effects of electrostatic and hydrophobic interactions on the translocating potential are cooperative and nonequivalent due to the interaction-dependent reorganization of the FG-Nups in the presence of the translocating particle. The combination of electrostatic and hydrophobic interactions can give rise to complex translocation potentials displaying a combination of wells and barriers, in contrast to the simple barrier potential observed for a hydrophilic/neutral translocating particle. This work demonstrates the importance of explicitly considering the amino acid sequence and hydrophobic, electrostatic, and steric interactions in understanding the translocation through the NPC.

The Application of Seismic Attribute in the Prediction of Inner Front Facies Sands

The south of Daqing placanticline is mainly front facies reservoir which is chiefly the smooth, direct, narrow and small river. The size of the river is small and the reservoir thickness is mainly 1.0m-1.2m.The prediction accuracy of the interwell sandbody is only up to 60~70% under the condition of existing well network and well spacing, causing the relatively worse development effect. In order to raise the prediction accuracy of the interwell sandbody, it proposes the thinking of identifying the boundary and orientation of the inner front facies by means of the combination of wells and seismos of 3D seismic data. After the comparative analysis of the wells and the seismos, it determines the seismic attributes which can reflect the sandstone and identify mudstone preferablely, and proposes the method of reservoir description by means of the combination of wells and seismos which makes the prediction accuracy of the interwell sandbody reach to 80.77%.

Quantification of dsDNA using the Hitachi F-7000 Fluorescence Spectrophotometer and PicoGreen Dye

Quantification of DNA, especially in small concentrations, is an important task with a wide range of biological applications including standard molecular biology assays such as synthesis and purification of DNA, diagnostic applications such as quantification of DNA amplification products, and detection of DNA molecules in drug preparations. During this video we will demonstrate the capability of the Hitachi F-7000 Fluorescence Spectrophotometer equipped with a Micro Plate Reader accessory to perform dsDNA quantification using Molecular Probes Quant-it PicoGreen dye reagent kit. The F-7000 Fluorescence Spectrophotometer offers high sensitivity and high speed measurements. It is a highly flexible system capable of measuring fluorescence, luminescence, and phosphorescence. Several measuring modes are available, including wavelength scan, time scan, photometry and 3-D scan measurement. The spectrophotometer has sensitivity in the range of 50 picomoles of fluorescein when using a 300 μL sample volume in the microplate, and is capable of measuring scan speeds of 60,000 nm/minute. It also has a wide dynamic range of up to 5 orders of magnitude which allows for the use of calibration curves over a wide range of concentrations. The optical system uses all reflective optics for maximum energy and sensitivity. The standard wavelength range is 200 to 750 nm, and can be extended to 900 nm when using one of the optional near infrared photomultipliers. The system allows optional temperature control for the plate reader from 5 to 60 degrees Celsius using an optional external temperature controlled liquid circulator. The microplate reader allows for the use of 96 well microplates, and the measuring speed for 96 wells is less than 60 seconds when using the kinetics mode. Software controls for the F-7000 and Microplate Reader are also highly flexible. Samples may be set in either column or row formats, and any combination of wells may be chosen for sample measurements. This allows for optimal utilization of the microplate. Additionally, the software allows importing micro plate sample configurations created in Excel and saved in comma separated values, or "csv" format. Microplate measuring configurations can be saved and recalled by the software for convenience and increased productivity. Data results can be output to a standard report, to Excel, or to an optional Report Generator Program.

Quantification of dsDNA using the Hitachi F-7000 Fluorescence Spectrophotometer and PicoGreen Dye

Quantification of DNA, especially in small concentrations, is an important task with a wide range of biological applications including standard molecular biology assays such as synthesis and purification of DNA, diagnostic applications such as quantification of DNA amplification products, and detection of DNA molecules in drug preparations. During this video we will demonstrate the capability of the Hitachi F-7000 Fluorescence Spectrophotometer equipped with a Micro Plate Reader accessory to perform dsDNA quantification using Molecular Probes Quant-it PicoGreen dye reagent kit. The F-7000 Fluorescence Spectrophotometer offers high sensitivity and high speed measurements. It is a highly flexible system capable of measuring fluorescence, luminescence, and phosphorescence. Several measuring modes are available, including wavelength scan, time scan, photometry and 3-D scan measurement. The spectrophotometer has sensitivity in the range of 50 picomoles of fluorescein when using a 300 μL sample volume in the microplate, and is capable of measuring scan speeds of 60,000 nm/minute. It also has a wide dynamic range of up to 5 orders of magnitude which allows for the use of calibration curves over a wide range of concentrations. The optical system uses all reflective optics for maximum energy and sensitivity. The standard wavelength range is 200 to 750 nm, and can be extended to 900 nm when using one of the optional near infrared photomultipliers. The system allows optional temperature control for the plate reader from 5 to 60 degrees Celsius using an optional external temperature controlled liquid circulator. The microplate reader allows for the use of 96 well microplates, and the measuring speed for 96 wells is less than 60 seconds when using the kinetics mode. Software controls for the F-7000 and Microplate Reader are also highly flexible. Samples may be set in either column or row formats, and any combination of wells may be chosen for sample measurements. This allows for optimal utilization of the microplate. Additionally, the software allows importing micro plate sample configurations created in Excel and saved in comma separated values, or "csv" format. Microplate measuring configurations can be saved and recalled by the software for convenience and increased productivity. Data results can be output to a standard report, to Excel, or to an optional Report Generator Program.

Simple and safe exclusion of pulmonary embolism in outpatients using quantitative D-dimer and Wells’ simplified decision rule

A safe and effective management strategy is pivotal in excluding pulmonary embolism (PE). The combination of Wells' simplified dichotomous clinical decision rule and D-dimer test is non-invasive and could be highly efficient, though its safety has not been widely studied. We evaluated safety and efficiency of this combination in excluding PE. Wells clinical decision rule was performed in 941 consecutive patients with suspected PE and, if patients had a score <or=4.0 points, a VIDAS D-dimer test followed. Patients with a normal D-dimer concentration had no further tests, PE was considered excluded, and patients did not receive anticoagulant treatment. Patients, in whom PE was excluded, were followed up for three months. Four hundred fifty patients (51.2%) had a clinical decision score =4.0 points and a normal D-dimer concentration. In 45 of these patients, during the initial diagnostic period additional objective testing, although not indicated, was performed, and PE was established in two patients. During three months of follow up no venous thromboembolic events (VTE) occurred. Therefore, the overall VTE failure rate was two of 450 (0.4% [95%CI 0-1.1]); the overall prevalence of PE was 12.3%. The diagnostic protocol could be completed and allowed a decision to be made in 90% of the study patients. This study has prospectively established the safety of a combination of a dichotomized clinical decision rule and D-dimer test in ruling out PE. The strategy proved highly efficient, since more than 50% of patients could be managed without the need for more invasive and expensive tests.