Correction: Pericyclic reaction benchmarks: hierarchical computations targeting CCSDT(Q)/CBS and analysis of DFT performance.

Correction for 'Pericyclic reaction benchmarks: hierarchical computations targeting CCSDT(Q)/CBS and analysis of DFT performance' by Pascal Vermeeren et al., Phys. Chem. Chem. Phys., 2022, 24, 18028-18042, https://doi.org/10.1039/D2CP02234F.

Evaluation of Detected Medication Errors Within the Operating Room at an Academic Medical Center.

Background: Medication errors are preventable events that lead to inappropriate medication use and potential patient harm. This is especially prevalent within the operating room (OR) where one practitioner is involved in the entire medication-use process. Despite recent implementation of BD Pyxis™ Anesthesia ES, Codonics Safe Label System, and Epic One Step at the University of Kentucky Healthcare (UKHC) to prevent medication errors, errors continue to be reported. Curatolo et al found human error was the most frequent cause of medication error within the OR. Clumsy automation may be an explanation for this, which imposes burdens and promotes work arounds. This study endeavors to assess potential medication errors via chart review to identify risk reduction strategies. Methods: This a single-center retrospective cohort review of patients admitted to a UK HealthCare Main Operating Room, defined OR1A-OR5A and OR7A-OR16A, who were administered medications from 8/1/2021 to 9/30/2021. Results: Over a 2-month period, 145 cases were conducted at UK HealthCare. Of the 145 cases, 98.6% (n = 143) involved a medication error and 93.7% (n = 136) of the errors involved a high-alert medication. The top 5 classes of drugs involved in errors were all high-alert medications. Lastly, 46.6% (n = 67) of cases had documentation that Codonics was utilized. In addition to analyzing medication errors, the financial analysis found that $3154.04 in drug cost was lost in the study period. When extrapolating these results to all BD™ Pyxis Anesthesia Machines at UK HealthCare, $107 237.36 of drug cost is potentially lost per year. Conclusions: These findings add to previous data that have described the increased rate of medication errors when conducting chart review rather than rely on self-reported data. In this study, 98.6% of all cases involved a medication error. In addition, these findings provide additional insight in the increased use of technology within the operating room despite medication errors still occurring. These results can be applied to like institutions to critically evaluate anesthesia workflow to determine risk reduction strategies.

Artemis inhibition as a therapeutic strategy for acute lymphoblastic leukemia.

As effective therapies for relapse and refractory B-cell acute lymphoblastic leukemia (B-ALL) remain problematic, novel therapeutic strategies are needed. Artemis is a key endonuclease in V(D)J recombination and nonhomologous end joining (NHEJ) of DNA double-strand break (DSB) repair. Inhibition of Artemis would cause chromosome breaks during maturation of RAG-expressing T- and B-cells. Though this would block generation of new B- and T-cells temporarily, it could be oncologically beneficial for reducing the proliferation of B-ALL and T-ALL cells by causing chromosome breaks in these RAG-expressing tumor cells. Currently, pharmacological inhibition is not available for Artemis. According to gene expression analyses from 207 children with high-risk pre-B acute lymphoblastic leukemias high Artemis expression is correlated with poor outcome. Therefore, we evaluated four compounds (827171, 827032, 826941, and 825226), previously generated from a large Artemis targeted drug screen. A biochemical assay using a purified Artemis:DNA-PKcs complex shows that the Artemis inhibitors 827171, 827032, 826941, 825226 have nanomolar IC50 values for Artemis inhibition. We compared these 4 compounds to a DNA-PK inhibitor (AZD7648) in three patient-derived B-ALL cell lines (LAX56, BLQ5 and LAX7R) and in two mature B-cell lines (3301015 and 5680001) as controls. We found that pharmacological Artemis inhibition substantially decreases proliferation of B-ALL cell lines while normal mature B-cell lines are not markedly affected. Inhibition of DNA-PKcs (which regulates Artemis) using the DNA-PK inhibitor AZD7648 had minor effects on these same primary patient-derived ALL lines, indicating that inhibition of V(D)J hairpin opening requires direct inhibition of Artemis, rather than indirect suppression of the kinase that regulates Artemis. Our data provides a basis for further evaluation of pharmacological Artemis inhibition of proliferation of B- and T-ALL.

Influences on the development of imaginary worlds.

Dubourg and Baumard's paper takes a different, and fruitful, approach to the study of imaginary worlds than what is usually found in Media Studies, but omits certain circumstances and influences that shaped their history; this article argues that psychological or behavioral factors are not enough to explain the growth of imaginary worlds, even as they may be important influences.

Toward the Observation of the Tin and Lead Analogs of Formaldehyde.

Heavy aldehyde and ketone analogues, R2X═O (X = Si, Ge, Sn, or Pb), differ from their R2C═O counterparts due to their greater tendency to oligeramize as the X═O bond polarity increases as one goes down the periodic table. To date, H2Sn═O and H2Pb═O have eluded experimental detection. Herein we present the most rigorous theoretical study to date on these structures, providing CCSD(T)/pwCVTZ fundamental frequencies computed on CCSD(T)/CBS optimized structures for the H2X═O (X = Sn, Pb) potential energy surface. The focal point approach is employed to produce the CCSDTQ/CBS relative energies. For the Sn and Pb structures, the carbene-like cis-HXOH was the global minima, with the trans species being less than 0.6 and 1.1 kcal mol-1 above the cis structures, respectively. The formaldehyde-like H2X═O structure is in an energy well of at least 34.8 and 25.4 kcal mol-1 for Sn and Pb, respectively. Our results provide guidance for future work that may detect H2Sn═O or H2Pb═O for the first time.

Pericyclic reaction benchmarks: hierarchical computations targeting CCSDT(Q)/CBS and analysis of DFT performance.

Hierarchical, convergent ab initio benchmark computations were performed followed by a systematic analysis of DFT performance for five pericyclic reactions comprising Diels-Alder, 1,3-dipolar cycloaddition, electrocyclic rearrangement, sigmatropic rearrangement, and double group transfer prototypes. Focal point analyses (FPA) extrapolating to the ab initio limit were executed via explicit quantum chemical computations with electron correlation treatments through CCSDT(Q) and correlation-consistent Gaussian basis sets up to aug'-cc-pV5Z. Optimized geometric structures and vibrational frequencies of all stationary points were obtained at the CCSD(T)/cc-pVTZ level of theory. The FPA reaction barriers and energies exhibit convergence to within a few tenths of a kcal mol-1. The FPA benchmarks were used to evaluate the performance of 60 density functionals (eight dispersion-corrected), covering the local-density approximation (LDA), generalized gradient approximations (GGAs), meta-GGAs, hybrids, meta-hybrids, double-hybrids, and range-separated hybrids. The meta-hybrid M06-2X functional provided the best overall performance [mean absolute error (MAE) of 1.1 kcal mol-1] followed closely by the double-hybrids B2K-PLYP, mPW2K-PLYP, and revDSD-PBEP86 [MAE of 1.4-1.5 kcal mol-1]. The regularly used GGA functional BP86 gave a higher MAE of 5.8 kcal mol-1, but it qualitatively described the trends in reaction barriers and energies. Importantly, we established that accurate yet efficient meta-hybrid or double-hybrid DFT potential energy surfaces can be acquired based on geometries from the computationally efficient and robust BP86/DZP level.

Catalyzed reaction of isocyanates (RNCO) with water.

The reactions between substituted isocyanates (RNCO) and other small molecules (e.g. water, alcohols, and amines) are of significant industrial importance, particularly for the development of novel polyurethanes and other useful polymers. We present very high-level ab initio computations on the HNCO + H2O reaction, with results targeting the CCSDT(Q)/CBS//CCSD(T)/cc-pVQZ level of theory. Our results affirm that hydrolysis can occur across both the N[double bond, length as m-dash]C and C[double bond, length as m-dash]O bonds of HNCO via concerted mechanisms to form carbamate or imidic acid with ΔH0K barrier heights of 38.5 and 47.5 kcal mol-1. A total of 24 substituted RNCO + H2O reactions were studied. Geometries obtained with a composite method and refined with CCSD(T)/CBS single point energies determine that substituted RNCO species have a significant influence on these barrier heights, with an extreme case like fluorine lowering both barriers by close to 15 kcal mol-1 and most common alkyl substituents lowering both by approximately 3 kcal mol-1. Natural Bond Orbital (NBO) analysis provides evidence that the predicted barrier heights are strongly associated with the occupation of the in-plane C-O* orbital of the RNCO reactant. Key autocatalytic mechanisms are considered in the presence of excess water and RNCO species. Additional waters (one or two) are predicted to lower both barriers significantly at the CCSD(T)/aug-cc-pV(T+d)Z level of theory with strongly electron withdrawing RNCO substituents also increasing these effects, similar to the uncatalyzed case. The 298 K Gibbs energies are only marginally lowered by a second catalyst water molecule, indicating that the decreasing ΔH0K barriers are offset by loss of translational entropy with more than one catalyst water. Two-step 2RNCO + H2O mechanisms are characterized for the formation of carbamate and imidic acid. The second step of these two pathways exhibits the largest barrier and presents no clear pattern with respect to substituent choice. Our results indicate that an additional RNCO molecule might catalyze imidic acid formation but have less influence on the efficiency of carbamate formation. We expect that these results lay a firm foundation for the experimental study of substituted isocyanates and their relationship to the energetic pathways of related systems.

Group 15 and 16 Nitrene-Like Pnictinidenes.

Pnictinidenes are an increasingly relevant species in main group chemistry and generally exhibit proclivity for the triplet electronic ground state. However, the elusive singlet electronic states are often desired for chemical applications. We predict the singlet-triplet energy differences (ΔEST =ESinglet -ETriplet ) of simple group 15 and 16 substituted pnictinidenes (Pn-R; Pn=P, As, Sb, or Bi) with highly reliable focal-point analyses targeting the CCSDTQ/CBS level of theory. The only cases we predict to have favorable singlet states are P-PH2 (-3.2 kcal mol-1 ) and P-NH2 (-0.2 kcal mol-1 ). ΔEST trends are discussed in light of the geometric predictions as well as qualitative natural bond order analysis to elucidate some of the important electronic structure features. Our work provides a rigorous benchmark for the ΔEST of fundamental Pn-R moieties and provides a firm foundation for the continued study of heavier pnictinidenes.

Highly Strained Pn(CH)3 (Pn = N, P, As, Sb, Bi) Tetrahedranes: Theoretical Characterization.

Recent experimental research by Cummins and co-workers has established the existence of a tetrahedrane molecule with one CH moiety replaced by phosphorus. We present here the first theoretical studies of the entire Pn(CH)3 (Pn = N, P, As, Sb, Bi) class of molecules. Geometries are obtained at the highly reliable CCSD(T)/aug-cc-pwCVTZ(-PP) level of theory. Harmonic vibrational frequencies are determined and analyzed to confirm the nature of each stationary point and provide helpful findings that may aid in the detection of each species. Most notable is the result that the geometric parameters associated with the (CH)3 moiety in the tetrahedranes exhibit little change under pnictogen substitution, while the Pn-C bonds and C-Pn-C bond angles greatly increase and decrease, respectively. Strain energies are predicted and range from 122.3 kcal mol-1 (N(CH)3) to 99.4 kcal mol-1 (Bi(CH)3) at the DF-CCSD(T)//B3LYP-D3/aug-cc-pV(T+d)Z(-PP) level of theory. The obtained geometries are further analyzed with Natural Bond Orbital (NBO) methods to understand the bonding and electronic structure of each species. We also provide insight into how different substituents can help make the tetrahedrane structure more energetically favorable due to electron delocalization into substituent antibonding orbitals. The effect of additional delocalization also weakens the Pn-C bonds, especially for the heavier pnictogens. This work concludes with a list of considerations that summarize our key findings and motivate future work aimed at producing novel pnictogen-substituted tetrahedrane molecules.

The HOX⋯SO2 (X=F, Cl, Br, I) Binary Complexes: Implications for Atmospheric Chemistry.

Sulfur dioxide and hypohalous acids (HOX, X=F, Cl, Br, I) are ubiquitous molecules in the atmosphere that are central to important processes like seasonal ozone depletion, acid rain, and cloud nucleation. We present the first theoretical examination of the HOX⋯SO2 binary complexes and the associated trends due to halogen substitution. Reliable geometries were optimized at the CCSD(T)/aug-cc-pV(T+d)Z level of theory for HOF and HOCl complexes. The HOBr and HOI complexes were optimized at the CCSD(T)/aug-cc-pV(D+d)Z level of theory with the exception of the Br and I atoms which were modeled with an aug-cc-pwCVDZ-PP pseudopotential. 27 HOX⋯SO2 complexes were characterized and the focal point method was employed to produce CCSDT(Q)/CBS interaction energies. Natural Bond Orbital analysis and Symmetry Adapted Perturbation Theory were used to classify the nature of each principle interaction. The interaction energies of all HOX⋯SO2 complexes in this study ranged from 1.35 to 3.81 kcal mol-1 . The single-interaction hydrogen bonded complexes spanned a range of 2.62 to 3.07 kcal mol-1 , while the single-interaction halogen bonded complexes were far more sensitive to halogen substitution ranging from 1.35 to 3.06 kcal mol-1 , indicating that the two types of interactions are extremely competitive for heavier halogens. Our results provide insight into the interactions between HOX and SO2 which may guide further research of related systems.

High level ab initio investigation of the catalytic effect of water on formic acid decomposition and isomerization.

Formic acid (FA) is a ubiquitous molecule found in the atmosphere, and is relevant to many important processes. The FA molecule generally exists as the trans isomer, which can decompose into H2O and CO (dehydration). It can also exist in the less favorable cis isomer which can decompose into H2 and CO2 (decarboxylation). Our work examines the complexes formed between each isomer of FA with water. We present geometries and vibrational frequencies obtained at the reliable CCSD(T)/aug-cc-pVTZ level of theory for seven FAwater complexes. We utilize the focal point method to determine CCSDT(Q)/CBS plus corrections binding energies of 7.37, 3.36, and 2.02 kcal mol-1 plus 6.07, 3.79, 2.60, and 2.55 kcal mol-1 for the trans-FAwater and cis-FAwater complexes, respectively. Natural bond orbital analysis is used to further decompose the interactions in each complex and gain insight into their relative strengths. Furthermore, we examine the effect that a single water molecule has on the barrier heights to each decomposition pathway by optimizing the transition states and verifying their connectivity with intrinsic reaction coordinate computations as well as utilizing a kinetic model. Water lowers the barrier to dehydration by at most 15.78 kcal mol-1 and the barrier to decarboxylation by up to 15.90 kcal mol-1. Our research also examines for the first time the effect of one water molecule on the interconversion barrier and we find that the barrier from trans to cis is not catalyzed by water due to the strong FA and water interactions. Our results highlight some instances where different binary complexes result in different decomposition pathways and even a case where one binary complex can form the same decomposition products via two distinct mechanisms. Our results provide a reliable benchmark of the FAH2O system as well as provide insight into future studies of similar atmospheric systems.

Quality of anticoagulant therapy and the incidence of in-stent thrombosis after venous stenting.

BACKGROUND: In patients with a venous outflow obstruction following iliofemoral deep vein thrombosis stenting of the venous tract to prevent or alleviate postthrombotic syndrome is applied with increasing frequency. The impact of the quality of anticoagulant therapy with vitamin K antagonists (VKAs) on the development of in-stent thrombosis is currently unknown. OBJECTIVES: To determine the association between the quality of postinterventional VKA treatment and the occurrence of in-stent thrombosis. METHODS: Seventy-nine patients with iliofemoral and/or caval venous stent placement for obstruction of the venous outflow were included in this study. All patients received postinterventional VKA. The quality of VKA anticoagulant therapy was expressed as the time within therapeutic range (TTR) calculated using the linear interpolation method and as the proportion of International Normalized Ratio (INR) values < 2.0. In-stent thrombosis was assessed by the use of duplex ultrasound. Survival analysis (Kaplan-Meier curves, Cox regression) was used to analyze the data. RESULTS: In-stent thrombosis developed in 16 patients (20.3%). The total population had a mean TTR of 64.0% (±19.0) and a mean proportion of INR values < 2.0 of 11.6% (±12.0). Overall, a TTR < 49.9% was associated with an increased risk of in-stent thrombosis. The multivariable adjusted analysis showed a hazard ratio (HR) of 0.96 (95% confidence interval [CI], 0.92-0.99; P = .02) per 1% increase in TTR. The proportion of INR values < 2.0 had no significant association with the occurrence of in-stent thrombosis: HR 0.98 (95% CI, 0.91-1.06; P = .66). CONCLUSIONS: We conclude that the quality of anticoagulant treatment reflected in the TTR following a venous stenting procedure is an important independent determinant for the risk of in-stent thrombosis. The role of anticoagulant treatment for the prevention of in-stent thrombosis following stenting procedures therefore merits further research.

Important features of the potential energy surface of the methylamine plus O(1D) reaction.

This research presents an ab initio characterization of the potential energy surface for the methylamine plus 1D oxygen atom reaction, which may be relevant to interstellar chemistry. Geometries and harmonic vibrational frequencies were determined for all stationary points at the CCSD(T)/aug-cc-pVTZ level of theory. The focal point method along with several additive corrections was used to obtain reliable CCSDT(Q)/CBS potential energy surface features. Extensive conformational analysis and intrinsic reaction coordinate computations were performed to ensure accurate chemical connectivity of the stationary points. Five minima were determined to be possible products of this reaction and three novel transition states were found that were previously unreported or mislabeled in the literature. The pathways we present can be used to guide further searches for NH2 containing species in the interstellar medium.

A comparison between hydrogen and halogen bonding: the hypohalous acid-water dimers, HOXH2O (X = F, Cl, Br).

Hypohalous acids (HOX) are a class of molecules that play a key role in the atmospheric seasonal depletion of ozone and have the ability to form both hydrogen and halogen bonds. The interactions between the HOX monomers (X = F, Cl, Br) and water have been studied at the CCSD(T)/aug-cc-pVTZ level of theory with the spin free X2C-1e method to account for scalar relativistic effects. Focal point analysis was used to determine CCSDT(Q)/CBS dissociation energies. The anti hydrogen bonded dimers were found with interaction energies of -5.62 kcal mol-1, -5.56 kcal mol-1, and -4.97 kcal mol-1 for X = F, Cl, and Br, respectively. The weaker halogen bonded dimers were found to have interaction energies of -1.71 kcal mol-1 and -3.03 kcal mol-1 for X = Cl and Br, respectively. Natural bond orbital analysis and symmetry adapted perturbation theory were used to discern the nature of the halogen and hydrogen bonds and trends due to halogen substitution. The halogen bonds were determined to be weaker than the analogous hydrogen bonds in all cases but close enough in energy to be relevant, significantly more so with increasing halogen size.

The Effect of Stenting on Venous Hypertension: Results Using a Treadmill Stress Test with Invasive Pressure Measurements in Patients with Iliofemoral Venous Obstruction.

OBJECTIVES: The primary aim was to investigate whether stenting of post-thrombotic iliofemoral obstruction reduces venous hypertension. The secondary aim was to establish whether improvement in haemodynamic parameters impacts on quality of life. METHODS: In this prospective observational study, 12 participants with unilateral post-thrombotic obstruction of the iliac and/or common femoral veins (CFVs) underwent a treadmill stress test with invasive pressure measurements in the CFVs and dorsal foot veins of both affected and non-affected limbs. This was performed the day before and 3 months after stenting the obstructed tract. Paired sample t-tests were used to compare the treatment effect and univariable linear regression analysis to determine the association with improvement in quality of life. RESULTS: Before treatment, CFV pressure increased 34.8 ± 23.1 mmHg during walking in affected limbs compared with 3.9 ± 5.8 mmHg in non-affected limbs. This pressure rise decreased to 22.3 ± 24.8 mmHg after 3 months follow up compared with a 4.0 ± 6.0 mmHg increase in non-affected limbs (-26.2 mmHg difference; 95% CI -41.2 to -11.3). No such effect was found in the dorsal foot veins. The VEINES-QOL increased 25.3 ± 11.3 points after stenting and was significantly associated with a decrease in CFV pressure rise during walking (regression coefficient 0.4; 95% CI 0.1-0.6). CONCLUSION: Stenting of post-thrombotic iliofemoral obstruction significantly reduces venous hypertension in the common femoral vein and correlates with an improvement in the quality of life. Larger studies with a broader range of degree of obstruction need be performed to assess whether pre-stenting pressure measurements can predict post stenting clinical success.

The inability of venous occlusion air plethysmography to identify patients who will benefit from stenting of deep venous obstruction.

Background The aim of this study was to assess whether venous occlusion plethysmography can be used to identify venous obstruction and predict clinical success of stenting. Method Receiver operated characteristic curves were used to determine the ability of venous occlusion plethysmography to discriminate between the presence and absence of obstruction, measured by duplex ultrasound and magnetic resonance venography, and to discriminate between successful and non-successful stenting, measured by VEINES-QOL/Sym. Result Two hundred thirty-seven limbs in 196 patients were included. Areas under the curve for post-thrombotic obstruction were one-second outflow volume 0.71, total venous volume 0.69 and outflow fraction 0.59. Stenting was performed in 45 limbs of 39 patients. Areas under the curve for identifying patients with successful treatment at one year after stenting were 0.57, 0.54 and 0.63, respectively. Conclusion Venous occlusion plethysmography cannot be used to identify venous obstruction proximal to the femoral confluence or to distinguish which patients will benefit from treatment.

Stent extension into a single inflow vessel is a valuable option after endophlebectomy.

Background Venous stenting with an endophlebectomy and arteriovenous fistula can be performed in patients with extensive post-thrombotic changes. However, these hybrid procedures can induce restenosis, sometimes requiring stent extension, into a single inflow vessel. This study investigates the effectiveness of stenting into a single inflow vessel. Methods All evaluated patients had temporary balloon occlusion of the arteriovenous fistula to evaluate venous flow into the stents. When stent inflow was deemed insufficient, AVF closure was postponed and additional stenting was performed. Patency rates and clinical outcomes were evaluated. Results Twenty-four (38%) of 64 patients had additional stenting. The primary, assisted primary and secondary patency were 60 %, 70% and 70% respectively. Villalta score reduced by 6.1 points ( p < 0.001), and venous clinical severity score by 2.7 points ( p = 0.034). Conclusion Stenting through the femoral confluence into a single inflow vessel is a feasible bailout option if primary hybrid intervention fails with relative high patency rates and clinical improvement.

Risk factors of postthrombotic syndrome before and after deep venous thrombosis treatment.

Postthrombotic syndrome is the most common complication after deep venous thrombosis. Postthrombotic syndrome is a debilitating disease and associated with decreased quality of life and high healthcare costs. Postthrombotic syndrome is a chronic disease, and causative treatment options are limited. Prevention of postthrombotic syndrome is therefore very important. Not all patients develop postthrombotic syndrome. Risk factors have been identified to try to predict the risk of developing postthrombotic syndrome. Age, gender, and recurrent deep venous thrombosis are factors that cannot be changed. Deep venous thrombosis location and extent seem to predict severity of postthrombotic syndrome and are potentially suitable as patient selection criteria. Residual thrombosis and reflux are known to increase the incidence of postthrombotic syndrome, but are of limited use. More recently developed treatment options for deep venous thrombosis, such as new oral factor X inhibitors and catheter-directed thrombolysis, are available at the moment. Catheter-directed thrombolysis shows promising results in reducing the incidence of postthrombotic syndrome after deep venous thrombosis. The role of new oral factor X inhibitors in preventing postthrombotic syndrome is still to be determined.

Abdominal and pubic collateral veins as indicators of deep venous obstruction.

OBJECTIVE: Chronic deep venous obstruction can cause a significant loss of quality of life, although it can be treated successfully by stenting. A clear referral pattern for additional imaging is warranted in patients with lower limb complaints. The aim of this study was to determine the value of clinically visible abdominal wall collateral veins in the diagnosis of a potentially treatable deep venous obstruction. METHODS: A total of 295 patients referred for evaluation at a tertiary venous clinic with a collateral vein on the abdominal wall or pubic bone, visible on physical examination, were retrospectively analyzed and compared with a randomly selected control group of 365 patients without such a collateral vein. Duplex ultrasound, magnetic resonance venography, computed tomography venography, and conventional venography were used to determine the presence or absence of deep venous obstruction. RESULTS: Mean age of the group with a positive collateral was 43.5 ± 13.7 (6-76) years compared with 44.7 ± 14.2 (16-89) years in the control group. In the collateral group, 66.1% were female compared with 63.3% in the control group. Sensitivity of the abdominal wall collateral vein for any obstruction at the level of the groin or more proximal was 53% (95% confidence interval [CI], 48-57); specificity, 86% (95% CI, 79-91); positive predictive value, 93% (95% CI, 90-96); and negative predictive value, 32% (95% CI, 28-37). Sensitivity was 68% (95% CI, 62-73) for higher degrees of post-thrombotic obstruction and 27% (95% CI, 19-36) in iliac vein compression. CONCLUSIONS: A collateral vein on the abdominal wall or across the pubic bone in patients with complaints of the lower limb has an excellent positive predictive value for deep venous obstructive disease at the level of the groin or higher. Such collateral veins should therefore not be removed, and symptomatic patients could be offered further diagnostics and treatment.