What common substances can cause false positives on urine screens for drugs of abuse?

False-positive reports on urine drug screens by immunoassay are rare (strength of recommendation [SOR]: C, small controlled-exposure studies, small case series). Nonsteroidal anti-inflammatory drugs, fluoroquinolones, and Vicks Inhaler are most frequently implicated (TABLE). Ruling out a false-positive result requires confirmation with a more specific test, usually gas chromatography/mass spectrometry (GC-MS). A true-positive drug screen may occur in a urine specimen from a patient who legally or unknowingly ingests a product that is metabolized to a drug of abuse. Passive exposure to a substance is unlikely to cause a positive drug screen (SOR: B, small controlled-exposure studies)

Group Medical Visits for the Management of Chronic Pain

Improvements of possible practical significance were seen for various clinical measures in studies of group treatment sessions for patients with back pain, arthritis, and rheumatic disease. However, studies on group treatment for patients with nonspecific pain are lacking, especially in the primary care setting. (Strength of Recommendation: B)

Examination of diffusion versus advection dominated sediment suspension on the inner shelf under storm and swell conditions, Duck, North Carolina

[1] A benthic boundary layer tripod supporting six current meters and three profiling acoustic backscatter sensors (ABS) documented storm and swell conditions during the fall of 1996 at a depth of 13 m on the inner shelf off Duck, North Carolina. Sediment concentration was higher in the wave boundary layer (WBL) during storm conditions but higher similar to40 cm above the bed (cm ab) during swell conditions. To test the applicability of a diffusive balance during storm versus swell, ABS data were used to invert the vertical diffusion equation and solve for eddy diffusivity from 1 to 50 cm ab. During the storm period, diffusivity derived from the ABS up to similar to40 cm ab agreed well with viscosity derived above the WBL from observed current profiles and from the Grant-Madsen-Glenn (GMG) model. During the swell period, diffusivity derived from the ABS up to similar to40 cm ab did not agree with observed mean current shear above this level nor with the GMG model. Diffusivity did agree with viscosity derived from shear stress due to waves within the WBL extrapolated to a height greater than the modeled WBL. We speculate that during swell conditions, shedding vortices enhanced mass and momentum exchange, extending the eddy viscosity associated with waves above the predicted WBL; during storm conditions, strong currents prevented vortices from penetrating beyond the predicted WBL. Rouse diffusion models with two- and three-layered eddy diffusivity and combined diffusion-advection models with one and three-layer were applied to the observational data set. During the storm the two- and three-layered Rouse models including multiple grain sizes and bed armoring reproduced the observed concentration well. During swell (weak current conditions) all the models considered underpredicted the observed concentration if applied with a standard WBL thickness. To correct this, enhanced vertical exchange was represented by a thickened WBL whenever mean currents were weak relative to the estimated jet velocity associated with wave-induced vortex shedding. The two- layer Rouse model then reproduced the concentrations observed during swell remarkably well. This implies that mean sediment suspension dominated by wave-induced advection may still be approximated by a diffusion-like process under some circumstances

How safe and effective is ondansetron for nausea and vomiting in pregnancy?

Q: How safe and effective is ondansetron for nausea and vomiting in pregnancy? Evidence-based answer: oral ondansetron is more effective than a combination of pyridoxine and doxylamine for outpatient treatment of nausea and vomiting in pregnancy (strength of recommendation [SOR]: B, randomized controlled trial [RCT]). For moderate to severe nausea and vomiting, intravenous (IV) ondansetron is at least as effective as IV metoclopramide and may cause fewer adverse reactions (SOR: B, RCTs). Disease registry, case-control, and cohort studies report a slight increase in the risk of cardiac defects with ondansetron use in first-trimester pregnancies, but no major or other birth defects are associated with ondansetron exposure (SOR: B, a systematic review of observational trials and a single retrospective cohort study). A specialty society guideline recommends weighing the risks and benefits of ondansetron use before 10 weeks' gestational age and suggests reserving ondansetron for patients who have persistent nausea and vomiting unresponsive to first- and second-line treatments (SOR: C, expert opinion).Kimberly L. Collins, MD; Megan Wilson, MD; E. Chris Vincent, MD, University of Washington, Seattle ; Sarah Safranek, MLIS, University of Washington, SeattleIncludes bibliographical reference

What are the benefits and risks of inhaled corticosteroids for COPD?

Q: What are the benefits and risks of inhaled corticosteroids for COPD? A: Inhaled corticosteroids (ICS), either alone or with a long-acting [beta] agonist (LABA), reduce the frequency of exacerbations of chronic obstructive pulmonary disease (COPD) and statistically, but not clinically, improve quality of life (QOL) (strength of recommendation [SOR]: B, meta-analyses of heterogeneous studies). However, ICS have no mortality benefit and don't consistently improve forced expiratory volume in 1 second (FEV1) (SOR: B, meta-analyses of secondary outcomes). They increase the risk of pneumonia, oropharyngeal candidiasis, and bruising (SOR: B, meta-analyses of secondary outcomes). Withdrawal of ICS doesn't significantly increase the risk of COPD exacerbation (SOR: B, a meta-analysis)

Spectral estimates of bed shear stress using suspended-sediment concentrations in a wave-current boundary layer

High-resolution time series of suspended-sediment profiles have been obtained using an acoustic backscatter system at an inner shelf site (North Carolina) where flows are dominated by wind-driven currents and waves. We analyzed the spatial and temporal structure of near-bed turbulence in particle-transporting flows and scalar-like fluctuations of suspended-sediment concentrations. An important element of our analysis is a new inertial dissipation method for passive tracers to estimate the shear stress acting on the seabed, using the spectral properties of suspended sediment concentrations observed by acoustic backscatter sensors. In flows that provide adequate separation of the scales of turbulence production and dissipation, a sufficiently thick constant stress wall layer, and significant sediment suspension, frequency (or associated wave number) spectra of near-bed sediment concentration exhibit a -5/3 slope in the inertial subrange that spans frequencies of order 1 Hz. This observation suggests that the suspended sediment is effectively a passive tracer of turbulent fluid motions. Inversion of the relevant, Kolmogorov scaling equations yields estimates of the shear velocity that agree reasonably well with other, independent and widely used measures. High- and low-frequency limits on application of the inertial dissipation method to sediment concentration are related to the inertial response time of sediment particles and the sediment settling timescale. We propose that, in future applications, the inertial dissipation method for passive tracers can be used to estimate either the shear velocity, effective settling velocity of suspended sediment (or equivalent particle size) or dynamic bed roughness if two of these three quantities are independently known

Pacing Equilibrium in First-Price Auction Markets

In the isolated auction of a single item, second price often dominates first price in properties of theoretical interest. But, single items are rarely sold in true isolation, so considering the broader context is critical when adopting a pricing strategy. In this paper, we study a model centrally relevant to Internet advertising and show that when items (ad impressions) are individually auctioned within the context of a larger system that is managing budgets, theory offers surprising endorsement for using a first price auction to sell each individual item. In particular, first price auctions offer theoretical guarantees of equilibrium uniqueness, monotonicity, and other desirable properties, as well as efficient computability as the solution to the well-studied Eisenberg-Gale convex program. We also use simulations to demonstrate that a bidder's incentive to deviate vanishes in thick markets