Effectiveness of interventions designed to reduce the use of imaging for low-back pain: a systematic review

Background:Rates of imaging for low-back pain are high and are associated with increased health care costs and radiation exposure as well as potentially poorer patient outcomes. We conducted a systematic review to investigate the effectiveness of interventions aimed at reducing the use of imaging for low-back pain.Methods:We searched MEDLINE, Embase, CINAHL and the Cochrane Central Register of Controlled Trials from the earliest records to June 23, 2014. We included randomized controlled trials, controlled clinical trials and interrupted time series studies that assessed interventions designed to reduce the use of imaging in any clinical setting, including primary, emergency and specialist care. Two independent reviewers extracted data and assessed risk of bias. We used raw data on imaging rates to calculate summary statistics. Study heterogeneity prevented meta-analysis.Results:A total of 8500 records were identified through the literature search. Of the 54 potentially eligible studies reviewed in full, 7 were included in our review. Clinical decision support involving a modified referral form in a hospital setting reduced imaging by 36.8% (95% confidence interval [CI] 33.2% to 40.5%). Targeted reminders to primary care physicians of appropriate indications for imaging reduced referrals for imaging by 22.5% (95% CI 8.4% to 36.8%). Interventions that used practitioner audits and feedback, practitioner education or guideline dissemination did not significantly reduce imaging rates. Lack of power within some of the included studies resulted in lack of statistical significance despite potentially clinically important effects.Interpretation:Clinical decision support in a hospital setting and targeted reminders to primary care doctors were effective interventions in reducing the use of imaging for low-back pain. These are potentially low-cost interventions that would substantially decrease medical expenditures associated with the management of low-back pain.Current evidence-based clinical practice guidelines recommend against the routine use of imaging in patients presenting with low-back pain.^1–3 Despite this, imaging rates remain high,^4,5 which indicates poor concordance with these guidelines.^6,7Unnecessary imaging for low-back pain has been associated with poorer patient outcomes, increased radiation exposure and higher health care costs.⁸ No short- or long-term clinical benefits have been shown with routine imaging of the low back, and the diagnostic value of incidental imaging findings remains uncertain.^9–12 A 2008 systematic review found that imaging accounted for 7% of direct costs associated with low-back pain, which in 1998 translated to more than US$6 billion in the United States and £114 million in the United Kingdom.¹³ Current costs are likely to be substantially higher, with an estimated 65% increase in spine-related expenditures between 1997 and 2005.¹⁴Various interventions have been tried for reducing imaging rates among people with low-back pain. These include strategies targeted at the practitioner such as guideline dissemination,^15–17 education workshops,^18,19 audit and feedback of imaging use,^7,20,21 ongoing reminders⁷ and clinical decision support.^22–24 It is unclear which, if any, of these strategies are effective.²⁵ We conducted a systematic review to investigate the effectiveness of interventions designed to reduce imaging rates for the management of low-back pain.     

Food web structure changes with elevation but not rainforest stratum

Changes in species richness along elevational gradients are well documented. However, little is known about how trophic interactions between species and, in particular, the food webs that these interactions comprise, change with elevation. Here we present results for the first comparison of quantitative food webs in forest understorey and canopy along an elevational gradient. Replicate quantitative food webs were constructed for assemblages involving 23 species of cavity‐nesting Hymenoptera and 12 species of their parasitoids and kleptoparasites in subtropical rainforest in Australia. A total of 1589 insects were collected using trap nests across 20 plots distributed at sites ranging from 300 to 1100 m a.s.l. Insect abundance, insect diversity and parasitism rate generally decreased with increasing elevation. Food web structure significantly changed with elevation. In particular, weighted quantitative measures of linkage density, interaction evenness, nestedness (weighted NODF) and potential for enemy mediated interactions (PAC) decreased with increasing elevation, and network specialisation (H₂′) increased with increasing elevation, even after controlling for matrix size; but there was no change in weighted connectance. Changes in forest type and temperature along the elevational gradient are likely to be, at least partly, responsible for the patterns observed. We found no significant differences in insect abundance, insect diversity or parasitism rate between canopy and understorey. Furthermore, there were no differences in food web structure between strata. These results contribute further evidence to studies revealing changes in food web structure along natural environmental gradients and provide information that can potentially be used for predicting how communities may respond to climate change.     

Multiple environmental stressors increase the realised niche breadth of a forest‐dwelling fish

Understanding the determinants of species' niche breadth is important due to the negative relationship between niche breadth and extinction probability. Species tolerant to extremely harsh abiotic conditions (e.g. low pH or hypoxia) often have relatively small realised niches due to a trade‐off between abiotic and biotic stress tolerance, and are therefore particularly vulnerable to extinction. We hypothesised that tolerance to multiple extreme conditions (e.g. low pH, hypoxia and drought) in brown mudfish Neochanna apoda, would increase their realised niche breadth because each extreme would provide additive refuge against a dominant species, the banded kokopu Galaxias fasciatus. Fish distributions were surveyed in 65 peat‐swamp‐forest streams and pools in New Zealand, which varied in dissolved oxygen, acidity and hydroperiod. Mudfish distribution was extremely patchy, and almost completely allopatric with kokopu. Allopatry was driven mainly by pool hydroperiod; mudfish occupied 88 percent of temporary pools due to their tolerance of habitat drying, whereas kokopu were absent from temporary pools. Within permanent pools, mudfish occurrence was negatively related to pool oxygen and pH, whereas kokopu occurrence was positively related to these conditions. Pool conditions were independently distributed in the landscape, suggesting that each abiotic stressor offered additive refuge for mudfish from kokopu predation/competition. Consequently, the mudfish realised niche breadth depended on the number of abiotic factors driving their allopatry with kokopu. Given the widespread negative relationships between niche breadth and species extinction probabilities, our results indicate that tolerance to multiple stressors may play an important role in insuring species persistence against the multiple drivers of global environmental change.     

Using multiple‐source occurrence data to identify patterns and drivers of decline in arid‐dwelling Australian marsupials

Many of the world's terrestrial mammal species are imperilled, but recent extinctions and declines have been most severe in Australia. In particular, arid‐dwelling marsupials in a critical weight range (35–5500 g) have declined dramatically following European settlement. In the absence of long‐term monitoring, documenting these declines or distribution shifts and their causes often relies on occurrence data from multiple sources. Using atlas records, we compared the distributions of all currently extant marsupials in the critical weight range in Australia's arid Northern Territory pre‐ and post‐1975. For taxa with evidence of range contraction, we evaluated alternative hypotheses to explain this contraction (i.e. competition, predation, productivity, climate) using several techniques to improve our confidence in the results. Despite a substantial increase in the number of mammal records across the study region post‐1975, the bilby Macrotis lagotis and desert form of the common brushtail possum Trichosurus vulpecula appear to have contracted in distribution by 25 and 40%, respectively. These changes in distribution were best explained by hypotheses of competition and climate‐change, respectively. Macrotis lagotis was more likely to occur on land without a history of cattle grazing and with low rabbit densities, while T. vulpecula has contracted to parts of its distribution that experience cooler maximum temperatures over the hottest months of the year. For five other taxa (including the vulnerable black‐footed rock‐wallaby Petrogale lateralis) we recorded increases in distribution post‐1975, probably reflecting increased survey effort rather than actual range expansion. We conclude that models using multiple‐source occurrence data can provide key insights into the patterns and drivers of contemporary species’ declines, and represent useful tools for conservation.     

Oxidative stress conditions increase the frequency of de novo formation of the yeast [PSI+] prion

Prions are self‐perpetuating amyloid protein aggregates which underlie various neurodegenerative diseases in mammals and heritable traits in yeast. The molecular basis of how yeast and mammalian prions form spontaneously into infectious amyloid‐like structures is poorly understood. We have explored the hypothesis that oxidative stress is a general trigger for prion formation using the yeast [PSI⁺] prion, which is the altered conformation of the Sup35 translation termination factor. We show that the frequency of [PSI⁺] prion formation is elevated under conditions of oxidative stress and in mutants lacking key antioxidants. We detect increased oxidation of Sup35 methionine residues in antioxidant mutants and show that overexpression of methionine sulphoxide reductase abrogates both the oxidation of Sup35 and its conversion to the [PSI⁺] prion. [PSI⁺] prion formation is particularly elevated in a mutant lacking the Sod1 Cu,Zn‐superoxide dismutase. We have used fluorescence microscopy to show that the de novo appearance of [PSI⁺] is both rapid and increased in frequency in this mutant. Finally, electron microscopy analysis of native Sup35 reveals that similar fibrillar structures are formed in both the wild‐type and antioxidant mutants. Together, our data indicate that oxidative stress is a general trigger of [PSI⁺] formation, which can be alleviated by antioxidant defenses.