A critical review of the kinetic direct peptide reactivity assay (kDPRA) for skin sensitizer potency assessment - taking it forward.

It is widely recognized that the ability of chemicals to sensitize, and the potency of those chemicals that are sensitizers, is related to their ability to covalently modify protein in the skin. With the object of putting non-animal-based prediction of skin sensitization on a more quantitative footing, a recent paper describes the development of the kinetic Direct Protein Reactivity Assay (kDPRA), in which a matrix of peptide depletion values for different reaction times and test chemical concentrations is generated and analyzed so as to derive a reactivity parameter, logkmax, which is used to classify chemicals into one of two potency categories. The present paper demonstrates that the reaction chemistry is not always consistent with the mathematical analysis of the data matrix and the kDPRA protocol does not identify such cases. Consequently the derived logkmax value is not always mechanistically meaningful and its application to predict potency can lead to misleading conclusions. It is shown that by adopting a data analysis protocol based on conventional kinetics practice, the kDPRA can be made to provide more reliably meaningful and more extensive information that can be used for purposes such as potency estimation for deriving No Expected Sensitization Induction Level (NESILs) required for quantitative risk assessment (QRA), deriving quality specifications in terms of acceptable impurity levels, and development of structure-activity relationships. Secondly, the paper addresses applicability domain issues, in particular the problem of deciding whether or not the kDPRA is applicable for a given chemical.

Application of the dermal sensitization threshold concept to chemicals classified as high potency category for skin sensitization assessment of ingredients for consumer products.

Skin sensitization evaluation is a key part of the safety assessment of ingredients in consumer products, which may have skin sensitizing potential. The dermal sensitization threshold (DST) concept, which is based on the concept of the thresholds of toxicological concern, has been proposed for the risk assessment of chemicals to which skin exposure is very low level. There is negligible risk of skin sensitization if a skin exposure level for the substance of interest was below the reactive DST which would protect against 95% of protein-reactive chemicals. For the remaining 5%, the substance with the defined knowledge of chemical structure (i.e., High Potency Category (HPC) rules) needs to be excluded from the application. However, the DST value for HPC chemicals has not yet been proposed. In this study, we calculated the 95th percentile probabilities estimate from distributions of skin sensitization potency data and derived a novel DST for HPC chemicals (HPC DST) of 1.5 µg/cm2. This value presents a useful default approach for unidentified substances in ingredients considering, as a worst-case scenario, that the unidentified compound may be a potent skin sensitizer. Finally, we developed a novel risk assessment workflow incorporating the HPC DST along with the previously published DSTs.

Is a combination of assays really needed for non-animal prediction of skin sensitization potential? Performance of the GARD™ (Genomic Allergen Rapid Detection) assay in comparison with OECD guideline assays alone and in combination.

To meet regulatory requirements, and avoid or minimize animal testing, there is a need for non-animal methods to assess the potential of chemicals to cause skin sensitization. It is widely assumed that no one test will be sufficient and that combined data from several assays spanning key events from the adverse outcome pathway will be required. This paper challenges that assumption. The predictive performance of a single assay, the Genomic Allergen Rapid Detection (GARD™) assay, was compared with the performance, singly and in combination, of three formally validated non-animal approaches that appear as OECD test guidelines: the direct peptide reactivity assay (DPRA), the ARE-Nrf2 luciferase test method, and the human cell line activation test (h-CLAT). It is shown here that GARD™ alone outperforms each of DPRA, ARE-Nrf2 luciferase or h-CLAT, alone or in any combination as a 2 out of 3 strategy, in terms of sensitivity, specificity and accuracy. Based on the datasets analysed here, the sensitivity and specificity of GARD™ alone are 90-92% and 79-84% ("2 out of 3", 86% and 76%). Thus, in any situation where the 2 out of 3 strategy is considered adequate, GARD™ alone could be used with equal or better performance.

Landscape assessment of side channel plugs and associated cumulative side channel attrition across a large river floodplain.

Determining the influences of anthropogenic perturbations on side channel dynamics in large rivers is important from both assessment and monitoring perspectives because side channels provide critical habitat to numerous aquatic species. Side channel extents are decreasing in large rivers worldwide. Although riprap and other linear structures have been shown to reduce side channel extents in large rivers, we hypothesized that small "anthropogenic plugs" (flow obstructions such as dikes or berms) across side channels modify whole-river geomorphology via accelerating side channel senescence. To test this hypothesis, we conducted a geospatial assessment, comparing digitized side channel areas from aerial photographs taken during the 1950s and 2001 along 512 km of the Yellowstone River floodplain. We identified longitudinal patterns of side channel recruitment (created/enlarged side channels) and side channel attrition (destroyed/senesced side channels) across n = 17 river sections within which channels were actively migrating. We related areal measures of recruitment and attrition to the density of anthropogenic side channel plugs across river sections. Consistent with our hypothesis, a positive spatial relationship existed between the density of anthropogenic plugs and side channel attrition, but no relationship existed between plug density and side channel recruitment. Our work highlights important linkages among side channel plugs and the persistence and restoration of side channels across floodplain landscapes. Specifically, management of small plugs represents a low-cost, high-benefit restoration opportunity to facilitate scouring flows in side channels to enable the persistence of these habitats over time.

Stereovision Co-Registration in Image-Guided Spinal Surgery: Accuracy Assessment Using Explanted Porcine Spines.

BACKGROUND: Current methods of spine registration for image guidance have a variety of limitations related to accuracy, efficiency, and cost. OBJECTIVE: To define the accuracy of stereovision-mediated co-registration of a spinal surgical field. METHODS: A total of 10 explanted porcine spines were used. Dorsal soft tissue was removed to a variable degree. Bone screw fiducials were placed in each spine and high-resolution computed tomography (CT) scanning performed. Stereoscopic images were then obtained using a tracked, calibrated stereoscopic camera system; images were processed, reconstructed, and segmented in a semi-automated manner. A multistart registration of the reconstructed spinal surface with preoperative CT was performed. Target registration error (TRE) in the region of the laminae and facets was then determined, using bone screw fiducials not included in the original registration process. Each spine also underwent multilevel laminectomy, and TRE was then recalculated for varying amounts of bone removal. RESULTS: The mean TRE of stereovision registration was 2.19 ± 0.69 mm when all soft tissue was removed and 2.49 ± 0.74 mm when limited soft tissue removal was performed. Accuracy of the registration process was not adversely affected by laminectomy. CONCLUSION: Stereovision offers a promising means of registering an open, dorsal spinal surgical field. In this study, overall mean accuracy of the registration was 2.21 mm, even when bony anatomy was partially obscured by soft tissue or when partial midline laminectomy had been performed.

Non-animal assessment of skin sensitization hazard: Is an integrated testing strategy needed, and if so what should be integrated?

There is an expectation that to meet regulatory requirements, and avoid or minimize animal testing, integrated approaches to testing and assessment will be needed that rely on assays representing key events (KEs) in the skin sensitization adverse outcome pathway. Three non-animal assays have been formally validated and regulatory adopted: the direct peptide reactivity assay (DPRA), the KeratinoSens™ assay and the human cell line activation test (h-CLAT). There have been many efforts to develop integrated approaches to testing and assessment with the "two out of three" approach attracting much attention. Here a set of 271 chemicals with mouse, human and non-animal sensitization test data was evaluated to compare the predictive performances of the three individual non-animal assays, their binary combinations and the "two out of three" approach in predicting skin sensitization potential. The most predictive approach was to use both the DPRA and h-CLAT as follows: (1) perform DPRA - if positive, classify as sensitizing, and (2) if negative, perform h-CLAT - a positive outcome denotes a sensitizer, a negative, a non-sensitizer. With this approach, 85% (local lymph node assay) and 93% (human) of non-sensitizer predictions were correct, whereas the "two out of three" approach had 69% (local lymph node assay) and 79% (human) of non-sensitizer predictions correct. The findings are consistent with the argument, supported by published quantitative mechanistic models that only the first KE needs to be modeled. All three assays model this KE to an extent. The value of using more than one assay depends on how the different assays compensate for each other's technical limitations. Copyright © 2017 John Wiley & Sons, Ltd.

Sub-diffuse optical biomarkers characterize localized microstructure and function of cortex and malignant tumor.

This study uses a sub-diffusive light transport model to analyze fiber-optic measurements of reflectance spectra to recover endogenous tissue biomarkers and to correct raw fluorescence emissions for distortions from background optical properties. Measurements in tissue-simulating phantoms validated accurate recovery of the reduced scattering coefficient [(0.3-3.4 mm-1), error 10%], blood volume fraction [(1-3 vol%), error 7%], and a dimensionless metric of anisotropic scattering, γ, that is sensitive to submillimeter tissue ultrastructure [(1.29-2.06), error 11%]. In vivo sub-diffusive optical data acquired during clinical neurosurgeries characterize differences in microstructure (γ), perfusion (blood volume), and metabolism (PpIX fluorescence) between normal cortex and malignant tumor.

A predictive model of hospitalization cost after cerebral aneurysm clipping.

BACKGROUND: Cost containment is the cornerstone of the Affordable Care Act. Although studies have compared the cost of cerebral aneurysm clipping (CAC) and coiling, they have not focused on identification of drivers of cost after CAC, or prediction of its magnitude. The objective of the present study was to develop and validate a predictive model of hospitalization cost after CAC. METHODS: We performed a retrospective study involving CAC patients who were registered in the Nationwide Inpatient Sample (NIS) database from 2005 to 2010. The two cohorts of ruptured and unruptured aneurysms underwent 1:1 randomization to create derivation and validation subsamples. Regression techniques were used for the creation of a parsimonious predictive model. RESULTS: Of the 7798 patients undergoing CAC, 4505 (58%) presented with unruptured and 3293 (42%) with ruptured aneurysms. Median hospitalization cost was US$24,398 (IQR $17,079 to $38,249) and $73,694 (IQR $46,270 to $115,128) for the two cohorts, respectively. Common drivers of cost identified in the multivariate analyses included the following: length of stay, number of admission diagnoses and procedures, hospital size and region, and patient income. The models were validated in independent cohorts and demonstrated final R(2) values very similar to the initial models. The predicted and observed values in the validation cohort demonstrated good correlation. CONCLUSIONS: This national study identified significant drivers of hospitalization cost after CAC. The presented model can be utilized as an adjunct in the cost containment debate and the creation of data driven policies.

Statins and subarachnoid hemorrhage in Medicare patients with unruptured cerebral aneurysms.

BACKGROUND: Statins have been shown to decrease aneurysm progression and rupture in two experimental settings: animals with cerebral aneurysm and humans with abdominal aortic aneurysms. AIMS: To investigate statin use and outcomes in humans with unruptured cerebral aneurysms through Medicare administrative data. METHODS: We used a 40% random sample Medicare denominator file and corresponding inpatient, outpatient (2003-2011), and prescription (2006-2011) claims to conduct a retrospective cohort study of patients diagnosed with unruptured cerebral aneurysms, between 2003 and 2011. We used propensity score-adjusted models to investigate the association between statin use and risk of subarachnoid hemorrhage. Secondary analyses repeated the main models stratified on tobacco use status and separately assessed other composite outcomes. RESULTS: We identified 28 931 patients with unruptured cerebral aneurysms (average age 72·0 years, 72·6% female); mean follow-up was 30·0 months; 41·3% used statins. Overall, 593 patients developed subarachnoid hemorrhage, and 703 underwent treatment before subarachnoid hemorrhage. Current or recent statin use was not associated with a difference in subarachnoid hemorrhage risk (odds ratio, 1·03; 95% conflict of interest 0·86-1·23); models stratified on tobacco use status were nearly identical. No association was observed between statin use and the composite outcome of subarachnoid hemorrhage or aneurysm treatment (odds ratio, 0·94; 95% conflict of interest, 0·84-1·06). The risk of subarachnoid hemorrhage or out-of-hospital death was lower among statin users (odds ratio, 0·69; 95% conflict of interest, 0·64-0·74). CONCLUSIONS: Statin use by patients with unruptured cerebral aneurysms was not associated with subarachnoid hemorrhage risk. Given the prior animal experimental studies demonstrating a protective effect, further prospective studies are needed to investigate the potential relationship.

Advancing Molecular-Guided Surgery through probe development and testing in a moderate cost evaluation pipeline.

Molecular guided oncology surgery has the potential to transform the way decisions about resection are done, and can be critically important in areas such as neurosurgery where the margins of tumor relative to critical normal tissues are not readily apparent from visual or palpable guidance. Yet there are major financial barriers to advancing agents into clinical trials with commercial backing. We observe that development of these agents in the standard biological therapeutic paradigm is not viable, due to the high up front financial investment needed and the limitations in the revenue models of contrast agents for imaging. The hypothesized solution to this problem is to develop small molecular biologicals tagged with an established fluorescent reporter, through the chemical agent approval pathway, targeting a phase 0 trials initially, such that the initial startup phase can be completely funded by a single NIH grant. In this way, fast trials can be completed to de-risk the development pipeline, and advance the idea of fluorescence-guided surgery (FGS) reporters into human testing. As with biological therapies the potential successes of each agent are still moderate, but this process will allow the field to advance in a more stable and productive manner, rather than relying upon isolated molecules developed at high cost and risk. The pathway proposed and tested here uses peptide synthesis of an epidermal growth factor receptor (EGFR)-binding Affibody molecules, uniquely conjugated to IRDye 800CW, developed and tested in academic and industrial laboratories with well-established records for GMP production, fill & finish, toxicity testing, and early phase clinical trials with image guidance.

Towards AOP application--implementation of an integrated approach to testing and assessment (IATA) into a pipeline tool for skin sensitization.

Since the OECD published the Adverse Outcome Pathway (AOP) for skin sensitization, many efforts have focused on how to integrate and interpret nonstandard information generated for key events in a manner that can be practically useful for decision making. These types of frameworks are known as Integrated Approaches to Testing and Assessment (IATA). Here we have outlined an IATA for skin sensitization which focuses on existing information including non testing approaches such as QSAR and read-across. The IATA was implemented into a pipeline tool using OASIS technology to provide a means of systematically collating and compiling relevant information which could be used in an assessment of skin sensitization potential. A test set of 100 substances with available skin sensitization information was profiled using the pipeline IATA. In silico and in chemico profiling information alone was able to correctly predict skin sensitization potential, with a preliminary accuracy of 73.85%. Information from other relevant endpoints (e.g., Ames mutagenicity) was found to improve the accuracy (to 87.6%) when coupled with a reaction chemistry mechanistic understanding. This pipeline platform could be useful in the assessment of skin sensitization potential and marks a step change in how non testing approaches can be practically applied.

Fragmentation of care and the use of head computed tomography in patients with ischemic stroke.

BACKGROUND: Computed tomographic (CT) scans are central diagnostic tests for ischemic stroke. Their inefficient use is a negative quality measure tracked by the Centers for Medicare and Medicaid Services. METHODS AND RESULTS: We performed a retrospective analysis of Medicare fee-for-service claims data for adults admitted for ischemic stroke from 2008 to 2009, with 1-year follow-up. The outcome measures were risk-adjusted rates of high-intensity CT use (≥4 head CT scans) and risk- and price-adjusted Medicare expenditures in the year after admission. The average number of head CT scans in the year after admission, for the 327 521 study patients, was 1.94, whereas 11.9% had ≥4. Risk-adjusted rates of high-intensity CT use ranged from 4.6% (Napa, CA) to 20.0% (East Long Island, NY). These rates were 2.6% higher for blacks than for whites (95% confidence interval, 2.1%-3.1%), with considerable regional variation. Higher fragmentation of care (number of different doctors seen) was associated with high-intensity CT use. Patients living in the top quintile regions of fragmentation experienced a 5.9% higher rate of high-intensity CT use, with the lowest quintile as reference; the corresponding odds ratio was 1.77 (95% confidence interval, 1.71-1.83). Similarly, 1-year risk- and price-adjusted expenditures exhibited considerable regional variation, ranging from $31 175 (Salem, MA) to $61 895 (McAllen, TX). Regional rates of high-intensity CT scans were positively associated with 1-year expenditures (r=0.56; P<0.01). CONCLUSIONS: Rates of high-intensity CT use for patients with ischemic stroke reflect wide practice patterns across regions and races. Medicare expenditures parallel these disparities. Fragmentation of care is associated with high-intensity CT use.

Integrated testing and assessment approaches for skin sensitization: a commentary.

A Bayesian integrated testing strategy (ITS) approach, aiming to assess skin sensitization potency, has been presented, in which data from various types of in vitro assays are integrated and assessed in combination for their ability to predict in vivo skin sensitization data. Here we discuss this approach and compare it to our quantitative mechanistic modeling (QMM) approach based on physical organic chemistry. The main findings of the Bayesian study are consistent with our chemistry-based approach and our previously published assessment of the key determinants of sensitization potency, in particular the relatively high predictive value found for chemical reactivity data and the relatively low predictive value for bioavailability parameters. As it stands at present the Bayesian approach does not utilize the full range of predictive capability that is already available, and aims only to assign potency categories rather than numerical potency values per se. In contrast, for many chemicals the QMM approach can already provide numerical potency predictions. However, the Bayesian approach may have potential for those chemicals where a chemistry modeling approach cannot provide a complete answer (e.g. pro-electrophiles whose in cutaneo activation cannot currently be modeled confidently). Nonetheless, our main message is of the importance of leveraging chemistry insights and read-across approaches to the fullest extent possible.

Predicting inpatient complications from cerebral aneurysm clipping: the Nationwide Inpatient Sample 2005-2009.

OBJECT: Precise delineation of individualized risks of morbidity and mortality is crucial in decision making in cerebrovascular neurosurgery. The authors attempted to create a predictive model of complications in patients undergoing cerebral aneurysm clipping (CAC). METHODS: The authors performed a retrospective cohort study of patients who had undergone CAC in the period from 2005 to 2009 and were registered in the Nationwide Inpatient Sample (NIS) database. A model for outcome prediction based on preoperative individual patient characteristics was developed. RESULTS: Of the 7651 patients in the NIS who underwent CAC, 3682 (48.1%) had presented with unruptured aneurysms and 3969 (51.9%) with subarachnoid hemorrhage. The respective inpatient postoperative risks for death, unfavorable discharge, stroke, treated hydrocephalus, cardiac complications, deep vein thrombosis, pulmonary embolism, and acute renal failure were 0.7%, 15.3%, 5.3%, 1.5%, 1.3%, 0.6%, 2.0%, and 0.1% for those with unruptured aneurysms and 11.5%, 52.8%, 5.5%, 39.2%, 1.7%, 2.8%, 2.7%, and 0.8% for those with ruptured aneurysms. Multivariate analysis identified risk factors independently associated with the above outcomes. A validated model for outcome prediction based on individual patient characteristics was developed. The accuracy of the model was estimated using the area under the receiver operating characteristic curve, and it was found to have good discrimination. CONCLUSIONS: The featured model can provide individualized estimates of the risks of postoperative complications based on preoperative conditions and can potentially be used as an adjunct in decision making in cerebrovascular neurosurgery.

Institutional charges and disparities in outpatient brain biopsies in four US States: the State Ambulatory Database (SASD).

Several groups have demonstrated the safety of ambulatory brain biopsies, with no patients experiencing complications related to early discharge. Although they appear to be safe, the reasons factoring into the selection of patients have not been investigated. We performed a cross-sectional study involving 504 patients who underwent outpatient and 10,328 patients who underwent inpatient brain biopsies and were registered in State Ambulatory Surgery Databases and State Inpatient Databases respectively for four US States (New York, California, Florida, North Carolina). In a multivariate analysis private insurance (OR 2.45, 95 % CI, 1.85, 3.24), was significantly associated with outpatient procedures. Higher Charlson Comorbidity Index (OR 0.16, 95 % CI, 0.08, 0.32), high income (OR 0.37, 95 % CI, 0.26, 0.53), and high volume hospitals (OR 0.30, 95 % CI, 0.23, 0.39) were associated with a decreased chance of outpatient procedures. No sex, or racial disparities were observed. Institutional charges were significantly less for outpatient brain biopsies. There was no difference in the rate of 30-day postoperative readmissions among inpatient and outpatient procedures. The median charge for inpatient surgery was 51,316 as compared to 12,266 for the outpatient setting (P < 0.0001, Student's t test). Access to ambulatory brain biopsies appears to be more common for patients with private insurance and less comorbidities, in the setting of lower volume hospitals. Further investigation is needed in the direction of mapping these disparities in resource utilization.

Workshop: use of "read-across" for chemical safety assessment under REACH.

Read-across has generated much attention, since it may be used as an alternative approach for addressing the information requirements under REACH. Experience in the application of "read-across" has undoubtedly been gained within the context of the 2010 registrations (>1000 tonnes/annum). Industry, European Chemicals Agency (ECHA) and EU Member States all conceptually accept read-across approaches but difficulties still remain in applying them consistently in practice. A workshop on the 'Use of Read-Across for Chemical Safety Assessment under REACH', organised by ECHA with the active support of Cefic LRI was held on the 3rd October 2012 to gain insight on how ECHA evaluates read-across justifications, to share Industry experiences with read-across approaches and to discuss practical strategies to help develop scientifically valid read-across for future submissions.

Integrated decision-tree testing strategies for environmental toxicity with respect to the requirements of the EU REACH legislation.

Liverpool John Moores University and FRAME recently conducted a research project sponsored by Defra on the status of alternatives to animal testing with regard to the European Union REACH (Registration, Evaluation and Authorisation of Chemicals) system for safety testing and risk assessment of chemicals. The project covered all the main toxicity endpoints associated with the REACH system. This paper focuses on the prospects for using alternative methods (both in vitro and in silico) for environmental (aquatic) toxicity testing. The manuscript reviews tests based on fish cells and cell lines, fish embryos, lower organisms, and the many expert systems and QSARs for aquatic toxicity testing. Ways in which reduction and refinement measures can be used are also discussed, including the Upper Threshold Concentration--Step Down (UTC) approach, which has recently been retrospectively validated by ECVAM and subsequently endorsed by the ECVAM Scientific Advisory Committee (ESAC). It is hoped that the application of this approach could reduce the number of fish used in acute toxicity studies by around 65-70%. Decision-tree style integrated testing strategies are also proposed for acute aquatic toxicity and chronic toxicity (including bioaccumulation), followed by a number of recommendations for the future facilitation of aquatic toxicity testing with respect to environmental risk assessment.