Universal Thresholds Research Articles

Assessing the relationship between vector indices and dengue transmission: a systematic review of the evidence.

BackgroundDespite doubts about methods used and the association between vector density and dengue transmission, routine sampling of mosquito vector populations is common in dengue-endemic countries worldwide. This study examined the evidence from published studies for the existence of any quantitative relationship between vector indices and dengue cases.Methodology/Principal FindingsFrom a total of 1205 papers identified in database searches following Cochrane and PRISMA Group guidelines, 18 were included for review. Eligibility criteria included 3-month study duration and dengue case confirmation by WHO case definition and/or serology.A range of designs were seen, particularly in spatial sampling and analyses, and all but 3 were classed as weak study designs. Eleven of eighteen studies generated Stegomyia indices from combined larval and pupal data. Adult vector data were reported in only three studies. Of thirteen studies that investigated associations between vector indices and dengue cases, 4 reported positive correlations, 4 found no correlation and 5 reported ambiguous or inconclusive associations. Six out of 7 studies that measured Breteau Indices reported dengue transmission at levels below the currently accepted threshold of 5.Conclusions/SignificanceThere was little evidence of quantifiable associations between vector indices and dengue transmission that could reliably be used for outbreak prediction. This review highlighted the need for standardized sampling protocols that adequately consider dengue spatial heterogeneity. Recommendations for more appropriately designed studies include: standardized study design to elucidate the relationship between vector abundance and dengue transmission; adult mosquito sampling should be routine; single values of Breteau or other indices are not reliable universal dengue transmission thresholds; better knowledge of vector ecology is required.

Analysis of allelic drop-out using the Identifiler(®) and PowerPlex(®) 16 forensic STR typing systems.

Low-template (LT) DNA profiles continue to present interpretational challenges to the forensic community. Whether the LT contribution comprises the main profile, or whether it is present as the minor component of a mixture, ambiguity arises from the possibility that alleles present in the biological sample may not be detected in the resulting DNA profile. This phenomenon is known as allelic drop-out. This ambiguity complicates both the assessment of the potential number of contributors and estimation of the weight of the DNA evidence for or against specific propositions. One solution to estimating the weight of the evidence is to use a likelihood ratio (LR) that incorporates the probability of allelic drop-out P(DO) estimated for the specific evidence sample under consideration. However, although a vast repository of data exists, few empirical studies to determine allelic drop-out probabilities have been performed to date. Here we characterized patterns of allelic drop-out in single-source samples using both universal and run-specific analytical thresholds. Not surprisingly, we found fewer instances of apparent drop-out when using a lower (run-specific) detection threshold. Also, unsurprisingly, a positive correlation exists between allele drop-out and allele length, even in good quality samples. We used logistic regression to model the fraction of alleles that dropped out of a profile as a function of the average height of the detected peaks. The equation derived from the logistic regression model allowed us to estimate the expected drop-out probability for an evidentiary sample based on the average peak height of the profile. We show that the LRs calculated using the estimated drop-out probabilities were similar to those calculated using the benchmark drop-out probabilities, suggesting that the estimates of the drop-out probability are accurate and useful. This trend holds even when using the data from the PowerPlex(®) 16 typing system to estimate the drop-out probability for an Identifiler(®) profile, and vice versa. Thus we demonstrate that use of a LR that incorporates empirically estimated allelic drop-out probabilities provides a reliable means for extracting additional information from LT forensic DNA profiles.

A data-driven threshold for wavelet sliding window denoising in mechanical fault detection

Wavelet denoising is an effective approach to extract fault features from strong background noise. It has been widely used in mechanical fault detection and shown excellent performance. However, traditional thresholds are not suitable for nonstationary signal denoising because they set universal thresholds for different wavelet coefficients. Therefore, a data-driven threshold strategy is proposed in this paper. First, the signal is decomposed into different subbands by wavelet transformation. Then a data-driven threshold is derived by estimating the noise power spectral density in different subbands. Since the data-driven threshold is dependent on the noise estimation and adapted to data, it is more robust and accurate for denoising than traditional thresholds. Meanwhile, sliding window method is adopted to set a flexible local threshold. When this method was applied to simulation signal and an inner race fault diagnostic case of dedusting fan bearing, the proposed method has good result and provides valuable advantages over traditional methods in the fault detection of rotating machines.

Patient-specific thresholds of intracranial pressure in severe traumatic brain injury

Based on continuous monitoring of the pressure reactivity index (PRx), the authors defined individualized intracranial pressure (ICP) thresholds by graphing the relationship between ICP and PRx. These investigators hypothesized that an "ICP dose" based on individually assessed ICP thresholds would correlate more closely with the 6-month outcome when compared with ICP doses derived by the recommended universal thresholds of 20 and 25 mm Hg. This study was a retrospective analysis of prospectively collected data from 327 patients with severe traumatic brain injury. Individualized thresholds were visually identified from graphs of PRx versus ICP; PRx > 0.2 was the cutoff. Intracranial pressure doses were then computed as the cumulative area under the curve above the defined thresholds in graphing ICP versus time. The term "Dose 20" (D20) was used to refer to an ICP threshold of 20 mm Hg; the markers D25 and DPRx were calculated similarly. Separate logistic regression models were fit with death as the outcome and each dose as the predictor, both alone and adjusted for covariates. The discriminative ability of each dose for mortality was assessed by receiver operating characteristic AUC analysis in which 5-fold cross-validation was used. A clearly identifiable PRx-based threshold was possible in 224 patients (68%). The DPRx (AUC 0.81, 95% CI 0.74-0.87) was found to have the highest area under the curve (AUC) over both D20 (0.75, 95% CI 0.68-0.81) and D25 (0.77, 95% CI 0.70-0.83); in the cross-validation model, DPRx remained the best discriminator of mortality (DPRx: AUC 0.77 [95% CI 0.68-0.89]; D20: 0.72 [95% CI 0.66-0.81]; and D25: 0.65 [95% CI 0.56-0.73]). The authors explored the importance of different ICP thresholds for outcome by calculating patient-specific ICP doses based on the continuous monitoring of cerebrovascular pressure reactivity. They found that these individualized doses of intracranial hypertension were stronger predictors of death than doses derived from the universal thresholds of 20 and 25 mm Hg. The PRx could offer a method that can be directed toward individualizing the ICP threshold.

A systematic review of factors associated with the deferral of donors failing to meet low haemoglobin thresholds

Blood donors attending a donation session may be deemed ineligible to donate blood due to a failure to meet low haemoglobin (Hb) thresholds. Several studies have identified factors associated with a donor falling below these Hb thresholds. A review of these factors will inform future prospective studies and form the basis for predictive models of deferral due to low Hb. Studies were identified by searching MEDLINE, EMBASE, The Cochrane Library and the WHO International Clinical Trials Registry from 1980 to September 2012. Demographic data, donor history, haematological/biological factors and the primary outcome of deferral due to low Hb were extracted. Analyses were descriptive and quantitative; pooled odds ratios (ORs) were obtained by meta-analysis. Fifty-five studies met the inclusion criteria. A consistently higher rate of low Hb deferral was reported in females compared with males; meta-analysis showed a significantly greater risk of deferral due to low Hb in females compared with males in studies with universal Hb thresholds for males and females (OR 14.91, 95% confidence interval (CI) 12.82-17.34) and in studies with sex-specific Hb thresholds (OR 8.19, 95% CI 4.88-13.74). Greater rates of deferral due to low Hb were also associated with increasing age, higher ambient temperature, low body weight, shorter inter-donation interval and in donors of Hispanic or African descent. This work will help to define the criteria that should be considered in any large scale study of blood donor deferral, especially those that measure or aim to change failure to meet low Hb thresholds.

CKD and Cardiovascular Disease in the Atherosclerosis Risk in Communities (ARIC) Study: Interactions With Age, Sex, and Race

Estimated glomerular filtration rate (eGFR) and albuminuria are central for diagnosis, staging, and risk evaluation in chronic kidney disease (CKD). Universal thresholds regardless of age, sex, and race are recommended, but relatively little is known about how these demographic factors alter the relationship of eGFR and albuminuria to cardiovascular outcomes. Observational cohort study. 11,060 whites and blacks aged 52-75 years in the Atherosclerosis Risk in Communities (ARIC) Study with median follow-up of 11.2 years. eGFR by the CKD-EPI (CKD Epidemiology Collaboration) creatinine equation (reference, 95 mL/min/1.73 m(2)) and urinary albumin-creatinine ratio (ACR; reference, 5 mg/g). Cardiovascular events (coronary disease, stroke, and heart failure) and all-cause mortality. Adjusted HRs associated with eGFR and ACR in subgroups according to age, sex, and race. Cardiovascular risk significantly increased at eGFR <70 mL/min/1.73 m(2) in all subgroups according to age (<65 vs ≥65 years), sex, and race (P for interaction >0.2 for these subgroups; eg, at eGFR of 30 mL/min/1.73 m(2), the adjusted HR was 2.19 [95% CI, 1.10-4.35] at age 52-64 years vs 2.23 [95% CI, 1.33-3.72] at age 65-75 years). Results were similar for mortality. Log(ACR) was associated linearly with cardiovascular risk without threshold effects in all subgroups, with some quantitative interactions. HRs according to ACR tended to be lower in men versus women (eg, at ACR of 40 mg/g, 1.18 [95% CI, 0.98-1.41] vs 1.77 [95% CI, 1.45-2.15]) and in the older versus younger population (1.24 [95% CI, 1.04-1.49] vs 1.73 [95% CI, 1.42-2.12]; P for interaction <0.01 for sex and age). Less evident interactions were observed for mortality. Single measurement of eGFR with creatinine and ACR and relatively narrow age range. The associations of eGFR and ACR with cardiovascular events were largely similar, with some quantitative interactions, in age, sex, and racial subgroups, generally supporting universal thresholds of GFR and ACR for CKD definition/staging.

Policy innovation and tertiary education graduation rates: a cross-country analysis

This study extends Trow’s theory of higher education development to examine changes in national-level tertiary education graduation rates. Applying Trow’s framework we arrive at three stages: (1) elite systems with gross tertiary graduation rates less than 15%, (2) massified systems with gross tertiary graduation rates between 15% and 50%, and (3) universal systems with gross tertiary graduation rates above 50%. This study conducts event history analyses using a unique cross-national panel dataset, which spans the time period from 1999–2005. Following the work of Berry and Berry, our event history analyses model both the internal features of each country and the influence that nation-states have on each other with regard to setting tertiary education graduation policy. We find significant influences of both internal determinants and diffusion factors. We find a positive, significant effect of membership in the OECD consistent across both the massified and universal thresholds. We also find a positive, significant effect of having a more stable political system for crossing the 15% threshold. In addition, being located near a pioneering nation, the UK, has a positive, significant effect of crossing the 50% threshold.

Child Abuse Intervention: Reporting Protocols in the New Zealand Health Sector

Reporting child abuse has been the subject of a long running socio-legal debate in New Zealand. Its most recent iteration is the Government’s 2012 proposal to require all agencies working with children to institute protocols for referring maltreatment. However, New Zealand’s health sector already operates under such a regime, with little investigation of its success. This article offers a critical analysis of the sector’s protocol framework. It argues that the protocols have established a detailed and enforceable structure for referring maltreatment, but identifies inconsistencies that risk discrepancies in the treatment of vulnerable children. Accordingly, the article recommends that the framework be rationalised and suggests that the legislative proposal include universal thresholds for referral to avoid replication of this problem on a national scale.

Validity of Food Consumption Indicators in the Lao Context: Moving toward Cross-Cultural Standardization

Cross-cultural validity of food security indicators is commonly presumed without questioning the suitability of generic indicators in different geographic settings. However, ethnic differences in the perception of and reporting on, food insecurity, as well as variations in consumption patterns, may limit the comparability of results. Although research on correction factors for standardization of food security indicators is in process, so far no universal indicator has been identified. The current paper considers the ability of the Food Consumption Score (FCS) developed by the World Food Programme in southern Africa in 1996 to meet the requirement of local cultural validity in a Laotian context. The analysis is based on research that seeks to identify options for correcting possible biases linked to cultural disparities. Based on the results of a household survey conducted in different agroecological zones of Laos in 2009, the FCS was validated against a benchmark of calorie consumption. Changing the thresholds and excluding small amounts of food items consumed were tested as options to correct for biases caused by cultural disparities. The FCS in its original form underestimates the food insecurity level in the surveyed villages. However, the closeness of fit of the FCS to the benchmark classification improves when small amounts of food items are excluded from the assessment. Further research in different cultural settings is required to generate more insight into the extent to which universal thresholds can be applied to dietary diversity indicators with or without locally determined correction factors such as the exclusion of small amounts of food items.

Clinical Practice Guidelines for Endovascular Abdominal Aortic Aneurysm Repair: Written by the Standards of Practice Committee for the Society of Interventional Radiology and Endorsed by the Cardiovascular and Interventional Radiological Society of Europe and the Canadian Interventional Radiology Association

From the Department of Radiology, Division of Vascular Imaging and Intervention (T.G.W., S.P.K., K.Y., S.W.), Massachusetts General Hospital, Boston, Massachusetts; Department of Medical Imaging (S.K.), Scarborough General Hospital, Toronto, Ontario, Canada; Department of Interventional Radiology (P.D.), West Allis Memorial Hospital, Milwaukee, Wisconsin; Department of Radiology, Division of Interventional Radiology (B.J.D.), University of Maryland Medical Center, Baltimore, Maryland; Department of Radiology (S.C.R.), University of California San Diego Medical Center, San Diego, California; and Department of Radiology (J.F.C.), Geisinger Health System, Danville, Pennsylvania. Received May 4, 2010; final revision received May 24, 2010; accepted July 11, 2010. Address corre-

Quality Improvement Guidelines for the Treatment of Lower Extremity Deep Vein Thrombosis with Use of Endovascular Thrombus Removal

Suresh Vedantham, MD, Akhilesh K. Sista, MD, Seth J. Klein, MD, Lina Nayak, MD, Mahmood K. Razavi, MD, Sanjeeva P. Kalva, MD, Wael E. Saad, MD, Sean R. Dariushnia, MD, Drew M. Caplin, MD, Christine P. Chao, MD, Suvranu Ganguli, MD, T. Gregory Walker, MD, and Boris Nikolic, MD, MBA, for the Society of Interventional Radiology and Cardiovascular and Interventional Radiological Society of Europe Standards of Practice Committees

Bifurcations, order and chaos in the Bose–Einstein condensation of dipolar gases

We apply a variational technique to solve the time-dependent Gross–Pitaevskii equation for Bose–Einstein condensates in which an additional dipole–dipole interaction between the atoms is present with the goal of modelling the dynamics of such condensates. We show that universal stability thresholds for the collapse of the condensates correspond to bifurcation points where always two stationary solutions of the Gross–Pitaevskii equation disappear in a tangent bifurcation, one dynamically stable and the other unstable. We point out that the thresholds also correspond to ‘exceptional points’, i.e. branching singularities of the Hamiltonian. We analyse the dynamics of excited condensate wave functions via Poincaré surfaces of section for the condensate parameters and find both regular and chaotic motion, corresponding to (quasi-) periodically oscillating and irregularly fluctuating condensates, respectively. Stable islands are found to persist up to energies well above the saddle point of the mean-field energy, alongside collapsing modes. The results are applicable when the shape of the condensate is axisymmetric.

Waist circumference percentile thresholds for identifying adolescents with insulin resistance in clinical practice

We formally evaluated waist circumference (WC) percentile cutoffs for predicting insulin resistance (IR) and whether different cutoffs should be used for adolescents of different race/ethnicities. Analysis was performed for 1575 adolescents aged 12-18 yr from the National Health and Nutrition Examination Survey 1999-2002. Adolescents were classified as having IR if they had a homeostasis model assessment-insulin resistance level, a validated measure of IR, of >4.39, and WC percentile was classified according to previously published universal (all races combined) and race/ethnicity-specific WC percentile cutoffs. Receiver operating characteristic curves for predicting IR were constructed comparing the race/ethnicity-specific vs. universal WC percentile cutoffs, and area under the curve (AUC) was calculated. Comparing universal with race/ethnicity-specific WC percentiles, there were no significant differences in AUC for Black, Mexican-American, or White adolescents. Because race/ethnicity-specific thresholds did not discriminate better than universal WC thresholds, universal WC thresholds may be used effectively to identify adolescents with IR in primary care practices. A WC > or =75th or > or =90th percentile for all race/ethnicities combined would be appropriate to apply in clinical practice for identification of adolescents with IR, a risk factor for development of type 2 diabetes.

Towards a conceptual and operational union of bacterial systematics, ecology, and evolution.

To completely understand the ecology of a bacterial community, we need to identify its ecologically distinct populations (ecotypes). The greatest promise for enumerating a community's constituent ecotypes is held by molecular approaches that identify bacterial ecotypes as DNA sequence clusters. These approaches succeed when ecotypes correspond with sequence clusters, but some models of bacterial speciation predict a one-to-many and others a many-to-one relationship between ecotypes and sequence clusters. A further challenge is that sequence-based phylogenies often contain a hierarchy of clusters and subclusters within clusters, and there is no widely accepted theory to guide systematists and ecologists to the size of cluster most likely to correspond to ecotypes. While present systematics attempts to use universal thresholds of sequence divergence to help demarcate species, the recently developed 'community phylogeny' approach assumes no universal thresholds, but demarcates ecotypes based on the analysis of a lineage's evolutionary dynamics. Theory-based approaches like this one can give a conceptual framework as well as operational criteria for hypothesizing the identity and membership of ecotypes from sequence data; ecology-based approaches can then confirm that the putative ecotypes are actually ecologically distinct. Bacterial ecotypes that are demonstrated to have a history of coexistence as ecologically distinct lineages (based on sequence analysis) and as a prognosis of future coexistence (based on ecological differences), are the fundamental units of bacterial ecology and evolution, and should be recognized by bacterial systematics.

Quality Improvement Guidelines for the Treatment of Lower Extremity Deep Vein Thrombosis with Use of Endovascular Thrombus Removal

Quality Improvement Guidelines for the Treatment of Lower Extremity Deep Vein Thrombosis with Use of Endovascular Thrombus Removal

Blood volume monitoring in intermittent hemodialysis for acute renal failure

Although hypotension commonly accompanies intermittent hemodialysis for acute renal failure (ARF) in the intensive care unit (ICU), little is known about how it may be prevented. Online relative blood volume (RBV) monitoring has been used to reduce hypotension in chronic hemodialysis, but is of unproven benefit in ARF. This study tested the hypothesis that hypotension is predictable using online RBV monitoring in patients dialyzed for ARF in an ICU setting. The primary definition of hypotension was mean arterial pressure (MAP) <70 mm Hg; systolic blood pressure (SBP) <100 mm Hg was used as a secondary outcome. Fifty-seven treatments were prospectively studied in twenty consecutive adult patients treated with intermittent hemodialysis. RBV was continuously measured using the Hemoscan device (Gambro). Hypotension occurred in 30% of treatments as defined by MAP, and 18% as defined by SBP. There was no evidence of patient-specific or universal RBV thresholds that were associated with hypotension. Analysis using the kappa statistic showed that concordance of RBV and hypotension (that is, RBV falling prior to hypotensive episodes rather than rising or remaining stable) was no greater than chance. RBV and rate of change in RBV slopes did not predict hypotension as a dichotomous outcome, and were not correlated with MAP or SBP whether autocorrelation was corrected for or neglected. Substituting rate of change in RBV (RBV slopes) for absolute RBV values did not improve predictive power. These results suggest that strategies based on online RBV monitoring are unlikely to reduce hypotension in intermittent hemodialysis for ARF that is delivered through central venous catheters.

Phantoms and automated system for testing the resolution of ultrasound scanners

Tissue-mimicking phantoms and an automated system have been developed for testing the resolution performance of ultrasound scanners by determining detectability of low to higher contrast spherical lesions over the entire depth of field. Axial, lateral and elevational resolutions are accounted for simultaneously and equally. Tissue-mimicking spherical simulated lesions are either 3 or 4 mm in diameter and have one of four different intrinsic material contrasts. For each diameter and contrast, there is a set of 109 lesions in a regular array with coplanar centers extending from 0.5–15.5 cm in depth. With the scan slice superimposed on the spheres, the image is frame-grabbed for automated analysis. A diameter-dependent lesion signal-to-noise ratio is computed for each pixel position in the image, excluding a 5-mm boundary. Two universal thresholds, resulting from maximization of agreement between the automated system and human observers, give rise to a depth range, or “resolution zone”, over which detection exists for each type lesion.

Automatic Image Annotation Using Adaptive Color Classification

We describe a system which automatically annotates images with a set of prespecified keywords, based on supervised color classification of pixels intoNprespecified classes using simple pixelwise operations. The conditional distribution of the chrominance components of pixels belonging to each class is modeled by a two-dimensional Gaussian function, where the mean vector and the covariance matrix for each class are estimated from appropriate training sets. Then, a succession of binary hypothesis tests with image-adaptive thresholds has been employed to decide whether each pixel in a given image belongs to one of the predetermined classes. To this effect, a universal decision threshold is first selected for each class based on receiver operating characteristics (ROC) curves quantifying the optimum “true positive” vs “false positive” performance on the training set. Then, a new method is introduced for adapting these thresholds to the characteristics of individual input images based on histogram cluster analysis. If a particular pixel is found to belong to more than one class, a maximuma posterioriprobability (MAP) rule is employed to resolve the ambiguity. The performance improvement obtained by the proposed adaptive hypothesis testing approach over using universal decision thresholds is demonstrated by annotating a database of 31 images.

A Comparison of Vascular Pulsatility and Resistive Indices in Gynecological Tumor Detection Using Transvaginal Ultrasound

Transvaginal Doppler ultrasound was applied to 85 patients to determine whether pelvic malignancy could be predicted by pulsatility (PI) and resistive indices (RI) of intratu-moral, ovarian, and uterine vessels. Thirty-five of the patients in the study were confirmed to have malignant tumors of the cervix, uterus, or ovary. The mean intratu-moral PI and RI from malignant tumors were 0.81 (SD 0.24; range 0.3-1.2) and 0.54 (SD 0.10; range 0.27-0.62), respectively. They were significantly lower than those of the benign group (both with P &lt; 0.05, Student's t test). Thresholds of intratumoral PI &lt; 1.0 and RI &lt; 0.6, which differentiate malignant from benign tumors, were determined by using two receiver operating characteristic (ROC) curves. These gave a sensitivity of 94% and specificity of 63% for PI and a sensitivity of 71% and specificity of 63% for RI. The mean PI and RI from individual ovarian and uterine vessels were also significantly lower for the malignant group than those for the benign group. The authors conclude that PIs and RIs from intratumoral, ovarian, and uterine vessels are all useful in differentiating malignant tumors from benign ones, but universal thresh-olds for this purpose are far from determined. Also, comparison of intratumoral PI and RI showed that neither PI nor RI was statistically better than the other in malignancy prediction, because the areas under the two ROC curves were not statistically different (P &gt; 0.2, chi-square method).