Ideal Thresholds Research Articles

Increasing surgeon volume correlates with patient survival following open abdominal aortic aneurysm repair

ObjectiveThe annual number of open abdominal aortic aneurysm (AAA) repairs has decreased dramatically over the last decade, making the search for physician case volume thresholds more important. The purpose of this study was to identify a minimum threshold for annual surgeon case volume in open AAA repair. MethodsThe New York Statewide Planning and Research Cooperative System inpatient database was used to identify all patients undergoing open repair of an intact AAA between 2000 and 2008. Thirty-day survival was calculated using New York State vital records, which contain all New York State death certificates. The annual case volume for each surgeon was defined as the number of open AAA repairs performed in the year of the index procedure. The Contal and O'Quigley method was used to identify a minimum volume threshold. ResultsA total of 11,086 patients were included in the analysis. The selected cutpoint was six or more cases per year based on maximization of the Contal and O'Quigley test statistic. The high-volume group had comparable rates of cardiovascular comorbidities, but significantly improved 30-day and 5-year survival rates as well as shorter lengths of stay in the hospital. ConclusionsThis study identifies an ideal threshold for minimum annual surgeon case volume for open AAA repair. Over the study period, perioperative mortality would not have occurred in up to 150 patients if all procedures had been done by high-volume surgeons performing at least six repairs per year. However, even a minimum annual threshold of at least two repairs per year provided a mortality benefit. Ideal minimum volume thresholds should be developed using rigorous statistical analysis as well as local information about practice patterns.

Wednesday, September 26, 2018 7:35 AM–9:00 AM ePosters: P95. Quantitative age-adjusted targets for ideal cervicothoracic sagittal alignment in asymptomatic adults

BACKGROUND CONTEXT Recent research has identified increased C2-T3 angle as a risk factor for persistent sagittal malalignment following thoracolumbar surgery. Despite this, no ideal cervicothoracic alignment thresholds exist in the literature. As several studies have demonstrated a clear relationship between the normal aging spine and sagittal spinal alignment, such ideal-alignment thresholds should also account for patient age. PURPOSE This study proposes age-specific cervicothoracic alignment targets using previously published age-specific normative Neck Disability Index (NDI) values. STUDY DESIGN/SETTING Single center retrospective review. PATIENT SAMPLE A total of 223 patients with available biplanar full-body stereographic x-rays. OUTCOME MEASURES C2-T3 lordosis; Neck Disability Index score. METHODS Patients >18 years with cervical sagittal vertical axis RESULTS Overall, 223 patients (50±20years, 65% F) met inclusion criteria, presenting with a mean sagittal vertical axis (SVA) of 17.8±47.7 mm, cervical SVA 19.8±11.2 mm, T1 Slope-C2-C7 lordosis 24.7°±16.2°, and C2-T3 of 2.1°±16.5°. At baseline, increased C2-T3 angle was significantly correlated with both NDI score (r=0.266, p 75 years: 27.8. Liner regression analysis showed a significant relationship between NDI score, age, and baseline cervicothoracic alignment, as assessed by C2-T3 angle (r=0.497, p 75 years: 6.7°. CONCLUSIONS Significant relationships exist between age, neck disability, and cervicothoracic alignment, suggesting broad measurements across the cervicothoracic junction may be clinically relevant in predicting postoperative outcomes of surgical spine deformity patients. Taking into account patient age and USA-normative values of neck disability, this study offers a set of ideal age-adjusted alignment targets for C2-T3. By proposing a set of normative, age-specific cervicothoracic alignment targets, this study better facilitates individual optimization of surgical planning.

Abstract TMP3: Age-Adjusted Infarct Volume Cut-off For Favorable Outcome After Large Vessel Occlusion Stroke Endovascular Therapy

Background: Optimal selection paradigms for large vessel occlusion acute stroke endovascular therapy are yet to be established. Previous studies have shown the benefit of adjusting infarct size to age. We sought to study the impact of age-adjusted final infarct volumes (FIV), a surrogate for pre-reperfusion infarct core, on functional outcomes and determine the ideal thresholds for good outcome discrimination (90-day mRS 0-2). Methods: We reviewed our prospectively collected endovascular database at a tertiary care academic institution between 9/2010- 8/2016. All patients that underwent endovascular therapy for large vessel occlusion anterior circulation acute ischemic stroke were stratified into five age groups: (G1) <50 years, (G2) 50-69, (G3) 70-79 (G4) 80-89 and (G5) ≥90. Baseline, procedural, and radiological characteristics, as well as outcome parameters were compared. FIV was measure on follow-up MRI or CT within 5 days of treatment. : 966 patients were studied (G1:136, G2:408, G3:233, G4:160, G5:29). Overall, the mean FIV was 59.9±79.9mL and 46% had good outcome. Patients with poor outcome had larger FIV in each group (Mean/Median[IQR]) (G1:46.8/29.2[8.7-64.6] vs 145.3/91.5[51.9-223.5], G2:26.9/15.8[7.7-37.2] vs 93.6/68.1[22.2-146.8], G3:26.2/17.6[7.6-34.1] vs 96.1/61.9[25.5-130.9], G4:14.7/8.7[3.9-16.4] vs 60.2/29[13.6-85.2], G5:2.9/1.3[0.6-4.3] vs 58.3/36.6[18.2-91.1], p<0.01 for all). The target FIV cut-off (mL) decreased with increased age: G1:52.4(SE 75%, SP 65%); G2:23.2(SE 75%,SP 64%); G3:24.6(SE 76%,SP 64%); G4:13.4(SE 75%,SP 70%); G5:12.8(SE 79%,SP 100%). In multivariate analysis, after adjusting for age, baseline NIHSS, glucose level, reperfusion status, parenchymal hematoma and FIV, achieving a final infarct volume less than the age-adjusted target was an independent predictor of good outcome (OR:1.94 95%CI [1.06-3.53], p=0.03). Conclusions: Age-adjusted infarct volume represents a strong outcome discriminator substitute and might help refine patient selection for stroke endovascular therapy

Evidence-Based Cutoff Threshold Values from Receiver Operating Characteristic Curve Analysis for Knee Osteoarthritis in the 50-Year-Old Korean Population: Analysis of Big Data from the National Health Insurance Sharing Service

We aimed to investigate the characteristics of patients with osteoarthritis (OA), using the data of all Koreans registered in the National Health Insurance Sharing Service Database (NHISS DB), and to provide ideal alternative cutoff thresholds for alleviating OA symptoms. Patients with OA (codes M17 and M17.1–M17.9 in the Korean Standard Classification of Disease and Causes of Death) were analyzed using SAS software. Optimal cutoff thresholds were determined using receiver operating characteristic curve analysis. The 50-year age group was the most OA pathogenic group (among 40~70 years, n = 2088). All exercise types affected the change of body mass index (p < 0.05) and the sex difference in blood pressure (BP) (p < 0.01). All types of exercise positively affected the loss of waist circumference and the balance test (standing time on one leg in seconds) (p < 0.01). The cutoff threshold for the time in seconds from standing up from a chair to walking 3 m and returning to the same chair was 8.25 (80% sensitivity and 100% specificity). By using the exercise modalities, categorized multiple variables, and the cutoff threshold, an optimal alternative exercise program can be designed for alleviating OA symptoms in the 50-year age group.

Urinary Luteinizing Hormone Tests: Which Concentration Threshold Best Predicts Ovulation?

To study the best possible luteinizing hormone (LH) threshold to predict ovulation within the 24, 48, and 72 h. Observational study. Multicenter collaborative study. A total of 107 women. Women collected daily first morning urine for hormonal assessment and underwent serial ovarian ultrasound. This is a secondary analysis of 283 cycles. The sensitivity, specificity, positive and negative predictive values, and positive and negative likelihood ratios were estimated for varying ranges of LH thresholds. Receiver operating characteristic curves and cost-benefit ratios were used to estimate the best thresholds to predict ovulation. The best scenario to predict ovulation at random was within 24 h after the first single positive test. The false-positive rate was found to increase as (1) the cycle progressed or (2) two or three consecutive tests were used, or (3) ovulation was predicted within 48 or 72 h. Testing earlier in the cycle increases the predictive value of the test. The ideal thresholds to predict ovulation ranged between 25 and 30 mIU/ml with a PPV (50-60%), NPV (98%), LR+ (20-30), and LR- (0.5). At least, one day with LH ≥25 mIU/ml followed by three negatives (LH <25) occurred before ovulation in 31% of all cycles. When used throughout the cycle and evaluated together, peak-fertility type mucus with a positive LH test ≥25 mIU/ml provides a higher specificity than either mucus or LH testing alone (97-99 vs. 77-95 vs. 91%, respectively). We identified that beginning LH testing earlier in the cycle (day 7) with a threshold of 25-30 mIU/ml may present the best predictive value for ovulation within 24 h. However, prediction by LH testing alone may be affected negatively by several confounding factors so LH testing alone should not be used to define the end of the fertile window. Complementary markers should be further investigated to predict ovulation and identify the fertile window. The use of the peak cervical mucus along with an LH test may provide a higher specificity and predictive value than either of them alone. We recommend that manufacturers disclose their tests' threshold to the public.

Treatment for Degenerative Lumbar Spondylolisthesis: Current Concepts and New Evidence.

Current guidelines for the optimal treatment degenerative spondylolisthesis are weak and based on limited high-quality evidence. There is some moderate evidence that decompression alone may be a feasible treatment with lower surgical morbidity and similar outcomes to fusion when performed in a select population with a low-grade slip. Similarly, addition of interbody fusion may be best suited to a subset of patients with high-grade degenerative spondylolisthesis, although this remains controversial. Minimally invasive techniques are increasingly being utilized for both decompression and fusion surgeries with more and more studies showing similar outcomes and lower postoperative morbidity for patients. This will likely be an area of continued intense research. Finally, the role of spondylolisthesis reduction will likely be determined as further investigation into optimal sagittal balance and spinopelvic parameters is conducted. Future identification of ideal thresholds for sagittal vertical axis and slip angle that will prevent progression and reoperation will play an important role in surgical treatment planning. Current evidence supports surgical treatment of degenerative spondylolisthesis. While posterolateral spinal fusion remains the treatment of choice, the use of interbodies and decompressions without fusion may be efficacious in certain populations. However, additional high-quality evidence is needed, especially in newer areas of practice such as minimally invasive techniques and sagittal balance correction.

Defining an “ideal” continuous dose-volume constraint curve using literature recommended individual dose-volume thresholds for reducing rectal toxicity from external beam prostate radiation therapy

Objective We postulated that a contiguous rectal dose-volume threshold curve obtained via a best mathematical fit of the toughest literature recommended dose-volume thresholds could be deemed as “safe” related to the risk of rectal toxicity. The practicality of restricting rectal doses to such ideal volume thresholds in clinical practice was tested by comparing data collected from a pool of prostate patients treated with external beam radiation therapy (EBRT) in our institution.

Diagnosability of mtDNA with Random Forests: Using sequence data to delimit subspecies

AbstractWe examine the use of an ensemble method, Random Forests, to delimit subspecies using mitochondrial DNA (mtDNA) sequences. Diagnosability, a measure of the ability to correctly determine the taxon of a specimen of unknown origin, has historically been used to delimit subspecies, but few studies have explored how to estimate it from DNA sequences. Using simulated and empirical data sets, we demonstrate that Random Forests produces classification models that perform well for diagnosing subspecies and species. Populations with strong social structure and relatively low abundances (e.g., killer whales, Orcinus orca) were found to be as diagnosable as species. Conversely, comparisons involving subspecies that are abundant (e.g., spinner and spotted dolphins, Stenella longirostris and S. attenuata), are only as diagnosable as many population comparisons. Estimates of diagnosability reported in subspecies and species descriptions should include confidence intervals, which are influenced by the sample sizes of the training data. We also stress the importance of reporting the certainty with which individuals in the training data are classified in order to communicate the strength of the classification model and diagnosability estimate. Guidance as to ideal minimum diagnosability thresholds for subspecies will improve with more comprehensive analyses; however, values in the range of 80%–90% are considered appropriate.

The Granulocyte-to-Lymphocyte Ratio as a Marker of Surgical Stress and a Predictor of Postoperative Infectious Complications After Gastric Cancer Surgery: An Analysis of Patients Enrolled in a Prospective Randomized Trial.

The granulocyte-to-lymphocyte ratio (GLR) in the blood may be a useful marker of surgical stress (SS) following surgery for cancer. The aim of the present study was to compare the SS by measuring the GLR, and further study the value of the GLR in predicting postoperative infectious complications (ICs). Data from 201 gastric cancer patients at Fujian Medical University Union Hospital who were enrolled in our prospective randomized controlled trial were extracted for this study. Blood samples to perioperatively measure the GLR were routinely taken. Additional external validation was performed using the dataset (n=135) from Nanfang Hospital who were enrolled in the same trial. Patients undergoing either laparoscopic or open resection showed a similar preoperative GLR, as well as similar GLRs, on postoperative days (PODs) 1 and 3. The GLR on POD 5 was lower in the laparoscopic group compared with the open group (p=0.014), and the optimal predictive GLR thresholds of postoperative ICs in both the laparoscopic and open groups were the same on POD 5, i.e. 6.5 and 7.4, respectively. The GLR on POD 5 was identified as an independent factor for postoperative ICs in both the laparoscopic and open groups. Similar results were found in the validation dataset. The GLR status not only correlates with SS but may also be a reliable predictor of ICs for gastric cancer patients after gastrectomy. The ideal GLR thresholds on POD 5 for ICs following laparoscopic and open gastrectomy are 6.5 and 7.4, respectively.

Abstract B09: Multivariable Models for Predicting Likely Metastatic Sites for Triple Negative Breast Cancers

Abstract Background: Unique organ microenvironment may preferentially support growth of specific tumor clones because of which different breast cancer subtypes show distinct tropisms for sites of metastasis. While a few gene expressionbased signatures are known to predict sitespecific metastasis of breast cancer, little work has focused on identification of clinically facile immunohistochemical predictors of metastasis to specific sites, especially for triple negative breast cancers (TNBCs). Methods: Primary tumor samples from 322 TNBC patients were stained for 133 biomarkers and assessed by immunohistochemistry. Differences in average levels of these biomarkers were compared between patients with or without metastasis to specific sites (brain, bone, lungs, liver, lymph nodes). Significantly different biomarkers were then analyzed within a Cox regression model to evaluate their prognostic value when patients with metastasis to the site of interest were compared to patients with no metastasis. Ideal thresholds, based on maximizing model fit, stratified cohorts that show high and low expression of each biomarker. A combination of a biomarker found high for each site, low for each site, and the Nottingham Prognostic Index (NPI) was used to stratify patients. Results: Our analysis uncovered several biomarkers whose expression levels in primary tumors can predict the site of future metastasis in TNBCs. Our models for brain (PARP1 &amp; BRCA2), bone (MTA1 &amp;Tumor-Adjacent CD8), liver (TFF1 &amp; N-Cadherin), and lung (ROR) were able to identify patients who had at least a 500% risk of site specific distant metastasis. Conclusion: Relatively simple and inexpensive immunohistochemical analyses of biomarkers, combined with logical model building, in primary tumors of TNBCs may allow prediction of the site of future metastasis. Highrisk patients may benefit from increased surveillance of such sites. Citation Format: Sergey Klimov, Andrew Green, Mohammed Aleskandarany, Emad Rakha, Ian Ellis, Michelle Reid, Rida C. G. Padmashree, Ritu Aneja. Multivariable Models for Predicting Likely Metastatic Sites for Triple Negative Breast Cancers. [abstract]. In: Proceedings of the Ninth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2016 Sep 25-28; Fort Lauderdale, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2017;26(2 Suppl):Abstract nr B09.

Inclusive production of plus a recoil for the LHC Run-II

This letter presents a study of the inclusive production of plus a recoil, using simulated samples of pp collisions at for an integrated luminosity in the range between and . The case for experiments to include un-prescaled b-tag multijet triggers for this topology is made and the ideal jet thresholds are discussed. The sensitivity to the Standard Model Higgs boson with a transverse momentum of at least 200 GeV is evaluated with respect to a continuous background, dominated by multijet processes. The mass of b-jet-pairs is analysed, quoting sensitivity to cross-sections in the range from 1 to 2 pb, for , covering the total Higgs-boson production cross-section of 1.8 pb. The trigger strategy presented in this letter is compared to triggers already in use, showing an increase on the signal efficiency for masses below 200 GeV and a performance comparable to a logical OR of all the currently available akin triggers for higher masses. The robustness of the expected sensitivity against systematic uncertainties is estimated by considering various typical sources, such as those on the fitting parameters of the continuous background, shape uncertainties affecting the signal acceptance and the background modelling. The accuracy of the Higgs-boson production cross-section measurements is also discussed, quoting sensitivity to deviations of 50% for and 10% for .

A Novel Approach for Discovery Quantitative Fuzzy Multi-Level Association Rules Mining Using Genetic Algorithm

Quantitative multilevel association rules mining is a central field to realize motivating associations among data components with multiple levels abstractions. The problem of expanding procedures to handle quantitative data has been attracting the attention of many researchers. The algorithms regularly discretize the attribute fields into sharp intervals, and then implement uncomplicated algorithms established for Boolean attributes. Fuzzy association rules mining approaches are intended to defeat such shortcomings based on the fuzzy set theory. Furthermore, most of the current algorithms in the direction of this topic are based on very tiring search methods to govern the ideal support and confidence thresholds that agonize from risky computational cost in searching association rules. To accelerate quantitative multilevel association rules searching and escape the extreme computation, in this paper, we propose a new genetic-based method with significant innovation to determine threshold values for frequent item sets. In this approach, a sophisticated coding method is settled, and the qualified confidence is employed as the fitness function. With the genetic algorithm, a comprehensive search can be achieved and system automation is applied, because our model does not need the user-specified threshold of minimum support. Experiment results indicate that the recommended algorithm can powerfully generate non-redundant fuzzy multilevel association rules.

Influence of Background Activity on Volume Estimation Using Iterative Thresholding Method in Single-Photon-Emission Computed Tomography with Technetium-99m: A Phantom Study

IntroductionThe aim of this study was to assess the influence of background activity on the accuracy of volume estimation of target objects using an iterative thresholding method. MethodsSingle-photon-emission computed tomography studies were carried out for plastic bottles of various sizes as target objects containing Technetium-99m placed in a cylindrical water phantom. The phantoms were created to have varying ratios of target activity concentration to background activity concentration (T/B) ranging from 4.00 to 1.25. From the single-photon-emission computed tomography slices, the volume of the target object was estimated using an iterative thresholding method. A unique threshold that estimated the volume of the target object was determined and declared as ideal threshold for each level of background activity. Simple linear regression analysis was carried out to explore the relationship between the actual volume and estimated volume. ResultsThe analysis shows a statistically significant linear relationship (P < .01) between actual volume and estimated volume. For all ratios of target activity concentration to background activity concentration studied, the relative errors in estimated volumes of target objects are within ±7%. Thresholds that estimated volume of target objects vary depending on the level of background activity. ConclusionsIt is clearly demonstrated that background activity highly influenced the volume estimation. Therefore, background activity of the target object needs to be considered when selecting the ideal thresholds to obtain accurate volume estimation of target objects.

Abstract P5-10-15: Empowering the Nottingham Grading System: An integrated Ki67-mitosis classifier yields a better patient stratification tool

Abstract Therapeutic decision-making for personalized management of breast cancer relies on patient stratification based on the risk conferred by clinicopathologic factors, such as stage, Ki67 Index (KI) and tumor histological grade. The most widely used histologic grading system for breast cancer, the Nottingham Grading System (NGS) provides prognostic information about breast tumor samples by combining analysis of the extent of glandular differentiation, nuclear pleomorphism and mitotic activity present in the tumor sample. In the NGS, the mitotic Index (MI) is defined as the number of mitotic cells per ten high-power fields. KI is a universal prognostic indicator but is not part of the NGS. Although the NGS has been widely used owing to its reproducibility and significant prognostic value, its accuracy in predicting disease prognosis and aggressiveness is limited. Our earlier work has demonstrated that by rationally integrating KI and MI into a new metric called the Ki67-Adjusted Mitotic Score (KAMS), which is a measure of the proportion of mitotic cells amongst Ki67-positive cells, we are able to glean a new layer of prognostic information about metastatic risk. We found that for Nottingham Grade II and III patients, high KAMS values predicted relatively better overall survival (OS) than low KAMS values. We therefore asked if the incorporation of a KAMS-based classifier subsequent to conventional Nottingham classification, would improve patient stratification to enable their funneling towards more optimal treatment choices. Ideal KAMS thresholds were established by analyzing the KAMS-stratified survival groups and selecting the thresholds which created the widest survival stratification that was additionally confirmed to be statistically significant via a Log-Rank test. For Nottingham Grade II and III patients, an above-threshold KAMS value was deemed as low-risk and a below-threshold KAMS value was deemed as high-risk for the purpose of grade adjustment. Grade adjustments were based solely on the patients’ KAMS values. Thus the adjusted Nottingham Grade I consisted of the original Nottingham Grade I patients along with KAMS determined low-risk original Nottingham Grade II patients. Adjusted Nottingham Grade II patients were composed of KAMS determined high-risk patients originally in Nottingham Grade II along with KAMS determined low-risk original Nottingham Grade III patients. Finally, the adjusted Nottingham Grade III was made up exclusively of high-risk patients from the original Nottingham Grade III. We found that the adjusted system represents a wider separation between OS curves with adjusted Grade I (n = 774) OS being 95.48%, adjusted grade II (n = 727) OS at 87.62%, and adjusted Grade III (n = 110) having an OS of 78.18%. Overall survival groups between adjusted grade I and II and I and III (p &amp;lt; 0.001) showed statistical significance. We also found that the hazard ratios for all Nottingham grades are significantly better after adjustment (2.875 versus 2.034 for Grade II and 5.115 versus 3.456 for Grade III) indicating that the KAMS can function as an effective risk-stratification biomarker and that incorporation of a KAMS-based classifier enhances patient stratification. Citation Format: Vaishali Pannu, Padmashree CG Rida, Sergey Klimov, Nikita Wright, Guilherme Cantuaria, Michelle Reid, Ritu Aneja. Empowering the Nottingham Grading System: An integrated Ki67-mitosis classifier yields a better patient stratification tool [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P5-10-15.

Were you identified to be at high fracture risk by FRAX® before your osteoporotic fracture occurred?

With the increasing longevity and the growing size of the aging population, China is among the developing countries with the greatest burden of osteoporotic fractures (OFs). Identification of individuals at high fracture risk to provide early treatment in developing countries with limited resources remains a challenge. Our aim was to calculate the FRAX® values in a selected mainland Chinese population the day before the occurrence of an OF and to compare the results with the Osteoporosis Foundation (NOF) thresholds. To define a population at high fracture risk, we selected patients in the orthopedic emergency cohort from Shanghai Sixth People's Hospital, China. To calculate the FRAX® the day before the actual OF, the actual fracture was not considered as a previous fracture. Subjects with a FRAX® value lower than the NOF thresholds were not considered at high risk. One-hundred ninety-eight patients were included with a mean age of 69.9 ± 10.1years old, and 78.8% were female. Major fracture sites included hip (41.9%), proximal humerus (22.2%), forearm (27.8%), spine (6.6%), and pelvis (1.5%). Overall, only two (1.0%) patients had a 10-year major fracture probability ≥20%, and 84 (42.4%) patients had a 10-year hip fracture probability ≥3%. More than half of the population was not identified to be at high risk by the FRAX® BMI (body mass index). For age groups 55-59, 60-69, 70-79, and 80-90years old, respectively, the mean FRAX® BMI values (major OF/hip fracture) were 3.5/0.7, 5.7/1.8, 8.2/4.7, and 8.6/4.8%. Dual-energy X-ray absorptiometry was available for 58 patients, and 41.2% had a T-score ≤ -2.5 standard deviation (lumbar spine and/or femoral neck and/or total hip). Only six (17.6%) patients with a normal or osteopenic BMD were classified at high risk by the FRAX® BMD (bone mineral density). The NOF thresholds could only identify fewer than half of the studied population to be at high risk the day before an actual OF, and the 10-year hip fracture probability seemed to perform better than the 10-year major fracture probability. Prospective population-based studies are needed to validate the prediction of Chinese FRAX® model and to establish ideal thresholds.

Willingness to pay and benefit–cost analysis of modern contraceptives in Nigeria

ObjectiveTo determine the willingness to pay (WTP) and the benefit–cost of modern contraceptives delivered through the public sector in Nigeria. MethodsData were collected from 4517 randomly selected households. The WTP for the 6 major contraceptive methods available in the public sector was elicited. Logistic regression was used to determine whether the decision to state a positive WTP amount was valid; Tobit regression was used to test the validity of the elicited WTP amounts. For each contraceptive, 3 BCR values were computed, based on the official unit price, the unit cost per couple-year of protection (CYP), and the average actual expenditure for contraceptives in the month preceding the interview. ResultsThe mean WTP for the different contraceptives varied by socioeconomic status and geographic (urban versus rural) location (P<0.01). The BCR analysis showed that the benefits of providing contraceptives through the public sector far outweighed the costs, except for female condoms, where the CYP-based BCR was 0.9. ConclusionThe benefits of providing contraceptives outweigh the costs, making public sector investment worthwhile. The median WTP amounts, which reflect the ideal upper thresholds for pricing, indicate that cost recovery is feasible for all contraceptives.

Dynamic and static expressions of emotion are recognized with equal efficiency

Natural human facial expressions of emotion are dynamic events that progressively unfold over time. The question of whether humans can better recognize dynamic than static expressions has been a source of recent debate (e.g., Edwards, 1998; Ambadar, Schooler & Cohn, 2005; Fiorentini & Viviani, 2011; Landers, Christie & Bruce, 1999). Here, we take a novel approach to this issue by asking: 1) Does the information contained in a dynamic facial expression differ from that of a static expression? 2) How does the information content in dynamic expressions evolve over time? and 3) How efficiently do human observers make use of information when recognizing dynamic versus static facial expressions? To answer these questions, we measured both human and ideal observer contrast energy thresholds for recognizing dynamic and static facial expressions of 8 human actors (4 male, 4 female) making 6 different expressions of emotion (anger, disgust, fear, happiness, sadness, surprise). Dynamic stimuli evolved from a neutral to a full expression of emotion over the course of 30 frames (~1 second). Corresponding static stimuli were created by repeating the final frame of each dynamic stimulus for 30 frames. Ideal observer simulations revealed significantly lower thresholds for static than dynamic expressions, indicating more information was available in the static than the dynamic expressions. Additionally, a frame-by-frame ideal observer analysis of the dynamic expressions revealed a monotonic decrease in ideal thresholds across frames, indicating that the amount of information available at a given moment during the production of an expression systematically increased over time. Similar to the ideal observer, human thresholds were significantly lower for static than dynamic expressions, yielding efficiencies (ideal/human thresholds) that were nearly identical across conditions. These results support the idea that the presence of dynamic cues offers no discernible processing efficiency advantage for human observers when recognizing facial expressions of emotion. Meeting abstract presented at VSS 2012

Hemodynamic Changes after Eversion Carotid Endarterectomy: A Reason for Concern?

Hemodynamic Changes after Eversion Carotid Endarterectomy: A Reason for Concern?

Oriented texture detection: Ideal observer modelling and classification image analysis

Perception of visual texture flows contributes to object segmentation, shape perception, and object recognition. To better understand the visual mechanisms underlying texture flow perception, we studied the factors limiting detection of simple forms of texture flows composed of local dot dipoles (Glass patterns) and related stimuli. To provide a benchmark for human performance, we derived an ideal observer for this task. We found that human detection thresholds were 8.0 times higher than ideal. We considered three factors that might account for this performance gap: (1) false matches between dipole dots (correspondence errors), (2) loss of sensitivity with increasing eccentricity, and (3) local orientation bandwidth. To estimate the effect of correspondence errors, we compared detection of Glass patterns with detection of matched line-segment stimuli, where no correspondence uncertainty exists. We found that eliminating correspondence errors reduced human thresholds by a factor of 1.8. We used a novel form of classification image analysis to directly estimate loss of sensitivity with eccentricity and local orientation bandwidth. Incorporating the eccentricity effects into the ideal observer model increased ideal thresholds by a factor of 2.9. Interestingly, estimated orientation bandwidth increased ideal thresholds by only 8%. Taking all three factors into account, human thresholds were only 58% higher than model thresholds. Our findings suggest that correspondence errors and eccentricity losses account for the great majority of the perceptual loss in the visual processing of Glass patterns.

Prediction Modeling to Assess the Prognostic Significance of a Biomarker Panel

Prediction models are often used to stratify individuals on the basis of their risk for a future event, such as death or development of disease. Such information can be valuable to a wide range of stakeholders, including patients and clinicians as they evaluate potential treatment strategies and