Erik Sauleau

Bayesian semi-parametric ZIP models with space-time interactions: an application to cancer registry data.

We analyse lymphoid leukemia incidence data collected between 1988 and 2002 from the cancer registry of Haut-Rhin, a region in north-east France. For each patient, sex, area of residence, date of birth and date of diagnosis are available. Incidence summaries in the registry are grouped by 3-year periods. A disproportionately large frequency of zeros in the data leads to a lack of fit for Poisson models of relative risk. The aim of our analysis was to model the spatio-temporal variations of the disease taking into account some non-standard requirements, such as count data with many zeros and space-time interactions. For this purpose, we consider a flexible zero-inflated Poisson model for semi-parametric regression which incorporates space-time interactions (modelled by means of varying coefficient model) using an extension of the methodology proposed in Fahrmeir & Osuna (2006, Structured additive regression for overdispersed and zero-inflated count data. Stoc. Models Bus. Ind., 22, 351-369). Inference is carried out from a Bayesian perspective using Markov chain Monte Carlo methods by means of the BayesX software. Our analysis of the geographical distribution of the disease and its evolution in time may be considered as a starting point for further studies.

Pullout characteristics of percutaneous pedicle screws with different cement augmentation methods in elderly spines: An in vitro biomechanical study

BACKGROUND Vertebroplasty prefilling or fenestrated pedicle screw augmentation can be used to enhance pullout resistance in elderly patients. It is not clear which method offers the most reliable fixation strength if axial pullout and a bending moment is applied. The purpose of this study is to validate a new in vitro model aimed to reproduce a cut out mechanism of lumbar pedicle screws, to compare fixation strength in elderly spines with different cement augmentation techniques and to analyze factors that might influence the failure pattern. MATERIALS AND METHODS Six human specimens (82-100 years) were instrumented percutaneously at L2, L3 and L4 by non-augmented screws, vertebroplasty augmentation and fenestrated screws. Cement distribution (2 ml PMMA) was analyzed on CT. Vertebral endplates and the rod were oriented at 45° to the horizontal plane. The vertebral body was held by resin in a cylinder, linked to an unconstrained pivot, on which traction (10 N/s) was applied until rupture. Load-displacement curves were compared to simultaneous video recordings. RESULTS Median pullout forces were 488.5 N (195-500) for non-augmented screws, 643.5 N (270-1050) for vertebroplasty augmentation and 943.5 N (750-1084) for fenestrated screws. Cement augmentation through fenestrated screws led to significantly higher rupture forces compared to non-augmented screws (P=0.0039). The pullout force after vertebroplasty was variable and linked to cement distribution. A cement bolus around the distal screw tip led to pullout forces similar to non-augmented screws. A proximal cement bolus, as it was observed in fenestrated screws, led to higher pullout resistance. This cement distribution led to vertebral body fractures prior to screw pullout. CONCLUSION The experimental setup tended to reproduce a pullout mechanism observed on radiographs, combining axial pullout and a bending moment. Cement augmentation with fenestrated screws increased pullout resistance significantly, whereas the fixation strength with the vertebroplasty prefilling method was linked to the cement distribution.

Predictive value of cardiovascular parameters in stages 1 and 2 of twin-to-twin transfusion syndrome

The Quintero staging of twin‐to‐twin transfusion syndrome (TTTS) does not include a comprehensive cardiovascular assessment. The aim of this study is to assess the predictive value of the myocardial performance index (MPI) and the Childrens Hospital of Philadelphia (CHOP) score on recipient survival in Quintero stages 1 and 2 TTTS.

Large sample confidence intervals for the skewness parameter of the skew-normal distribution based on Fisher's transformation

The skew-normal model is a class of distributions that extends the Gaussian family by including a skewness parameter. This model presents some inferential problems linked to the estimation of the skewness parameter. In particular its maximum likelihood estimator can be infinite especially for moderate sample sizes and is not clear how to calculate confidence intervals for this parameter. In this work, we show how these inferential problems can be solved if we are interested in the distribution of extreme statistics of two random variables with joint normal distribution. Such situations are not uncommon in applications, especially in medical and environmental contexts, where it can be relevant to estimate the distribution of extreme statistics. A theoretical result, found by Loperfido [7], proves that such extreme statistics have a skew-normal distribution with skewness parameter that can be expressed as a function of the correlation coefficient between the two initial variables. It is then possible, using some theoretical results involving the correlation coefficient, to find approximate confidence intervals for the parameter of skewness. These theoretical intervals are then compared with parametric bootstrap intervals by means of a simulation study. Two applications are given using real data.

High-Force Versus Low-Force Lumbar Traction in Acute Lumbar Sciatica Due to Disc Herniation: A Preliminary Randomized Trial

OBJECTIVE This study compared the effects of high-force versus low-force lumbar traction in the treatment of acute lumbar sciatica secondary to disc herniation. METHODS A randomized double blind trial was performed, and 17 subjects with acute lumbar sciatica secondary to disc herniation were assigned to high-force traction at 50% body weight (BW; LT50, n = 8) or low force traction at 10% BW (LT10, n = 9) for 10 sessions in 2 weeks. Radicular pain (visual analogue scale [VAS]), lumbo-pelvic-hip complex motion (finger-to-toe test), lumbar-spine mobility (Schöber-Macrae test), nerve root compression (straight-leg-raising test), disability (EIFEL score), drug consumption, and overall evaluation of each patient were measured at days 0, 7, 1, 4, and 28. RESULTS Significant (P < .05) improvements were observed in the LT50 and LT10 groups, respectively, between day 0 and day 14 (end of treatment) for VAS (-44% and -36%), EIFEL score (-43% and -28%) and overall patient evaluation (+3.1 and +2.0 points). At that time, LT50 specifically improved in the finger-to-toe test (-42%), the straight-leg-raising test (+58), and drug consumption (-50%). No significant interaction effect (group-by-time) was revealed, and the effect of traction treatment was independent of the level of medication. During the 2-week follow-up at day 28, only the LT10 group improved (P < .05) in VAS (-52%) and EIFEL scores (-46%). During this period, no interaction effect (group-by-time) was identified, and the observed responses were independent of the level of medication. CONCLUSIONS For this preliminary study, patients with acute lumbar sciatica secondary to disc herniation who received 2 weeks of lumbar traction reported reduced radicular pain and functional impairment and improved well-being regardless of the traction force group to which they were assigned. The effects of the traction treatment were independent of the initial level of medication and appeared to be maintained at the 2-week follow-up.

Multilocus sequence typing of clinical Borreliella afzelii strains: population structure and differential ability to disseminate in humans

BackgroundLyme borreliosis in humans results in a range of clinical manifestations, thought to be partly due to differences in the pathogenicity of the infecting strain. This study compared European human clinical strains of Borreliella afzelii (previously named Borrelia afzelii) using multilocus sequence typing (MLST) to determine their spatial distribution across Europe and to establish whether there are associations between B. afzelii genotypes and specific clinical manifestations of Lyme borreliosis. For this purpose, typing was performed on 63 strains, and data on a further 245 strains were accessed from the literature.ResultsAll 308 strains were categorized into 149 sequence types (STs), 27 of which are described here for the first time. Phylogenetic and goeBURST analyses showed short evolutionary distances between strains. Although the main STs differed among the countries with the largest number of strains of interest (Germany, the Netherlands, France and Slovenia), the B. afzelii clinical strains were less genetically structured than those previously observed in the European tick population. Two STs were found significantly more frequently in strains associated with clinical manifestations involving erythema migrans, whereas another ST was found significantly more frequently in strains associated with disseminated manifestations, especially neuroborreliosis.ConclusionsThe MLST profiles showed low genetic differentiation between B. afzelii strains isolated from patients with Lyme borreliosis in Europe. Also, clinical data analysis suggests the existence of lineages with differential dissemination properties in humans.

Cervical sagittal alignment in adult hyperkyphosis treated by posterior instrumentation and in situ bending

BACKGROUND In the normal adult spine, a link between thoracolumbar and cervical sagittal alignment exists, suggesting adaptive cervical positional changes allowing horizontal gaze. In patients with thoracic hyperkyphosis, cervical adaptation to sagittal global alignment might be different from healthy individuals. However, this relationship has not clearly been reported in hyperkyphotic deformity. PURPOSE The purpose of this study was to identify cervical sagittal alignment types observed on radiographs in young adults with thoracic hyperkyphosis. The relationship between cervical and thoracolumbar alignment as well as the effect of posterior instrumentation and adaptive positional changes of the mobile cervical segment were retrospectively analyzed. PATIENTS AND METHODS Twenty-three patients (32.7 years; 5-year follow-up) were included. Full spine radiographic measurements were: T1 slope, T1-T4 kyphosis, T4-T12 kyphosis, L1-S1 lordosis, pelvic incidence, pelvic tilt, sacral slope, SVA C7, SVA C2, lordosis between C0-C2, C2-C7, C2-C4 and C4-C7. A Bayesian model and Spearman correlation were used. RESULTS Two alignment types existed: cervical lordosis (group A) and cervical kyphosis (group B). Preoperatively, T4-T12 kyphosis and L1-S1 lordosis were significantly higher in group A: 76.6° versus 59.4° and -72.8° versus -65.8° (probability of>5° difference P (β>5)>0.95). Pelvic incidence was higher in group A (49.8° versus 44.2°) and C0-C2 lordosis in group B (-29.4° versus -21.6°). A significant correlation existed between: T4-T12 kyphosis and C2-C7 lordosis, L1-S1 lordosis and pelvic incidence, C2-C7 lordosis and T1 slope, C2-C7 lordosis and T1-T4 kyphosis. Postoperatively, T4-T12 kyphosis decreased by 33.1° P (β>5)=0.9995), L1-S1 lordosis decreased by 17.7° (P (β>5)=0.961), T1-T4 kyphosis increased by 14.1° (P (β>5)=0.973). SVA C2 (translation) increased by 13.8mm. C0-C2 lordosis (head rotation) remained unchanged. Six patients changed cervical alignment. PJK occurred in 15 patients, unrelated to cervical alignment or proximal instrumentation level. DISCUSSION Two cervical alignment types, lordotic or kyphotic, were observed thoracic hyperkyphosis patients. This alignment was mainly triggered by the amount of thoracic kyphosis and lumbar lordosis, linked to pelvic incidence. Moreover, the inclination of the C7-T1 junctional area plays a key role in the amount of cervical lordosis. The correction of T4-T12 kyphosis induced compensatory modifications at adjacent segments: T1-T4 kyphosis increase (PJK) and L1-S1 lordosis decrease. Global spino-pelvic alignment and head position did not change in the sagittal plane. The cervical spine tented to keep in its preoperative position in most patients. LEVEL OF EVIDENCE Level IV.

Outcome of endoscopy-negative iron deficiency anemia in patients above 65: A longitudinal multicenter cohort.

AbstractAfter the age of 65 years, iron deficiency anemia (IDA) requires the elimination of digestive neoplasia and is explored with upper and lower gastrointestinal (GI) endoscopy. However, such explorations are negative in 14% to 37% of patients. To further evaluate this issue, we evaluated the outcomes of patients aged over 65 years with endoscopy-negative IDA.We retrospectively analyzed the outcomes of in-patients over the age of 65 years with IDA (hemoglobin <12 g/dL and ferritin <70 &mgr;g/L) who had negative complete upper and lower GI endoscopies in 7 tertiary medical hospitals. Death, the persistence of anemia, further investigations, and the final diagnosis for IDA were analyzed after at least 12 months by calling the patients’ general practitioners and using hospital records.Between 2004 and 2011, 69 patients (74% women) with a median age of 78 (interquartile range (IQR) 75–82) years and hemoglobin and ferritin levels of 8.4 (IQR 6.8–9.9) g/dL and 14 (IQR 8–27) &mgr;g/L, respectively, had endoscopy-negative IDA, and 73% of these patients received daily antithrombotics. After a follow-up of 41 ± 22 months, 23 (33%) of the patients were dead; 5 deaths were linked with the IDA, and 45 (65%) patients had persistent anemia, which was significantly associated with death (P = 0.007). Further investigations were performed in 45 patients; 64% of the second-look GI endoscopies led to significant changes in treatment compared with 25% for the capsule endoscopies. Conventional diagnoses of IDA were ultimately established for 19 (27%) patients and included 3 cancer patients. Among the 50 other patients, 40 (58%) had antithrombotics.In endoscopy-negative IDA over the age of 65 years, further investigations should be reserved for patients with persistent anemia, and second-look GI endoscopy should be favored. If the results of these investigations are negative, the role of antithrombotics should be considered.

O-0020SOCIO-ECONOMIC AND GEOGRAPHICAL DISPARITIES IN COLORECTAL ADENOMAS AND COLORECTAL CANCERS DETECTION : A POPULATION-BASED STUDY

Background: Rural areas were previously shown to be associated with colorectal adenoma detection rates that were lower than in urban areas, with no significant difference for colorectal cancer (CRC) incidence. However, this analysis was relatively crude and did not include socio-economic data. The present study aimed at assessing the impact of socio-geographical disparities on colorectal adenoma detection and CRC incidence in the Department of Cote d’Or, France, before mass screening implementation. Methods: The Cote d’Or registry of digestive tumours has collected all cases of colorectal polyps and cancers diagnosed in a well-defined geographical area (Cote d’Or, France) since 1976. The study population included all patients > 20 years, residing in Cote d’Or with a known place of residence, diagnosed for the first time either with colorectal adenomas or incident CRC between 01/01/1995 and 12/31/2002. Socio-geographical variables included distance to primary care physician (PCP), distance to gastroenterologist (GE) and the European Deprivation Index (EDI) collected in the smallest French areas available. Heterogeneity and spatial autocorrelation were tested. Spatial Bayesian poisson regression models were used and compared using the Deviance Information Criteria (DIC). Results: On the whole, 5,399 patients were diagnosed with at least one adenoma and 2,125 with invasive incident CRC. Age- and gender-standardized adenoma detection rate (/100 000) was 151 [CI95% 147-156], with variations according to the EDI and the distance to PCP. Thus, age- and gender-standardized adenoma detection rate ranged from 164 [CI95% : 155-173] for the most affluent quintile to 144 [CI95% : 134-154] and 151 [CI95% : 141-161] for the two most deprived quintiles. Regarding distance to PCP, adenoma detection rates were 161 [CI95% : 155-167] in the lowest quintile (lowest distance to PCP), versus 117 [CI95%: 102-133] for the highest quintile (highest distance to PCP). On the contrary, no significant differences were observed according to distance to GE. Age-and gender-standardized CRC incidence rate was 48 [CI95% : 46-51] without any significant variation according to socio-economic deprivation or according to the distance to physicians. Age and gender adjusted Bayesian model identified geographical disparities in colorectal adenoma detection: overdetection around the regional capital city and underdetection on the periphery of the