Improving the Hosmer-Lemeshow goodness-of-fit test in large models with replicated Bernoulli trials.

The Hosmer-Lemeshow (HL) test is a commonly used global goodness-of-fit (GOF) test that assesses the quality of the overall fit of a logistic regression model. In this paper, we give results from simulations showing that the type I error rate (and hence power) of the HL test decreases as model complexity grows, provided that the sample size remains fixed and binary replicates (multiple Bernoulli trials) are present in the data. We demonstrate that a generalized version of the HL test (GHL) presented in previous work can offer some protection against this power loss. These results are also supported by application of both the HL and GHL test to a real-life data set. We conclude with a brief discussion explaining the behavior of the HL test, along with some guidance on how to choose between the two tests. In particular, we suggest the GHL test to be used when there are binary replicates or clusters in the covariate space, provided that the sample size is sufficiently large.

A generalized Hosmer-Lemeshow goodness-of-fit test for a family of generalized linear models.

Generalized linear models (GLMs) are very widely used, but formal goodness-of-fit (GOF) tests for the overall fit of the model seem to be in wide use only for certain classes of GLMs. We develop and apply a new goodness-of-fit test, similar to the well-known and commonly used Hosmer-Lemeshow (HL) test, that can be used with a wide variety of GLMs. The test statistic is a variant of the HL statistic, but we rigorously derive an asymptotically correct sampling distribution using methods of Stute and Zhu (Scand J Stat 29(3):535-545, 2002) and demonstrate its consistency. We compare the performance of our new test with other GOF tests for GLMs, including a naive direct application of the HL test to the Poisson problem. Our test provides competitive or comparable power in various simulation settings and we identify a situation where a naive version of the test fails to hold its size. Our generalized HL test is straightforward to implement and interpret and an R package is publicly available. Supplementary Information: The online version contains supplementary material available at 10.1007/s11749-023-00912-8.

Random forests for survival data: which methods work best and under what conditions?

Few systematic comparisons of methods for constructing survival trees and forests exist in the literature. Importantly, when the goal is to predict a survival time or estimate a survival function, the optimal choice of method is unclear. We use an extensive simulation study to systematically investigate various factors that influence survival forest performance - forest construction method, censoring, sample size, distribution of the response, structure of the linear predictor, and presence of correlated or noisy covariates. In particular, we study 11 methods that have recently been proposed in the literature and identify 6 top performers. We find that all the factors that we investigate have significant impact on the methods' relative accuracy of point predictions of survival times and survival function estimates. We use our results to make recommendations for which methods to use in a given context and offer explanations for the observed differences in relative performance.

Comparative Analysis of Instrumental Variables on the Assignment of Buprenorphine/Naloxone or Methadone for the Treatment of Opioid Use Disorder.

BACKGROUND: Instrumental variable (IV) analysis provides an alternative set of identification assumptions in the presence of uncontrolled confounding when attempting to estimate causal effects. Our objective was to evaluate the suitability of measures of prescriber preference and calendar time as potential IVs to evaluate the comparative effectiveness of buprenorphine/naloxone versus methadone for treatment of opioid use disorder (OUD). METHODS: Using linked population-level health administrative data, we constructed five IVs: prescribing preference at the individual, facility, and region levels (continuous and categorical variables), calendar time, and a binary prescriber's preference IV in analyzing the treatment assignment-treatment discontinuation association using both incident-user and prevalent-new-user designs. Using published guidelines, we assessed and compared each IV according to the four assumptions for IVs, employing both empirical assessment and content expertise. We evaluated the robustness of results using sensitivity analyses. RESULTS: The study sample included 35,904 incident users (43.3% on buprenorphine/naloxone) initiated on opioid agonist treatment by 1585 prescribers during the study period. While all candidate IVs were strong (A1) according to conventional criteria, by expert opinion, we found no evidence against assumptions of exclusion (A2), independence (A3), monotonicity (A4a), and homogeneity (A4b) for prescribing preference-based IV. Some criteria were violated for the calendar time-based IV. We determined that preference in provider-level prescribing, measured on a continuous scale, was the most suitable IV for comparative effectiveness of buprenorphine/naloxone and methadone for the treatment of OUD. CONCLUSIONS: Our results suggest that prescriber's preference measures are suitable IVs in comparative effectiveness studies of treatment for OUD.

Development and validation of the Kids Disability Screen for children with juvenile idiopathic arthritis: results from the CAPRI Registry.

OBJECTIVE: The aim of this study was to develop and validate a brief disability screen for children with JIA, the Kids Disability Screen (KDS). METHODS: A total of 216 children enrolled in the Canadian Alliance of Pediatric Rheumatology Investigators (CAPRI) Registry in 2017-2018 formed a development cohort, and 220 children enrolled in 2019-2020 formed a validation cohort. At every clinic visit, parents answered two questions derived from the Childhood Health Assessment Questionnaire (CHAQ): 'Is it hard for your child to run and play BECAUSE OF ARTHRITIS?' ('Hard' 0-10), and 'Does your child usually need help from you or another person BECAUSE OF ARTHRITIS?' ('Help', 0-10). We used 36-fold cross-validation and tested nine different mathematical methods to combine the answers and optimize psychometric properties. The results were confirmed in the validation cohort. RESULTS: Expressed as the mean of the two answers, KDS best balanced ease of use and psychometric properties, while a LASSO regression model combining the two answers with other patient characteristics [estimated CHAQ [eCHAQ]) had the highest responsiveness. In the validation cohort, 22.7%, 25.9% and 28.6% of patients had a score of 0 at enrolment for the KDS, eCHAQ and CHAQ, respectively. Responsiveness was 0.67, 0.74 and 0.62, respectively. Sensitivity to detect a CHAQ > 0 was 0.90 and specificity 0.56, KDS detecting some disability in 44% of children with a CHAQ = 0. CONCLUSION: This simple KDS has psychometric properties comparable with those of a full CHAQ and may be used at every clinic visit to identify those children who need a full disability assessment.

Causal pathways to health-related quality of life in children with juvenile idiopathic arthritis: results from the ReACCh-Out cohort.

OBJECTIVE: Structural equation modelling was applied to data from the Research in Arthritis in Canadian Children emphasizing Outcomes (ReACCh-Out) cohort to help elucidate causal pathways to decreased health-related quality of life (HRQoL) in children with JIA. METHODS: Based on published literature and clinical plausibility, a priori models were constructed with explicit root causes (disease activity, treatment intensity) and mediators (pain, disease symptoms, functional impairments) leading to HRQoL [measured by the Quality of my Life (QoML) scale and the Juvenile Arthritis Quality of Life Questionnaire (JAQQ)] at five disease stages: (i) diagnosis, (ii) 3-9 months after diagnosis, (iii) flare, (iv) remission on medications, (v) remission off medications. Following structural equation modelling, a posteriori models were selected based on data fit and clinical plausibility. RESULTS: We included 561, 887, 137, 186 and 182 patients at each stage, respectively. In a posteriori models for active disease stages, paths from disease activity led through pain, functional impairments, and disease symptoms, directly or through restrictions in participation, to decreased QoML scores. Treatment intensity had detrimental effects through psychosocial domains; while treatment side effects had a lesser role. Pathways were similar for QoML and JAQQ, but JAQQ models provided greater specificity. Models for remission stages were not supported by the data. CONCLUSION: Our findings support disease activity and treatment intensity as being root causes of decreased HRQoL in children with JIA, with pain, functional impairments, and participation restrictions being mediators for disease activity; they support psychosocial effects and side effects as being mediators for treatment intensity.

Evaluation of cardiovascular disease risk in individuals with chronic spinal cord injury.

STUDY DESIGN: Multicentre, cross-sectional study. OBJECTIVES: To identify which markers of obesity, injury characteristics and autonomic function variables are related to cardiovascular disease (CVD) risk after spinal cord injury (SCI), and establish cut-points for detection and risk management. SETTING: Eight SCI rehabilitation centres in the Netherlands. METHODS: Individuals (n = 257) with a traumatic, chronic (≥10 years) SCI, with age at injury between 18 and 35 years, completed a self-report questionnaire and a one-day visit to a rehabilitation centre for testing. Three anthropometric measures were tested: body mass index (BMI); waist circumference (WC); and waist-to-height ratio (WHtR). Injury characteristics included: American Spinal Injury Association impairment scale (AIS); duration of injury (DOI); and neurological level of injury (LOI). Cardiovascular autonomic function was assessed from peak heart rate during maximal exercise (HRpeak). Systolic arterial pressure (SAP) and aerobic capacity (VO2peak) were also determined. CVD risk was calculated using the Framingham risk score (FRS). RESULTS: All anthropometric variables were associated with FRS, with WC showing the strongest correlation (r = 0.41, p < 0.001) and greatest area under the curve (0.73) for 10-year CVD risk (%). WC, DOI, SAP, HRpeak, LOI, and VO2peak (variable importance: 0.81, 1.0, 0.98, 0.98, 0.66, 0.68, respectively) were important predictive variables for 10-year CVD risk in individuals with SCI. CONCLUSIONS: We confirm that WC is a simple, practical measure of CVD risk, and along with DOI and markers of cardiovascular autonomic function, plays a role in the increased CVD risk following SCI.

Validation of prediction models of severe disease course and non-achievement of remission in juvenile idiopathic arthritis part 2: results of the Nordic model in the Canadian cohort.

BACKGROUND: Validated clinical prediction models to identify children with poor prognosis at the time of juvenile idiopathic arthritis (JIA) diagnosis would be very helpful for tailoring treatments, and avoiding under- or over-treatment. Our objective was to externally validate Nordic clinical prediction models in Canadian patients with JIA. METHODS: We used data from 513 subjects at the 3-year follow-up from the Research in Arthritis in Canadian Children emphasizing Outcomes (ReACCh-Out) cohort. The predicted outcomes were non-achievement of remission, severe disease course, and functional disability. The Nordic models were evaluated exactly as published and after fine-tuning the logistic regression coefficients using multiple data splits of the Canadian cohort. Missing data was handled with multiple imputation, and prediction ability was assessed with C-indices. C-index values > 0.7 were deemed to reflect helpful prediction. RESULTS: Overall, 81% of evaluable patients did not achieve remission off medications, 15% experienced a severe disease course, and 38% reported disability (CHAQ score > 0). The Nordic model for predicting non-achievement of remission had a C-index of 0.68 (95% CI 0.62-0.74), and 0.74 (0.67-0.80) after fine-tuning. For prediction of severe disease course, it had a C-index of 0.69 (0.61-0.78), and 0.79 (0.68-0.91) after fine-tuning. The fine-tuned Nordic model identified 85% of the cohort as low risk for a severe disease course (< 20% chance) and 7% as high risk (> 60% chance). The Nordic model to predict functional disability had a C-index of 0.57 (0.50-0.63), and 0.51 (0.39-0.63) after fine-tuning. CONCLUSIONS: Fine-tuned Nordic models, combining active joint count, physician global assessment of disease activity, morning stiffness, and ankle involvement, predicted well non-achievement of remission and severe disease course in Canadian patients with JIA. The Nordic model for predicting disability could not predict functional disability in Canadian patients.

Validation of prediction models of severe disease course and non-achievement of remission in juvenile idiopathic arthritis: part 1-results of the Canadian model in the Nordic cohort.

BACKGROUND: Models to predict disease course and long-term outcome based on clinical characteristics at disease onset may guide early treatment strategies in juvenile idiopathic arthritis (JIA). Before a prediction model can be recommended for use in clinical practice, it needs to be validated in a different cohort than the one used for building the model. The aim of the current study was to validate the predictive performance of the Canadian prediction model developed by Guzman et al. and the Nordic model derived from Rypdal et al. to predict severe disease course and non-achievement of remission in Nordic patients with JIA. METHODS: The Canadian and Nordic multivariable logistic regression models were evaluated in the Nordic JIA cohort for prediction of non-achievement of remission, and the data-driven outcome denoted severe disease course. A total of 440 patients in the Nordic cohort with a baseline visit and an 8-year visit were included. The Canadian prediction model was first externally validated exactly as published. Both the Nordic and Canadian models were subsequently evaluated with repeated fine-tuning of model coefficients in training sets and testing in disjoint validation sets. The predictive performances of the models were assessed with receiver operating characteristic curves and C-indices. A model with a C-index above 0.7 was considered useful for clinical prediction. RESULTS: The Canadian prediction model had excellent predictive ability and was comparable in performance to the Nordic model in predicting severe disease course in the Nordic JIA cohort. The Canadian model yielded a C-index of 0.85 (IQR 0.83-0.87) for prediction of severe disease course and a C-index of 0.66 (0.63-0.68) for prediction of non-achievement of remission when applied directly. The median C-indices after fine-tuning were 0.85 (0.80-0.89) and 0.69 (0.65-0.73), respectively. Internal validation of the Nordic model for prediction of severe disease course resulted in a median C-index of 0.90 (0.86-0.92). CONCLUSIONS: External validation of the Canadian model and internal validation of the Nordic model with severe disease course as outcome confirm their predictive abilities. Our findings suggest that predicting long-term remission is more challenging than predicting severe disease course.

Predicting disease severity and remission in juvenile idiopathic arthritis: are we getting closer?

PURPOSE OF REVIEW: To summarize current research on the prediction of severe disease or remission in children with juvenile arthritis, and define further steps needed towards developing prediction tools with sufficient accuracy for clinical use. RECENT FINDINGS: High disease activity, poor patient-reported outcomes, ankle or wrist involvement, and a longer time from onset to the start of treatment herald a severe disease course and a low chance of remission. Other studies confirmed that age less than 7 years and positive ANA are the strongest predictors of uveitis development. Preliminary evidence suggests ultrasound findings may predict flare in patients with clinically inactive disease, and several new biomarkers show promise. A few prediction tools that combine predictors to estimate the chance of remission or a severe disease course in the medium-term to long-term have shown good accuracy when internally validated in the population in which they were developed. SUMMARY: Promising candidate tools for predicting disease severity and long-term remission in juvenile arthritis are now available. These tools need external validation in other populations, and ideally formal trials to assess whether their use in practice improves patient outcomes. We are definitively getting closer, but we are not there yet.

Predicting Which Children with Juvenile Idiopathic Arthritis Will Not Attain Early Remission with Conventional Treatment: Results from the ReACCh-Out Cohort.

OBJECTIVE: To estimate the probability of early remission with conventional treatment for each child with juvenile idiopathic arthritis (JIA). Children with a low chance of remission may be candidates for initial treatment with biologics or triple disease-modifying antirheumatic drugs (DMARD). METHODS: We used data from 1074 subjects in the Research in Arthritis in Canadian Children emphasizing Outcomes (ReACCh-Out) cohort. The predicted outcome was clinically inactive disease for ≥ 6 months starting within 1 year of JIA diagnosis in patients who did not receive early biologic agents or triple DMARD. Models were developed in 200 random splits of 75% of the cohort and tested on the remaining 25% of subjects, calculating expected and observed frequencies of remission and c-index values. RESULTS: Our best Cox logistic model combining 18 clinical variables a median of 2 days after diagnosis had a c-index of 0.69 (95% CI 0.67-0.71), better than using JIA category alone (0.59, 95% CI 0.56-0.63). Children in the lowest probability decile had a 20% chance of remission and 21% attained remission; children in the highest decile had a 69% chance of remission and 73% attained remission. Compared to 5% of subjects identified by JIA category alone, the model identified 14% of subjects as low chance of remission (probability < 0.25), of whom 77% failed to attain remission. CONCLUSION: Although the model did not meet our a priori performance threshold (c-index > 0.70), it identified 3 times more subjects with low chance of remission than did JIA category alone, and it may serve as a benchmark for assessing value added by future laboratory/imaging biomarkers.

Determinants of staff commitment to hip protectors in long-term care: A cross-sectional survey.

BACKGROUND: If worn, certain models of hip protectors are highly effective at preventing hip fractures from falls in residents of long-term care, but modest acceptance and adherence have limited the effectiveness of hip protectors. Residents of long-term care are more likely to accept the initial offer of hip protectors and to adhere to recommendations concerning the use of hip protectors when staff are committed to supporting the application of hip protectors. Yet, we know very little about the nature of and factors associated with staff commitment to hip protectors in long-term care. OBJECTIVE: To identify factors associated with staff commitment to hip protectors in long-term care. DESIGN: A cross-sectional survey. SETTING: Thirteen long-term care homes (total beds = 1816) from a single regional health district in British Columbia, Canada. PARTICIPANTS: A convenience sample of 535 paid staff who worked most of their time (>50% of work hours) at a participating long-term care home, for at least one month, and for at least 8 h per week. We excluded six (1.1%) respondents who were unaware of hip protectors. Of the remaining 529 respondents, 90% were female and 55% were health care assistants. METHODS: Respondents completed the Commitment to Hip Protectors Index to indicate their commitment to hip protectors. We used Bayesian Model Averaging logistic regression to model staff commitment as a function of personal variables, experiences with hip protectors, intraorganizational communication and influence, and organizational context. RESULTS: Staff commitment was negatively related to organizational tenure >20 years (posterior probability = 97%; logistic regression coefficient = -0.28; 95% confidence interval = -0.48, -0.08), and awareness of a padded hip fracture (100%; -0.57; -0.69, -0.44). Staff commitment was positively related to the existence of a champion of hip protectors within the home (100%; 0.24; 0.17, 0.31), perceived quality of intraorganizational communication (100%; 0.04; 0.02, 0.05), extent of mutual respect between residents and staff and perceived contribution to quality of life of the residents they serve (100%; 0.10; 0.05, 0.15), and frequency of transformational leadership practices by respondents' primary supervisors (100%; 0.01; 0.01, 0.02). CONCLUSIONS: We provide novel insight into the factors governing staff commitment to hip protectors in long-term care. Targeting of these factors could improve acceptance and adherence with hip protectors, thereby contributing to enhanced effectiveness of hip protectors to prevent hip fractures in long-term care.

Predicting Which Children with Juvenile Idiopathic Arthritis Will Have a Severe Disease Course: Results from the ReACCh-Out Cohort.

OBJECTIVE: We studied an inception cohort of children with juvenile idiopathic arthritis (JIA) to (1) identify distinct disease courses based on changes over 5 years in 5 variables prioritized by patients, parents, and clinicians; and (2) estimate the probability of a severe disease course for each child at diagnosis. METHODS: Assessments of quality of life, pain, medication requirements, patient-reported side effects, and active joint counts were scheduled at 0, 6, 12, 18, 24, 36, 48, and 60 months. Patients who attended at least 6 assessments were included. Multivariable cluster analysis, r2, and silhouette statistics were used to identify distinct disease courses. One hundred candidate prediction models were developed in random samples of 75% of the cohort; their reliability and accuracy were tested in the 25% not used in their development. RESULTS: Four distinct courses were identified in 609 subjects. They differed in prioritized variables, disability scores, and probabilities of attaining inactive disease and remission. We named them Mild (43.8% of children), Moderate (35.6%), Severe Controlled (9%), and Severe Persisting (11.5%). A logistic regression model using JIA category, active joint count, and pattern of joint involvement at enrollment best predicted a severe disease course (Controlled + Persisting, c-index = 0.87); 91% of children in the highest decile of risk actually experienced a severe disease course, compared to 5% of those in the lowest decile. CONCLUSION: Children in this JIA cohort followed 1 of 4 disease courses and the probability of a severe disease course could be estimated with information available at diagnosis.

Cardiovascular responses to orthostasis and their association with falls in older adults.

BACKGROUND: Orthostatic hypotension (OH) refers to a marked decline in blood pressure when upright. OH has a high incidence and prevalence in older adults and represents a potential intrinsic risk factor for falls in these individuals. Previous studies have not included more recent definitions for blood pressure responses to orthostasis, including initial, delayed, and recovery blood pressure responses. Furthermore, there is little research examining the relationships between cerebrovascular functioning and falling risk. Therefore, we aimed to: (i) test the association between different blood pressure responses to orthostatic stress and retrospective falling history and; (ii) test the association between cerebrovascular responses to orthostatic stress and falling history. METHODS: We tested 59 elderly residents in long term care facilities who underwent a passive seated orthostatic stress test. Beat-to-beat blood pressure and cerebral blood flow velocity (CBFV) responses were assessed throughout testing. Risk factors for falls and falling history were collected from facility records. Cardiovascular responses to orthostasis were compared between retrospective fallers (≥1 fall in the previous year) and non-fallers. RESULTS: Retrospective fallers had larger delayed declines in systolic arterial pressure (SAP) compared to non-fallers (p = 0.015). Fallers also showed poorer early (2 min) and late (15 min) recovery of SAP. Fallers had a greater decline in systolic CBFV. CONCLUSIONS: Older adults with a positive falling history have impaired orthostatic control of blood pressure and CBFV. With better identification and understanding of orthostatic blood pressure impairments earlier intervention and management can be implemented, potentially reducing the associated risk of morbidity and mortality. Future studies should utilize the updated OH definitions using beat-to-beat technology, rather than conventional methods that may offer less accurate detection.

The effect of orthostatic stress type on cardiovascular control.

OBJECTIVES: We aimed to compare the cardiovascular responses of a novel orthostatic stress test, the passive seated orthostatic stress test (PSOST), with those during passive head-up tilt testing (HUTT). We hypothesized that cardiovascular responses during PSOST would be similar to those during HUTT (the 'gold standard'). METHODS: We tested 15 healthy volunteers, who underwent both PSOST and HUTT during one session in a random order. We measured beat-to-beat blood pressure, heart rate, peripheral resistance, stroke volume, cardiac output, and middle cerebral artery blood flow velocity during each test. RESULTS: Blood pressure responses were not significantly different between PSOST and HUTT, except for a significantly lower delayed nadir and 15-min recovery value in systolic arterial pressure during HUTT. HUTT elicited a significantly larger increase in heart rate during all test intervals in comparison with PSOST, as well as a larger decline in stroke volume during almost all test intervals. Responses for the other hemodynamic variables were not significantly different between the tests at any test interval. Repeated HUTT has large inherent variability, which was also evident from the variability in the mean differences on comparing PSOST and HUTT. There was a significant bias for larger heart rate increases (P<0.01) and a greater delayed systolic arterial pressure decline during HUTT. CONCLUSION: We have shown that PSOST and HUTT elicit similar blood pressure and cerebrovascular responses in the early stages of the upright phase. We believe that PSOST is a reasonable surrogate for HUTT in assessing orthostatic hypotension in population groups that are unable to stand for prolonged periods of time.

Isolation and morphological and metabolic characterization of common endophytes in annually burned tallgrass prairie.

Dark septate endophytes (DSE) are common and abundant root-colonizing fungi in the native tallgrass prairie. To characterize DSE fungi were isolated from roots of mixed tallgrass prairie plant communities. Isolates were grouped according to morphology, and the grouping was refined by ITS-RFLP and/or sequencing of the ITS region. Sporulating species of Periconia, Fusarium, Microdochium and Aspergillus were isolated along with many sterile fungi. Leek resynthesis was used to quickly screen for DSE fungi among the isolates. Periconia macro-spinosa and Microdochium sp. formed typical DSE structures in the roots; Periconia produced melanized intracellular microsclerotia in host root cortex, whereas Microdochium produced abundant melanized inter- and intracellular chlamydospores. To further validate the results of the leek resynthesis growth responses of leek and a dominant prairie grass, Andropogon gerardii, were assessed in a laboratory resynthesis system. Leek growth mainly was unresponsive to the inoculation with Periconia or Microdochium, whereas Andropogon tended to respond positively. Select Periconia and Microdochium isolates were tested further for their enzymatic capabilities and for ability to use organic and inorganic nitrogen sources. These fungi tested positive for amylase, cellulase, polyphenol oxidases and gelatinase. Periconia isolates used both organic and inorganic nitrogen sources. Our study identified distinct endophytes in a tallgrass prairie ecosystem and indicated that these endo-phytes can use a variety of complex nutrient sources, suggesting facultative biotrophic and saprotrophic habits.

Coprophenomena in Tourette syndrome.

The aims of this descriptive study were to examine the prevalence and associations of coprophenomena (involuntary expression of socially unacceptable words or gestures) in individuals with Tourette syndrome. Participant data were obtained from the Tourette Syndrome International Database Consortium. A specialized data collection form was completed for each of a subset of 597 consecutive new patients with Tourette syndrome from 15 sites in seven countries. Coprolalia occurred at some point in the lifetime of 19.3% of males and 14.6% of females, and copropraxia in 5.9% of males and 4.9% of females. Coprolalia was three times as frequent as copropraxia, with a mean onset of each at about 11 years, 5 years after the onset of tics. In 11% of those with coprolalia and 12% of those with copropraxia these coprophenomena were one of the initial symptoms of Tourette syndrome. The onsets of tics, coprophenomena, smelling of non-food objects, and spitting were strongly intercorrelated. Early onset of coprophenomena was not associated with its longer persistence. The most robust associations of coprophenomena were with the number of non-tic repetitive behaviors, spitting, and inappropriate sexual behavior. Although coprophenomena are a frequently feared possibility in the course of Tourette syndrome, their emergence occurs in only about one in five referred patients. Because the course and actual impact of coprophenomena are variable, additional prospective research is needed to provide better counseling and prognostic information.

Geographic variation in rodent-flea relationships in the presence of black-tailed prairie dog colonies.

We characterized the relationship between fleas and their rodent hosts in the presence of prairie dog colonies and compared them to adjacent assemblages away from colonies. We evaluated the rodent-flea relationship by quantifying prevalence, probability of infestation, flea load, and intensity of fleas on rodents. As prairie dog burrows provide refugia for fleas, we hypothesized that prevalence, flea load, and intensity would be higher for rodents that are associated with black-tailed prairie dog colonies. Rodents were trapped at off- and on-colony grids, resulting in the collection of 4,509 fleas from 1,430 rodents in six study areas. The rodent community composition varied between these study areas. Flea species richness was not different between prairie dog colonies and the surrounding grasslands (p = 0.883) but was positively correlated with rodent species richness (p = 0.055). Prairie dog colonies did not increase the prevalence of fleas (p > 0.10). Flea loads on rodents did not vary between off- and on-colony grids at three of the study areas (p > 0.10). Based on the prevalence, infestation rates, and flea loads, we identified Peromyscus maniculatus, Onychomys leucogaster, and two Neotoma species as important rodent hosts for fleas and Aetheca wagneri, Orchopeus leucopus, Peromyscopsylla hesperomys, Pleochaetis exilis, and Thrassisfotus as the most important fleas associated with these rodents. Prairie dog colonies did not seem to facilitate transmission of fleas between rodent hosts, and the few rodent-flea associations exhibited significant differences between off- and on-colony grids.

Assessing pitcher and catcher influences on base stealing in Major League Baseball.

A formal statistical analysis is performed to determine the extent to which pitchers and catchers can influence stolen-base attempts and successes. Two response proportions, attempt/opportunity and success/attempt, are modelled separately using mixed-effects logistic regression models applied to situations with a runner on first and other bases empty. Data include the first innings of all Major League Baseball games played between 1978 and 1990, which encompasses over 48,000 opportunities and 9000 attempts. Pitchers and catchers are entered as random effects and various other factors thought to influence stolen-base attempts and successes are entered as fixed effects. Variance components are estimated and hypotheses tests indicate that the population variance components for both pitchers and catchers are significant for both response proportions. The presence of variation among players at the respective positions is interpreted as evidence that stolen-base defence is a real skill exhibited to varying extents by different players. Furthermore, the variance component for pitchers is greater than that for catchers for both response proportions, indicating that pitchers have greater potential to affect stolen-base attempts and successes. Under usual conditions, it is estimated that 95% of pitchers have first-inning stolen-base success/attempt probabilities between 0.50 and 0.84, while 95% of catchers have probabilities between 0.59 and 0.79.

Consumer sensory analysis of organically and conventionally grown vegetables.

Consumers of organically grown fruits and vegetables often believe that these products taste better than conventional produce. However, comparison of produce from supermarket shelves does not permit adequate assessment of this consumer perception, given potentially confounding cultivar and environmental effects. We used replicated side-by-side plots to produce organic and conventional vegetables for consumer sensory studies. In one test, red loose leaf lettuce, spinach, arugula, and mustard greens, grown organically and conventionally, were evaluated for overall liking as well as for intensity of flavor and bitterness. Another consumer test was conducted comparing organically and conventionally grown tomatoes, cucumbers, and onions. Overall, organically and conventionally grown vegetables did not show significant differences in consumer liking or consumer-perceived sensory quality. The only exception was in tomatoes where the conventionally produced tomato was rated as having significantly stronger flavor than the organically produced tomato. However, overall liking was the same for both organic and conventional samples. As conventional tomatoes also were scored marginally significantly higher in ripeness and a positive correlation was found between ratings of flavor intensity and ripeness, the flavor difference observed could not be simply ascribed to the contrasting growing conditions. Consumer panelists in both tests considered organic produce to be healthier (72%) and more environmentally friendly (51%) than conventional produce, while 28% considered organic produce to have better taste. Covariance analysis indicated that consumer demographics affected sensory comparisons of organic and conventional lettuce and cucumbers. Future study is needed to substantiate the influence of segmentation of consumers on their preference for organic food.