Protein tyrosine kinase activity in breast cancer and its relation to prognostic indicators

Tyrosine kinase dependent oncogenes and growth factor receptors are of prognostic importance in breast cancer, but the relation of cytosolic protein tyrosine kinase (PTK) activity to traditional prognostic indicators is poorly defined. We determined cytosolic PTK activity in tumor extracts of 61 women with invasive breast cancer, including 51 primary specimens and 12 nodal or metastatic specimens, 7 women with in situ breast cancer, and 8 control breast specimens. PTK activity (pmol/min/mg) was measured in a dot blot assay using phosphotyrosine antibodies to detect phosphorylated tyrosyl residues in the tissue extracts. Compared with control specimens (mean PTK = 20.5), tyrosine kinase activity was significantly greater in invasive primary cancers (mean PTK = 298.1; p = 0.0008), and nodal/metastatic specimens (mean PTK = 491.5; p = 0.0009). PTK levels of invasive cancers did not correlate with age (p = 0.36), tumor size (p = 0.83), nodal status (p = 0.37), estrogen receptor status (p = 0.66), or progesterone receptor status (p = 0.09). Thus, while tyrosine kinase activity is increased in breast cancer, correlations with traditional prognostic indicators were not found.

Robust analysis of within-unit variances in repeated measurement experiments

The objective of some experiments is to compare the within-unit variances of two or more treatments, products, or techniques. In this situation, a repeated measurement design involving a random effects model, with possibly heterogeneous variances, is appropriate. Under the assumption that the random errors have a normal or a multivariate t-distribution, this design was analyzed in Chinchilli, Esinshart, and Miller (1995, Biometrics 51, 215-216). However, the resulting methodology is quite vulnerable to skewness and outliers. We propose two distribution-free procedures that are quite robust for balanced designs when the number of repeated measurements is the same for all units and for all treatments. We then show how these procedures are modified to handle unbalanced situations. We illustrate the methodology with an example from a trial comparing serum cholesterol measurements from a routine laboratory analyzer with those of a standardized method.

Mobile health lifestyle intervention program leads to clinically significant loss of body weight in patients with NASH

BACKGROUND AIMS

Lifestyle intervention remains the foundation of clinical care for patients with NASH; however, most patients are unsuccessful in enacting sustained behavioral change. There remains a clear unmet need to develop lifestyle intervention programs to support weight loss. Mobile health (mHealth) programs offer promise to address this need, yet their efficacy remains unexplored.

APPROACH RESULTS

We conducted a 16-week randomized controlled clinical trial involving adults with NASH. Patients were randomly assigned (1:1 ratio) to receive Noom Weight (NW), a mHealth lifestyle intervention program, or standard clinical care. The primary end point was a change in body weight. Secondary end points included feasibility (weekly app engagement), acceptability (>50% approached enrolled), and safety. Of 51 patients approached, 40 (78%) were randomly assigned (20 NW and 20 standard clinical care). NW significantly decreased body weight when compared to standard clinical care (-5.5 kg vs. -0.3 kg, p = 0.008; -5.4% vs. -0.4%, p = 0.004). More NW subjects achieved a clinically significant weight loss of ≥5% body weight (45% vs. 15%, p = 0.038). No adverse events occurred, and the majority (70%) of subjects in the NW arm met the feasibility criteria.

CONCLUSIONS

This clinical trial demonstrated that NW is not only feasible, acceptable, and safe but also highly efficacious because this mHealth lifestyle intervention program led to significantly greater body weight loss than standard clinical care. Future large-scale studies are required to validate these findings with more representative samples and to determine if mHealth lifestyle intervention programs can lead to sustained, long-term weight loss in patients with NASH.

Berry Consumption in Relation to Allostatic Load in US Adults: The National Health and Nutrition Examination Survey, 2003-2010

INTRODUCTION

Berries are a rich source of antioxidant polyphenols and other nutrients that are associated with good health. Allostatic load (AL) is an aggregate measure of chronic stress-induced physiological dysregulations across cardiovascular, metabolic, autonomic, and immune systems; the extent of these dysregulations, collectively or in each system, can be characterized by a composite score or a domain score assessed by integrated biomarkers. It was hypothesized that the anti-inflammatory and other effects of berries lower AL. The association was determined between berry consumption and AL composite and domain scores in the 2003-2010 National Health and Nutrition Examination Survey (NHANES).

METHODS

Berry intake was measured using two 24 h dietary recalls collected from US adults in the 2003-2010 NHANES (n = 7684). The association with AL and its specific domains was examined using population weight-adjusted multivariable linear regression.

RESULTS

The mean AL composite scores for consumers of any berries (11.9), strawberries (11.6), and blueberries (11.6), respectively, were significantly lower than nonconsumers (12.3), after fully adjusting for sociodemographic, lifestyle, and dietary confounders. A significant dose-response relationship was determined between greater consumption of total berries, strawberries, and blueberries and lower mean AL composite scores (p-trend < 0.05, for all). Consistently, mean cardiovascular and metabolic domain scores remained significantly lower in the consumers of total berries (mean cardiovascular domain score: 4.73 versus 4.97 for nonconsumers; mean metabolic domain score: 2.97 versus 3.1), strawberries (4.73 versus 4.95; 2.99 versus 3.1), and blueberries (4.6 versus 4.95; 2.92 versus 3.11). Berry consumers also had significantly lower mean AL immune scores (1.52 versus 1.56) and lower mean AL autonomic scores (2.49 versus 2.57) than nonconsumers (initial sample: n = 15,620).

CONCLUSIONS

The current study indicates that consumption of berries lowers the AL composite scores and potentially reduces stress-related disease risks in the US adult population.

Relationship of serum HER-2/neu and serum CA 15-3 in patients with metastatic breast cancer

BACKGROUND

Serum HER-2/neu antigen concentrations have been reported to correlate with increased tumor volume in patients with breast cancer. We measured serum CA 15-3, a surrogate marker of disease burden, and correlated serum CA 15-3 with serum HER-2/neu and analyzed the association of both markers with clinical outcomes.

METHODS

Pretreatment serum samples from 566 patients were retrospectively analyzed from 2 phase III clinical trials of estrogen receptor-positive (ER(+)), ER(-)/progesterone receptor-positive, or ER status unknown metastatic breast cancer patients randomized in two similar studies to receive second-line hormone therapy with either megestrol acetate or an aromatase inhibitor (fadrozole). The extracellular domain of the HER-2/neu (c-erbB-2) oncogene and serum CA 15-3 were measured by ELISA on the Bayer Immuno 1.

RESULTS

Serum HER-2/neu protein was increased in 168 patients (30%), and CA 15-3 was increased in 337 (60%) patients. Serum CA 15-3 and HER-2/neu were weakly correlated (r = 0.39; P <0.0001). The clinical benefit (complete responses plus partial responses plus stable disease) of endocrine therapy was significantly lower in patients with increased serum HER-2/neu. When adjusted for serum HER-2/neu, serum CA 15-3 was not predictive of response rates. The median time to progression was shorter in patients with increased serum HER-2/neu (89 days) compared with patients with normal serum HER-2/neu (176 days). Survival was significantly shorter in patients with increased serum HER-2/neu (513 vs 869 days; P <0.0001) or increased serum CA 15-3 (689 vs 939 days; P <0.0001). This observation was confirmed by multivariate analysis.

CONCLUSIONS

Serum HER-2/neu is a significant independent predictive and prognostic factor in hormone receptor-positive metastatic breast cancer, even when adjusted for tumor burden as measured by CA 15-3. The combination of increased serum HER-2/neu and increased serum CA 15-3 predicts a worse prognosis than does increased CA 15-3 alone.

Evaluating test methods by estimating total error

A common procedure for evaluating a test method by comparison with another, well-accepted method has been to use a repeated measurements design, in which several individual subjects' specimens are assayed with both methods. We propose the use of the intrasubject relative mean square error, which is a function of the intrasubject relative bias and the coefficient of variation of the test method, as a measure of total error. We construct for each individual subject a score that is based on how well an individual's estimate of total error compares with a maximum allowable value. If the individual's score is > 100%, then that individual's estimate of total error exceeds the maximum allowable value. We present a distribution-free statistical methodology for evaluating the sample of scores. This involves the construction of an upper tolerance limit to determine whether the test method yields values of the total error that are acceptable for most of the population with some level of confidence. Our definition of total error is very different from that defined in the National Cholesterol Education Program (NCEP) guidelines. The NCEP bound for total error has three main problems: (a) it incorrectly assumes that the standard error of the estimated relative bias is the test coefficient of variation; (b) it incorrectly assumes that the individual estimated relative biases follow gaussian distributions; (c) it is based on requiring the relative bias of the average individual in the population to lie within prescribed limits, whereas we believe it is more important to require the total error for most of the individuals in the population, say 95%, to lie within prescribed limits.

Comparison of the Toponomes of Alveolar Macrophages From Wild Type and Surfactant Protein A Knockout Mice and Their Response to Infection

Background

Surfactant protein-A (SP-A) plays a critical role in lung innate immunity by regulating alveolar macrophages (AM), expression of inflammatory mediators, and other host defense proteins. The toponome imaging system (TIS), a serial immunostainer, was used to study the AM toponome because it characterizes the localization of multiple markers and identifies marker combinations in each pixel as combinatorial molecular phenotypes (CMPs). We used TIS to study the AM toponome from wild type (WT) and SP-A knockout (KO) mice and changes following Klebsiella pneumoniae exposure.

Methods

WT or KO mice received intratracheal K. pneumoniae or vehicle and AM were obtained by bronchoalveolar lavage after one hour. AM were attached to slides and underwent TIS analysis. Images were analyzed to characterize all pixels. AM CMPs from WT vehicle (n=3) and infected (n=3) mice were compared to each other and to AM from KO (n=3 vehicle; n=3 infected). Histograms provided us with a tool to summarize the representation of each marker in a set of CMPs.

Results

Using the histograms and other tools we identified markers of interest and observed that: 1) Both comparisons had conserved (present in all group members) CMPs, only in vehicle AM and only in infected AM, or common to both vehicle and infected AM, (i.e., unaffected by the condition). 2) the CMP number decreased with infection in WT and KO versus vehicle controls. 3) More infection-specific CMPs in WT vs KO AM. 4) When AM from WT and KO vehicle or infected were compared, there were more unique CMPs exclusive to the KO AM. 5) All comparisons showed CMPs shared by both groups.

Conclusions

The decrease of CMPs exclusive to infected AM in KO mice may underlie the observed susceptibility of KO mice to infection. However, both KO groups had more exclusive CMPs than the corresponding WT groups, perhaps indicating a vigorous effort by KO to overcome deficits in certain proteins and CMPs that are dysregulated by the absence of SP-A. Moreover, the presence of shared CMPs in the compared groups indicates that regulation of these CMPs is not dependent on either infection or the presence or absence of SP-A.

A Retrospective Cohort Study That Examined the Impact of Cannabis Consumption on Long-Term Kidney Outcomes

Background: Cannabis consumption for recreational and medical use is increasing worldwide. However, the long-term effects on kidney health and disease are largely unknown. Materials and Methods: Post hoc analysis of cannabis use as a risk factor for kidney disease was performed using data from the Assessment, Serial Evaluation, and Subsequent Sequelae of Acute Kidney Injury (ASSESS-AKI) study that enrolled hospitalized adults with and without acute kidney injury from four U.S. centers during 2009-2015. Associations between self-reported cannabis consumption and the categorical and continuous outcomes were determined using multivariable Cox regression and linear mixed models, respectively. Results: Over a mean follow-up of 4.5±1.8 years, 94 participants without chronic kidney disease (CKD) (estimated glomerular filtration rate [eGFR] >60 mL/min/1.73 m2) who consumed cannabis had similar rates of annual eGFR decline versus 889 nonconsumers (mean difference=-0.02 mL/min/1.73 m2/year, p=0.9) and incident CKD (≥25% reduction in eGFR compared with the 3-month post-hospitalization measured eGFR and achieving CKD stage 3 or higher) (adjusted hazard ratio [aHR]=1.2; 95% confidence interval [CI]=0.7-2.0). Nineteen participants with CKD (eGFR <60 mL/min/1.73 m2) who consumed cannabis had more rapid eGFR decline versus 597 nonconsumers (mean difference=-1.3 mL/min/1.73 m2/year; p=0.02) that was not independently associated with an increased risk of CKD progression (≥50% reduction in eGFR compared with the 3-month post-hospitalization eGFR, reaching CKD stage 5, or receiving kidney replacement therapy) (aHR=1.6; 95% CI=0.7-3.5). Cannabis consumption was not associated with the rate of change in urine albumin to creatinine ratio (UACR) over time among those with (p=0.7) or without CKD (p=0.4). Conclusions: Cannabis consumption did not adversely affect the kidney function of participants without CKD but was associated with a faster annual eGFR decline among participants with CKD. Cannabis consumption was not associated with changes in UACR over time, incident CKD, or progressive CKD regardless of baseline kidney function. Additional research is needed to investigate the kidney endocannabinoid system and the impact of cannabis use on kidney disease outcomes.

Psychometric properties of the revised internalized skin bias questionnaire

BACKGROUND

The psychological impacts of skin disease are well documented, with patients reporting increased anxiety, depression and poorer quality of life. More recent studies suggest that adverse psychopathology is associated with re-direction of skin-disease-related social stigma towards oneself or internalized skin bias (ISB).

OBJECTIVES

To refine the Internalized Skin Bias Questionnaire (ISBQ) to reflect the construct of ISB with additional skin-specific biases as well as to evaluate its psychometric properties in a diverse sample of individuals with various skin conditions.

METHODS

Two-part observational design including consensus-building surveys among a dermatology expert group and a cross-sectional survey among participants with self-reported dermatological conditions to assess instrument psychometric properties. Eligible participants completed an online survey comprised of the revised ISBQ (ISBQ-R), the Questionnaire on Experiences with Skin Diseases-Short Form (QES-SF), the Dermatology Life Quality Index (DLQI), the Beck Depression Inventory-II (BDI-II) and the Burns Anxiety Inventory (BAI).

RESULTS

Overall, 33 experts participated including 22 (66.7%) dermatologists or dermatology researchers and 11 (33.3%) patients. Except for three items in the first round, all items received high agreement for inclusion from the expert group. The revised survey was completed by 214 participants who identified mostly as female (n = 185; 86.9%), White (n = 182; 85.5%) and non-Hispanic/Latino (n = 200; 93.4%). Adding and modifying new items resulted in an instrument with stronger internal consistency (Cronbach's alpha = 0.92) and a stronger correlation with other existing stigma measures (QES-SF; ρ = 0.72).

CONCLUSIONS

The ISBQ-R is a modified instrument with stronger internal consistency and a stronger correlation with other existing stigma measures. Additionally, the study further expanded upon previous research by exploring a two-factor structure, suggesting that the ISBQ-R could be used as a single- or a dual-factor instrument depending on investigator goals.

Are universal precautions effective in reducing the number of occupational exposures among health care workers? A prospective study of physicians on a medical service

Using a daily questionnaire, we prospectively studied 277 physicians from two hospital medical services for incidents of exposure to blood and body fluids and barrier use before and after the implementation of universal precautions. We found that implementation significantly increased the frequency of barrier use during exposure incidents from 54% before implementation to 73% after implementation of universal precautions. Implementation led to a decrease in the number of exposure incidents that resulted in direct contact with blood and body fluids (actual exposures), from 5.07 to 2.66 exposures per physician per patient care month, and to an increase in averted exposures in which direct contact was prevented by the use of barrier devices, from 3.41 exposures per patient care month before implementation to 5.90 exposures per patient care month after implementation. Implementation affected neither the types of body fluid or procedures involved nor the overall rate of exposure incidents (8.5 per patient care month) but, through an increase in barrier use, it did prevent direct contact with blood and body fluids and thus converted what would have been an actual exposure into an averted one. We conclude that universal precautions were effective in reducing the risk of occupational exposures among physicians on a medical service.

Partial likelihood analysis of within-unit variances in repeated measurement experiments

The objectives of some experiments are to compare the variances of two or more treatments, products, or techniques. If the investigator is more concerned about within-unit variances rather than between-unit variances, then a repeated measurement design is needed. We invoke a random effects model with heterogeneous within-unit variances for certain repeated measurement designs. We do not impose any distributional assumptions for the random effects, whereas we assume either a normal or multivariate t distribution for the random errors. We propose a partial likelihood analysis for population-based inference and individual-based inference. We illustrate the methodology with an example from a trial comparing serum cholesterol measurements from a routine laboratory analyzer to those of a standardized method.

Goodness-of-fit in generalized nonlinear mixed-effects models

In recent years, generalized linear and nonlinear mixed-effects models have proved to be powerful tools for the analysis of unbalanced longitudinal data. To date, much of the work has focused on various methods for estimating and comparing the parameters of mixed-effects models. Very little work has been done in the area of model selection and goodness-of-fit, particularly with respect to the assumed variance-covariance structure. In this paper, we present a goodness-of-fit statistic which can be used in a manner similar to the R2 criterion in linear regression for assessing the adequacy of an assumed mean and variance-covariance structure. In addition, we introduce an approximate pseudo-likelihood ratio test for testing the adequacy of the hypothesized convariance structure. These methods are illustrated and compared to the usual normal theory likelihood methods (Akaike's information criterion and the likelihood ratio test) using three examples. Simulation results indicate the pseudo-likelihood ratio test compares favorably with the standard normal theory likelihood ratio test, but both procedures are sensitive to departures from normality.

Peak expiratory flow in normals: comparison of the mini Wright versus spirometric predicted peak flows

OBJECTIVES

U.S. prediction equation estimated peak flows were obtained spirometrically and may not correctly predict actual peak flows that are obtained using a peak flow meter. The purpose of this investigation was to compare actual Mini Wright peak flows in normal volunteers as compared with spirometric predicted values to determine whether they are similar.

METHODS

Nonsmoking, nonobese adult volunteers with no history of lung disease underwent peak flow testing with an American Thoracic Society (ATS) Mini Wright peak flow meter. All subjects did three peak flows by taking a maximal deep breath and expiring as hard and fast as possible while in the standing position. The best of three efforts was taken as the peak flow value for analysis and compared with prediction equation estimates. The paired t test compared differences between actual and predicted values. The concordance correlation coefficient evaluated whether the actual peak flows were interchangeable with predicted.

RESULTS

Seventy-two volunteers, average age 44 +/- 10 years and mean BMI 25.2 +/- 2.9, were included. The Mini Wright peak flow values of 508 +/- 113 L/min were significantly different than the predicted values of 471 +/- 84 (p < 0.01). The predicted values were reduced on average by 7.3 percent compared to actual values. The concordance correlation coefficient was 0.72 (95% C.I.; 0.60 - 0.80) suggesting the actual and predicted values are not interchangeable.

CONCLUSIONS

The ATS Mini Wright peak flow values are slightly higher than spirometrically derived predicted peak flow values in subjects without lung disease. This suggests that predicted peak flow values should be generated by a peak flow meter and would be higher than current spirometrically predicted values.

Factors associated with pediatric febrile illnesses in 27 countries of Sub-Saharan Africa

BACKGROUND

Evidence on the relative importance of various factors associated with febrile illness in children and their heterogeneity across countries can inform the prevention, identification, and management of communicable diseases in resource-limited countries. The objective of the study is to assess the relative significance of factors associated with childhood febrile illness in 27 sub-Saharan African countries.

METHODS

This cross-sectional study of 298,327 children aged 0 to 59 months assessed the strengths of associations of 18 factors with childhood fevers, using Demographic and Health Surveys (2010-2018) from 27 sub-Saharan African countries. A total of 7 child level factors (i.e., respiratory illness, diarrhea, breastfeeding initiation; vitamin A supplements; child's age; full vaccination; sex), 5 maternal factors (maternal education; maternal unemployment; antenatal care; maternal age, and maternal marriage status) and 6 household factors (household wealth; water source; indoor pollution, stool disposal; family planning needs and rural residence) were assessed. Febrile illness was defined as the presence of fever in 2 weeks preceding the survey.

RESULTS

Among the 298,327 children aged 0 to 59 months included in the analysis, the weighted prevalence of fever was 22.65% (95% CI, 22.31%-22.91%). In the pooled sample, respiratory illness was the strongest factor associated with fever in children (adjusted odds ratio [aOR], 5.46; 95% CI, 5.26-5.67; P < .0001), followed by diarrhea (aOR, 2.96; 95% CI, 2.85-3.08; P < .0001), poorest households (aOR, 1.33; 95% CI,1.23-1.44; P < .0001), lack of maternal education (aOR, 1.25; 95% CI, 1.10-1.41; P < .0001), and delayed breastfeeding (aOR, 1.18; 95% CI, 1.14-1.22; P < .0001. Febrile illnesses were more prevalent in children older than >6 months compared to those 6 months and younger. Unsafe water, unsafe stool disposal, and indoor pollution were not associated with child fever in the pooled analysis but had a large country-level heterogeneity.

CONCLUSIONS

Major causes of fevers in sub-Saharan Africa could be attributed to respiratory infections and possibly viral infections, which should not be treated by antimalarial drugs or antibiotics. Point-of-care diagnostics are needed to identify the pathogenic causes of respiratory infections to guide the clinical management of fevers in limited-resource countries.

Association of pancreatitis with risk of diabetes: analysis of real-world data

Introduction

Diabetes is a major cause of disease burden with considerable public health significance. While the pancreas plays a significant role in glucose homeostasis, the association between pancreatitis and new onset diabetes is not well understood. The purpose of this study was to examine that association using large real-world data.

Materials and methods

Utilizing the IBM® MarketScan® commercial claims database from 2016 to 2019, pancreatitis and diabetes regardless of diagnostic category, were identified using International Classification of Diseases, Tenth Revision [ICD-10] codes. We then performed descriptive analyses characterizing non-pancreatitis (NP), acute pancreatitis (AP), and chronic pancreatitis (CP) cohort subjects. Stratified Cox proportional hazards regression models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CI) of diabetes across the three clinical categories.

Results

In total, 310,962 individuals were included in the analysis. During 503,274 person-years of follow-up, we identified 15,951 incident diabetes cases. While men and women had higher incidence rates of CP and AP-related diabetes, the rates were significantly greater in men and highest among individuals with CP (91.6 per 1000 persons-years (PY)) followed by AP (75.9 per 1000-PY) as compared to those with NP (27.8 per 1000-PY). After adjustment for diabetes risk factors, relative to the NP group, the HR for future diabetes was 2.59 (95% CI: 2.45-2.74) (P<0.001) for the CP group, and 2.39 (95% CI: 2.30-2.48) (P<0.001) for the AP group.

Conclusion

Pancreatitis was associated with a high risk of diabetes independent of demographic, lifestyle, and comorbid conditions.

Biochemical markers of bone turnover in patients with metastatic bone disease

Several biochemical markers of bone formation and bone resorption have recently been developed. These markers have been evaluated for clinical utility in patients with metabolic bone disease, including Paget disease and osteoporosis, and for their potential use in cancer patients whose disease has metastasized to bone. We have evaluated seven markers of bone turnover in the plasma and urine of 94 patients with newly diagnosed or progressive malignancy with and without clinical evidence of bone metastases. As determined by a positive bone scan and (or) bone survey, 30 patients had metastases to bone; 51 patients had metastatic cancer without overt bony involvement; and 13 patients had local disease without bone metastases. To evaluate the predictive value of these markers in the metastatic population, we utilized a "Z-score" and logistic regression analysis to distinguish patients with documented bone metastatic disease from those patients without clinical evidence of bone metastases. The higher the Z-score, the better the marker predicts the presence of bone metastases. With this statistical approach, urine N-telopeptide measurements had the highest Z-score and the most significant association with the probability of bone metastases. Urine deoxypyridinoline was the second most predictive marker of bone metastases. Thus, biochemical markers of bone resorption might be of use to predict the presence of bone metastases in cancer patients and to monitor the efficacy of antiresorptive therapy in patients treated for metastatic bone disease.

Sampling from a skewed population distribution as exemplified by estimation of the creatine kinase upper reference limit

Creatine kinase (EC 2.7.3.2) was measured in sera from 580 females, ages 1-77 years, and 550 males, ages 1-63 years. The distribution of results for male and female groups shows pronounced skewing toward higher values. The observed distribution of results could not be described by any of six mathematical formulas for skewed distributions, an indication of the unsuitability of such formulas to transform these data for parametric analysis. The range of 97.5 percentile estimates produced by six independent samples of 100, 200, and 400 observations randomly selected from a mathematical model defined by the adult female distribution showed progressive narrowing from the 150-380 U/L interval for the samples of 100 observations to 200-265 U/L for the samples of 400 observations; no further improvement was seen when 800 observations were used. The samples of 100 and 200 observations contained extreme value points that might appear as "outliers" but were shown to be valid members of the population distribution when larger sample sizes were collected.

Evaluation of virus neutralization antibody levels in diabetic mutant mice

Experiments were designed to determine whether genetic predisposition to diabetes or overt diabetes in the identical genotype had an effect on the level of neutralization antibodies to coxsackievirus B4 (CB4). Quantitation of neutralization antibody (NT) levels against CB4 was performed using both the 50% endpoint procedure and the multivariate Wilcoxon rank sum test. The results of these experiments demonstrate that the use of the multivariate procedure for the analysis of neutralization antibody levels provides both quantitative and qualitative information not evident when only the classical 50% end point procedure is used. Moreover, when comparison on antibody levels between different groups is being considered, the power of the comparison is markedly greater using the multivariate Wilcoxon rank sum test results. The present report provide an illustration of the difference in the qualitative and quantitative information obtained by the end-point procedure and the more comprehensive multivariate procedure for the analysis of neutralization antibody levels in diabetic mutant mice infected with coxsackievirus B4.

A weighted concordance correlation coefficient for repeated measurement designs

The need to quantify agreement between two raters or two methods of measuring a response often arises in research. Kappa statistics (unweighted and weighted) are appropriate when the data are nominal or ordinal, whereas the concordance correlation coefficient is more appropriate when the data are measured on a continuous scale. We develop weighted product-moment and concordance correlation coefficients which are applicable for repeated measurements study designs. We consider two distinct situations in which the repeated measurements are paired or unpaired over time. We illustrate the methodology with examples comparing (1) two assays for measuring serum cholesterol, (2) two estimates of dietary intake, from a food frequency questionnaire and dietary recalls, and (3) two measurements of percentage body fat, from skinfold calipers and dual energy x-ray absorptiometry.