Non-parametric paired two-sample tests for censored survival data incorporating longitudinal covariate information

In this manuscript, we present non-parametric two-sample tests for paired censored survival data incorporating longitudinal covariate information. These tests take advantage of information collected at baseline and post-baseline to provide efficiency gains when censoring is uninformative. Additionally, these methods adjust for potential bias from informative censoring that is captured by the baseline and longitudinal covariates. Finite sample properties are investigated with simulation, and we illustrate methodology with an example from the Early Treatment Diabetic Retinopathy Study. Copyright © 2004 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/55815/1/1888_ftp.pd

Long-Term Effects of G-CSF Therapy in Cyclic Neutropenia

Cyclic neutropenia is a rare hematologic disease that is characterized by regular oscillations in blood neutrophil counts from normal levels (absolute neutrophil count [ANC], \u3e1.5×109 per liter) to severe neutropenia (ANC, \u3c0.2×109 per liter), usually with a cycle length of about 21 days.When patients with this disorder have neutropenia, they often have fever and mouth ulcers and are at risk for severe infections. Cyclic neutropenia is usually an autosomal dominant disorder caused by mutations in the gene encoding neutrophil elastase (ELANE)

Semiparametric Multivariate Accelerated Failure Time Model with Generalized Estimating Equations

The semiparametric accelerated failure time model is not as widely used as the Cox relative risk model mainly due to computational difficulties. Recent developments in least squares estimation and induced smoothing estimating equations provide promising tools to make the accelerate failure time models more attractive in practice. For semiparametric multivariate accelerated failure time models, we propose a generalized estimating equation approach to account for the multivariate dependence through working correlation structures. The marginal error distributions can be either identical as in sequential event settings or different as in parallel event settings. Some regression coefficients can be shared across margins as needed. The initial estimator is a rank-based estimator with Gehan's weight, but obtained from an induced smoothing approach with computation ease. The resulting estimator is consistent and asymptotically normal, with a variance estimated through a multiplier resampling method. In a simulation study, our estimator was up to three times as efficient as the initial estimator, especially with stronger multivariate dependence and heavier censoring percentage. Two real examples demonstrate the utility of the proposed method

Individual variation in levels of haptoglobin-related protein in children from Gabon

Background: Haptoglobin related protein (Hpr) is a key component of trypanosome lytic factors (TLF), a subset of highdensity lipoproteins (HDL) that form the first line of human defence against African trypanosomes. Hpr, like haptoglobin (Hp) can bind to hemoglobin (Hb) and it is the Hpr-Hb complexes which bind to these parasites allowing uptake of TLF. This unique form of innate immunity is primate-specific. To date, there have been no population studies of plasma levels of Hpr, particularly in relation to hemolysis and a high prevalence of ahaptoglobinemia as found in malaria endemic areas. Methods and Principal Findings: We developed a specific enzyme-linked immunosorbent assay to measure levels of plasma Hpr in Gabonese children sampled during a period of seasonal malaria transmission when acute phase responses (APR), malaria infection and associated hemolysis were prevalent. Median Hpr concentration was 0.28 mg/ml (range 0.03-1.1). This was 5-fold higher than that found in Caucasian children (0.049 mg/ml, range 0.002-0.26) with no evidence of an APR. A general linear model was used to investigate associations between Hpr levels, host polymorphisms, parasitological factors and the acute phase proteins, Hp, C-reactive protein (CRP) and albumin. Levels of Hpr were associated with Hp genotype, decreased with age and were higher in females. Hpr concentration was strongly correlated with that of Hp, but not CRP

Prealbumin is Not Sensitive Indicator of Nutrition and Prognosis in Critical Ill Patients

It was reported that 30-50% of inpatients are in a malnutrition status. Measuring the prealbumin level is a sensitive and cost-effective method for assessing the severity of illness in critically or chronically ill patients. However it is uncertain whether or not the prealbumin level correlates with the level of nutrition support and outcomes in critically ill patients. The aim of this study was to evaluate serum prealbumin level as an indicator of the effectiveness of nutrition support and the prognosis in critically ill patients. Forty-four patients who received total parenteral nutrition for more than 7 days at an intensive care unit (ICU) were studied. The serum prealbumin was measured at the initial time of nutrition support and at the almost seventh day since the first measurement. The patients were allocated into two groups. In Group 1 (n=31) and 2 (n=13), the prealbumin level increased and decreased, respectively. Age, APACHE II score, nutrition status, nutritional requirement and amount of supply, mortality, hospital day and ICU day in the two groups were compared. The serum prealbumin level increased in 31 out of the 44 patients. The average calorie intake was 1334 Kcal/day (83% of energy requirement) in Group 1 and 1170 kcal/day (76% of energy requirement) in Group 2 (p=0.131). The mortality was 42% in Group 1 and 54% in Group 2 (p=0.673). The average hospital day/ ICU day in Groups 1 and 2 were 80 days/38 days and 60 days/31 days respectively. In conclusion, in critically ill patients, the serum prealbumin level did not respond sensitively to nutritional support. In addition an increase in the prealbumin level dose not indicate a better prognosis for critically ill patients

Lead exposure and periodontitis in US adults

Lead is known to have significant effects on bone metabolism and the immune system. This study tested the hypothesis that lead exposure affects periodontitis in adults. Material and Methods:  This study used the data from the Third National Health and Nutrition Examination Survey (NHANES III, 1988–94). It analyzed data from 2500 men and 2399 women, 20–56 yr old, who received complete periodontal examination. Periodontitis was defined as the presence of > 20% of mesial sites with ≥ 4 mm of attachment loss. Lead exposure was grouped into three categories:  7 μg/dL. Covariates were cotinine levels, poverty ratio, race/ethnicity, education, bone mineral density, diabetes, calcium intake, dental visit, and menopause (for women). All analyses were performed separately for men and women and considering the effect design. Univariate, bivariate, and stratified analysis was followed by multivariable analysis by estimating prevalence ratios through poisson regression. Results:  After adjustment for confounders, the prevalence ratios, comparing those with a lead blood level of > 7 μg/dL to those with a lead blood level of < 3 μg/dL was 1.70 (95% confidence interval (CI): 1.02, 2.85) for men and 3.80 (95% CI: 1.66, 8.73) for women. Conclusion:  The lead blood level was positively and statistically associated with periodontitis for both men and women. Considering the public health importance of periodontitis and lead exposure, further studies are necessary to confirm this association.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65253/1/j.1600-0765.2006.00913.x.pd