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S N Rai

Publications and source records attributed to S N Rai.

10 recordsLinked to original sources
PubMed2005

Testing threshold and hormesis in a random effects dose-response model applied to developmental toxicity data.

Here we describe a random effects threshold dose-response model for clustered binary-response data from developmental toxicity studies. For our model we assume that a hormetic effect occurs in addition to a threshold effect. Therefore, the dose-response curve is based on two components: relationships below the threshold (hormetic u-shaped model) and those above the threshold (logistic model). In the absence of hormesis and threshold effects, the estimation procedure is straightforward. We introduce score tests that are derived from a random effects hormetic-threshold dose-response model. The model and tests are applied to clustered binary data from developmental toxicity studies of animals to test for hormesis and threshold effects. We also compare the score test and likelihood ratio test to test for hormesis and threshold effects in a simulated study.

Animals↗
PubMed2004

Quality of life as conveyed by pediatric patients with cancer.

Quality-of-life instruments have provided important advances in measuring the quality of life of pediatric patients receiving treatment for cancer. However, the bases of these instruments have not included first-hand reports from the patients; thus, these instruments may be conceptually incomplete. We directly solicited from pediatric patients their perspectives regarding their quality of life during treatment for cancer. We conducted two pilot studies: 23 patients (aged 8-15 years) participated in the first, a cross-sectional study; and 13 patients (aged 10-18 years) participated in the second, a 2-year longitudinal study. Data were analyzed by using a semantic-content method, and the following six domains were recognized in data from both of the studies: symptoms, usual activities, social/family interactions, health status, mood, and the meaning of being ill. These domains were compared with those of seven established pediatric oncology quality-of-life instruments, none of which included all six of these domains; the domain most frequently missing was the meaning of being ill domain. Here we present a new definition of the quality of life of pediatric oncology patients that is based on six domains; this definition may ensure the completeness and sensitivity of these important instruments.

Adolescent↗
PubMed2002

Acute health-related quality of life in children undergoing stem cell transplant: II. Medical and demographic determinants.

Medical and demographic variables were examined as predictors of acute health-related quality of life (HRQL), specifically, somatic distress, mood disturbance and activity levels, during the period of bone marrow transplant (BMT) hospitalization, and the transition phase in the months following hospital discharge. The responses of 153 children undergoing BMT were assessed by both parent report and patient self-report in a prospective longitudinal design. Type of transplant, diagnosis, age, gender, and socio-economic status (SES) were examined as predictor variables of patient outcome. Type of transplant, patient age, and SES emerged as significant determinants of patient response. Children undergoing unrelated donor (MUD) transplants experiencing the highest levels of distress, followed by those undergoing matched-sibling BMT, while those undergoing autologous transplant experienced the lowest levels of distress. Younger patients experienced lower levels of distress and better HRQL than older children and adolescents. Although patients from different SES backgrounds appeared very similar at the time of hospital admission, those from lower SES backgrounds demonstrated greater distress and disturbance in HRQL subsequently, and throughout the first 6 months post BMT. These findings help to target specific subgroups of patients that may be in greater need of preventive interventions or more aggressive supportive care.

Adolescent↗
PubMed2002

Acute health-related quality of life in children undergoing stem cell transplant: I. Descriptive outcomes.

There has been little empirical documentation of the acute effects of bone marrow or stem cell transplant (BMT) on children. In the present study, the responses of 153 children undergoing BMT were assessed in a prospective, longitudinal design. Children were assessed at the time of admission for transplant, then underwent weekly assessments to week +6, followed by monthly assessment to month +6. Data were obtained both by parent report and patient report (for patients age 5 and up) using the BASES scales. The major findings are: (1) children undergoing BMT enter the hospital with an already heightened level of distress (defined by high levels of somatic symptoms and mood disturbance, and low levels of activity) that increases dramatically following conditioning, reaching a peak approximately 1 week following transplant; (2) this increased distress is transient, declining rapidly back to admission levels by week +4 to week +5, followed by a further decline to presumed basal levels by months 4-6; and (3) the trajectories of distress depicted by both parent and child report are remarkably similar, each providing confirmatory support for the validity of the findings. These findings confirm a number of widely held clinical impressions that had not previously been documented empirically, and point to the need for new interventions or more intensive approaches to supportive care aimed at reducing levels of distress during the acute phase of transplant.

Adolescent↗
PubMed2000

Hydatid disease in children may have an atypical presentation.

Although there is voluminous literature describing various aspects of hydatid disease in children, little attention has been paid to the small group of patients whose symptoms result in atypical presentation. This article addresses this problem, describing the features in ten children aged from 2 to 12 years. The sites of involvement were within a choledochal cyst (1). the pelvic cavity (1), the spleen (1), and transverse mesocolon. Albendazole was efficacious in the treatment of one recurrent case, as well as in preventing recurrence.

Adolescent↗
PubMed1999

Characterization of uncertainty and variability in residential radon cancer risks.

Radon, a naturally occurring gas found at some level in most homes, is an established risk factor for human lung cancer. The U.S. National Research Council has recently completed a comprehensive evaluation of the health risks of residential exposure to radon and developed models for projecting radon lung cancer risks to the general population. This analysis suggests that radon may play a role in the etiology of 10-15% of all lung cancer cases in the United States, although these estimates are subject to considerable uncertainty. In this article, we present a detailed analysis of uncertainty and variability in estimates of lung cancer risk due to residential exposure to radon. We use a general framework for the analysis of uncertainty and variability that we developed previously. Specifically, we focus on estimates of the age-specific excess relative risk (ERR) and lifetime relative risk (LRR), both of which vary substantially among individuals. We also consider estimates of the population attributable risk (PAR), which reflects the proportion of the lung cancer burden attributable to radon. Variability in the ERR and LRR is largely determined by variability in residential exposure levels and in the dosimetric K-factor used to extrapolate from occupational to environmental settings. Uncertainty in the ERR and LRR is due to uncertainty in the model parameters, notably those reflecting the carcinogenic potency of radon and the modifying effect of attained age. Uncertainty in the PAR is determined by uncertainty about the values of the parameters in the risk models used to estimate the PAR. Uncertainty in radon levels in homes and the dosimetric K-factor contribute comparatively little to uncertainty in the PAR. These results suggest that reduction in uncertainty about the PAR for radon induced lung cancer can only be achieved if more reliable risk projection models can be developed.

Air Pollutants, Radioactive↗
PubMed1998

Uncertainty and variability analysis in multiplicative risk models.

Currently, there is a trend away from the use of single (often conservative) estimates of risk to summarize the results of risk analyses in favor of stochastic methods which provide a more complete characterization of risk. The use of such stochastic methods leads to a distribution of possible values of risk, taking into account both uncertainty and variability in all of the factors affecting risk. In this article, we propose a general framework for the analysis of uncertainty and variability for use in the commonly encountered case of multireplicative risk models, in which risk may be expressed as a product of two or more risk factors. Our analytical methods facilitate the evaluation of overall uncertainty and variability in risk assessment, as well as the contributions of individual risk factors to both uncertainty and variability which is cumbersome using Monte Carlo methods. The use of these methods is illustrated in the analysis of potential cancer risks due to the ingestion of radon in drinking water.

Analysis of Variance↗
PubMed1976

Ecology of microbial population of soils of North Bihar as affected by soil factors.

The determination of the number of bacteria, actinomycetes, and fungi in 72 soil samples of different sugar cane soils in North Bihar (India) and the calculation of the correlations between these values and the content of organic carbon, total nitrogen, total soluble salts, available P2O5, and water-soluble K2O gave these results: 1. Significant and positive correlations were found between the content of organic carbon in the soil and the number of actinomycetes and fungi. 2. Significant and negative correlations were found between the content of water-soluble salts and the number of microorganisms. 3. There is a significant and positive correlatin between the number of bacteria and fungi and the total nitrogen content and and the available P2O5.

Actinomycetales↗