Biomedical subjects

X Joan Hu

Publications and source records attributed to X Joan Hu.

7 recordsLinked to original sources

PubMed2007

Pseudoscore-based estimation from biased observations.

There are many practical situations where observation of the primary variable Y for individuals in a population is incomplete and depends on some auxiliary variables X that are potentially correlated with Y. We consider parameter estimation for the distribution of Y with the incomplete data, without specifying the underlying association between Y and X. The approach is based on a class of pseudoscore functions using available information of X. We demonstrate the consistency and asymptotic normality of the estimators and study their finite-sample properties in various situations via simulation. The methodology is illustrated by an example involving kindergarten readiness skills in children with sickle cell disease.

Anemia, Sickle Cell↗

PubMed2007

Nonparametric estimation of the mean function of a stochastic process with missing observations.

In an attempt to identify similarities between methods for estimating a mean function with different types of response or observation processes, we explore a general theoretical framework for nonparametric estimation of the mean function of a response process subject to incomplete observations. Special cases of the response process include quantitative responses and discrete state processes such as survival processes, counting processes and alternating binary processes. The incomplete data are assumed to arise from a general response-independent observation process, which includes right-censoring, interval censoring, periodic observation, and mixtures of these as special cases. We explore two criteria for defining nonparametric estimators, one based on the sample mean of available data and the other inspired by the construction of Kaplan-Meier (or product-limit) estimator [J. Am. Statist. Assoc. 53 (1958) 457] for right-censored survival data. We show that under regularity conditions the estimated mean functions resulting from both criteria are consistent and converge weakly to Gaussian processes, and provide consistent estimators of their covariance functions. We then evaluate these general criteria for specific responses and observation processes, and show how they lead to familiar estimators for some response and observation processes and new estimators for others. We illustrate the latter with data from an recently completed AIDS clinical trial.

Acquired Immunodeficiency Syndrome↗

PubMed2004

Natural history of moderate aplastic anemia in children.

BACKGROUND: Moderate aplastic anemia (MAA) in children is a rare, idiopathic condition of bone marrow insufficiency that can resolve spontaneously, persist for months or years, or progress to severe aplastic anemia (SAA). We evaluated the rate of progression to SAA. METHODS: We reviewed the records of 136 children referred for evaluation of bone marrow failure from 1978 to 2002 at St. Jude Children's Research Hospital. MAA was defined by a hypocellular bone marrow (<50%) and 2 or 3 cytopenias (absolute neutrophil count <1,500/mm(3), absolute reticulocyte count <40,000/mm(3), platelet count <100,000/mm(3)) lasting at least 6 weeks. RESULTS: Twenty-four patients met the criteria for MAA. At a median follow-up of 66 months (range, 10-293), 16 patients (67%) progressed to SAA, 5 (21%) had persistent MAA, and 3 (12%) had complete resolution of MAA. No risk factors for progression could be identified. CONCLUSIONS: When childhood MAA is treated with supportive care alone, 2/3 of patients progress to SAA.

Adolescent↗

PubMed2004

In situ diagnosis of central venous catheter-related bloodstream infection without peripheral blood culture.

BACKGROUND: Catheter-related bloodstream infections (CRBIs) are frequent complications of the use of long term central venous catheters (CVCs). Comparative quantitative culture of blood obtained via the CVC and a peripheral vein (PV) is a well-accepted method of diagnosing CRBI; however, an alternative definition for use when a PV culture is not available is desirable. METHODS: A computerized search of patient records identified all positive blood culture results from the St. Jude Children's Research Hospital Microbiology Laboratory between January 1996 and May 2001. Demographic data, catheter information and culture results were abstracted. Sensitivity, specificity, positive predictive value (PPV), and likelihood ratio were calculated for 2 alternative definitions of CRBI. RESULTS: Review of the medical records revealed 136 episodes of bacteremia that were evaluable for alternative definition 1 and 241 episodes that were evaluable for alternative definition 2. In patients with a double lumen CVC, CRBI can be diagnosed by a > or = 5-fold difference in colony-forming units/mL between the 2 lumens (alternative definition 1) with sensitivity, specificity, PPV and likelihood ratio of 61.8, 93.3, 92.2 and 9.22, respectively. In patients with a single or double lumen CVC, CRBI can be diagnosed when the CVC culture yields > or = 100 colony-forming units/mL (alternative definition 2) with sensitivity, specificity, PPV and likelihood ratio of 75.5, 69.1, 79.3, and 2.44, respectively. CONCLUSIONS: Our study suggests that comparison of colony counts from 2 lumens of a double lumen catheter is acceptable for diagnosis of CRBI when a PV culture is not available. Further validation is needed before discontinuing the recommendation to obtain a PV culture.

Adolescent↗

PubMed2002

Durability of response to treatment among antiretroviral-experienced subjects: 48-week results from AIDS Clinical Trials Group Protocol 359.

The 24-week extension of AIDS Clinical Trials Group Protocol 359, a study of human immunodeficiency virus (HIV)-infected, indinavir-experienced patients, was designed to study the durability of "salvage" treatment regimens. Patients received saquinavir in combination with either ritonavir or nelfinavir and, in addition, delavirdine, adefovir, or both. Patients who demonstrated a virologic response at weeks 12-16 were eligible to continue therapy in the extension through week 48. Of the 105 eligible subjects who were enrolled in the extension, 86 (82%) completed 48 weeks, and 49 (57%) of those 86 had HIV RNA levels <or=500 copies/mL at week 48. For these 86 subjects who completed 48 weeks, the median change in CD4 cell count from baseline was +72 cells/mm(3). Greater body weight, higher CD4 cell count, and greater degree of phenotypic susceptibility to indinavir and saquinavir at baseline were significantly associated with durable virologic suppression. These results show that some patients who experience treatment failure can demonstrate durable virologic and immunologic responses with salvage antiretroviral regimens.

Antiviral Agents↗

PubMed2002

Kindergarten readiness skills in children with sickle cell disease: evidence of early neurocognitive damage?

Young children with sickle cell disease are at risk of brain damage, including stroke. We tested the hypothesis that such patients are also at risk of cognitive impairment. We characterized the cognitive ability of kindergarten children to minimize the effect of disease-related school absence. The Memphis City Schools use the Developing Skills Checklist, a teacher-administered test given in the classroom, to assess kindergarten-appropriate skills. Data were obtained for 34 patients, who were matched to controls by gender, race, date of birth, school, and approximate income. Two controls were selected for each patient, and paired t-tests were used to compare patient's scores to composite control scores. Patients scored lower than controls in auditory discrimination (P < .01), and there was a trend (P < .10) toward lower patient scores in language. Deficits cannot be attributed to school absence and may predict academic problems for patients with sickle cell disease.

Anemia, Sickle Cell↗

PubMedDate not supplied

A comparison of calorie and protein intake in hospitalized pediatric oncology patients dining with a caregiver versus patients dining alone: a randomized, prospective clinical trial.

Hospitalization and cancer therapy can contribute to decreased food intake in children and adolescents with cancer, making it a challenge to meet their nutritional needs. The affect of hospitalization and the eating environment for pediatric oncology patients has not been studied very well, and the effect of altering the social aspect of mealtime for hospitalized pediatric oncology patients has not been studied at all. The authors conducted a randomized, prospective clinical trial to determine if hospitalized pediatric oncology patients consume more protein and calories when eating with a family member or when eating alone in their room at mealtime. All food and beverage intake was recorded for 3 consecutive days, and a food service satisfaction survey was completed on Day 3. Food records were analyzed for calorie and protein intake, and surveys were analyzed for patient/parent satisfaction. The study was completed by 200 hospitalized patients and their parent/caregiver. Overall, neither calorie nor protein intake differed significantly between the two groups, but patient/parent satisfaction was significantly higher in the group of patients who dined with their caregiver. By using analysis of variance, the authors found that ideal body weight and years of sickness were significantly associated with calorie and protein intake.

Adolescent↗