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Biomedical subjects

J Shults

Publications and source records attributed to J Shults.

15 recordsLinked to original sources
PubMed2007

Power analyses for longitudinal study designs with missing data.

Existing methods for power analysis for longitudinal study designs are limited in that they do not adequately address random missing data patterns. Although the pattern of missing data can be assessed during data analysis, it is unknown during the design phase of a study. The random nature of the missing data pattern adds another layer of complexity in addressing missing data for power analysis. In this paper, we model the occurrence of missing data with a two-state, first-order Markov process and integrate the modelling information into the power function to account for random missing data patterns. The Markov model is easily specified to accommodate different anticipated missing data processes. We develop this approach for the two most popular longitudinal models: the generalized estimating equations (GEE) and the linear mixed-effects model under the missing completely at random (MCAR) assumption. For GEE, we also limit our consideration to the working independence correlation model. The proposed methodology is illustrated with numerous examples that are motivated by real study designs.

Adolescent↗
PubMed2006

Childhood onset arthritis is associated with an increased risk of fracture: a population based study using the General Practice Research Database.

BACKGROUND: Childhood onset arthritis is associated with low bone mass and strength. OBJECTIVE: To determine whether childhood onset arthritis is associated with greater fracture risk. METHODS: In a retrospective cohort study all subjects with onset of arthritis between 1 and 19 years of age in the United Kingdom General Practice Research Database were identified. As controls, all sex and age matched subjects from a practice that included a subject with arthritis were included. Incidence rate ratios (IRRs) for first fracture were generated using Mantel-Haenszel methods and Poisson regression. RESULTS: 1939 subjects with arthritis (51% female) and 207 072 controls (53% female) were identified. The median age at arthritis diagnosis was 10.9 years. A total of 129 (6.7%) first fractures were noted in subjects with arthritis compared with 6910 (3.3%) in controls over a median follow up of 3.90 and 3.95 years in the subjects with arthritis and controls, respectively. The IRR (95% confidence interval) for first fracture among subjects with arthritis, compared with controls, according to the age at the start of follow up were 1.49 (0.91 to 2.31) for age <10 years, 3.13 (2.21 to 4.33) at 10-15 years, 1.75 (1.18 to 2.51) at 15-20 years, 1.40 (0.91 to 2.08) at 20-45 years, and 3.97 (2.23 to 6.59) at >45 years. CONCLUSIONS: Childhood onset arthritis is associated with a clinically significant increased risk of fracture in children, adolescents and, possibly, adults. Studies are urgently needed to characterise the determinants of structural bone abnormalities in childhood arthritis and devise prevention and treatment strategies.

Adolescent↗
PubMed2005

A phase II trial of gefitinib with 5-fluorouracil, leucovorin, and irinotecan in patients with colorectal cancer.

Inhibition of epidermal growth factor receptor (EGFR) signalling contributes to the therapy of colorectal cancer. Gefitinib, an oral EGFR tyrosine kinase inhibitor, shows supra-additive growth inhibition with irinotecan and fluoropyrimidines in xenograft models. We designed a study to determine the tolerability and efficacy of gefitinib in combination with irinotecan, infusional 5-fluorouracil (5-FU) and leucovorin (LV), on a 2-week schedule. Among 13 patients with advanced colorectal cancer, 10 required dose reductions of irinotecan and 5-FU because of dehydration, diarrhoea, and neutropenia, seven of whom required hospitalisation, three with neutropenic fever. One patient achieved partial response and seven had disease stabilisation. The combination of this standard chemotherapy regimen with gefitinib is associated with excessive toxicity, suggesting an interaction at a pharmacokinetic or pharmacodynamic level.

Adenocarcinoma↗
PubMed2004

A multicentre randomised controlled trial of an intervention to improve the accuracy of linear growth measurement.

AIMS: To evaluate linear growth assessment and the effect of an intervention on measurement accuracy in primary care practices (PCP) within eight US geographical areas. METHODS: In this multicentre randomised controlled intervention study, paediatric endocrine nurses as site coordinators (SC) visited 55 randomly assigned PCP to evaluate growth assessment of staff performing linear measurements. SC observed 127 measurers assessing a total of 878 children: 307 (baseline), 282 (3 months), and 289 (6 months). Accuracy was determined by SC re-measuring each child with correct technique and equipment. State of the art equipment and a standardised growth training session were provided to the intervention group (IG) following the baseline visit. SC repeated data collection at all PCP at 3 and 6 months. RESULTS: There were no baseline differences between IG and CG equipment, technique, or accuracy; only 30% of measurements were accurate (< or =0.5 cm from SC). Post-intervention, significantly more IG measurements were accurate: IG = 55%, CG = 37% at 3 months; IG = 70%, CG = 34% at 6 months. Odds ratio of accuracy for IG versus CG was 2.1 at 3 months and 4.5 at 6 months. At 6 months, mean difference from the SC measurements was 0.5 cm in IG and 1.1 cm in CG. CONCLUSIONS: In PCP, children are measured inaccurately. Our intervention significantly improved measurement accuracy. Improved accuracy could yield more rapid detection and diagnosis of paediatric growth disorders.

Adolescent↗
PubMed2000

Serum antibody as a marker of protection against natural rotavirus infection and disease.

To determine whether naturally acquired serum IgA and IgG antibodies were associated with protection against rotavirus infection and illness, a cohort of 200 Mexican infants was monitored weekly for rotavirus excretion and diarrhea from birth to age 2 years. Serum samples collected during the first week after birth and every 4 months were tested for anti-rotavirus IgA and IgG. Children with an IgA titer >1:800 had a lower risk of rotavirus infection (adjusted relative risk [aRR], 0.21; P<.001) and diarrhea (aRR, 0. 16; P=.01) and were protected completely against moderate-to-severe diarrhea. However, children with an IgG titer >1:6400 were protected against rotavirus infection (aRR, 0.51; P<.001) but not against rotavirus diarrhea. Protective antibody titers were achieved after 2 consecutive symptomatic or asymptomatic rotavirus infections. These findings indicate that serum anti-rotavirus antibody, especially IgA, was a marker of protection against rotavirus infection and moderate-to-severe diarrhea.

Antibodies, Viral↗
PubMed2000

Outcomes evaluation of a comprehensive intervention program for asthmatic children enrolled in medicaid.

OBJECTIVES: To evaluate health care and financial outcomes in a population of Medicaid-insured asthmatic children after a comprehensive asthma intervention program. DESIGN: Controlled clinical trial. SETTING: Pediatric allergy clinic in an urban, tertiary care children's hospital. SUBJECTS: Eighty children, 2 to 16 years old, with a history of frequent use of emergent health care services for asthma. Intervention. Children in the intervention group received asthma education and medical treatment in the setting of a tertiary care pediatric allergy clinic. An asthma outreach nurse maintained monthly contact with the families enrolled in the intervention group. OUTCOME MEASURES: Emergency department (ED) visits, hospitalizations, and health care charges per patient in the year after enrollment. RESULTS: Baseline demographics did not differ significantly between the 2 groups. In the year before the study, there were no significant differences between intervention and control children in ED visits (mean, 3.5 per patient), hospitalizations (mean,.6 per patient) or health care charges ($2969 per patient). During the study year, ED visits decreased to a mean of 1.7 per patient in the intervention group and 2.4 in controls, while hospitalizations decreased to a mean of.2 per patient in the intervention group and.5 in the controls. Average asthma health care charges decreased by $721/child/year in the intervention group and by $178/patient/year in the control group. CONCLUSIONS: A comprehensive asthma intervention program for Medicaid-insured asthmatic children can significantly improve health outcomes while reducing health care costs.asthma education, health care outcomes, Medicaid, asthma outreach, utilization.

Adolescent↗
PubMed2000

Does candidemia predict threshold retinopathy of prematurity in extremely low birth weight (</=1000 g) neonates?

BACKGROUND: Extreme prematurity is a risk factor for both candidemia and threshold retinopathy of prematurity (ROP) and may confound the reported association between these conditions. OBJECTIVE: To determine if candidemia is an independent risk factor for threshold ROP. METHODS: A cohort study was conducted of infants weighing </=1000 g at birth using a prospectively maintained neonatal database. The study included infants admitted to the neonatal intensive care unit at </=3 days of age between January 1, 1993 and December 31, 1997. We excluded infants not screened for ROP because they died, were discharged, or transferred. Threshold ROP (ie, requiring ablative therapy within 72 hours of diagnosis) was defined by the criteria of the American Academy of Pediatrics Section on Ophthalmology ROP subcommittee. Candidemia was defined as Candida species growth from at least 1 blood culture. Cox proportional hazards regression was used to determine independent risk factors for threshold ROP. RESULTS: Six hundred fourteen infants weighing </=1000 g at birth, of which 165 were excluded: 120 died before ROP screening, 40 were admitted >3 days of age, and 5 were discharged or transferred before ROP screening. A total of 449 infants were included in the study; 58 (13%) developed threshold ROP. Candidemia occurred in 58 (13%) infants before developing the worst stage of ROP. Candidemia occurred in 27 of 73 (37%) at 23 to 24 weeks' gestational age (GA), 25 of 197 (13%) at 25 to 26 weeks' GA, and 6 of 129 (5%) at 27 to 28 weeks' GA, 0 of 50 >28 weeks' GA. Similarly, threshold ROP occurred in 25 of 73 (34%) at 23 to 24 weeks' GA, 26 of 197 (13%) at 25 to 26 weeks' GA, and 6 of 129 (5%) at 27 to 28 weeks' GA, and 1 of 50 (2%) >28 weeks' GA. Threshold ROP developed in 19 of 58 (33%) infants with a history of candidemia and 39 of 391 (10%) without candidemia. Proportional hazards analysis indicated that GA in weeks (hazard ratio =.75; 95% confidence interval [CI]:. 61,.93) and non-black ethnicity (hazard ratio = 1.8; 95% CI: 1.05, 3. 08) were significantly associated with threshold ROP. After controlling for GA and other factors, candidemia did not remain significantly associated with threshold ROP (hazard ratio = 1.6; 95% CI:.89, 2.89). CONCLUSION: Candidemia may not be an independent risk factor for threshold ROP in extremely low birth weight infants. The magnitude of the previously reported association between candidemia and threshold ROP (more than fivefold) is unlikely and much of the clinically observed association appears to be mediated by gestational age.

Candidiasis↗
PubMed2000

Predictors of bacteremia in febrile children 3 to 36 months of age.

PURPOSE: To develop an improved model for the prediction of bacteremia in young febrile children. METHODS: A retrospective review was performed on patients 3 to 36 months of age seen in a children's hospital emergency department between December 1995 and September 1997 who had a complete blood count and blood culture ordered as part of their regular care. Exclusion criteria included current use of antibiotics or any immunodeficient state. Clinical and laboratory parameters reviewed included age, gender, race, weight, temperature, presence of focal bacterial infection, white blood cell count (WBC), polymorphonuclear cell count (PMN), band count, and absolute neutrophil count (ANC). Logistic regression analyses were used to identify factors associated with bacteremia, defined as growth of a pathogen in a blood culture. The model that was developed was then validated on a second dataset consisting of febrile patients 3 to 36 months of age collected from a second children's hospital (validation set). RESULTS: There were 633 patients in the derivation set (46 bacteremic) and 9465 patients in the validation set (149 bacteremic). The mean age of patients in the derivation and validation sets were 15.8 months (95% confidence interval [CI]: 15.2-16.5) and 16.6 months (95% CI: 16.5-16.8), respectively; the mean temperatures were 39.1 degrees C (95% CI: 39. 0-39.2) and 39.8 degrees C (95% CI: 39.7-39.8); 56% were male in the derivation set and 55% male in the validation set. Predictors of bacteremia identified by logistic regression included ANC, WBC, PMN, temperature, and gender. Receiver operator characteristic (ROC) analysis showed similar performance of ANC and WBC as predictors of bacteremia. When placed into a multivariate logistic regression model, band count was not significantly associated with bacteremia. Information regarding focal infection was available for 572 patients in the derivation set. The percentage of patients diagnosed with bacteremia with a focal bacterial infection was not significantly different from the percentage who had bacteremia without a focal bacterial infection (16/200 vs 30/372). Based on this dataset, a logistic regression formula was developed that could be used to develop a unique risk value for each patient based on temperature, gender, and ANC. When the final model was applied to the validation set, the area under the ROC curve (AUC) constructed from these data indicated that the model retained good predictive value (AUC for the derivation vs validation data =.8348 vs 0.8221, respectively). CONCLUSIONS: Use of the formulas derived here allows the clinician to estimate a child's risk for bacteremia based on temperature, ANC, and gender. This approach offers a useful alternative to predictions based on fever and WBC alone.bacteremia, detection, white blood cell.

Age Factors↗
PubMed1999

Efficacy of home-based peer counselling to promote exclusive breastfeeding: a randomised controlled trial.

BACKGROUND: Exclusive breastfeeding is recommended worldwide but not commonly practised. We undertook a randomised controlled study of the efficacy of home-based peer counselling to increase the proportion of exclusive breastfeeding among mothers and infants residing in periurban Mexico City. METHODS: Two intervention groups with different counselling frequencies, six visits (44) and three visits (52), were compared with a control group (34) that had no intervention. From March, 1995, to September, 1996, 170 pregnant women were identified by census and invited to participate in the study. Home visits were made during pregnancy and early post partum by peer counsellors recruited from the same community and trained by La Leche League. Data were collected by independent interview. Exclusive breastfeeding was defined by WHO criteria. FINDINGS: 130 women participated in the study. Only 12 women refused participation. Study groups did not differ in baseline factors. At 3 months post partum, exclusive breastfeeding was practised by 67% of six-visit, 50% of three-visit, and 12% of control mothers (intervention groups vs controls, p<0.001; six-visit vs three-visit, p=0.02). Duration of breastfeeding was significantly (p=0.02) longer in intervention groups than in controls, and fewer intervention than control infants had an episode of diarrhoea (12% vs 26%, p=0.03). INTERPRETATION: This is the first reported community-based randomised trial of breastfeeding promotion. Early and repeated contact with peer counsellors was associated with a significant increase in breastfeeding exclusivity and duration. The two-fold decrease in diarrhoea demonstrates the importance of breastfeeding promotion to infant health.

Breast Feeding↗
PubMed1998

Role of human-milk lactadherin in protection against symptomatic rotavirus infection.

BACKGROUND: Human milk contains a 46 kDa mucin-associated glycoprotein, lactadherin, which binds specifically to rotavirus and inhibits its replication. This study tested the hypothesis that lactadherin protects against symptoms of rotavirus infection. METHODS: 200 infants in Mexico City were recruited at birth and monitored by regular stool EIA for rotavirus, serology, and recording of feeding and stool patterns. Milk samples were obtained from the mothers weekly until 4 weeks post partum then monthly. The sample taken immediately before an infant's episode of rotavirus infection was assayed for lactadherin, butyrophilin, mucin, and secretory IgA. An infection was defined as symptomatic if diarrhoea occurred in the 5 days before or after detection of the virus. FINDINGS: 31 infants developed rotavirus infection; 15 were symptomatic and 16 had no symptoms. The median concentration of lactadherin in the milk samples (obtained 4-41 days [median 13] before the infection) was 48.4 (range 5.6-180) microg/mL in the asymptomatic group and 29-2 (6.2-103-4) microg/mL in the symptomatic group. Although these medians did not differ significantly, in logistic regression analysis adjusted for age at infection and secretory IgA concentration there was a significant difference between the groups (p=0O01). No association between symptom status and concentrations of butyrophilin, mucin, or secretory IgA was found. INTERPRETATION: Protection against rotavirus by human milk is associated with the glycoprotein lactadherin. This association is independent of products of the secretory immune system.

Adult↗
PubMed1996

Prediabetic markers in children with stress hyperglycemia.

BACKGROUND: Previous studies have shown that children with stress hyperglycemia have an increased risk for development of type I or insulin-dependent diabetes mellitus. OBJECTIVE: To determine whether stress hyperglycemia in prospectively screened pediatric patients represents a prediabetic state. DESIGN: Prospective, cohort analytic study. SETTING: The Children's Hospital of the King's Daughters is an urban pediatric emergency department at a tertiary care, university-based children's hospital in Norfolk, Va. PATIENT POPULATION: All patients who required a venipuncture for evaluation of an acute illness or injury from October 1992 through March 1993 were screened prospectively for hyperglycemia (blood glucose level > or = 8.3 mmol/L [> or = 150 mg/dL]). Each hyperglycemic patient was age matched to a stress control subject (defined as a nonhyperglycemic but acutely ill child) from the emergency department and a healthy control subject from a well-child clinic. INTERVENTION: Blood samples were obtained at the time of initial evaluation in the emergency department from 30 hyperglycemic patients (age range, 4 weeks to 12.4 years; median, 2 years), 30 stress control subjects, and 30 healthy control subjects. All samples were tested for islet cell antibodies, insulin autoantibodies, glutamic acid decarboxylase (GAD) antibodies, and HLA typing, specifically the genotypes at the DQB1 gene. MAIN OUTCOME MEASURES: The presence of immunologic or genetic markers for insulin-dependent diabetes mellitus and/or the clinical development of insulin-dependent diabetes mellitus. RESULTS: No patients or control subjects were positive for islet cell antibodies. One hyperglycemic patient and 3 stress control subjects were positive for insulin autoantibodies; all 4 of these subjects had sickle-cell disease and fever. Four of the 8 patients with sickle-cell disease had insulin autoantibodies, compared with none of the 52 patients and stress control subjects without sickle-cell disease (P < .001). One healthy control subject had antibodies to GAD65. The patient group did not show increased genotypes at the DQB1 gene that were indicative of an enhanced risk for insulin-dependent diabetes mellitus. Of the 32 hyperglycemic patients, 27 healthy control subjects, and 25 stress control subjects contacted for follow-up at 31 to 36 months, none has developed insulin-dependent diabetes mellitus. CONCLUSIONS: Children with stress hyperglycemia do not have an increased prevalence of immunologic or genetic markers of insulin-dependent diabetes mellitus and thus do not appear to be at an increased risk for development of insulin-dependent diabetes mellitus. Our data suggest that insulin autoantibodies develop in children subject to sickle cell crises.

Acute Disease↗
PubMed1994

Prevalence of stress hyperglycemia among patients attending a pediatric emergency department.

OBJECTIVE: To determine the prevalence and clinical characteristics associated with stress hyperglycemia among children and adolescents attending a pediatric emergency department. DESIGN: Patients who required a venipuncture for evaluation of an acute illness or injury from October 1992 to March 1993 in an urban pediatric emergency department were enrolled and screened prospectively for hyperglycemia (glucose level > or = 8.3 mmol/L; > or = 150 mg/dl). Data were collected regarding demographic characteristics, history, clinical findings, and admission status. RESULTS: A total of 926 patients ranging in age from 3 days to 21 years were enrolled. Blood glucose values ranged from 1.94 mmol/L (35 mg/L) to 14.65 mmol/L (264 mg/dl); 35 patients (3.8%) had hyperglycemia. The prevalence of stress hyperglycemia was significantly increased among patients if they (1) had temperatures greater than 39.5 degrees C (9.3%) versus normal temperatures (2.8%) (p < 0.001), (2) had been admitted to a critical care unit of the hospital (24.1%) or to any hospital unit (4.4%) versus not having been admitted (2.6%) (p < 0.001), and (3) had received fluids intravenously (6.0%) versus having received no fluids intravenously (2.7%) (p = 0.014). CONCLUSIONS: Stress hyperglycemia is a frequent clinical occurrence in a pediatric emergency department. It does not appear to be associated with a particular diagnostic category but is significantly associated with severity of illness as measured by elevated temperature, hospital admission, and hydration status.

Adolescent↗
PubMed1993

Prevalence of von Willebrand disease in children: a multiethnic study.

OBJECTIVE: Von Willebrand disease (vWD) was thought to be a rare disorder until a recent survey reported a prevalence of 0.8% in an ethnically homogenous community in northern Italy. The purpose of this study was to determine the prevalence of vWD in an ethnically heterogenous population. METHODS: Von Willebrand factor (vWF) was measured by the ristocetin cofactor method in 600 healthy children, aged 2 to 18 years, seen for routine school physical examinations in a three-state region. Personal and family bleeding symptoms were determined by questionnaire. The diagnosis of vWD required a personal history of bleeding symptoms, an abnormal vWF activity concentration, and a family history of at least one immediate family member with bleeding symptoms. RESULTS: A total of 315 subjects were white, 212 were black, 16 were Hispanic, 10 were from other groups, and 47 were biracial. Eight subjects (four black, four white) met the criteria for vWD, for a prevalence of 1.3%. Seven subjects with vWD had blood group O (mean vWF = 32 U/dl; range, 10 to 42 U/dl), and one had blood group A (vWF = 41 U/dl). Children who had blood group O had significantly (p < 0.001) lower vWF activities (median, 83 U/dl, range, 43 to 162 U/dl) than those from non-O blood groups (median, 98 U/dl; range, 51 to 190 U/dl). There were no significant differences in vWF activity by ethnicity. The vWF activity was significantly (p < 0.02) greater for boys than girls in both blood groups. CONCLUSION: Von Willebrand disease is the most common congenital hemostatic disorder; its high prevalence is not limited to one ethnic group.

Adolescent↗