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J B Carlin

Publications and source records attributed to J B Carlin.

At least 37 records · Page 2Linked to original sources
PubMed2001

Epidemiological patterns of rotaviruses causing severe gastroenteritis in young children throughout Australia from 1993 to 1996.

Rotavirus strains that caused severe diarrhea in 4,634 (2,533 male) children aged less than 5 years and admitted to major hospitals in eight centers throughout Australia from 1993 to 1996 were subject to antigenic and genetic analyses. The G serotypes of rotaviruses were identified in 81.9% (3,793 of 4,634) children. They included 67.8% (from 3,143 children) serotype G1 isolates (containing 46 electropherotypes), 11.5% (from 531 children) serotype G2 isolates (27 electropherotypes), 0.8% (from 39 children) serotype G3 isolates (8 electropherotypes), and 1.6% (from 76 children) serotype G4 isolates (9 electropherotypes). G6 (two strains) and G8 (two strains) isolates were identified during the same period. G1 serotypes were predominant in all centers, with intermittent epidemics of G2 serotypes and sporadic detection of G3 and G4 strains. With the exception of two strains (typed as G1P2A[6] and G2P2A[6]) all serotype G1, G3, and G4 strains were P1A[8] and all serotype G2 strains were P1B[4]. Two contrasting epidemiological patterns were identified. In all temperate climates rotavirus incidence peaked during the colder months. The genetic complexity of strains (as judged by electropherotype) was greatest in centers with large populations. Identical electropherotypes appeared each winter in more than one center, apparently indicating the spread of some strains both from west to east and from east to west. Centers caring for children in small aboriginal communities showed unpredictable rotavirus peaks unrelated to climate, with widespread dissemination of a few rotavirus strains over distances of more than 1,000 km. Data from continued comprehensive etiological studies of genetic and antigenic variations in rotaviruses that cause severe disease in young children will serve as baseline data for the study of the effect of vaccination on the incidence of severe rotavirus disease and on the emergence of new strains.

Australia↗
PubMed2001

Interlobar differences in bronchoalveolar lavage fluid from children with cystic fibrosis.

Bronchoalveolar lavage (BAL) performed in specialist centres has improved the understanding of infant cystic fibrosis (CF) lung disease. As most researchers sample from a single lobe, it was determined whether BAL results could be generalized to other lung segments. Thirty-three CF children, aged 1.5-57 months, underwent in random order sequential BAL of their right middle and lingula lobes. Specimens from each lobe had separate quantitative bacteriology, cytology and cytokine analysis. Bacterial counts > or = 1 x 10(5) colony forming units (cfu) x mL(-1) were observed in nine (27%) subjects, including six involving only the right middle lobe. These six children had similar inflammatory indices in their right middle and lingula lobes, and interleukin (IL)-8 concentrations in the latter were significantly higher than that observed within the lingula lobes of the 24 CF children with bacterial counts < 1 x 10(5) cfu x mL(-1). Lingula neutrophil and IL-8 levels correlated best with right middle lobe bacteria numbers. This observational study in cystic fibrosis children suggests that while inflammation is detected in both lungs, bacterial distribution may be more inhomogeneous. Bronchoalveolar lavage microbiological findings from a single lobe may therefore, not be generalized to other lung segments. When performing bronchoalveolar lavage in cystic fibrosis children, it is important to sample from multiple sites.

Bronchoalveolar Lavage Fluid↗
PubMed2000

Anticonvulsant teratogenesis 4: inter-rater agreement in assessing minor physical features related to anticonvulsant therapy.

BACKGROUND: We report on inter-rater agreement in the assessment of newborn infants with respect to a range of minor physical features in a cohort study of the fetal effects of maternal anticonvulsant use during pregnancy. METHODS: Infants from three groups (exposed to anticonvulsants, seizure history but no medication exposure, and unexposed controls) were examined by both a pediatrician/teratologist, who was blinded with respect to the mother's exposure status, and an unblinded research assistant. Agreement on assessments for selected anomalies associated with anticonvulsant therapy was measured by kappa-statistics, as well as by more sensitive log-linear modeling techniques, which allow examination of possible covariate effects on the strength of agreement. Although the physician and research assistant agreed on a high proportion of cases (80-90%), kappa values were modest (0.2-0. 5), partly because of the low prevalence of the anomalies considered. To explore how agreement varies within subgroups, we used recently developed methods for studying agreement based on log-linear models. RESULTS: Log-linear modeling indicated that there was substantial variation in pattern of agreement between different individual research assistants but that other factors (e.g., exposure category, sex, and birthweight) did not appear to be related to agreement. Our results suggest that research assistants with more experience showed the highest degree of agreement with the physicians. CONCLUSIONS: Our results have implications for both clinical practice and epidemiologic research and underline the importance of thorough training of staff in the definitions to be used and also the need for multiple independent assessments of these subtle anomalies.

Abnormalities, Drug-Induced↗
PubMed2000

Adolescent depressive disorder: a population-based study of ICD-10 symptoms.

OBJECTIVE: Earlier studies have suggested that symptoms of depressive disorder in adolescents may differ from those found in adults. Even so, diagnostic criteria developed in adults have come to be widely applied to younger subjects. This study examines the frequency of ICD-10 symptoms in depressive disorder and their association with severity in a large community sample of adolescents aged 15 to 18 years. METHOD: A six-wave prospective study of adolescent health and emotional wellbeing in 2032 Australian secondary school students provided an opportunity to conduct a two-phase study of adolescent onset depression. A self-administered computerised form of the revised Clinical Interview Schedule (CIS-R) was used as a first phase diagnostic measure. Second phase assessment using the Composite International Diagnostic Interview (CIDI) allowed the delineation of a group fulfilling criteria on both instruments. The ICD-10 symptoms and severity profiles for depression were generated with standard algorithms. RESULTS: 1947 (95.8%) out of 2032 subjects in the designated sample completed phase 1 assessment at least once. Participation rates at phase 2 interviews were 93%. Over the 30-month study period 69 subjects (10 male, 59 female) fulfilled criteria for ICD-10 depressive episodes on both the CIS-R and CIDI. Thirty-one per cent (n = 21) had experienced a severe episode, 46% (n = 32) moderate and 23% (n = 16) mild episodes. Loss of interest and pleasure, decreased energy and fatigue, sleep disturbance, suicidal ideation and diminished concentration most clearly distinguished adolescents with depressive disorder from controls. Self-reproach and guilt, psychomotor agitation and/or retardation and appetite disturbance with weight change showed the clearest increase in frequency with increasing severity of episode. The somatic syndrome was reported by close to one in three of those with a severe depressive episode, but was uncommon in those with mild and moderate episodes. CONCLUSIONS: The ICD-10 diagnostic criteria are applicable to depressive disorder in older adolescents. With the exception of depressed mood, found in one in five non-cases, all other symptoms were common in cases and uncommon in non-cases. Practitioner awareness of symptoms indicating the presence and severity of disorder should enhance early identification and choice of treatment in adolescent depression.

Adolescent↗
PubMed2000

Association between allergy and asthma from childhood to middle adulthood in an Australian cohort study.

A cohort of 378 asthmatic children was studied from 7 to 35 yr of age at 7-yr intervals. On selection for inclusion in the study sample, the children had a wide range of severity of wheezing. At each 7-yr review, asthma severity, the presence of eczema or hay fever, and skin test reactivity to house dust mite or rye grass were recorded by questionnaire or clinical interview. We report on the course of asthma and these atopic conditions over the study period and discuss associations between the two phenomena. The presence of an atopic condition in childhood was found to increase the odds of more severe asthma in later life (odds ratio [OR] = 1.66, 95% confidence interval [CI]: 1.17 to 2.36 in the case of eczema; OR = 1. 39, 95% CI: 1.00 to 1.92 for hay fever; and OR = 2.25, 95% CI: 1.49 to 3.39 for skin test reactivity). Additionally, the odds of eczema and hay fever in later life increased with severity of asthma in childhood. The findings of this study provide substantially new quantitative information on the extent of association between asthma and atopic conditions from childhood into middle adulthood.

Adolescent↗
PubMed2000

Evidence for genetic associations between asthma, atopy, and bronchial hyperresponsiveness: a study of 8- to 18-yr-old twins.

We measured asthma in the last 12 mo, diagnosed by a respiratory physician at interview; atopy, defined by a positive skin prick test to any of eight common allergens; and bronchial hyperresponsiveness (BHR) to hypertonic saline, in 381 twin pairs aged 8 to 18 yr selected from the Australian Twin Registry-183 monozygous (MZ) and 198 dizygous (DZ). The associations between twins, as measured by an odds ratio, were greater in MZ pairs compared with DZ pairs for asthma: 25.6 (95% confidence interval 11.3- 57.8) versus 1.9 (1.0-3. 5); atopy: 14.6 (7.1-30.1) versus 2.5 (1.4- 4.5); and BHR: 14.1 (6. 4-31.0) versus 4.2 (2.1-8.6) (all p < 0.002). The associations between each pair of traits within an individual were slightly greater than the association between one trait in a twin and the other trait in the cotwin (cross-trait cross-pair) in MZ pairs. Further, the associations in MZ pairs were greater than in DZ pairs (p < 0.05). Under the assumptions of the classic twin model, these data suggest that the strong cross-sectional associations between these three traits are due to an overlap between the genetic factors involved in each of these three traits.

Adolescent↗
PubMed1999

Analysis of binary outcomes in longitudinal studies using weighted estimating equations and discrete-time survival methods: prevalence and incidence of smoking in an adolescent cohort.

Longitudinal studies are increasingly popular in epidemiology. In this tutorial we provide a detailed review of methods used by us in the analysis of a longitudinal (multiwave or panel) study of adolescent health, focusing on smoking behaviour. This example is explored in detail with the principal aim of providing an introduction to the analysis of longitudinal binary data, at a level suited to statisticians familiar with logistic regression and survival analysis but not necessarily experienced in longitudinal analysis or estimating equation methods. We describe recent advances in statistical methodology that can play a practical role in applications and are available with standard software. Our approach emphasizes the importance of stating clear research questions, and for binary outcomes we suggest these are best organized around the key epidemiological concepts of prevalence and incidence. For prevalence questions, we show how unbiased estimating equations and information-sandwich variance estimates may be used to produce a valid and robust analysis, as long as sample size is reasonably large. We also show how the estimating equation approach readily extends to accommodate adjustments for missing data and complex survey design. A detailed discussion of gender-related differences over time in our smoking outcome is used to emphasize the need for great care in separating longitudinal from cross-sectional information. We show how incidence questions may be addressed using a discrete-time version of the proportional hazards regression model. This approach has the advantages of providing estimates of relative risks, being feasible with standard software, and also allowing robust information-sandwich variance estimates.

Adolescent↗
PubMed1999

Onset of adolescent eating disorders: population based cohort study over 3 years.

OBJECTIVE: To study the predictors of new eating disorders in an adolescent cohort. DESIGN: Cohort study over 3 years with six waves. SUBJECTS: Students, initially aged 14-15 years, from 44 secondary schools in the state of Victoria, Australia. OUTCOME MEASURES: Weight (kg), height (cm), dieting (adolescent dieting scale), psychiatric morbidity (revised clinical interview schedule), and eating disorder (branched eating disorders test). Eating disorder (partial syndrome) was defined when a subject met two criteria for either anorexia nervosa or bulimia nervosa according to the Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV). RESULTS: At the start of the study, 3.3% (29/888) of female subjects and 0.3% (2/811) of male subjects had partial syndromes of eating disorders. The rate of development of new eating disorder per 1000 person years of observation was 21.8 in female subjects and 6.0 in male subjects. Female subjects who dieted at a severe level were 18 times more likely to develop an eating disorder than those who did not diet, and female subjects who dieted at a moderate level were five times more likely to develop an eating disorder than those who did not diet. Psychiatric morbidity predicted the onset of eating disorder independently of dieting status so that those subjects in the highest morbidity category had an almost sevenfold increased risk of developing an eating disorder. After adjustment for earlier dieting and psychiatric morbidity, body mass index, extent of exercise, and sex were not predictive of new eating disorders. CONCLUSIONS: Dieting is the most important predictor of new eating disorders. Differences in the incidence of eating disorders between sexes were largely accounted for by the high rates of earlier dieting and psychiatric morbidity in the female subjects. In adolescents, controlling weight by exercise rather than diet restriction seems to carry less risk of development of eating disorders.

Adolescent↗
PubMed1999

Likelihood-based approach to estimating twin concordance for dichotomous traits.

Genetic epidemiologists are well aware that the casewise and pairwise twin concordances are two different measures. In determining appropriate estimators for each of these measures, the method of ascertainment must be considered. Here, we derive expressions for the concordance estimators and their asymptotic variances appropriate to different twin ascertainment schemes using a likelihood framework, and apply these formulas to existing data. We emphasize the distinction between concordance measures (i.e., the parameters of interest) and the concordance estimators based on the number of pairs observed. Under random or complete ascertainment the casewise estimator is asymptotically unbiased for the casewise concordance, and the pairwise estimator is asymptotically unbiased for the pairwise concordance. Under incomplete ascertainment, the casewise estimator is biased for the casewise concordance, the pairwise estimator is biased for the pairwise concordance, but the probandwise estimator is asymptotically unbiased for the casewise concordance. One can extend the likelihood equations presented here to allow the concordance parameter of interest to depend on zygosity and, if measured, other factors such as cohabitation status and similarity for genetic markers, while concurrently allowing the disease prevalence to depend on measured covariates.

Humans↗
PubMed1999

A computerised screening instrument for adolescent depression: population-based validation and application to a two-phase case-control study.

Computer-administered questionnaires have been little explored as a potentially effective and inexpensive alternative to pencil and paper screening tests. A self-administered computerised form of the revised Clinical Interview Schedule (CIS-R) was compared with the Composite International Diagnostic Interview (CIDI) in a two-phase study of 2032 Australian high school students (mean age 15.7 years) drawn from a stratified random sample of 44 schools in the state of Victoria, Australia. Prevalence, sensitivity and specificity were estimated using weighting to compensate for the two-phase sampling. Point prevalence estimates of depression using the CIS-R were 1.8% for males and 5.6% for females--an overall prevalence of 3.2%. Prevalence estimates for depression in the past 6 months using the CIDI were 5.2% for males and 16.9% for females--an overall estimate of 12.1%. The CIS-R had a positive predictive value (PPV) of 0.49 and negative predictive value (NPV) of 0.91 for CIDI depression in the past 6 months. Specificity was very high (0.97) but sensitivity low (0.18), indicating that a majority of those with a CIDI-defined depressive episode in the past 6 months were not recognised at a single screening using the CIS-R. Even so, the CIS-R has proved at least as good as any pencil and paper questionnaire in identifying cases for nested case-control studies of adolescent depression. Further exploration of strategies such as serial screening to enhance sensitivity is warranted.

Adolescent↗
PubMed1999

Sample-size calculation for a log-transformed outcome measure.

The outcome measure of interest in clinical trials sometimes requires transformation to the logarithmic scale for analysis. This paper examines sample-size calculation for both independent groups and matched-pairs trials for log-transformed outcomes. For both types of trial, we demonstrate how the calculation can be formulated in terms of a relative treatment effect and a statement of relative variability, both specified on the original scale of measurement. For a comparison of two independent groups, the relative treatment effect is the ratio of group geometric means (or alternatively, group arithmetic means) and the coefficient of variation is used as a summary of relative variability. For a matched-pairs comparison, the appropriate relative treatment effect is the geometric mean of the within-pair ratios, and relative variability can be specified as an upper bound on within-pair ratios under a null hypothesis of the relative effect being equal to 1 (i.e., no difference). We discuss the clinical study that motivated this work and demonstrate the application of the sample-size calculation to this study.

Algorithms↗
PubMed1999

High- or low- technology measurements of energy expenditure in clinical gait analysis?

The repeatability of energy-expenditure measurements were studied in five children and four adults without disabilities using the Cosmed K4 (high technology). The ability to detect change in measurements was compared between this instrument and the Physiological Cost Index (PCI; low technology). The results of repeatability (95% range) for oxygen cost were 13.1% in children and 13% in adults. In contrast, the SD of PCI was 6 to 72% of the mean in adults and wider in children (91%; 95% range). The validity of PCI as an outcome measure was questioned. In addition, 177 children with motor disability were prospectively studied using the Cosmed K4. Previous experience with the Cosmed K2 (intermediate technology) helped to develop a practical and repeatable protocol for testing children with disability using the Cosmed K4. The protocol commenced with 5 minutes of rest to achieve baseline values of heart rate and oxygen consumption, followed by 10 minutes of continuous walking at a self-selected speed on a 10-metre level oval walking track. The test concluded with 5 minutes of rest to monitor the return to baseline values. Ninety-one percent of the children with disability quickly reached a steady-state of oxygen consumption and carbon-dioxide production. The carbon-dioxide sensor in the Cosmed K4 has enabled a new group of severely involved children with cerebral palsy (9%) to be defined. These children have been termed 'physiologically marginal ambulators'.

Adult↗
PubMed1999

Cost effectiveness of rotavirus vaccination in Australia.

OBJECTIVE: Rotavirus gastroenteritis causes substantial morbidity, including hospital admission, in young children. In the context of recent vaccine developments, this study aimed to estimate the cost-effectiveness of a rotavirus vaccination program in Australia. METHOD: Standard methods of health economic evaluation were used to assess the total cost of rotavirus immunisation (as the difference between estimated vaccination program costs and the cost of disease that would be avoided by immunisation) and relate this to the number of cases of disease that would be prevented. Estimates were made from both societal and health care systems perspectives. RESULTS: Based on Australian data on disease incidence and cost of hospitalisation, the current annual cost of rotavirus disease is about $26.0 million. Using conservative vaccine efficacy estimates, current immunization uptake rates and a cost of $30 per dose of vaccine, rotavirus immunisation would incur a net societal cost of $2.9 million ($11 per child), at a gross program cost of $21.6 million. These estimates are sensitive to two sources of uncertainty in the estimation of program delivery costs: vaccine price and whether separate immunization visits would be required. CONCLUSION: A rotavirus immunisation program would be cost-neutral to Australian society at a vaccine price of $26 per dose (or $19 when health care system costs only are considered). IMPLICATIONS: Rotavirus immunization may be cost-effective in Australia, but considerable uncertainty remains. Policy decisions will depend heavily on pricing of the vaccine and may also need to consider intangible costs not accounted for in this analysis.

Child, Preschool↗