Search PubMed⌕ Search

Biomedical subjects

A S Rigby

Publications and source records attributed to A S Rigby.

At least 19 recordsLinked to original sources
PubMed2001

The effect of ribavirin to treat previously healthy infants admitted with acute bronchiolitis on acute and chronic respiratory morbidity.

The role of ribavirin in the treatment of acute bronchiolitis is controversial. It has been suggested that the use of ribavirin may be of benefit during the acute illness and may reduce subsequent recurrent respiratory morbidity. This randomized, double-blind, placebo-controlled study was designed to determine whether ribavirin administered during the acute illness would have an influence on respiratory morbidity during both the acute illness and during the following year. Bronchial reactivity 6 months after the acute illness was also assessed. Forty previously well infants with moderately severe acute bronchiolitis were recruited during three winter epidemics. Subjects received study medication for 18 h a day. Management was otherwise unaltered. Subjects were evaluated daily by the investigator and subsequently assessed at 6 weeks, 6 months and 1 year following the acute illness. Assessment of bronchial hyper-responsiveness was assessed at 6 months of age using total body plethysmography and an established ultra-sonically nebulized distilled water challenge. A total of 40 patients (21 ribavirin, 19 placebo) were entered into the study. The two groups did not differ with respect to age, gender or clinical severity on entry to the trial. No significant differences were identified in the rate of clinical improvement over the first 24 h, the time to discharge, bronchial responsiveness at 6 months of age, frequency of significant respiratory symptoms over the first year of life and the frequency of prescribed bronchodilators and inhaled steroids during the year of follow-up. This study was unable to demonstrate any clinical benefit from the use of ribavirin in the acute illness or during subsequent follow-up for 1 year.

Antiviral Agents↗
PubMed2000

Statistical methods in epidemiology. VI. Correlation and regression: the same or different?

PURPOSE: The statistical terms 'correlation' and 'regression' are frequently mistaken for each other in the scientific literature. Why this is so is unclear. This paper discusses their differences/ similarities arguing that in most circumstances regression is the most appropriate technique to use, since regression incorporates a notion of dependency of one variable on another. METHOD: Pearson's correlation coefficient (r) is introduced as a method for estimating the degree of linear association between two normally distributed variables. The problem of least squares' regression (when y depends on x) is introduced by considering the best-fitting straight line between points on a scatter plot. RESULTS: Correlation, regression analysis and residual estimation are discussed by taking examples from the author's own teaching experiences. CONCLUSIONS: Correlation and regression share some similarities. However, regression is the better technique to use because with it comes a notion of dependency of one variable upon another. Regression model checking includes residual examination. The importance of plotting and examination of residuals cannot be overemphasized. Residual examination should become as much a part of a regression analysis as the estimation of the regression coefficients themselves.

Epidemiologic Methods↗
PubMed2000

Statistical methods in epidemiology. v. Towards an understanding of the kappa coefficient.

PURPOSE: This paper introduces readers to the problem of measuring interrater agreement in observer variation studies. The most usual statistic to quote is the kappa coefficient which measures agreement having corrected for chance. METHOD: The kappa coefficient for measuring agreement between two observers is introduced. Some pointers are given to determining sample size estimation. RESULTS: Some properties of the kappa coefficient are illustrated by taking examples from the author's teaching experiences. CONCLUSION: The kappa coefficient is recommended for measuring agreement in observer variation studies.

Epidemiology↗
PubMed2000

Statistical methods in epidemiology. IV. Confounding and the matched pairs odds ratio.

PURPOSE: This paper introduces readers to the problem of confounding in epidemiology, how it differs from effect modification and how to deal with it statistically. There are several options for dealing with confounding. These include techniques based on matching, on stratification and on regression. This paper reviews the first method, matching and the matched pairs odds ratio. METHOD: For 1:1 pair matching (1 case and 1 matched control), the matched pairs odds ratio is introduced as the ratio of discordant pairs. A method for calculating confidence intervals based on the normal approximation is described. RESULTS: Some properties of the matched pair design are illustrated by taking examples from the authors' own teaching experiences. CONCLUSION: Matching remains a difficult design option in epidemiology. Its 'best' use is for special types of studies such as for those on twin pairs.

Confidence Intervals↗
PubMed2000

Characterizing the quantitative genetic contribution to rheumatoid arthritis using data from twins.

OBJECTIVE: Twin concordance data for rheumatoid arthritis (RA) on their own provide only limited insight into the relative genetic and environmental contribution to the disease. We applied quantitative genetic methods to assess the heritability of RA and to examine for evidence of differences in the genetic contribution according to sex, age, and clinical disease characteristics. METHODS: Data were analyzed from 2 previously published nationwide studies of twins with RA conducted in Finland and the United Kingdom. Heritability was assessed by variance components analysis. Differences in the genetic contribution by sex, age, age at disease onset, and clinical characteristics were examined by stratification. The power of the twin study design to detect these differences was examined through simulation. RESULTS: The heritability of RA was 65% (95% confidence interval [95% CI] 50-77) in the Finnish data and 53% (95% CI 40-65) in the UK data. There was no significant difference in the strength of the genetic contribution according to sex, age, age at onset, or disease severity subgroup. Both study designs had power to detect a contribution of at least 40% from the common family environment, and a difference in the genetic contribution of at least 50% between subgroups. CONCLUSION: Genetic factors have a substantial contribution to RA in the population, accounting for approximately 60% of the variation in liability to disease. Although tempered by power considerations, there is no evidence in these twin data that the overall genetic contribution to RA differs by sex, age, age at disease onset, and disease severity.

Adult↗
PubMed2000

Levels of satisfaction of 'low-risk' mothers with their current health visiting service.

AIMS AND OBJECTIVES: To assess the expressed levels of satisfaction of 'low-risk' mothers with the current health visiting service. Setting Sheffield, England, Autumn 1997. METHODOLOGY: Self-completion, postal questionnaire (initial postcard reminder followed by a second letter and questionnaire) to a sample of 403 mothers assessed as 'low priority' by their health visitor. Questions largely related to maternal opinion of the adequacy of the health visiting service delivered during the first 9-12 months. The local research ethics committee approved the study. RESULTS: A corrected response rate of 75% with little evidence of significant bias. A high proportion (86%) of women stated that they were either 'fairly' or 'very' satisfied with the service they had received from their health visitor with regard to their baby. A lower proportion (72%) was equally satisfied with the service they had received in respect of their own health. Despite an average number of approximately 10 contacts in relation to infant health with the health visitor during the first year of life, some 6% of women wanted more frequent contacts, particularly in the first few weeks. Study limitations The questionnaire was designed specifically for the study and validation was limited. The study population comprised a selected, 'low-risk' group. CONCLUSIONS: The number of reported contacts with the health visitor seemed to greatly exceed those indicated by a basic child health surveillance programme. The overall level of maternal satisfaction is high, though a minority of women would like more support. Dissatisfaction was expressed with the lack of an appointment system for clinics, poor punctuality in home visits, and inappropriate or inadequate advice.

Adolescent↗
PubMed2000

Hitting the target: the equitable distribution of health visitors across caseloads.

BACKGROUND: Health visitors in the United Kingdom work mainly with pre-school children and their mothers. Their distribution across the population is largely historical, highly variable and relates poorly to indicators of population need. METHODS: A range of largely routine data sources were used to describe the nature, variation and statistical determinants of the workload of individual health visitors in Sheffield, England, in 1996-1997. Regression models were tested relating measures of need and deprivation to the total number of client contacts. RESULTS: Caseloads were smaller in the most deprived areas, with wide variation. Most (93 per cent) contacts were with mothers and young children. Health visitors visited the clients designated as highest priority on average 4.7 times more often than routine clients. The main reasons for high priority ratings were child protection concerns, maternal mental health problems, child development and health concerns, and first-time mothers in the postnatal period. Half of all client contacts were with low-priority families for routine child health surveillance or were client initiated. Models based on the number of children under five and any one of a range of measures of social deprivation account for 57-59 per cent of variation in workload and could be used to allocate resources more equitably. CONCLUSIONS: Although most health visitors apparently subscribe to the principle of targeting, the extent varies widely. Constraints on targeting are routine child health surveillance reviews, and client demands. More equitable allocation of health visitors and more explicit targeting policies might increase the effectiveness of the health visiting service.

Child↗
PubMed1999

Assessment of stool colour in community management of prolonged jaundice in infancy.

Jaundice persisting beyond the first 2 wk of life is often regarded as an indication for investigation to exclude cholestatic liver disease. Most babies with prolonged jaundice have breast milk-related jaundice, which is a benign condition. Cholestatic liver disease is usually accompanied by pale stools and yellow or orange urine. A community programme was established to ascertain the incidence of prolonged jaundice and determine whether abnormal stool and urine colour could be used to assist primary care staff in referral decisions. Data were collected on normal stool and urine colour and used to devise a colour chart and information sheet for parents. Babies with prolonged jaundice were identified and referred for investigation. In all, 3661 babies were recruited into the study, of which 127 were jaundiced at 28 d of age. Of these, 125 were breastfed. The incidence of jaundice in breastfed babies at 28 d was 9.2% (95% CI 7.8%-11.0%) Abnormal liver function tests (LFTs) were common, but no baby had abnormal stool or urine colour and none was found to have liver disease. Jaundiced breastfed babies who are well are unlikely to have serious disease. Elevated LFTs are compatible with a diagnosis of breast milk-related jaundice. Prolonged jaundice in bottle-fed babies, and persistent pallor of stools or yellow/orange urine, are rare and merit immediate referral. Parents and professionals can be advised to report pale stools without generating a large number of unnecessary referrals. Further work is needed to determine whether a colour chart reduces the mean age of referral and treatment of infants with cholestatic liver disease.

Analysis of Variance↗
PubMed1999

Statistical methods in epidemiology. III. The odds ratio as an approximation to the relative risk.

PURPOSE: This paper introduces readers to case-control studies and how to analyse them. Specifically, the odds ratio statistic is discussed. The importance of the odds ratio in epidemiology is that it is used as an approximation to the true relative risk. METHOD: Data are presented in the form of 2 x 2 contingency tables, and a method for calculating the odds ratio is presented. An extension to 2 x k tables (where k > 2) is given, as is a graphical method for plotting odds ratios. Confidence intervals based on the Normal approximation are introduced. RESULTS: Some properties of the odds ratio statistic are illustrated by taking examples from the author's own teaching experiences. CONCLUSION: As long as the odds ratio is not used uncritically as an estimate of the relative risk, it remains an attractive statistic for epidemiologists to calculate.

Confidence Intervals↗
PubMed1999

The infant index: a new outcome measure for pre-school children's services.

BACKGROUND: The evaluation of community services for preschool children is hampered by the lack of valid and routinely available outcome measures. This study examines the use of data collected by teachers in response to educational legislation to determine whether a routine measure of attainments in primary school is sensitive to factors known to affect mental development. METHOD: A community child health dataset for the cohort of children born in Sheffield in 1990-1991 was matched with a dataset provided by schools in 1995-1996. The educational data consisted of the Infant Index scores which measure education attainments in reception class pupils. RESULTS: We matched 4487 children from both datasets, which represented 75 per cent of all children born in the 1990-1991 cohort. Factors which predicted a poor Infant Index included male gender (odds ratio (OR) = 2.1, 95 per cent confidence interval (CI)= 1.8-2.6), low birthweight (OR = 1.4, 95 per cent CI = 1.1-1.9) and lack of breast feeding either by intention to feed (OR = 1.3, 95 per cent CI = 1.1-1.7) or actual feeding practice at one month (OR = 1.5, 95 per cent CI = 1.1-2.0). Other factors associated with a poor outcome for the child were postnatal depression, number of pregnancies, ethnicity, pre-school educational experiences and poor housing. CONCLUSIONS: Although the results are interesting in themselves, the main significance of our project is in establishing a link between routinely collected health data and routine education data. This could facilitate research in the future thus leading to a considerable saving in the cost of long-term intervention studies.

Birth Weight↗
PubMed1998

HLA haplotype sharing in rheumatoid arthritis sibships: risk estimates subdivided by proband genotype.

There is a well-known association between rheumatoid arthritis (RA) and HLA-DR4. Recent research has indicated that both DR4 haplotypes are important in disease predisposition (favoring a recessive mode of inheritance). Others have suggested that certain combinations of genotypes, in particular Dw4/Dw14 heterozygotes, may be more important than others. We examined the mode of inheritance of RA using data from the Arthritis and Rheumatism Council's national repository of family material [Worthington et al. (1994) Br J Rheumatol 33:970-976]. There were 85 affected sibships consisting of 77 sib pairs, 6 trios, 1 quintuplet, and 1 sextuplet. The affected sibs shared two, one, and zero parental HLA haplotypes in a ratio of 0.42:0.43:0.15, which was significantly different from random expectations (P = 0.00009). Risk estimates for RA to sibs were calculated based on an overall sibling recurrence risk of 3.9%. Risks for those sharing two, one, and zero parental HLA haplotypes were 6.5% [95% confidence interval (CI) = 5.1-7.9%], 3.3% (95% CI = 2.6-4.0%), and 2.5% (95% CI = 1.5-3.5%), respectively. We also examined the risk of RA based on the DRbeta1 genotype status of sib and proband. After excluding genotypic combinations with small numbers, the highest genotype-specific risks were seen for sibs sharing two haplotypes with either a DRbeta1*0401/DRbeta1*0404 (12.5%, 95% CI = 6.9-15.2%) or a DRbeta1*0401/DRbeta1*0408 (11.1%, 95% CI = 4.5-15.1%) proband. An independent assessment based on the AGFAP methodology confirmed the increase in risk for these genotypes, in particular for DRbeta1*0401/DRbeta1*0408. The excess being due to *0401/*0408 rather than to *0401/*0404 may explain why the Dw4/Dw14 effect is not always observed.

Alleles↗
PubMed1998

Errors in postcode to enumeration district mapping and their effect on small area analyses of health data.

BACKGROUND: Health research often seeks to associate individuals to their socio-economic circumstances by linking an individual's postcode to their Census enumeration district (ED). As part of a study into health visitor resource allocation the objective here is to quantify the errors that arise in attaching ED level deprivation scores to records and counts of records by ED when records are matched to EDs via their postcodes rather than their exact address. METHODS: The result of routine matching of postcodes to EDs was compared with the more accurate method of matching addresses to EDs. Townsend scores were then attributed to records according to the two different methods and the results compared. A sample of 4013 births registered in Sheffield in 1996 was used. RESULTS: The comparative work showed that the mismatching of individual addresses arising from matching postcodes to EDs was 16.4 per cent. (The 95 per cent confidence interval is 15.1-17.7 per cent.) Over one-third of mismatched records (about 6 per cent of the total records) were found to have Townsend scores greater than +/- 2 compared with the score obtained through the more accurate process of address matching. CONCLUSIONS: The evidence of the study is that it is important to recognize there are errors inherent in matching individual addresses to EDs via the address postcode. For problems involving resource allocation and for research into relationships between health outcomes or service uptake and deprivation it may be necessary to seek to quantify the level of error introduced through using postcode to ED matching.

Bias↗
PubMed1998

Statistical methods in epidemiology: I. Statistical errors in hypothesis testing.

PURPOSE: Although scientific journal editors are making use of statisticians in the review process, the quality of statistical reporting in many journals remains poor. In many cases the problem for the scientist would appear to be a lack of understanding of basic statistics. The focus of the scientist is on showing 'p < 0.05', when what is actually required is a statement about effect size and interval estimation. The aim of this paper is to show the inadequacy of reporting of results using p-values alone. This paper is the first in a series detailing common statistical methods, with a view to aiding potential authors in their statistical presentation of data. METHOD: A review of the basic hypothesis test, using examples from the author's own teaching experiences. RESULTS: Type I and type II errors are defined; the problem of multiple comparisons is highlighted; interval estimation is introduced. CONCLUSIONS: The case for considering the p-value as an error probability is made which suggests ways of improving statistical presentation and thus expediting the statistical review process.

Confidence Intervals↗
PubMed1998

Statistical methods in epidemiology. II: A commonsense approach to sample size estimation.

PURPOSE: It has been argued, by many, that mathematical formulae for estimating sample size are unnecessarily complex, so much so that researchers may be reluctant to seek statistical advice. METHOD: This paper reviews methods of sample size estimation arguing that two formulae (one based on comparison of proportion of 'successes', the other based on comparison of means of normally distributed data) suffice for many situations. This paper argues the case by taking examples drawn mainly from clinical trials research. However, the methods outlined can also be used in epidemiology specifically in both case-control and cohort studies with no loss of information. RESULTS: For the situations outlined, worked examples are provided. CONCLUSIONS: Sample size estimation need not necessarily be a complex process. Simple techniques exist which enable the clinician and the statistician to work together. Continued dialogue between both parties is required so that good ideas do not go to waste.

Data Interpretation, Statistical↗
PubMed1996

Part I of Membership of the Faculty of Public Health Medicine (MFPHM). Trends over time and factors associated with success in recent years.

BACKGROUND: The examination for Membership of the Faculty of Public Health Medicine (MFPHM) Part I, has been held for nearly 20 years. It aims 'to test the candidate's knowledge and understanding of the basic sciences of public health'. This paper presents simple statistics from the earliest years up to June 1995 and additional information on more recent sittings. METHOD: The number of people taking the examination and the proportion passing were obtained for every sitting from February 1978 to June 1995. Further data have been extracted for all sittings of the examination since the current regulations were introduced. The variables included were pass or fail as the outcome variable, date of birth, gender of candidate, postgraduate qualifications, present post of employer, and attendance at a formal academic course. RESULTS: The number of candidates has ranged from 12 to 115, the proportion passing from 42 per cent to 93 per cent. During the period from June 1992 to June 1995, 472 people applied to sit the examination. Of these 33 withdrew, leaving 439 person attempts. The overall proportion passing was 270/439 (61.5 per cent). Factors associated with success include being female, being a UK graduate, attending an academic course and having more experience in the specialty. CONCLUSION: Candidates and their tutors are reminded of the need for adequate preparation for the examination. The authors welcome comments on how monitoring should be carried out in the future.

Adult↗