Biomedical subjects

L C Gurrin

Publications and source records attributed to L C Gurrin.

17 recordsLinked to original sources

PubMed2001

Statistical measures of foetal growth using linear mixed models applied to the foetal origins hypothesis.

Statistical models of the relationship between the distribution of each of five foetal dimensions and gestational age are developed based on serial ultrasound biometric data from a prospective longitudinal study in Perth, Western Australia. Both the response variable and the gestational age timescale are transformed to establish an approximately linear relationship within subjects. This relationship is modelled using a linear mixed effects model that accounts for between-subject heterogeneity by incorporating subject specific random effects for both intercept and gradient. These models are used to motivate three measures of foetal growth: the conditional centile or z-score of a current measurement given an earlier value for the same measurement; the best linear unbiased predictor (BLUP) of the subject specific random effect gradient (which is shown to be invariant to transformations of location and scale), and the standardized residual at a given gestational age, which characterizes departures from the modelled growth trajectory. We illustrate how these three measures of growth might be applied to subsequent health outcomes in later life by relating growth in foetal abdominal circumference to blood pressure in children from the same cohort at six years of age. Foetuses whose summary measures indicate poor growth in abdominal circumference have higher blood pressure in early childhood, supporting the 'foetal origins' hypothesis that many chronic diseases of adulthood have their origins before birth.

Anthropometry↗

PubMed2001

Placental weight and placental ratio as predictors of later blood pressure in childhood.

OBJECTIVE: A significant inverse relationship between blood pressure and birth weight is firmly established. This association may be the result of fetal adaptations to an adverse intrauterine environment. Further markers of intrauterine growth include the weight of the placenta and the placental ratio (the ratio of placental weight to birth weight). A number of studies suggest that a decreased placental weight or an elevated placental ratio may be independent risk factors for subsequent high blood pressure. The overall evidence for this is, however, inconclusive. The purpose of the present study was to clearly define the relationships between placental weight, placental ratio and subsequent blood pressure during childhood. DESIGN: Prospective cohort study of 2507 singleton children, born at term during 1989-1992. Blood pressures were recorded at ages 1, 3 and 6 years, using a semi-automated oscillometric device. RESULTS: Inverse relationships existed between both systolic and diastolic blood pressure and placental weight, adjusted for current weight at ages 1, 3 and 6 years. The relationships between placental weight and systolic blood pressure were statistically significant at ages 1 and 3 years. There was no consistent relationship between placental weight and later blood pressure within birth weight categories. No clinically or statistically significant association was seen between the placental ratio and either systolic or diastolic blood pressures at any age. CONCLUSIONS: Birth weight, rather than placental weight or their ratio, is the early life factor most importantly related to subsequent blood pressure in childhood.

Birth Weight↗

PubMed2001

Programming effects in sheep of prenatal growth restriction and glucocorticoid exposure.

Our aim was to determine the postnatal effects of single and repeated glucocorticoid injections during late gestation. Repeated (104, 111, 118, 125 days) or single (104 days) injections of betamethasone or saline were given to the ewe or by ultrasound guided injection to the fetus (term 150 days). Lambs were born spontaneously and studied at 3 and 6 mo and 1 yr of age. Arterial pressure was measured at each age, and we performed intravenous glucose tolerance tests at 6 mo and 1 yr. Repeated maternal, but not single maternal or fetal, betamethasone injections prolonged gestation, reduced weight at birth and 3 mo, and was associated with low arterial pressure at 3 mo but not at 6 mo and 1 yr. Glucose metabolism was altered in all betamethasone treatment groups, regardless of the number or route of injections. Our data demonstrate that glucocorticoid-induced fetal growth restriction is associated with a transient reduction in postnatal arterial pressure, but glucocorticoid exposure with or without growth restriction alters glucose metabolism.

Aging↗

PubMed2000

What do children with cystic fibrosis and their parents know about nutrition and pancreatic enzymes?

OBJECTIVE: To describe the development and validation of questionnaires designed to assess nutrition and pancreatic enzyme replacement therapy knowledge and cystic fibrosis self-management skills, and the results obtained when the questionnaires were used. DESIGN: A cross-sectional study using validated questionnaires to interview the respondents. The outcome measures were scores for knowledge, appropriate and inappropriate self-management, and Socioeconomic Index. SUBJECTS: Forty-two children with cystic fibrosis aged 6 to 11 years and 55 caregivers of 2 to 11-year-old patients of the Princess Margaret Hospital Cystic Fibrosis Clinic, Perth, Australia. STATISTICAL ANALYSES: Descriptive statistics and correlations between scores were used for statistical analyses. Associations between knowledge scores were examined using Pearson's correlation coefficient. Spearman's rank correlation was used to examine the associations between knowledge and self-management scores and socioeconomic index. RESULTS: Children's and caregivers' mean knowledge scores were 63% and 85%, respectively. Mean appropriate and inappropriate self-management scores for children were 55% and 21%, respectively, and for the caregivers were 74% and 32%, respectively. There was a statistically significant (P < .05) positive association between caregivers' and children's knowledge (r = 0.32), and children's knowledge and appropriate self-management scores (r = 0.41); and a statistically significant negative association between caregivers' knowledge and inappropriate self-management scores (r = -0.35); and no statistically significant associations between Socioeconomic Index and children's and caregivers' knowledge and self-management scores. APPLICATIONS: This study identified areas in which the nutrition knowledge of children with cystic fibrosis and their caregivers needs to be enhanced to increase the likelihood that optimum dietary and pancreatic enzyme therapy is achieved. The questionnaires that were developed for the study could be refined and used in the clinical setting to identify knowledge and self-management deficits. Alternatively, the questionnaires could become valuable research tools for assessing the type of intervention required and in planning and evaluating programs.

Adult↗

PubMed2000

Maternal cigarette smoking during pregnancy, low birth weight and subsequent blood pressure in early childhood.

Given the widely acknowledged inverse relationship between birth weight and blood pressure, a raised blood pressure in the offspring of smoking mothers as compared to those whose mothers did not smoke, would be anticipated by virtue of the reduction in birth weight associated with smoking during pregnancy. The objective of the present study was to test the hypothesis that maternal cigarette smoking during pregnancy has an effect on blood pressure in childhood independent of its effect on birth weight. Data was obtained from a prospective cohort study of 1708 pregnant women and their singleton offspring, delivered live at term, in Perth, Western Australia, commenced at 16 weeks gestation with serial blood pressure measurements through early childhood. Statistically significant associations were found between maternal smoking during pregnancy and systolic blood pressure at age six, between birth weight and systolic blood pressure at ages three and six, and between maternal smoking during pregnancy and birth weight. The relationship between birth weight and blood pressure in early childhood differed significantly on the basis of maternal cigarette smoking or not during pregnancy. This differential relationship persisted after adjustment for the child's current weight and socio-economic status. We concluded that intra-uterine exposure to maternal cigarette smoking increased children's blood pressure at age one through to age six. This was not wholly attributable to an effect on birth weight or confounding of the association between birth weight and subsequent blood pressure by the child's current weight or socio-economic factors. Furthermore, maternal smoking during pregnancy does not account for the acknowledged elevation in blood pressure associated with low birth weight. The present study is an exploration of a possible causal pathway underlying the birth weight/blood pressure association rather than simply a confirmation of such an association which has been detailed in many other papers.

Adult↗

PubMed2000

Bayesian statistics in medical research: an intuitive alternative to conventional data analysis.

Statistical analysis of both experimental and observational data is central to medical research. Unfortunately, the process of conventional statistical analysis is poorly understood by many medical scientists. This is due, in part, to the counter-intuitive nature of the basic tools of traditional (frequency-based) statistical inference. For example, the proper definition of a conventional 95% confidence interval is quite confusing. It is based upon the imaginary results of a series of hypothetical repetitions of the data generation process and subsequent analysis. Not surprisingly, this formal definition is often ignored and a 95% confidence interval is widely taken to represent a range of values that is associated with a 95% probability of containing the true value of the parameter being estimated. Working within the traditional framework of frequency-based statistics, this interpretation is fundamentally incorrect. It is perfectly valid, however, if one works within the framework of Bayesian statistics and assumes a 'prior distribution' that is uniform on the scale of the main outcome variable. This reflects a limited equivalence between conventional and Bayesian statistics that can be used to facilitate a simple Bayesian interpretation based on the results of a standard analysis. Such inferences provide direct and understandable answers to many important types of question in medical research. For example, they can be used to assist decision making based upon studies with unavoidably low statistical power, where non-significant results are all too often, and wrongly, interpreted as implying 'no effect'. They can also be used to overcome the confusion that can result when statistically significant effects are too small to be clinically relevant. This paper describes the theoretical basis of the Bayesian-based approach and illustrates its application with a practical example that investigates the prevalence of major cardiac defects in a cohort of children born using the assisted reproduction technique known as ICSI (intracytoplasmic sperm injection).

Bayes Theorem↗

PubMed2000

Reference ranges for blood pressure in preschool Australians, obtained by oscillometry.

OBJECTIVE: To derive reference centiles for blood pressure in children aged 1-6 years which seek to address shortcomings in available reference ranges. METHODS: Prospective cohort study of 2876 children in Perth, Western Australia, commenced in 1989 with serial blood pressure measurements through early childhood obtained by oscillometry under standardized conditions. RESULTS: Gender-specific reference centile charts for systolic and diastolic blood pressure, (i) across ages 1-6 years and (ii) across the range of corrected Body Mass Index values at ages 1, 3 and 6 years, were generated by fitting linear models with both fixed and random effects. CONCLUSIONS: Reference values for blood pressure for young children are of clinical use and may be of long-term predictive value.

Blood Pressure↗

PubMed2000

Adjustment for current weight and the relationship between birth weight and blood pressure in childhood.

OBJECTIVE: To determine the role of current weight in mediating the relationship between birth weight and blood pressure within the context of the 'fetal origins' hypothesis. DESIGN: Prospective cohort study of 2507 pregnant women and their singleton offspring, delivered live at term, in Perth, Western Australia between 1989 and 1992. The study commenced at 16 weeks gestation with serial weight and blood pressure measurements recorded through early childhood. RESULTS: Inverse associations were found between birth weight and systolic blood pressure at ages 1, 3 and 6. The effect of birth weight on systolic blood pressure at age 6 reached statistical significance and was increased fourfold in magnitude to -2.3 mmHg [95% confidence interval = (-3.3 to -1.3), P < 0.01] after adjustment for current weight. The interaction term for birth weight and current weight was not statistically significant. Including intermediate weights did not produce a statistically significantly better model but did increase the magnitude of the estimated regression coefficient of birth weight on blood pressure, and only the birth weight and current weight terms were significant CONCLUSIONS: Adjustment for current weight serves to highlight the relationship between birth weight and blood pressure in childhood. Nevertheless, birth weight, rather than birth weight adjusted for current weight, is still the relevant predictor of later blood pressure within the context of the 'fetal origins' hypothesis.

Adult↗

PubMed1999

Genetic variance components analysis for binary phenotypes using generalized linear mixed models (GLMMs) and Gibbs sampling.

The common complex diseases such as asthma are an important focus of genetic research, and studies based on large numbers of simple pedigrees ascertained from population-based sampling frames are becoming commonplace. Many of the genetic and environmental factors causing these diseases are unknown and there is often a strong residual covariance between relatives even after all known determinants are taken into account. This must be modelled correctly whether scientific interest is focused on fixed effects, as in an association analysis, or on the covariances themselves. Analysis is straightforward for multivariate Normal phenotypes, but difficulties arise with other types of trait. Generalized linear mixed models (GLMMs) offer a potentially unifying approach to analysis for many classes of phenotype including multivariate Normal traits, binary traits, and censored survival times. Markov Chain Monte Carlo methods, including Gibbs sampling, provide a convenient framework within which such models may be fitted. In this paper, Bayesian inference Using Gibbs Sampling (a generic Gibbs sampler; BUGS) is used to fit GLMMs for multivariate Normal and binary phenotypes in nuclear families. BUGS is easy to use and readily available. We motivate a suitable model structure for Normal phenotypes and show how the model extends to binary traits. We discuss parameter interpretation and statistical inference and show how to circumvent a number of important theoretical and practical problems that we encountered. Using simulated data we show that model parameters seem consistent and appear unbiased in smaller data sets. We illustrate our methods using data from an ongoing cohort study.

Binomial Distribution↗

PubMed1999

Adolescent pregnancy: psychopathology missed.

OBJECTIVES: Few data exist that explore the level of psychosocial problems and drug abuse in an Australian, adolescent, antenatal population. We set out to audit these data from a population of pregnant Western Australian adolescents. We also set out to examine whether social issues and the use of non-prescription drugs are routinely addressed in general public antenatal clinics. METHODS: One hundred and sixty patients were involved in the prospective cohort study. In the assessed group, 100 consecutive patients from the King Edward Memorial Hospital Adolescent Antenatal Clinic were interviewed during the antenatal period to determine if any major psychosocial issues or a history of non-prescription drug abuse was present. The control group consisted of 60 adolescent patients who delivered in general antenatal clinics at three Perth metropolitan hospitals. RESULTS: Sixty percent of the assessed group were identified as having a major psychosocial problem that interfered with their ability to carry out acts of daily living. Consumption of cigarettes, alcohol, marijuana, heroin and solvents were higher than that reported for the general Australian adolescent population. Of note, in the control group, many patients did not have a social, psychological, or drug use history taken by their caregivers. CONCLUSION: Failure to identify psychosocial problems and drug abuse during the antenatal period will result in missed opportunities for positive intervention. These problems are common in this population and interventions are required to offer these women alternative foundations upon which to base their mothercraft skills.

Adolescent↗

PubMed1999

Pregnancy loss rates following second trimester genetic amniocentesis.

Data from 3,953 consecutive second trimester genetic amniocenteses were analysed to determine pregnancy loss rates up to 6 weeks after the procedure. Information was prospectively collected on a cohort of 3,685 women in 3,896 singleton and 50 twin pregnancies, from 2 operating sites in Perth, Western Australia, using 9 operators over the 6-year period, 1989 to 1995. Complete information regarding pregnancy outcome was obtained for 3,643 of the 3,685 women (98.9%). There were 27 identified singletons and 1 set of twins lost within 6 weeks following amniocentesis. The overall pregnancy loss rate in this cohort was 29 of 3,911 (0.74%). The pregnancy loss rate associated with genetic amniocentesis is not excessive in comparison to the calculated background pregnancy loss rate of 1%, and it is suggested that each prenatal diagnostic team should determine their own complication rates for the purpose of counselling prior to amniocentesis.

Abortion, Spontaneous↗

PubMed1999

A survey of parturients using epidural analgesia during labour. Considerations relevant to antenatal educators.

The use of epidural analgesia (EA) during labour is increasing in Australasia. This highlights the need for improved educational and resource materials, current factual information about EA, and identification of consumer attitudes towards EA. In this survey, 350 parturients who had recently used EA for labour pain relief in a single maternity unit were asked to complete a questionnaire about their expectations and experience. The response rate was 90%. Prepartum information was most commonly derived from hearsay and least commonly from medical health professionals, 56% of respondents wanted pain to be made tolerable and 34% wanted complete pain relief. Almost half considered unrestricted mobility and delivery without obstetric assistance important. A minority were concerned about possible effects of EA on the baby or labour outcome. Anticipated pain during epidural placement was significantly greater than that experienced. Satisfaction with EA was high, although 36% described unpleasant or annoying effects associated with EA. Parent educators and epidural service providers should be aided by knowledge of where parturients obtain information and of consumer views about EA.

Adult↗

PubMed1998

High prevalence of chlamydia and Pap-smear abnormalities in pregnant adolescents warrants routine screening.

A prospective cohort of pregnant adolescent patients who planned to deliver at 1 of 3 Perth metropolitan hospitals was studied; 1 subgroup of this cohort was offered universal screening for cervical chlamydial infection and Pap-smear abnormalities (screened), and the remainder of the cohort were offered screening at the discretion of the attending medical staff (control). High prevalences of both chlamydial infection (27%) and Pap-smear abnormalities (38%) were detected in the screened cohort. The majority of Pap-smear abnormalities were inflammatory atypia, but high-grade Bethesda lesions were also diagnosed. In the control group, the prevalence of positive swabs and abnormal Pap-smear reports in those tested was also high (22% and 35% respectively), but significantly fewer patients were tested (18% and 33% respectively in the control group, compared to 92% and 94% in the screened group; both p<0.001). Screening and treatment of chlamydia was associated with a significant decrease in the incidence of newborn febrile morbidity (10% versus 25%; p=0.02). In view of the high prevalence of positive results, it is cost-effective to offer universal screening in this setting. Failure to introduce a specific screening policy can result in a significant number of patients being denied the advantages of diagnosis and treatment.

Adolescent↗

PubMed1998

Clinical significance not statistical significance: a simple Bayesian alternative to p values.

OBJECTIVES: To take the common "Bayesian" interpretation of conventional confidence intervals to its logical conclusion, and hence to derive a simple, intuitive way to interpret the results of public health and clinical studies. DESIGN AND SETTING: The theoretical basis and practicalities of the approach advocated is at first explained and then its use is illustrated by referring to the interpretation of a real historical cohort study. The study considered compared survival on haemodialysis (HD) with that on continuous ambulatory peritoneal dialysis (CAPD) in 389 patients dialysed for end stage renal disease in Leicestershire between 1974 and 1985. Careful interpretation of the study was essential. This was because although it had relatively low statistical power, it represented all of the data that were available at the time and it had to inform a critical clinical policy decision: whether or not to continue putting the majority of new patients onto CAPD. MEASUREMENTS AND ANALYSIS: Conventional confidence intervals are often interpreted using subjective probability. For example, 95% confidence intervals are commonly understood to represent a range of values within which one may be 95% certain that the true value of whatever one is estimating really lies. Such an interpretation is fundamentally incorrect within the framework of conventional, frequency-based, statistics. However, it is valid as a statement of Bayesian posterior probability, provided that the prior distribution that represents pre-existing beliefs is uniform, which means flat, on the scale of the main outcome variable. This means that there is a limited equivalence between conventional and Bayesian statistics, which can be used to draw simple Bayesian style statistical inferences from a standard analysis. The advantage of such an approach is that it permits intuitive inferential statements to be made that cannot be made within a conventional framework and this can help to ensure that logical decisions are taken on the basis of study results. In the particular practical example described, this approach is applied in the context of an analysis based upon proportional hazards (Cox) regression. MAIN RESULTS AND CONCLUSIONS: The approach proposed expresses conclusions in a manner that is believed to be a helpful adjunct to more conventional inferential statements. It is of greatest value in those situations in which statistical significance may bear little relation to clinical significance and a conventional analysis using p values is liable to be misleading. Perhaps most importantly, this includes circumstances in which an important public health or clinical decision must be based upon a study that has unavoidably low statistical power. However, it is also useful in situations in which a decision must be based upon a large study that indicates that an effect that is highly statistically significant seems too small to be of practical relevance. In the illustrative example described, the approach helped in making a decision regarding the use of CAPD in Leicestershire during the latter half of the 1980s.

Bayes Theorem↗

PubMed1997

Influence of driving pressure on raised-volume forced expiration in infants.

The raised-volume forced-expiration technique measures infant lung function over an extended volume range. To improve comparisons between individuals and populations, we investigated the influence of jacket pressure on outcome variables in 21 infants. To quantify pressure transmitted from the jacket to the pleural space at a given lung volume, the jacket was inflated against an occluded airway, and the increase in pressure at the mouth was measured. Flow-volume curves were recorded at transmitted pressure (Ptrans) values ranging from 0 to 41.9 cm H20. The effect of Ptrans on the FEV measures of FEV0.5, FEV0.75, and FVC, and on the forced expiratory flow measures of FEF25%, FEF50% and FEF75% was assessed. At Ptrans values between 0 to 20 cm H20, a significant positive relationship existed between transmitted pressure (Ptrans) and all outcome variables except FVC. At higher Ptrans values, all outcome variables demonstrated pressure independence, with the exception of FEF25% (which remained positive) and FVC (which was negative in a subgroup of wheezy infants). FEF75% values tended to decrease at Ptrans values > 25 cm H20. At Ptrans values between 20 and 25 cm H20, most outcome variables are pressure independent. This range is therefore the most suitable for use with the raised-volume forced expiration technique.

Female↗

PubMedDate not supplied

Quality of life in patients attending a low-risk gynaecological oncology follow-up clinic.

OBJECTIVES: (1) To assess the quality of life (QOL) of patients who had been treated for gynaecological malignancies and who were attending a low risk follow-up clinic. (2) To determine the accuracy of the clinic physicians' assessment of patients' QOL compared with the Functional Living Index-Cancer (FLI-C) [Schipper et al., 1984. Measuring the quality of life of cancer patients: the Functional Living Index-Cancer: development and validation. J Clin Oncol 2(5): 472-483]. (3) To examine a single subjective question about change in QOL. (4) To assess patient fear of cancer recurrence. DESIGN: Self-administered patient questionnaire. The questionnaire contained the FLI-C, with four additional questions. SETTING: Low risk (good prognosis) follow-up clinics in the Department of Gynaecological Oncology at King Edward Memorial Hospital (the tertiary centre for obstetrics and gynaecology for the state of Western Australia). PATIENTS: 202 consecutive attendees of the clinic. Non-English speaking patients attending without an interpreter were excluded. RESULTS: Most patients reported a good QOL. The range of FLI-C scores was 59-154 (possible range 22-154), with a median score of 140 and a mean of 134. Younger patients were more fearful of cancer recurrence. Radiotherapy was associated with a worsening of QOL. Patients living with partners experienced deterioration in sexual functioning. CONCLUSIONS: Patients attending the low risk follow-up clinic after gynaecological malignancy have a good overall QOL.

Activities of Daily Living↗

PubMedDate not supplied

Assessment of wound infiltration with bupivacaine in women undergoing day-case gynecological laparoscopy.

BACKGROUND AND OBJECTIVES: The effectiveness of local anesthetic wound infiltration for treatment of postoperative pain appears to be variable and partly dependent on the surgical procedure. Although evidence was lacking, it was common practice at our institution to infiltrate the trocar wound of patients undergoing day-case laparoscopic procedures with long acting local anesthetic agents. The aim of this study was to investigate the analgesic efficacy, and the influence of the timing, of local anesthetic infiltration into surgical wounds for day-case diagnostic gynecological laparoscopy. METHODS: A double-blind, randomized trial was conducted on 100 women having general anesthesia for day-case gynecological laparoscopy. Ninety-two patients who had been randomized to 1 of 4 groups for trocar wound infiltration with 30 mL of 0.25% bupivacaine or saline either before or after surgery completed the study. Incisional pain, pain on pressing the umbilicus, severity of nausea, and patient satisfaction with anesthetic technique were all assessed postoperatively until discharge and on the following day through a telephone interview. A P value of <.05 was considered significant. RESULTS: There was no difference between groups in the mean pain scores or analgesic requirements for incisional pain, pain on pressing firmly on the umbilicus, or for patient satisfaction. There was a trend for those patients who had received bupivacaine to use less postoperative morphine (P =.079). CONCLUSIONS: Wound infiltration with local anaesthetic did not significantly reduce pain or opioid requirement after gynecological laparoscopy.

Adult↗