J M Bland's research while affiliated with St George's, University of London and other places

Publications (115)

Article
Objective To assess the variability of fetal heart and thoracic area and circumference measurements using the ellipse and diameter methods at different gestational ages.DesignThis was a prospective cross-sectional study of 200 singleton pregnancies, with no apparent fetal abnormalities. The gestational age ranged between 19 and 42 weeks. At each ex...
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Studies have linked asthma death to either increased or decreased use of medical services. A population based case-control study of asthma deaths in 1994-8 was performed in 22 English, six Scottish, and five Welsh health authorities/boards. All 681 subjects who died were under the age of 65 years with asthma in Part I on the death certificates. Aft...
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We present a case of recurrent primary developmental microcephaly of late onset, the prenatal diagnosis of which could not be achieved despite performing targeted serial ultrasound scans that revealed no obvious fetal abnormality. Serial scans for head measurements and detailed examination of the brain anatomy by both transabdominal and transvagina...
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Female fetuses, on average, weigh less than male fetuses at all gestational ages. The purpose of this study was to compare female and male fetuses in terms of intrauterine ultrasound growth measurements and to develop gestational-age-related charts based on a computerized perinatal database. This was a retrospective study of unselected women in the...
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The study of measurement error, observer variation and agreement between different methods of measurement are frequent topics in the imaging literature. We describe the problems of some applications of correlation and regression methods to these studies, using recent examples from this literature. We use a simulated example to show how these proble...
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Uncontrolled studies suggest that psychosocial factors and health behaviour may be important in asthma death. A community based case-control study of 533 cases, comprising 78% of all asthma deaths under age 65 years and 533 hospital controls individually matched for age, district and asthma admission date corresponding to date of death was undertak...
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To determine uterine artery impedance using Doppler in the second and third trimesters at sea level and at high altitude. Uterine artery resistance and pulsatility indices (RI and PI, respectively) were obtained by Doppler velocimetry from 242 women in Cerro de Pasco (4300 m altitude) and 200 women in Lima (sea level), all with normal singleton pre...
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To determine impedance and velocity characteristics of the fetal circulation using Doppler ultrasound, at extremely high altitude (4300 m) in the Peruvian Andes compared to an ethnically similar population at sea level. This was a cross-sectional study of 196 women resident at high altitude (Cerro de Pasco, 4300 m above sea level) and 196 women res...
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To confirm the hypothesis that isolated cardiac echogenic foci at the second-trimester anomaly scan do not influence our current calculation of risk of trisomy 21 in individual pregnancies, which is based on maternal age and nuchal translucency thickness at 11-14 weeks. Observational study in a fetal medicine unit. In a general pregnant population...
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To assess the intraobserver repeatability and interobserver reproducibility of transabdominal Doppler ultrasound measurements of ductus venosus blood flow in fetuses between 10 and 14 weeks of gestation. A prospective study with the following end-points: coefficient of variation, intraclass correlation coefficients within and between observers, rep...
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The aims of this study were to establish prospectively the prevalence of objective bladder dysfunction before and after delivery by means of urodynamic investigations and to assess the effect of obstetric variables on bladder function. Prospective longitudinal study. Twin channel subtracted cystometry was performed in the standing and sitting posit...
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The aim of this study was to compare ultrasound fetal size at high altitude and sea level. Three hundred and thirty-four women in Cerro de Pasco at 4300 m (14,100 ft) altitude and 278 women in Lima (sea level) were recruited to the study. Ultrasound fetal biometry was carried out between 14 and 42 weeks of gestation. Biparietal diameter, occipitofr...
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In recent years odds ratios have become widely used in medical reports—almost certainly some will appear in today's BMJ. There are three reasons for this. Firstly, they provide an estimate (with confidence interval) for the relationship between two binary (“yes or no”) variables. Secondly, they enable us to examine the effects of other variables on...
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In clinical trials, the statistical concepts of significance and power are used in the determination of sample size for trials. The trialist must provide an estimate of standard deviation and a hypothetical population difference to be detected. This must be modified to deal with the designs encountered in guideline research. These are cluster rando...
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We have explained why random allocation of treatments is a required feature of controlled trials.1 Here we consider how to generate a random allocation sequence.Almost always patients enter a trial in sequence over a prolonged period. In the simplest procedure, simple randomisation, we determine each patient's treatment at random independently with...
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Agreement between two methods of clinical measurement can be quantified using the differences between observations made using the two methods on the same subjects. The 95% limits of agreement, estimated by mean difference +/- 1.96 standard deviation of the differences, provide an interval within which 95% of differences between measurements by the...
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Like all specialist areas, statistics has developed its own language. As we have noted before,1 much confusion may arise when a word in common use is also given a technical meaning. Statistics abounds in such terms, including normal, random, variance, significant, etc. Two commonly confused terms are variable and parameter; here we explain and cont...
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A previous study of the short term effects of air pollution in London from April 1987 to March 1992 found associations between all cause mortality and black smoke and ozone, but no clear evidence of specificity for cardiorespiratory deaths. London data from 1992 to 1994 were analysed to examine the consistency of results over time and to include pa...
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Many epidemiological studies have shown positive short-term associations between health and current levels of outdoor air pollution. The aim of this study was to investigate the association between air pollution and the number of visits to accident and emergency (A&E) departments in London for respiratory complaints. A&E visits include the less sev...
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Many epidemiological studies have shown positive short-term associations between health and current levels of outdoor air pollution. The aim of this study was to investigate the association between air pollution and the number of visits to accident and emergency (A&E) departments in London for respiratory complaints. A&E visits include the less sev...
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A study was undertaken to investigate the relationship between daily hospital admissions for asthma and air pollution in London in 1987-92 and the possible confounding and modifying effects of airborne pollen. For all ages together and the age groups 0-14, 15-64 and 65+ years, Poisson regression was used to estimate the relative risk of daily asthm...
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In many medical studies an outcome of interest is the time to an event. Such events may be adverse, such as death or recurrence of a tumour; positive, such as conception or discharge from hospital; or neutral, such as cessation of breast feeding. It is conventional to talk about survival data and survival analysis, regardless of the nature of the e...
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A cluster randomised study is one where a group of subjects are randomised to the same treatment together—for example, when women in some districts are offered breast cancer screening and compared with women in other districts, or when the patients of general practitioners who have been given special training are compared with the patients of those...
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When practices are randomized in a trial and observations are made on the patients to assess the relative effectiveness of the different interventions, sample size calculations need to estimate the number of practices required, not just the total number of patients. Our aims were to introduce the methodology for appropriate sample size calculation...
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Editor—Gerada and Ashworth state, “About 300 young teenagers die each year from misusing volatile substances, mainly through suffocation.”1 They do not give a source for this figure, which we believe to be grossly exaggerated. Their article has attracted considerable interest, including press attention, and we are concerned that a misleading statis...
Article
To assess geographical variations in mortality and the relationship of socio-economic correlates to deaths from volatile substance abuse (VSA) in Great Britain. Analysis of the National Register of deaths from VSA by linking the addresses (postcode) of the deceased to census enumeration districts and hence wards and counties. All 775 deaths in Grea...
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To be able to measure disability objectively in rheumatoid arthritis complicated by cervical myelopathy. The responses to the Stanford health assessment questionnaire disability index were recorded from 250 consecutive patients (group 1) referred to our unit for spinal surgery. Using principal components analysis the questionnaire was reduced from...
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Randomized controlled clinical trials are conducted to determine whether differences of clinical importance exist between selected treatment regimens. When statistical analysis of the study data finds a P value greater than 5%, it is convention to deem the assessed difference nonsignificant. Just because convention dictates that such study findings...
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The functional results of surgery in patients with myelopathic nonambulatory rheumatoid arthritis (Ranawat Class IIIb) are often disappointing, with high rates of postoperative morbidity and mortality. The authors therefore undertook a detailed investigation of a cohort of 55 Ranawat Class IIIb patients (11 men and 44 women) with a mean age of 64.7...
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Several measurements of the same quantity on the same subject will not in general be the same. This may be because of natural variation in the subject, variation in the measurement process, or both. For example, table 1 shows four measurements of lung function in each of 20 schoolchildren (taken from a larger study1). The first child shows typical...
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To investigate whether air pollution levels in London have short term effects on hospital admissions for respiratory disease. Poisson regression analysis of daily counts of hospital admissions, adjusting for effects of trend, seasonal and other cyclical factors, day of the week, holidays, influenza epidemic, temperature, humidity, and autocorrelati...
Article
The objective of this paper is to compare the cost effectiveness of a co- ordination service with standard services for terminally ill cancer patients with a prognosis of less than one year. We designed a randomized controlled trial, with patients randomized by the general practice with which they were registered. Co-ordination group patients recei...
Article
An interesting issue with the delivery of a data mining project is that in reality we spend more of our time working on and with the data than we do building actual models, as we suggested in Chapter 1. In building models, we will often be looking to improve their performance. The answer is often to improve our data. This might entail sourcing some...
Article
To investigate whether outdoor air pollution levels in London influence daily mortality. Poisson regression analysis of daily counts of deaths, with adjustment for effects of secular trend, seasonal and other cyclical factors, day of the week, holidays, influenza epidemic, temperature, humidity, and autocorrelation, from April 1987 to March 1992. P...
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Opinions differ on the timing of surgery for rheumatoid arthritis patients with atlanto-axial subluxation. Some clinicians wait for development of neurological signs; others favour prophylactic fusion and decompression. We examined the results of surgery in relation to neurological state at the time of operation. 134 patients underwent surgery for...
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In December 1991 London experienced a unique air pollution episode during which concentrations of nitrogen dioxide rose to record levels, associated with moderate increases in black smoke. The aim of this study was to investigate whether this episode was associated with adverse health effects and whether any such effects could be attributed to air...
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When comparing a new method of measurement with a standard method, one of the things we want to know is whether the difference between the measurements by the two methods is related to the magnitude of the measurement. A plot of the difference against the standard measurement is sometimes suggested, but this will always appear to show a relation be...
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Many published papers include large numbers of significance tests. These may be difficult to interpret because if we go on testing long enough we will inevitably find something which is “significant.” We must beware of attaching too much importance to a lone significant result among a mass of non-significant ones. It may be the one in 20 which we e...
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Despite the fundamental importance of measurement in medicine, studies which compare methods of clinical measurement are often analysed inappropriately and may thus come to incorrect conclusions. We explain the problems with the main methods used, notably correlation and regression, and describe the limits of agreement approach which we have propos...
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I investigate the cyclicality of the cost incentives for job creation in search and matching models distinguishing the user cost of labor from the wage payment. The user cost of labor includes the wage at the time of hiring as well as the expected eect of the economic conditions at the time of hiring on future wages. If wages are smoothed by implic...
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This is the ninth in a series of occasional notes on medical statistics In many medical studies a group of cases, people with a disease under investigation, are compared with a group of controls, people who do not have the disease but who are thought to be comparable in other respects. This happens in epidemiological case-control studies, where a p...
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When presenting or analysing measurements of a continuous variable it is sometimes helpful to group subjects into several equal groups. For example, to create four equal groups we need the values that split the data such that 25% of the observations are in each group. The cut off points are called quartiles, and there are three of them (the middle...
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EDITOR, - I believe that J Martin Bland and Douglas G Altman's strong preference for two sided significance tests results in one sided advice.1 The wide acceptance of two sided statistical alternative hypotheses in the case of clearly one sided clinical or biological hypotheses has always amazed me. To my mind the statistical alternative hypothesis...
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We have previously shown that regression towards the mean occurs whenever we select an extreme group based on one variable and then measure another variable for that group (4 June, p 1499).1 The second group mean will be closer to the mean for all subjects than is the first, and the weaker the correlation between the two variables the bigger the ef...
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The text of these letters is not availableDefining sensitivity and specificity Regression towards the mean S Fleminger
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We have previously considered diagnosis based on tests that give a yes or no answer.1, 2 Many diagnostic tests, however, are quantitative, notably in clinical chemistry. The same statistical approach can be used only if we can select a cut off point to distinguish “normal” from “abnormal,” which is not a trivial problem. Firstly, we can investigate...
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The simplest diagnostic test is one where the results of an investigation, such as an x ray examination or biopsy, are used to classify patients into two groups according to the presence or absence of a symptom or sign. For example, the table shows the relation between the results of a test, a liver scan, and the correct diagnosis based on either n...
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The statistical term “regression,” from a Latin root meaning “going back,” was first used by Francis Galton in his paper “Regression towards Mediocrity in Hereditary Stature.”1 Galton related the heights of children to the average height of their parents, which he called the mid- parent height (figure). Children and parents had the same mean height...
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In clinical research we are often able to take several measurements on the same patient. The correct analysis of such data is more complex than if each patient were measured once. This is because the variability of measurements made on different subjects is usually much greater than the variability between measurements on the same subject, and we m...
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To investigate the effects of anxiety and depression during pregnancy on obstetric complications using the data collected from the St George's Birthweight Study. Prospective population study. District general hospital in inner London. A consecutive series of 1860 white women booking for delivery were approached. Of these, 136 refused and 209 failed...
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To measure effects on terminally ill cancer patients and their families of coordinating the services available within the NHS and from local authorities and the voluntary sector. Randomised controlled trial. Inner London health district. Cancer patients were routinely notified from 1987 to 1990. 554 patients expected to survive less than one year e...
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Previous work found no effect on birthweight of alcohol and caffeine consumption in non-smokers but such an effect was found in smokers. This report investigates further the effects on birthweight of alcohol and caffeine at three stages of pregnancy in smoking women. This was a prospective population study. District general hospital in inner London...
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The relationship between nutrient intake and pregnancy outcome (adjusted birth weight and gestational age) was investigated in randomly selected non-smokers ( n 97) and in heavy smokers (15 + cigarettes/d) ( n 72) booking for ante-natal care at a hospital in South London. Weighed dietary intakes (7 d) were obtained at 28 and 36 weeks gestation. Bir...
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The contribution of rheological factors to be impedance of blood flow in the umbilical artery as determined by continuous wave Doppler ultrasound was investigated. Of the 51 pregnancies recruited, six were complicated by pre-eclampsia, 10 by intrauterine growth retardation, 15 by both pre-eclampsia and fetal growth retardation, and there were 20 co...
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This study investigated the effects of smoking and alcohol consumption in pregnancy on length, head circumference, upper arm circumference and ponderal index, of neonates born to 1513 Caucasian women who delivered at St George's Hospital, south London. All measurements were adjusted for gestational age, maternal height, parity and sex of infant. Ba...
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The aim was to investigate the effects of social factors (education, income, marital status, partners' employment status, housing tenure, social class), smoking, and maternal height on the dietary intake of pregnant women. The study was a prospective investigation on a two phase sample. The study involved women attending the antenatal clinic at a d...
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The influence of smoking and social class on dietary intake in pregnancy was investigated in a random sample of smokers (greater than or equal to 15 cigarettes/d) and nonsmokers. A total of 206 subjects (94 smokers and 112 nonsmokers) completed a 7-d weighed dietary intake at 28 wk gestation and 178 completed a second assessment at 36 wk. Nonsmoker...
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The intraclass correlation coefficient (rI) has been advocated as a statistic for assessing agreement or consistency between two methods of measurement, in conjunction with a significance test of the difference between means obtained by the two methods. We show that neither technique is appropriate for assessing the interchangeability of measuremen...
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The relationship of birthweight to gestational age is described. Two problems are discussed and solutions offered: the production of standard centile charts of birthweight for very early gestational ages, based on a small amount of data, and the adjustment of bithweight for gestational age in the analysis of factors associated with lower birthweigh...
Article
The contribution of rheological factors to the impedance of blood flow in the umbilical artery as determined by continuous-wave Doppler ultrasound was investigated. Of the 51 pregnancies recruited, six were complicated by pre-eclampsia, 10 by intrauterine growth retardation, 15 by both pre-eclampsia and fetal growth retardation, and there were 20 c...
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Full-text available
To investigate the effects of smoking, alcohol, and caffeine consumption and socio-economic factors and psychosocial stress on birth weight. Prospective population study. District general hospital in inner London. A consecutive series of 1860 white women booking for delivery were approached. 136 Refused and 211 failed to complete the study for othe...
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Sudden ischaemic death results either from an episode of acute myocardial ischaemia consequent upon coronary thrombosis or from an arrhythmia arising within a scarred left ventricle. Very different proportions of these two groups have been reported in both clinical studies in resuscitated subjects with out-of-hospital ventricular fibrillation, and...
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Mean birth weights and percentile charts are given for 161 singleton infants born between 24 and 30 weeks' gestation at the 2nd School of Medicine of Naples. This chart is the first for a Mediterranean population. Our data are similar to those reported from a United Kingdom population and from Japan, suggesting that ethnic differences in birth weig...
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According to the Poiseuille-Hagen law, viscosity influences flow resistance. A possible effect of blood viscosity upon the resistance index of the uteroplacental circulation as measured by continuous wave Doppler ultrasound was investigated in 50 pregnant women. It was found that blood viscosity variables explained only about 10% of the variation i...
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This study investigated alcohol consumption during pregnancy and its relationships with socio-economic, psychological and behavioural factors in 1463 women. Information about alcohol consumption in the preceding 7 days was obtained by structured interview at booking, 28 and 36 weeks gestation. The prevalence of current drinking was about 50% at eac...
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The link between chest illnesses in childhood to age 7 and the prevalence of cough and phlegm in the winter reported at age 23 was investigated in a cohort of 10,557 British children born in one week in 1958 (national child development study). Both pneumonia and asthma or wheezy bronchitis to age 7 were associated with a significant excess in the p...

Citations

... As reported by several studies, maternal caffeine consumptions between 300-500 mg/day were correlated to decrease in average birth weight (Martin and Bracken 1987;Haste et al. 1990;Bracken et al. 2002) and above than this quantity caused bowl irritability and sleep disturbance. It was further indicated that maternal coffee consumption has relations with greater risks of fetal development retardation in few reports (Hale et al. 2010;Rond o, Rodrigues, and Tomkins 1996;Vik et al. 2003), while others did not show any adverse effects (Fried and O'Connell, 1987;Grosso et al. 2001). ...
... The main effect of maternal smoking on fetal morphology is on the fetal growth. The association between cigarette smoke and FGR has been known for five decades [50]. Epidemiological data indicate that the risk of FGR is 2.07 times higher in mothers who smoked, and that smoking by the mother's partner also increased the risk of FGR [51]. ...
... We compared overall survival (OS) and disease-free survival (DFS) rates between ACC subtypes using the Kaplan-Meier (K-M) method [20]. The K-M curves were utilized to show the survival rate differences, and the log-rank test was used to evaluate the significance of survival rate differences. ...
... However, recently, some authors have started using the term ''response variable'' or ''variable'' (Pelletier and Giguère, 2009;Serikawa et al., 2013;Tjallingii, 2014). In statistical nomenclature, the correct term would be variable (Altman and Bland, 1999). A parameter in statistics is defined as ''a numerical characteristic of a population, as distinguished from a statistic obtained by sampling [the latter termed variable] (OED, 2014a).'' ...
... As required for a directional ("one-sided") test, the direction to be tested in Hitman is defined using prior knowledge before Hitman is applied 70 ; this must be the same as the observed direction of the exposure's effect on the outcome. The question of when directional tests are appropriate is often debated, but the primary criteria are that the direction of the test should align with prior evidence 71 and the scientific hypothesis [72][73][74][75] . These two criteria are related since scientific hypotheses are based on prior evidence. ...
... 18 Dr O'Shaughnessy discovered multiple new applications for cannabis, and ultimately recommended its use for an array of therapeutic purposes. 30,31 Through the administration of component extracts and tinctures, he effectively relieved tetanus-induced spasticity, reduced pain and suffering provoked by rheumatism, and calmed convulsions in children caused by epilepsy. [30][31] Following his seminal publication on the medical applications of cannabis in 1839 entitled 'On the preparations of Indian hemp, or gunjah', the availability of cannabis extracts in over-the-counter medications, as well as its use in Western medicine increased rapidly. ...
... This then is likely to lead to a spurious claim that it was the lighting that brought about the relaxation, rather than just natural statistical variation. RTM was first recognised by Galton (1886) and is described by Bland and Altman (1994) and Marchant (2008). ...
... Gemcitabine-related clinical and biological toxicities were retrospectively collected and graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE) version 5.0. 19 gemcitabine has clinically meaningful activity in advanced, heavily pre-treated angiosarcoma. ...
... A false-positive was defined as positive USG results in the absence of surgical findings, and a false-negative was defined as a negative USG result with a positive surgical finding. The specificity and sensitivity were calculated using the formula described by Dickie et al. (12). ...
... Participants were randomly assigned to the group PFMT protocol or the home PFMT protocol according to a random list generated by the software WinPepi, version 4.0. Participants were allocated in eight blocks of eight, as suggested in the literature [13]. The allocation sequence was concealed using numerically sequenced, opaque sealed envelopes opened after inclusion of patients in the study. ...