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P Elliott

Publications and source records attributed to P Elliott.

At least 19 recordsLinked to original sources
PubMed1999

Investigation of excess environmental risk around putative sources: Stone's test with covariate adjustment.

Stone (Statistics in Medicine, 7, 649-660 (1988)) proposed a method of testing for elevation of disease risk around a point source. Stone's test is appropriate to data consisting of counts of the numbers of cases, Yi say, in each of n regions which can be ordered in increasing distance from a point source. The test assumes that the Yi are mutually independent Poisson variates, with means mu i = Ei lambda i where the Ei are the expected numbers of cases, for example based on appropriately standardized national incidence rates, and the lambda i are relative risks. The null hypothesis that the lambda i are constant is then tested against the alternative that they are monotone non-increasing with distance from the source. We propose an extension to Stone's test which allows for covariate adjustment via a log-linear model, mu i = Ei lambda i exp (sigma jp = 1 xij beta j), where the xij are the values of each of p explanatory variables in each of the n regions, and the beta j are unknown regression parameters. Our methods are illustrated using data on the incidence of stomach cancer near two municipal incinerators.

Air Pollutants↗
PubMed1998

QT dispersion and risk factors for sudden cardiac death in patients with hypertrophic cardiomyopathy.

This study examines the relation of QT dispersion (QTd) on a surface electrocardiogram (ECG) to clinical features and established risk factors of sudden cardiac death (SCD) in patients with hypertrophic cardiomyopathy (HC). One hundred fifty-six consecutive patients with HC (91 men, mean age 41+/-15 years, range 7 to 79) and 72 normal subjects (41 men, mean age 39+/-9 years, range 20 to 60) were studied. Standard 12-lead ECGs were recorded from each subject using a MAC VU electrocardiograph. Patients with nonsinus rhythm, atrioventricular conduction block, QRS duration > 120 ms, age < 15 years, and low amplitude T waves were excluded from the analysis (n=51). Another 22 patients who were receiving amiodarone and/or sotalol therapy were also excluded. QT interval and QTd were measured using automated analysis in the remaining 83 patients (46 men, age 40+/-14 years, range 16 to 76). QT interval (406+/-38 ms), QTc interval (432+/-27 ms), and QTd (43+/-25 ms) were significantly greater in patients with HC than in normal controls (386+/-31 ms, 404+/-16 ms, 26+/-16 ms, respectively) (p <0.0001). QTd was significantly greater in patients with HC with chest pain compared with asymptomatic or mildly symptomatic patients (50+/-28 ms vs 37+/-20 ms, p=0.02). Increased QTd was found in patients with dyspnea New York Heart Association functional classes II/III than in those with dyspnea New York Heart Association functional class I (50+/-27 ms vs 38+/-22 ms, p=0.04). QTd was weakly correlated with maximum left ventricular wall thickness (r=0.228, p=0.038). No significant association was found between QTd and any risk factors for SCD. Thus, patients with HC have increased QTd. The QTd correlates with symptomatic status. Assessment of QTd might provide complementary clinical characterization of patients with HC but its relation to SCD remains uncertain.

Adolescent↗
PubMed1998

High-dose-rate brachytherapy alone post-hysterectomy for endometrial cancer.

PURPOSE: To evaluate the outcome of post-hysterectomy adjuvant vaginal high-dose-rate (HDR) brachytherapy. METHODS AND MATERIALS: A retrospective analysis was performed on a series of 143 patients with endometrial cancer treated with HDR brachytherapy alone post-hysterectomy from 1985 to June 1993. Of these patients, 141 received 34 Gy in four fractions prescribed to the vaginal mucosa in a 2-week period. The median follow-up was 6.9 years. Patients were analyzed for treatment parameters, survival, local recurrence, distant relapse, and toxicity. RESULTS: Five-year relapse free survival and overall survival was 100% and 88% for Stage 1A, 98% and 94% for Stage IB, 100% and 86% for Stage IC, and 92% and 92% for Stage IIA. The overall vaginal recurrence rate was 1.4%. The overall late-toxicity rate was low, and no RTOG grade 3, 4, or 5 complications were recorded. CONCLUSION: These results are similar to reported international series that have used either low-dose-rate or HDR brachytherapy. The biological effective dose was low for both acute and late responding tissues compared with some of the HDR brachytherapy series, and supports using this lower dose and possibly decreasing late side-effects with no apparent increased risk of vaginal recurrence.

Adult↗
PubMed1998

Coronary vasodilator reserve is impaired in patients with hypertrophic cardiomyopathy and left ventricular dysfunction.

BACKGROUND: We tested the hypothesis that a reduced delivery of blood to the myocardium is involved in the development of systolic dysfunction of patients with hypertrophic cardiomyopathy (HCM). METHODS AND RESULTS: Eighty-four patients with HCM (62 men, age 43 +/- 12 years) were studied. Left ventricular dimensions and function (fractional shortening) were evaluated by 2-dimensional echocardiography. Myocardial blood flow (MBF) was measured by N13 -ammonia or O15 -water and positron emission tomography at baseline and after dipyridamole; coronary vasodilator reserve (CVR) was calculated as dipyridamole/baseline MBF. Patients with HCM in advanced New York Heart Association (NYHA) classes had lower dipyridamole MBF (NYHA class I = 1.57 +/- 0.64 vs class II = 1.52 +/- 0.58 vs class III = 0.96 +/- 0.32 mL/min per gram; analysis of variance, P <.05) and CVR (NYHA class I = 1.93 +/- 0.64 vs class II = 1.69 +/- 0.54 vs class III = 1.40 +/- 0.43; analysis of variance, P <.05). A positive linear correlation between fractional shortening and dipyridamole MBF was demonstrated (R = 0.23, P <.05), and patients with abnormal fractional shortening had lower dipyridamole MBF (1.07 +/- 0.43 vs 1.58 +/- 0.62 mL/min per gram, P <.01). CONCLUSIONS: Systolic dysfunction in HCM may be caused by a more severe alteration of the coronary vasodilator capacity.

Adult↗
PubMed1998

Estimating the incidence rate ratio in cross-sectional studies using a simple alternative to logistic regression.

PURPOSE: Logistic regression is often used for the analysis of cross-sectional studies, and prevalence odds and odds ratios are obtained. Other methods have been proposed for estimating prevalence ratios. An alternative regression method is also available for estimating rate ratios. Its application to cross-sectional studies is discussed. METHODS: When dealing with chronic conditions, it is possible to model binomial data using the complementary log-log link function log(-log(1-pi)), where pi is the prevalence, an option available on many statistical software packages. In effect, these are models for the disease incidence rate lambda, which is assumed to be constant over the underlying follow-up period t. This approach is based on the well-known relationship 1-pi-exp(-lambda t). The cumulative effect of age on prevalence (effectively "time of follow up") can be accounted for in the model, by specifying it as an offset. RESULTS: The regression coefficients associated with the covariates included in the model estimate rate ratios, rather than odds or prevalence ratios. The method is applied to the analysis of the prevalence of respiratory symptoms in 4395 children aged 7-9 years who are residents of Huddersfield (northern England), surveyed in the framework of the SAVIAH (Small Area Variations of Air Quality and Health) study. CONCLUSIONS: By considering saturated models including only sex as a covariate, direct comparison of crude and fitted parameters (odds, prevalence, and rate ratios) shows that, for short follow-up periods, the complementary log-log model is a valid alternative to logistic regression. More complex models including other covariates are also discussed.

Air Pollution↗
PubMed1998

Patenting computer-designed peptides.

The problem of designing new peptides that possess specific properties, such as bactericidal activity, is of wide interest. Recently, attention has focused on the use of Computer-Aided Molecular Design techniques in parallel with more traditional 'synthesise and test' methods. These techniques may typically use Genetic Algorithms to optimise molecules based on Neural Network models that predict activity. In this paper we describe a successful application of this Molecular Design methodology that has resulted in novel bactericidal peptides of real value. A key issue for commercial utilisation of such results is the ability to protect the intellectual property rights associated with the discovery of new molecules. Typically peptide patents use structural templates of amino acid hydrophobicity-hydrophilicity that define highly regular peptide patent spaces. In an extension of established patenting practice we describe a patent application that uses a Neural Net predictive model to define the regions of peptide space that we claim within the patent. This formalism makes no a priori assumptions about the regularity of the patent space. A preliminary comparative investigation of the shape and size of this and other bactericidal peptide patent spaces is conducted.

Algorithms↗
PubMed1998

Dietary magnesium intake and blood pressure: a qualitative overview of the observational studies.

Published reports of 30 separate sets of analyses from 29 observational studies relating dietary intake of magnesium to blood pressure (BP) were identified through a comprehensive search using MEDLINE and BIDS-EMBASE. Three studies were prospective, 24 cross-sectional (25 reports), of which four also contained a longitudinal component, and two were obtained from baseline data in a trial. Various dietary methodologies were used: 24-h dietary recall (n = 12), food-frequency questionnaire (8), food record (7), and duplicate diet (2). Twelve reports compared magnesium intake or BP level between subgroups. Seven showed a negative association between magnesium intake and BP level, and five reported no association. From 18 of the 30 sets of analyses either a regression estimate or a Pearson correlation coefficient was reported. Many reports also allowed identification of subgroups by sex, age and race. Ninety population samples and subgroups could thus be identified from the 30 reports. All 11 Pearson-r correlation coefficients reported for systolic BP (SBP) (three significant, P < 0.05) and 10 (out of 12) Pearson-r correlation coefficients reported for diastolic BP (DBP) (four significant) were negative. Seven reports (13 subgroups for SBP, 11 subgroups for DBP) gave partial regression coefficients after adjustment; 10 (seven significant) and eight (six significant) were negative for SBP and DBP, respectively. For 13 subgroups in five papers, Pearson-r correlation coefficients were reported after adjustment for confounding factors. Eight (out of 13) showed a negative relationship for SBP and DBP. This review points to a negative association between dietary magnesium intake and BP. A systematic quantitative overview is needed to reconcile the inconsistencies of the results of individual studies and to quantify the size of such relationship.

Adolescent↗
PubMed1998

Perinatal mortality in an English health region: geographical distribution and association with socio-economic factors.

Although the international and regional variability of perinatal mortality rates have been widely studied, less is known about the variability at the small-area level. The geographical distribution of perinatal mortality in the former North-West Thames Health Region, England, during 1981-90, and its association with small-area socio-economic factors, as measured by the Carstairs index of deprivation, were studied. Recently developed methods of analysis, including use of Bayesian statistics, were applied to obtain descriptive results and maps, and for fitting regression models that allowed for the presence of unmeasured risk factors. Significant heterogeneity (P < 0.001) of perinatal mortality across census wards and districts was found. The 5% of wards with the highest mortality experienced a risk more than 1.7 times that of the 5% with lowest mortality. Significant, positive association between deprivation and perinatal mortality was also found. Assuming causality, social differentials at the small-area level accounted for between 1.3% and 14.1% of all perinatal deaths, depending on which level of the Carstairs index was selected as reference. Although a proportion of such variability might be explained by social characteristics, a better understanding of the nature of the association is necessary.

England↗
PubMed1998

Assessment of the reproducibility of clinical coding in routinely collected hospital activity data: a study in two hospitals.

BACKGROUND: The aim of the study was to assess the reproducibility of clinical coding in two National Health Service hospitals within North West Thames region. METHODS: A retrospective audit was carried out, of clinical coding in hospital episode statistics, involving comparison of the codes assigned by local staff with those assigned by members of an external team unaware of the locally assigned codes. Where local and external coders disagreed, the records were reviewed for a third time by a further independent coder. The subjects were a random sample of 1607 non-maternity, non-psychiatric admissions occurring between 1991 and 1993, stratified for year and type of disease (asthma, diabetes, appendicitis, fractured femur and 'general'--a random selection of any diagnoses). The main outcome measures were the levels of exact agreement between local and external teams over codes for main diagnosis and procedure, and the level of approximate agreement (over the first three characters of the ICD-9 code for diagnosis and the letter and first two digits of the OPCS-4 code for procedure). For disagreements, the outcome measure was the level of agreement between the 'third' coder and the local and external coders. RESULTS: For the main diagnosis in the 'general' group at hospital A, internal and external coders agreed exactly in 43 per cent of the admissions examined and agreed 'approximately' in 55 per cent (kappa = 0.54). For hospital B the corresponding figures were 60 per cent and 72 per cent (kappa = 0.72). Approximate agreement was higher for the specific diseases considered, particularly for asthma (A: 86 per cent; B: 91 per cent) and fractured femur (A: 84 per cent; B: 89 per cent). For the main procedure at hospital A, there was exact agreement for 58 per cent and approximate agreement for 70 per cent (kappa = 0.66). For hospital B, the corresponding figures were 76 per cent and 83 per cent (kappa = 0.80). In cases of disagreement over the first three digits of the ICD-9 code for main diagnosis, the third coder disagreed with both local and external coders in 53 per cent at hospital A and 38 per cent at hospital B. Agreement was slightly better for discharges in 1992-1993 than in 1991-1992. CONCLUSIONS: The full clinical codes in NHS hospital episode statistics (HES) data should be treated with caution. The first three characters of ICD-9 codes for diagnoses and the OPCS-4 codes for procedures were more reliable. For some specific conditions such as asthma and fractured femur, reliability of the first three characters is much higher (for example, 86 per cent and 91 per cent for asthma in the two hospitals), but for the full codes can be worse. Secondary diagnoses or comorbidities may be significantly undercoded. A higher level of agreement in 1992-1993 than in 1991-1992 suggests that coding may be improving.

Abstracting and Indexing↗
PubMed1998

T wave complexity in patients with hypertrophic cardiomyopathy.

The complexity of the T wave assessed by principal component analysis (PCA) has been proposed to reflect abnormal repolarization, which may be arrhythmogenic. To determine whether PCA can differentiate patients with hypertrophic cardiomyopathy (HCM) from normal subjects and whether PCA is of prognostic importance in HCM, 112 patients with HCM (41 +/- 14 years, 64 males) and 72 healthy subjects (39 +/- 9 years, 41 males) were studied. Patients with sinus node dysfunction, AV conduction block, flat T waves, QRS > 140 ms, and those < 15 years were excluded from this study. Standard 12-lead ECGs were recorded digitally using the MAC-VU system (Marquette Medical Systems). PCA parameters were computed using the QT Guard software package by Marquette. PCA ratio was significantly greater in HCM patients than in normal controls (23.9% +/- 12.4% vs 16.1% +/- 7.6%, P < 0.0001) and was correlated with QT-end dispersion (r = 0.24, P = 0.01) and QT peak (Q point to T peak) dispersion (r = 0.35, P < 0.0001). HCM patients with syncope (n = 23) had increased PCA ratios compared with those without syncope (29.1% +/- 11.5% vs 22.5% +/- 12.3%, P = 0.01). PCA ratio was similar in patients with and without nonsustained ventricular tachycardia on Holter (25.9% +/- 11.4% vs 22.7% +/- 12.1%, P = 0.2), as well as in patients treated with amiodarone or sotalol versus those not on therapy. In conclusion, assessment of the complexity of the T wave by PCA differentiates HCM patients from normal subjects. PCA ratio correlated with QT dispersion and an increased PCA ratio was associated with a history of syncope in HCM.

Adult↗
PubMed1998

Reported sexual abuse and subsequent psychopathology among women attending psychology clinics: the mediating role of dissociation.

OBJECTIVE: While there is now a good clinical research base that outlines the links between reported sexual abuse and psychological symptoms and disorders, there is less of an understanding of the psychological processes mediating that relationship. This study assessed the role of dissociation as a mediator between reported sexual abuse and a range of psychopathological characteristics. DESIGN: A patient-series design was used. METHOD: Participants were an unselected sample of 45 women attending clinical psychology services. Each woman was interviewed regarding a reported history of sexual abuse, and completed standardized measures of general psychopathology, borderline personality disorder characteristics and dissociation. RESULTS: Sexual abuse per se was associated with the extent of depression, somatization, compulsive behaviour, phobic symptoms and borderline personality disorder characteristics. In each case, dissociation served as a complete mediator in that link. However, the same mediating relationship was not found when attempting to explain the greater psychopathological impact of more 'severe' forms of abuse (childhood experiences; intra-familial abuse). CONCLUSION: These findings suggest that the effective of clinical work with these psychopathological features would be enhanced if dissociation symptoms were addressed in women with a reported history of sexual abuse. However, the importance of that therapeutic target may be unrelated to the severity of the psychological disturbance.

Adult↗
PubMed1998

Synaptic activity, induced rhythmic discharge patterns, and receptor subtypes in enriched primary cultures of embryonic rat motoneurones.

Long-term cultures of ventral horn neurones from embryonic rat spinal cord were established, after enrichment using density gradient centrifugation, to give a high proportion of cells (> 82%) with motoneurone characteristics. Neurones were grown on spinal cord glial monolayers for 4-83 days and investigated using whole-cell patch clamp. Synaptic activity interrupted by periods of quiescence increased in frequency with culture age and was suppressed by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and strychnine. However, strychnine (10 microM) or bicuculline (10-30 microM) or removal of Mg2+ alone induced patterned rhythmic bursting. Glutamate (3-300 microM), alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA, 0.3-30 microM), and kainate (1-300 microM) evoked inward currents, as did N-methyl-D-aspartic acid (NMDA, 100 microM) in the absence of Mg2+ and presence of glycine (3-10 microM). Inward currents carried by Cl- were elicited by glycine (10-300 microM) and GABA (1-300 microM), while adenosine (1-10 microM) and cyclopentyladenosine (10 nM-1 microM) evoked a K(+)-dependent hyperpolarization. 5-HT, GABAB, purine A, and metabotropic glutamate receptors modulated synaptic excitation of presumed motoneurones. The results suggest that long-term cultures, containing more than 82% developing motoneurones, are able to generate rhythmic bursting; they respond to many of the neurotransmitters that are likely to be released onto motoneurones developing in vivo.

Adenosine↗
PubMed1997

Cancer incidence near radio and television transmitters in Great Britain. I. Sutton Coldfield transmitter.

A small area study of cancer incidence in 1974-1986 was carried out to investigate an unconfirmed report of a "cluster" of leukemias and lymphomas near the Sutton Coldfield television (TV) and frequency modulation (FM) radio transmitter in the West Midlands, England. The study used a national database of postcoded cancer registrations, and population and socioeconomic data from the 1981 census. Selected cancers were hematopoietic and lymphatic, brain, skin, eye, male breast, female breast, lung, colorectal, stomach, prostate, and bladder. Expected numbers of cancers in small areas were calculated by indirect standardization, with stratification for a small area socioeconomic index. The study area was defined as a 10 km radius circle around the transmitter, within which 10 bands of increasing distance from the transmitter were defined as a basis for testing for a decline in risk with distance, and an inner area was arbitrarily defined for descriptive purposes as a 2 km radius circle. The risk of adult leukemia within 2 km was 1.83 (95% confidence interval 1.22-2.74), and there was a significant decline in risk with distance from the transmitter (p = 0.001). These findings appeared to be consistent over the periods 1974-1980, 1981-1986, and were probably largely independent of the initially reported cluster, which appeared to concern mainly a later period. In the context of variability of leukemia risk across census wards in the West Midlands as a whole, the Sutton Coldfield findings were unusual. A significant decline in risk with distance was also found for skin cancer, possibly related to residual socioeconomic confounding, and for bladder cancer. Study of other radio and TV transmitters in Great Britain is required to put the present results in wider context. No causal implications can be made from a single cluster investigation of this kind.

Adolescent↗
PubMed1997

Cancer incidence near radio and television transmitters in Great Britain. II. All high power transmitters.

A small area study of cancer incidence, 1974-1986, near 20 high power television (TV) and frequency modulation (FM) radio transmitters in Great Britain was carried out to place in context the findings of an earlier study around the Sutton Coldfield transmitter. The national database of postcoded cancer registrations was used with population and socioeconomic data from the 1981 census. Cancers examined were adult leukemias, skin melanoma, and bladder cancer, following the findings in the earlier study of significant declines in risk of these cancers with distance from the Sutton Coldfield transmitter. Childhood leukemia and brain cancer were also examined. Statistical analysis was performed for all transmitters combined, four overlapping groups of transmitters defined by their transmission characteristics, and for all transmitters separately. There were 3,305 adult leukemia cases from 0-10 km (observed/expected (O/E) ratio = 1.03, 95% confidence interval (CI) 1.00-1.07). A decline in risk of adult leukemia was found for all transmitters combined (p = 0.05), two of the transmitter groups, and three of the single transmitters; for all transmitters combined, observed excess risk was no more than 15% at any distance up to 10 km, and there was no observed excess within 2 km of transmitters (O/E ratio = 0.97, 95% CI 0.78-1.21). For childhood leukemia and brain cancer, and adult skin melanoma and bladder cancer, results were not indicative of a decline in risk with distance from transmitters. The magnitude and pattern of risk found in the Sutton Coldfield study did not appear to be replicated. The authors conclude that the results at most give no more than very weak support to the Sutton Coldfield findings.

Adolescent↗
PubMed1997

High-dose-rate brachytherapy in the management of high-grade intraepithelial neoplasia of the vagina.

The majority of women with high-grade intraepithelial neoplasia (VAIN 3) are over 60 years of age and have a history of premalignant or malignant disease of the cervix. Although the natural history of VAIN is not well defined, high-grade lesions are premalignant. Ablative treatment with laser or 5-fluorouracil cream is commonly unsatisfactory. Several series have reported a low rate of recurrence and complications if VAIN 3 is treated with low-dose-rate brachytherapy. This retrospective review reports the outcome of 14 patients treated with high-dose-rate brachytherapy, with a dose of 34 to 45 Gy in 4.5- to 8.5-Gy fractions. Treatment was well tolerated with no severe early or late toxicity observed. At a median follow-up of 46 months 1 patient progressed to invasive carcinoma of the vagina; in another patient VAIN 3 persisted.

Adult↗
PubMed1997

Small-area study of the incidence of neoplasms of the brain and central nervous system among adults in the West Midlands region, 1974-86. Small Area Health Statistics Unit.

This small-area study of incidence of cancers of the brain and central nervous system found evidence of trend (P = 0.02) of cancer risk with deprivation (8% higher risk in affluent areas), but no significant association with urban-rural status. Results were not indicative of a strong geographically determined risk at small-area level.

Adolescent↗