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Biomedical subjects

G Lewis

Publications and source records attributed to G Lewis.

At least 19 recordsLinked to original sources
PubMed2006

Determinants of health related quality of life and health state utility in patients with age related macular degeneration: the association of contrast sensitivity and visual acuity.

BACKGROUND: There has been increasing interest in the use of measures of health related quality of life (HRQoL) and health state utility values in Age Related Macular Degeneration (ARMD). Visual acuity has been found to be an important determinant of such measures in previous studies. More recently, another measure of visual impairment, contrast sensitivity has received considerable attention. We designed a study to examine whether the contribution of contrast sensitivity in explaining HRQoL and health utilities over and above that of visual acuity. METHODS: 209 patients with unilateral or bilateral ARMD were recruited into a cross-sectional study of patients from a large teaching hospital. Patients underwent visual tests (near and distant visual acuity, contrast sensitivity) and completed a vision function questionnaire, the VF-14, HUI3, and time trade-off. RESULTS: Using multivariate regression analysis, the study revealed that contrast sensitivity remained a statistically significant predictor of all outcome measures even when visual acuity was included. This result was supported by the correlation coefficients between measures. CONCLUSIONS: The measurement of contrast sensitivity appears to be better related to a person's HRQoL and health utility. Future studies should consider incorporating contrast sensitivity in addition to visual acuity. Studies, in particular economic evaluations, may underestimate the effect of treatment unless contrast sensitivity is considered.

Adult↗
PubMed2006

Hydroview lens implant calcification: 186 exchanges at a district general hospital.

AIM: This paper describes the experience at a district general hospital of coping with an abrupt onset of calcification of Hydroview intraocular lens (IOL) implants requiring exchange surgery mostly for symptoms of glare, even though the visual acuities were relatively good. METHODS: In this retrospective study, the operative details of 174 consecutive lens exchanges by one surgeon were retrieved from the surgeon's notes. Of these, pre and post-operative details of 106 consecutive patients were obtained from the hospital notes. RESULTS: Of the 174 lens exchanges, all were sutureless except one and 31 eyes (18%) had had previous capsulotomies. Of 143 eyes with intact posterior capsules, eight (5.6%) needed anterior vitrectomy. Lens replacements were in the bag in 136 (95%), in the sulcus in five (3.5%), and in the anterior chamber in two (1.5%). Of the 31 eyes with previous capsulotomies, 10 (32%) needed anterior vitrectomy. Lens replacements were in the bag in 22 (71%) and in the sulcus in the remaining nine cases (29%). Postoperatively the best-corrected visual acuity was improved in 53%, remained the same in 35%, and deteriorated in 12%. CONCLUSION: The lens exchange procedure was mostly predictable with satisfactory visual results allowing preoperative counselling of risks to be similar to that for cataract surgery. The onset and resolution of the period of implantation of lenses requiring exchange has not been explained.

Aged↗
PubMed2006

Optimisation of the composition of an acrylic bone cement: application to relative amounts of the initiator and the activator/co-initiator in Surgical Simplex P.

In cemented arthroplasties, the two-part self-curing acrylic bone cement is currently the only material used for anchoring the total joint replacement to the contiguous bone. In virtually all commercially available formulations of this cement, the agents used for the initiation and activation/co-initiation of the radical polymerisation reaction are benzoyl peroxide (BPO) and N, N dimethyl-para-toluidine (DMPT), respectively. There are no reports in the open literature on the rationale for the amounts of these and other constituents in the formulations of the cement. Given the concerns that have been raised in the literature regarding the effect of residual DMPT on the body, it is important to keep the starting amounts of BPO and DMPT as high and as low, respectively, as possible. In the present work, the focus is on the relative amounts of these two agents in the case of one widely used commercial formulation, Surgical Simplex(R) P. Thirty variants of this cement were formulated, covering three concentrations of the co-polymer/BPO (75%, 80%, and 85% of the mass of the powder) and DMPT amounts (ranging from 0.8 %v/v to 2.4% v/v.) The setting time (t(set)), the peak temperature reached during the cement polymerisation process (T(max)), and the ultimate compressive strength (UCS) of each of the formulations were determined in accordance with procedures specified in ISO 5833. A critical examination of all the results indicated that the optimum ratio of the concentration of the initiator (BPO embedded in the PMMA-sytrene co-polymer) to that of the activator/co-initiator (DMPT) in Surgical Simplex(R) P is 57.14 (80%w/w co-polymer + BPO per 1.4%v/v DMPT). The mean values of t(set), T(max), and UCS of this optimum formulation were determined to be 12.30 min, 68 degrees C, and 101 MPa, respectively, all of which are within the limits specified in ISO 5833. The commercially available formulation of this cement contains 2.5%v/v DMPT, while the optimum formulation, as found in the present work, has 44% less DMPT, which may translate to a smaller amount of residual DMPT that is available for elution into the periprosthetic tissue in a cemented arthroplasty, over the in vivo life of the joint replacement.

Adhesiveness↗
PubMed2006

Minimally invasive technique for ligation and stripping of the small saphenous vein guided by intra-operative duplex ultrasound.

BACKGROUND: Small saphenous vein (SSV) disconnection and removal are challenging and considered by some authors to have too high a morbidity and failure rate to justify their routine use. Our audited results are at variance with these views. METHODS: We describe a reliable, ultrasound guided, minimally invasive technique for ligation and stripping of the SSV with an incision usually <1 cm. From our total series, 50 random patients attended for ultrasound review. The sapheno-popliteal junction (SPJ), strip track and signs of recurrence were assessed and recorded. RESULTS: Since 1999, 627 patients (679 limbs) have undergone surgery for ultrasound proven SSV reflux. Fifty-two limbs (50 patients) were ultrasound assessed post-operatively. Fifty-one had flush ligation of the SPJ with one showing a 'stump' <1 cm. All showed successful SSV removal. Three limbs had minor strip track revascularisation but none had obvious clinical recurrence. Of the whole series, 11/627 (1.8%) developed proven deep vein thrombosis (DVT). There were six superficial wound infections and one strip track abscess. Sural nerve neurapraxia occurred in 13/627 (2.1%); one showing no sign of recovery at four weeks post-operatively. CONCLUSIONS: Ultrasound guided SSV is a safe, minimally invasive technique with high success and low recurrence and complication rates

Female↗
PubMed2006

Preparation and release of model drugs from thermally sensitive poly(N-isopropylacrylamide) based macrospheres.

Emulsion polymerization was employed to prepare poly(N-isopropylacrylamide) hydrogel spheres, which exhibited an LCST of 32 degrees C. The hydrogels were loaded with model drugs (benzoic acid (BA), sodium benzoate and diltiazem HCl (DHCl)) and release investigated at 25 degrees C and 37 degrees C. The temperature at which gel formation occurred was vital for successful hydrogel preparation, macrosphere formation not occurring when the temperature was close to the LCST. Sphere size increased on decreasing the stirring rate and on slowing the rate of addition of the aqueous phase. Pulsatile delivery was investigated using BA and DHCl. For both compounds a pulse was observed with a change in temperature. Pulsed release of the smaller model drug of lowest solubility, BA, was more successful. Drug release from hydrogel spheres was, therefore, found to be dependent on the physicochemical properties of the drugs, with pulsatile release of low molecular weight compounds, by temperature cycling, difficult to control.

Acrylic Resins↗
PubMed2005

The association of fetal and childhood growth with risk of schizophrenia. Cohort study of 720,000 Swedish men and women.

Previous investigations of the association of schizophrenia with patterns of pre- and post-natal growth have been based on small numbers of cases or have not taken account of the effects of prematurity on birthweight. We investigated the association of fetal growth with schizophrenia in a large cohort of Swedish males and females. We linked data from the Swedish Medical Birth Register (1973-1980), Inpatient and Discharge Register (1988-2002), Military Service Conscription Register (1990-1997), and the Population and Housing Censuses (1970 and 1990). Altogether 719,476 males and females were followed up from the age of 16 for a mean of 9.9 years. There were 736 incident cases of schizophrenia. Even in models that did not control for gestational age there was little evidence of an association between birthweight and schizophrenia (hazard ratio per kg increase in birthweight: 0.90 (95% CI 0.78 to 1.03); the hazard ratio in babies weighing <2.5 kg compared to 3.5-4.0 kg was 1.29 (95% CI 0.85 to 1.96). There was an inverse association of birth length with schizophrenia across the range of birth lengths. Short babies were at an increased risk (hazard ratio per 10 cm increase in birth length: 0.53, 95% CI 0.31 to 0.89 (fully adjusted model)). All associations were little changed when analyses were restricted to term (>36 week gestation) babies. In males, low body mass index and short height at age 18 were associated with increased risk. There is some evidence that patterns of risk in relation to fetal growth differ depending on post-natal growth patterns: the increased risk associated with low body mass index was restricted to long babies who became light adults. The exposures underlying these associations and the biological mechanisms mediating them require clarification.

Adolescent↗
PubMed2005

Cost-effectiveness of oral ibandronate compared with intravenous (i.v.) zoledronic acid or i.v. generic pamidronate in breast cancer patients with metastatic bone disease undergoing i.v. chemotherapy.

BACKGROUND: Ibandronate is the first third-generation bisphosphonate to have both oral and intravenous (i.v.) efficacy. An incremental cost-effectiveness model compared oral ibandronate with i.v. zoledronic acid and i.v. generic pamidronate in female breast cancer patients with metastatic bone disease, undergoing i.v. chemotherapy. METHODS: A global economic model was adapted to the UK National Health Service (NHS), with primary outcomes of direct healthcare costs and quality-adjusted life years (QALYs). Efficacy, measured as relative risk reduction of skeletal-related events (SREs), was obtained from clinical trials. Resource use data for i.v. bisphosphonates and the cost of managing SREs were obtained from published studies. Hospital management and SRE treatment costs were taken from unit cost databases. Monthly drug acquisition costs were obtained from the British National Formulary. Utility scores were applied to time with/without an SRE to adjust survival for quality of life. Model design and inputs were validated through expert UK clinician review. RESULTS: Total cost, including drug acquisition, was pound 386 less per patient with oral ibandronate vs. i.v. zoledronic acid and pound 224 less vs. i.v. generic pamidronate. Oral ibandronate gained 0.019 and 0.02 QALYs vs. i.v. zoledronic acid and i.v. pamidronate, respectively, making it the economically dominant option. At a threshold of pound 30,000 per QALY, oral ibandronate was cost-effective vs. zoledronic acid in 85% of simulations and vs. pamidronate in 79%. CONCLUSIONS: Oral ibandronate is a cost-effective treatment for metastatic bone disease from breast cancer due to reduced SREs, bone pain, and cost savings from avoidance of resource use commonly associated with bisphosphonate infusions.

Administration, Oral↗
PubMed2005

Borna disease virus and mental health: a cross-sectional study.

BACKGROUND: Borna disease is an infectious neurological disease of horses, sheep and possibly other animals. A role for Borna disease virus (BDV) in human neurological and psychiatric illness has been proposed, but this hypothesis remains controversial. AIM: To investigate the epidemiology of BDV in UK farming communities. DESIGN: Retrospective cohort study. METHODS: We measured the seroprevalence of BDV in the PHLS Farm Cohort, a representative sample of those employed in agriculture in the UK, and investigated the clinical significance of our findings by comparing the prevalence of symptoms of neurotic psychopathology in those found seropositive and seronegative. RESULTS: Seroprevalence was 2.3% (95%CI 1.3- 4.0%) in 1994, 3.1% in 1996 (95%CI 1.9-5.0%) and 2.6% in 1999 (95%CI 1.5%-4.6%). Those living or working on livestock farms had higher seroprevalence (2.6%) than those on mixed (2.3%) or arable (1.6%) farms, but this was not statistically significant. Exposure to horses, sheep and cats did not increase risk of seropositivity. Seropositives were no more likely to report symptoms of psychiatric morbidity. DISCUSSION: UK farming populations appear to be exposed to Borna disease virus. However, we found no evidence that exposure to BDV was associated with morbidity in this healthy occupational cohort.

Adult↗
PubMed2005

Studying suicide from the life course perspective: implications for prevention.

Suicide is an important contributor to premature mortality accounting for over 800 000 deaths worldwide every year. Environmental and genetic factors acting from before birth to old age affect an individual's risk of suicide. Risk is influenced not only by psychiatric illness and impulsive behaviour but also by factors such as the cultural acceptability of suicide, the ease of availability of lethal suicide methods, help-seeking behaviours in times of crisis and access to effective treatments following self-harm. Suicide prevention programmes might usefully focus on two discrete areas: the prevention of the psychiatric illnesses that precede suicide and tackling those risk factors particular to suicide such as media influences, help-seeking, the availability of methods and the medical management of self-harm.

Genetic Predisposition to Disease↗
PubMed2004

Assessing mental health in primary care research using standardized scales: can it be carried out over the telephone?

BACKGROUND: Telephone interviewing has economic and logistical advantages but has not been widely used in the UK. Most studies comparing face-to-face and telephone psychiatric assessment have been carried out in the US, often restricted to a population with known psychiatric disorder and involving comparisons between two separate sample groups rather than repeat interviews with the same group. The aim of the present study was to compare face-to-face and telephone administration of the 12-item General Health Questionnaire and the Revised Clinical Interview Schedule in a UK general practice sample. METHOD: Ninety-eight consecutive attenders at two general practices were assessed twice within 48 h. The order of face-to-face and telephone interviews was alternated. RESULTS: There was no evidence that the mode of administration led to a bias in scores on the CIS-R. For the GHQ, those aged over 60 tended to score higher on the telephone. There was good agreement between face-to-face and telephone scores for both GHQ and CIS-R and good agreement for case definition. Participants had a strong preference for face-to-face interviews. CONCLUSIONS: Telephone assessment of mental health using the GHQ and CIS-R is a reasonable method to be used in primary care research in the UK with the limitation that telephone responses from older people might be different from face-to-face assessments for the GHQ. However, telephone interviewing appeared less acceptable and should probably be used in the context of established or ongoing personal contact between researcher and subject.

Adolescent↗
PubMed2004

Factors influencing the development and amelioration of suicidal thoughts in the general population. Cohort study.

BACKGROUND: The incidence of suicidal thoughts in the British population is unknown. AIMS: To determine the factors associated with the development of, and recovery from, suicidal thoughts. METHOD: An 18-month follow-up survey investigated 2404 of the adults who took part in the second National Psychiatric Morbidity Survey. RESULTS: The annual incidence of suicidal thoughts was 2.3%. Incidence was highest in women and among 16- to 24-year-olds. Increased incidence was associated with not being in a stable relationship, low levels of social support and being unemployed. Fifty-seven per cent of those with suicidal thoughts at baseline had recovered by the 18-month follow-up interview. CONCLUSIONS: Risk factors for suicidal thoughts are similar to those for completed suicide, although the age and gender patterning is different. Fewer than 1 in 200 people who experience suicidal thoughts go on to complete suicide. Further study into explanations for the differences in the epidemiology of suicidal thoughts and suicide is crucial to understanding the pathways (protective and precipitating) linking suicidal thoughts to completed suicide and should help inform effective prevention of suicide.

Adolescent↗
PubMed2003

Fatigue and fracture toughness of acrylic bone cements modified with long-chain amine activators.

The composition of acrylic bone cement has been identified as one of the important parameters affecting its mechanical properties and may, in turn, ultimately influence the longevity of a cemented arthroplasty. Our aim in this study was to determine the influence of change of one compositional variable, the activator, on the fatigue performance and fracture toughness of specimens of the fully cured cement. To that end, three sets of cements were prepared, containing either the conventional activator, 4-N,N dimethyl p-toluidine (DMPT), or novel ones that are tertiary amines based on long-chain fatty acids, that is, 4-N,N dimethylaminobenzyl oleate (DMAO) and 4-N,N dimethylaminobenzyl laurate (DMAL). In the fatigue tests, the specimens were subjected to tension-tension loading, and the results (number of cycles to failure, Nf) were analyzed using the linearized form of the three-parameter Weibull equation. The fracture toughness (KIc) tests were conducted with rectangular compact tension specimens. All fracture surfaces were subsequently examined with scanning electron microscopy. We found that the Weibull mean fatigue lives for specimens fabricated using the DMPT, DMAL, and DMAO containing cements were 272,823, 453,551, and 583,396 cycles, respectively. The corresponding values for KIc were 1.94 +/- 0.05, 2.06 +/- 0.09, and 2.00 +/- 0.07 MPa radical m, respectively. Statistical analyses showed that for both the DMAL- and DMAO-containing cements, the mean values of Nf were significantly higher compared to the corresponding value for the DMPT-containing cement (Mann-Whitney test; alpha < 0.10). This result is attributed to the higher molecular weights of the former cements compared to the latter. The same trend was found for the mean KIc values (Mann-Whitney test; alpha < 0.05), with the trend being explained in terms of the differences seen in the crack morphologies. These results thus demonstrate that these novel amines are viable alternatives to DMPT for incorporation into acrylic bone cement formulations in the future.

Amines↗
PubMed2003

Isothermal microcalorimetry: an analytical technique for assessing the dynamic chemical stability of UHMWPE.

In this work, isothermal microcalorimetry (IMC) was utilized to measure the exothermic heat flow from specimens of ultra-high-molecular-weight polyethylene (UHMWPE), that had been sterilized by various standard methods, under simulated shelf storage (air at 25 degrees C, 30% r.h.) and simulated implantation (phosphate buffered saline, PBS, at 37 degrees C) conditions. Gamma-radiation sterilized UHMWPE yielded initial heat flow rates approximately 7-10 times higher in simulated shelf storage and 2-3 times higher in simulated implantation (even after 1 month in PBS) than specimens which were unsterilized or sterilized using either ethylene oxide gas (ETO) or gas plasma (GP). These results show that gamma sterilization of UHMWPE produces many more unstable bonds in the polymer than is the case when ETO or GP is used, and that the net exothermic physico-chemical change proceeds steadily in a diffusion-limited manner in air or saline. In addition, gamma sterilization in nitrogen rather than in air did not prevent the creation of unstable bonds, but did defer physico-chemical change until the UHMWPE was exposed to oxygen. These results demonstrate the usefulness of IMC as a viable method for studying the stability of polymeric implant materials.

Calorimetry↗
PubMed2003

Active versus passive anti-cytokine antibody therapy against cytokine-associated chronic diseases.

Current therapeutic vaccine trials in major chronic diseases including AIDS, cancer, allergy and autoimmunity, target antigenic pathogens but not the pathogenic stromal cytokines which can be major sources of histopathologic processes. Considering that the limited efficacy of these vaccines has been ascribed to local pathogen-induced cytokine dysfunction, we propose to antagonize pathogenic cytokine(s) by high affinity neutralizing auto-Abs triggered by specific anti-cytokine vaccines. As anticipated by theoretical considerations, animal experiments and initial clinical trials showed that anti-cytokine immunization was safe, well tolerated and triggered transient high titers Abs neutralizing pathogenic cytokines but, in contrast to conventional vaccines, no relevant cellular response was observed. Advantages of active versus passive anti-cytokine Ab therapy, particularly for long-term treatments, as those required in AIDS, cancer, allergy and autoimmunity include greater ease of maintaining high Ab titers, lack of anti-antibody responses and low cost.

Acquired Immunodeficiency Syndrome↗
PubMed2003

Social support networks and type of neurotic symptom among adults in British households.

BACKGROUND: Current knowledge about associations between psychosocial factors and non-psychotic symptoms provide little information about their relationship to specific types of neurotic symptoms such as symptoms of fatigue, worry, phobic anxiety and obsessional symptoms. METHOD: The British National Survey of Psychiatric Morbidity was based on a cross-sectional random sample of 10,108 householders. Neurotic symptoms were established by lay interviewers using the revised fully structured Clinical Interview Schedule (CIS-R). Subjects were asked about perceived social support, the size of their close primary social network and sociodemographic attributes. To assess possible associations between specific types of neurotic symptoms and psychosocial risk factors multivariate Huber logistic models (a modified form of repeated measures design modelling) was used taking account of correlation between symptom types and sampling design including clustering. RESULTS: After controlling for sociodemographic factors the risk of having a high total CIS-R score (> or = 12) was approximately doubled for both types of poor social functioning. Specific types of neurotic symptoms were associated both with a small primary group and with inadequate perceived social support. Depression, depressive ideas and panic symptoms had a higher prevalence in multivariate models. Poverty was associated with low support. CONCLUSIONS: Associations with deficiencies in social support and self-reported neurotic symptoms are better explained by symptom type and in particular by depression than by the total number of symptoms. If confirmed by longitudinal study findings this knowledge could be used to inform the development of interventions to improve social support in order to reduce specific neurotic symptom types.

Adolescent↗