On the estimation of the effect of weight change on a health outcome using observational data, by utilising the target trial emulation framework

BACKGROUND/OBJECTIVES

When studying the effect of weight change between two time points on a health outcome using observational data, two main problems arise initially (i) 'when is time zero?' and (ii) 'which confounders should we account for?' From the baseline date or the 1st follow-up (when the weight change can be measured)? Different methods have been previously used in the literature that carry different sources of bias and hence produce different results.

METHODS

We utilised the target trial emulation framework and considered weight change as a hypothetical intervention. First, we used a simplified example from a hypothetical randomised trial where no modelling is required. Then we simulated data from an observational study where modelling is needed. We demonstrate the problems of each of these methods and suggest a strategy.

INTERVENTIONS

weight loss/gain vs maintenance.

RESULTS

The recommended method defines time-zero at enrolment, but adjustment for confounders (or exclusion of individuals based on levels of confounders) should be performed both at enrolment and the 1st follow-up.

CONCLUSIONS

The implementation of our suggested method [adjusting for (or excluding based on) confounders measured both at baseline and the 1st follow-up] can help researchers attenuate bias by avoiding some common pitfalls. Other methods that have been widely used in the past to estimate the effect of weight change on a health outcome are more biased. However, two issues remain (i) the exposure is not well-defined as there are different ways of changing weight (however we tried to reduce this problem by excluding individuals who develop a chronic disease); and (ii) immortal time bias, which may be small if the time to first follow up is short.

The theory of a trapped degenerate mode resonator

Resonance based biosensors are used in the detection of biological molecules for medical diagnostics. Sensing in a liquid environment is very desirable for this application, but presents a significant challenge for resonators based upon conventional technologies. In this paper, the major originality lies in the development and exposition of a fundamental theory enabling design of an original elastic resonant sensor whose modes are engineered to simultaneously possess three separate but complementary dynamical properties: namely, (1) in-plane displacement of the free interface whereby the SH waves are uncoupled from the SV and P waves; (2) intrinsic modal trapping; and finally, (3) cyclic symmetry and modal degeneracy. The modal trapping is due to the physical configuration of the resonator resulting in an imaginary wavenumber for one region of the resonator. The wave will be evanescent in this region and propagating elsewhere. The fundamental principles are elucidated, and analytical techniques are presented that facilitate the efficient design of this unique class of device.

Alcohol use and depression during adolescence and young adulthood: a summary and interpretation of mixed findings

Alcohol Use Disorder (AUD) and alcohol misuse are common among adolescents and young adults and are associated with significant personal and societal problems. Similarly, Major Depressive Disorder (MDD) and depressive symptoms are prevalent in this population and when they co-occur with alcohol misuse lead to even more severe consequences. Numerous studies have investigated the association between depressive symptoms, AUD and various drinking behaviors presenting an unclear picture. In this review we summarize studies among adolescents and young adults that have examined these relationships. From this review it emerges that several factors affect results, including study design (cross-sectional vs longitudinal), participants' age (adolescents vs young adults), severity of problems considered (AUD vs heavy drinking; MDD vs depressive symptoms), and gender. Adolescents with AUD are at higher risk for MDD in particular at a younger age. During adolescence, several drinking behaviors, including weekly alcohol use and heavy drinking, increase the risk for depressive symptoms and MDD, while during young adulthood primarily AUD, but not other drinking behaviors, is associated with increased risk for MDD. Gender may have an effect on the association between depression and drinking behaviors but its role is still unclear. Some evidence suggests that the association between AUD and MDD is bidirectional such that mood problems contribute to the onset of alcohol problems and vice-versa. More longitudinal studies are needed to examine these associations in young adults and to clarify the effect of gender on these associations. To date, findings suggest the critical need to reduce any alcohol use at a young age and to treat both depressive symptoms and AUD to prevent the occurrence of comorbid disorders.

Assessment of a point-of-care test for paracetamol and salicylate in blood

BACKGROUND

Paracetamol and salicylate are commonly taken in acute overdose. Clinicians have a low threshold for excluding the presence of these two drugs, by ordering laboratory tests in any patient suspected of ingesting an overdose or with an altered mental state.

AIM

To test the effectiveness of a new point of care test that qualitatively detects paracetamol and salicylate in blood and to examine the potential time saved by its use.

DESIGN

Prospective multicentre trial.

METHODS

The new test was compared with laboratory analysis in a routine blood sample taken from patients presenting to emergency departments with suspected overdose.

RESULTS

The test had sensitivities of 98.5% and 88.5%, and specificities of 74.7% and 92%, for paracetamol and salicylate, respectively, at cut-off levels of 25 mg/l and 100 mg/l, respectively The point of care test results were available 2 h before the laboratory result.

DISCUSSION

This point-of-care test could be used to rule out an overdose with either of these two drugs, and could thus lead to earlier clinical decisions for suspected overdose patients. Recommendations have been made following this trial that the cut-off value for paracetamol should be reduced from 25 mg/l to 12.5 mg/l in order to increase its usefulness. To prevent the test being misread, we also suggest that each device should be embossed to remind users that the presence of a line indicates there is no drug present.

Modeling of RF head exposure in children

This study analyzes the main parameters that should influence the specific absorption rate (SAR) in children's heads. The evolution of their head shape and the growth of specific parameters, such as the skull thickness, are analyzed. The influence of these parameters on the radio frequency (RF) exposure of children's head is studied. The SAR over 1 g in specific tissue is assessed in different children's head models based on magnetic resonance imaging (MRI) and on non-uniformly down-scaled adult heads. Comparisons with SAR data in adults are reported using a handset with a patch antenna operating at 900 MHz.

Survival after liver transplantation for hepatocellular carcinoma

BACKGROUND

Selection criteria for patients with hepatocellular carcinoma (HCC) suitable for liver transplantation (LT) include tumor size and number and vascular invasion. There has been a recent trend to expand the transplant criteria for HCC. We reviewed our experience to determine survival following LT based on tumor characteristics.

METHODS

A retrospective analysis was performed on 72 patients with HCC who underwent LT between 1985 and July 2002. The Milan criteria were applied for LT candidacy for HCCs that were deemed unresectable from anatomical considerations and/or the severity of underlying cirrhosis. Patients were divided into four groups: group 1: patients with known HCC who satisfied the selection criteria (n = 22); group 2: patients with known HCC that exceeded the criteria (n = 17); group 3: patients with incidental HCC found at pathological examination of the explant (n = 33); group 4: contemporary LT recipients without HCC (n = 935).

RESULTS

In the known HCC group, the interval between listing as status 2 and transplantation was 72.2 +/- 133.6 days (median 23 days). Three-year patient survival was 80.2% in group 1, 35.8% in group 2, 63.2% in group 3, and 81.5% in group 4. In group 2 patients, the tumors were significantly larger, had more nodules, and were more often bilobar. In group 3, five (15%) exceeded the criteria mainly because of tumor size and four patients died within 3 years post-LT (three from tumor recurrence).

CONCLUSION

Liver transplantation for HCC yields acceptable survival in early-stage tumors, particularly if transplanted soon after listing. Long-term survival was inferior in patients with multiple tumors and tumors that were greater than 5 cm in diameter.

The endosymbionts of tsetse flies: manipulating host-parasite interactions

Through understanding the mechanisms by which tsetse endosymbionts potentiate trypanosome susceptibility in tsetse, it may be possible to engineer modified endosymbionts which, when introduced into tsetse, render these insects incapable of transmitting parasites. In this study we have assayed the effect of three different antibiotics on the endosymbiotic microflora of tsetse (Glossina morsitans morsitans). We showed that the broad-spectrum antibiotics, ampicillin and tetracycline, have a dramatic impact on tsetse fecundity and pupal emergence, effectively rendering these insects sterile. This results from the loss of the tsetse primary endosymbiont, Wigglesworthia glossinidia, which is eradicated by ampicillin and tetracycline treatment. Using the sugar analogue and antibiotic, streptozotocin, we demonstrated specific elimination of the tsetse secondary endosymbiont, Sodalis glossinidius, with no observed detrimental effect upon W. glossinidia. The specific eradication of S. glossinidius had a negligible effect upon the reproductive capability of tsetse but did effect a significant reduction in fly longevity. Furthermore, elimination of S. glossinidius resulted in increased refractoriness to trypanosome infection in tsetse, providing further evidence that S. glossinidius plays an important role in potentiating trypanosome susceptibility in this important disease vector. In the light of these findings, we highlight progress made towards developing recombinant Sodalis strains engineered to avoid potentiating trypanosome susceptibility in tsetse. In particular, we focus on the chitinase/N-acetyl-D-glucosamine catabolic machinery of Sodalis which has previously been implicated in causing immune inhibition in tsetse.

The insect endosymbiont Sodalis glossinidius utilizes a type III secretion system for cell invasion

Sodalis glossinidius is a maternally transmitted secondary endosymbiont residing intracellularly in tissues of the tsetse flies, Glossina spp. In this study, we have used Tn5 mutagenesis and a negative selection procedure to derive a S. glossinidius mutant that is incapable of invading insect cells in vitro and is aposymbiotic when microinjected into tsetse. This mutant strain harbors Tn5 integrated into a chromosomal gene sharing high sequence identity with a type III secretion system invasion gene (invC) previously identified in Salmonella enterica. With the use of degenerate PCR, we have amplified a further six Sodalis inv/spa genes sharing high sequence identity with type III secretion system genes encoded by Salmonella pathogenicity island 1. Phylogenetic reconstructions based on the inv/spa genes of Sodalis and other members of the family Enterobacteriaceae have consistently identified a well-supported clade containing Sodalis and the enteric pathogens Shigella and Salmonella. These results suggest that Sodalis may have evolved from an ancestor with a parasitic intracellular lifestyle, possibly a latter-day entomopathogen. These observations lend credence to a hypothesis suggesting that vertically transmitted mutualistic endosymbionts evolve from horizontally transmitted parasites through a parasitism-mutualism continuum.

Prospects for control of African trypanosomiasis by tsetse vector manipulation

The extensive antigenic variation phenomena African trypanosomes display in their mammalian host have hampered efforts to develop effective vaccines against trypanosomiasis. Human disease management aims largely to treat infected hosts by chemotherapy, whereas control of animal diseases relies on reducing tsetse populations as well as on drug therapy. The control strategies for animal diseases are carried out and financed by livestock owners, who have an obvious economic incentive. Sustaining largely insecticide-based control at a local level and relying on drugs for treatment of infected hosts for a disease for which there is no evidence of acquired immunity could prove extremely costly in the long run. It is more likely that a combination of several methods in an integrated, phased and area-wide approach would be more effective in controlling these diseases and subsequently improving agricultural output. New approaches that are environmentally acceptable, efficacious and affordable are clearly desirable for control of various medically and agriculturally important insects including tsetse. Here, Serap Aksoy and colleagues discuss molecular genetic approaches to modulate tsetse vector competence.

A risk assessment and management strategy for community nursing

Many nursing interventions carry risks of harm to the patient, the nurse or the general public, and the potential for subsequent litigation or censure. This article proposes a six-point risk management strategy, which, if implemented, could reduce the chance of potential harm and litigation within a community nursing service. The strategy encompasses organizational, cultural, clinical, employee, environmental, and incident-reporting issues. A policy statement is proposed from which a risk management strategy could be developed. This is underpinned by the acceptance and ownership of risk management by all managers and clinicians, which is best achieved through a culture of honesty and openness, and where the management of risk is considered one of the fundamental duties of every member of staff. The strategy aims to enable the creation of a more coordinated, systematic and focused approach to the management of risks.

Sodalis gen. nov. and Sodalis glossinidius sp. nov., a microaerophilic secondary endosymbiont of the tsetse fly Glossina morsitans morsitans

A secondary intracellular symbiotic bacterium was isolated from the haemolymph of the tsetse fly Glossina morsitans morsitans and cultured in Aedes albopictus cell line C6/36. Pure-culture isolation of this bacterium was achieved through the use of solid-phase culture under a microaerobic atmosphere. After isolation of strain M1T, a range of tests was performed to determine the phenotypic properties of this bacterium. Considering the results of these tests, along with the phylogenetic position of this micro-organism, it is proposed that this intracellular symbiont from G. m. morsitans should be classified in a new genus Sodalis gen. nov., as Sodalis glossinidius gen. nov., sp. nov. Strain M1T is the type strain for this new species.

In vitro culture and phylogenetic analysis of "Candidatus Arsenophonus triatominarum," an intracellular bacterium from the triatomine bug, Triatoma infestans

An intracellular symbiotic bacterium was isolated from the hemolymph of Triatoma infestans and cultured in an Aedes albopictus cell line. 16S ribosomal DNA sequence analysis revealed that the bacterium was a member of the gamma-3 subgroup of the class Proteobacteria, having 96.2% sequence identity with the most closely related bacterium, Arsenophonus nasoniae, the causative agent of the son-killer trait in the parasitoid wasp Nasonia vitripennis. These bacteria share morphological features and a common tissue distribution and transmission mode. The A. nasoniae-T. infestans symbiont branch represents a lineage of insect symbionts which may be capable of horizontal transmission between phylogenetically distant host insects. We propose that the intracellular symbiont from T. infestans be classified as "Candidatus Arsenophonus triatominarum." The bacterium found in the hemocytes of T. infestans is designated the type strain of this species.

Apoptosis in procyclic Trypanosoma brucei rhodesiense in vitro

Apoptosis is a phenomenon previously associated exclusively with metazoan organisms. We show here that procyclic insect form Trypanosoma brucei rhodesiense, a protozoan parasite, when treated in vitro with concanavalin A displayed several features normally associated with apoptosis in metazoan cells. Lectin treatment induced cleavage of nuclear DNA into oligonucleosomal fragments, suggesting activation of an endogenous nuclease in the parasite. Treated trypanosomes, although agglutinated and non-motile, exhibited fluorescence after treatment with the vital stain fluorescein diacetate and retained (3)H-uridine indicating that their cell membranes remained intact during the period of DNA fragmentation. Electron micrographs showed characteristic morphology of cells undergoing apoptosis, including surface membrane vesiculation and migration of chromatin to the periphery of the nuclear membrane while mitochondria remained intact. These results suggest that treatment with concanavalin A triggers a cell death mechanism in T. b. rhodesiense similar to the process of apoptosis described in metazoa.

The kinetics of maturation of trypanosome infections in tsetse

Estimates of the time delay between the infective bloodmeal and maturation (incubation or maturation time) for 4 trypanosome stocks (2 Trypanozoon and 2 Trypanosoma congolense) show that maturation time in tsetse is not a parasite species-specific constant. The mean incubation time of a Trypanosoma brucei rhodesiense stock (EATRO 2340 - 18 days) was not significantly different from one T. congolense stock (SIKUDA88 - 15.5 days) but was significantly greater than another (1/148 FLY9 - 12.5 days). There was no significant difference in incubation times between male and female Glossina morsitans morsitans for any of the stocks but in both of the Trypanozoon stocks the proportion of female flies producing mature infections was significantly less than in males. However, estimates of gene frequency, assuming a model in which maturation is controlled by an X-linked recessive allele, gave inconsistent results indicating that maturation cannot be controlled by a single sex-linked gene. Maturation was shown to be a tsetse sex-dependent phenomenon in Trypanozoon but not in T. congolense infections. Incubation time was quite variable even for a single trypanosome stock (e.g., standard deviation of 5 days for one Trypanozoon stock); we discuss how this variability can affect disease transmission, and the interpretation of age-prevalence data.

Changing the nursing culture in a special hospital

In August 1992 a damning report was published on the mental health services provided at Ashworth Special Hospital in Merseyside. It described a brutalising and damaging regime in which nurses were singled out for the strongest criticism. In November 1994 the Health Advisory Service (HAS), which has a watchdog role, spent three weeks at Ashworth reviewing developments in the wake of the inquiry report. The HAS report, published last March, praised the hospital for undergoing tremendous change and recovery. Areas of exemplary practice were evident and major dehumanising practices had been eliminated. This paper attempts to analyse some of the difficulties confronting nurses at the hospital during the years of change between the public inquiry and the HAS visit, and identifies recent major achievements and areas for further work.

Measles immunisation: feasibility of a 90% target uptake

A three part investigation of the factors that might influence uptake of immunisation was carried out in Maidstone Health Authority; this included studies of the computer system and attitudes of parents and professionals. Several problems with immunisation scheduling, information transfer between general practitioners and clinics and the computer centre, and validity of computer information were identified. The attitudes of parents, relatives, and friends were generally favourable, although parents reported a lack of knowledge about the disease and vaccine and lack of advice from professionals. Perceived contraindications to immunisation, particularly a history of measles, were important reasons for non-uptake. Professionals' perceptions of contraindications, however, were at variance with Department of Health and Social Security guidelines and none of the recorded contraindications was valid. Calculations of potential uptake suggest that a 90% target uptake is feasible and recommendations are made for changes in services.

Parents' attitudes to measles immunization

A study of a cohort of children in Maidstone Health Authority examined the reasons for the failure to achieve targets for the uptake of measles immunization. Parents were interviewed before they were notified about measles immunization to determine their attitudes, beliefs and intentions regarding measles immunization and a further review was held with those whose child had no record of the immunization by the age of 20 months. The initial interview showed that most parents have a favourable attitude to measles immunization. However, many lacked knowledge, especially about valid contraindications, and claimed not to have received advice from a doctor or health visitor. The most common reasons for non-uptake of measles immunization were: the child had already had measles, concern about contraindications and delay owing to illness. This points to the importance of increasing doctors' and health visitors' knowledge of Department of Health and Social Security guidelines regarding valid contraindications and to the role of health visitors in promoting uptake. However there is also evidence that the gap between actual and target levels of uptake may be less than official figures suggest.