Evaluation of prognostic risk models for postoperative pulmonary complications in adult patients undergoing major abdominal surgery: a systematic review and international external validation cohort study

BACKGROUND

Stratifying risk of postoperative pulmonary complications after major abdominal surgery allows clinicians to modify risk through targeted interventions and enhanced monitoring. In this study, we aimed to identify and validate prognostic models against a new consensus definition of postoperative pulmonary complications.

METHODS

We did a systematic review and international external validation cohort study. The systematic review was done in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We searched MEDLINE and Embase on March 1, 2020, for articles published in English that reported on risk prediction models for postoperative pulmonary complications following abdominal surgery. External validation of existing models was done within a prospective international cohort study of adult patients (≥18 years) undergoing major abdominal surgery. Data were collected between Jan 1, 2019, and April 30, 2019, in the UK, Ireland, and Australia. Discriminative ability and prognostic accuracy summary statistics were compared between models for the 30-day postoperative pulmonary complication rate as defined by the Standardised Endpoints in Perioperative Medicine Core Outcome Measures in Perioperative and Anaesthetic Care (StEP-COMPAC). Model performance was compared using the area under the receiver operating characteristic curve (AUROCC).

FINDINGS

In total, we identified 2903 records from our literature search; of which, 2514 (86·6%) unique records were screened, 121 (4·8%) of 2514 full texts were assessed for eligibility, and 29 unique prognostic models were identified. Nine (31·0%) of 29 models had score development reported only, 19 (65·5%) had undergone internal validation, and only four (13·8%) had been externally validated. Data to validate six eligible models were collected in the international external validation cohort study. Data from 11 591 patients were available, with an overall postoperative pulmonary complication rate of 7·8% (n=903). None of the six models showed good discrimination (defined as AUROCC ≥0·70) for identifying postoperative pulmonary complications, with the Assess Respiratory Risk in Surgical Patients in Catalonia score showing the best discrimination (AUROCC 0·700 [95% CI 0·683-0·717]).

INTERPRETATION

In the pre-COVID-19 pandemic data, variability in the risk of pulmonary complications (StEP-COMPAC definition) following major abdominal surgery was poorly described by existing prognostication tools. To improve surgical safety during the COVID-19 pandemic recovery and beyond, novel risk stratification tools are required.

FUNDING

British Journal of Surgery Society.

Dynamic self-assembly of DNA minor groove-binding ligand DB921 into nanotubes triggered by an alkali halide

We describe a novel self-assembling supramolecular nanotube system formed by a heterocyclic cationic molecule which was originally designed for its potential as an antiparasitic and DNA sequence recognition agent. Our structural characterisation work indicates that the nanotubes form via a hierarchical assembly mechanism that can be triggered and tuned by well-defined concentrations of simple alkali halide salts in water. The nanotubes assembled in NaCl have inner and outer diameters of ca. 22 nm and 26 nm respectively, with lengths that reach into several microns. Our results suggest the tubes consist of DB921 molecules stacked along the direction of the nanotube long axis. The tubes are stabilised by face-to-face π-π stacking and ionic interactions between the charged amidinium groups of the ligand and the negative halide ions. The assembly process of the nanotubes was followed using small-angle X-ray and neutron scattering, transmission electron microscopy and ultraviolet/visible spectroscopy. Our data demonstrate that assembly occurs through the formation of intermediate ribbon-like structures that in turn form helices that tighten and compact to form the final stable filament. This assembly process was tested using different alkali-metal salts, showing a strong preference for chloride or bromide anions and with little dependency on the type of cation. Our data further demonstrates the existence of a critical anion concentration above which the rate of self-assembly is greatly enhanced.

Structural and mechanistic insights into Helicobacter pylori NikR activation

NikR is a transcriptional metalloregulator central in the mandatory response to acidity of Helicobacter pylori that controls the expression of numerous genes by binding to specific promoter regions. NikR/DNA interactions were proposed to rely on protein activation by Ni(II) binding to high-affinity (HA) and possibly secondary external (X) sites. We describe a biochemical characterization of HpNikR mutants that shows that the HA sites are essential but not sufficient for DNA binding, while the secondary external (X) sites and residues from the HpNikR dimer–dimer interface are important for DNA binding. We show that a second metal is necessary for HpNikR/DNA binding, but only to some promoters. Small-angle X-ray scattering shows that HpNikR adopts a defined conformation in solution, resembling the cis-conformation and suggests that nickel does not trigger large conformational changes in HpNikR. The crystal structures of selected mutants identify the effects of each mutation on HpNikR structure. This study unravels key structural features from which we derive a model for HpNikR activation where: (i) HA sites and an hydrogen bond network are required for DNA binding and (ii) metallation of a unique secondary external site (X) modulates HpNikR DNA binding to low-affinity promoters by disruption of a salt bridge.

Synchrotron-based in vivo tracking of implanted mammalian cells

We have developed an X-ray imaging protocol that permits 3D visualisation of a small number of implanted cells within bulk tissue. The cells are marked using natural endocytosis of inert gold nano-particles. The resulting local increase in electron density allows high imaging contrast to be obtained from small clusters of these marked cells. Using this technique we have imaged C6 glioma cells within the brain of a model animal. The cells were marked by exposing them to colloidal gold incorporated in the growth media. Gold-loaded glioma cells were implanted into the brains of adult male Wistar rats. After tumours had been allowed to develop for up to 2 weeks, the animals were sacrificed and images of the intact cranium were acquired at the SYRMEP imaging station on the Elettra synchrotron in Italy. Computed tomography was performed using mixed absorption and phase contrast techniques at an X-ray energy of 24 keV. In the resulting volume datasets the tumour bulk is clearly visible and the infiltrating nature of the malignant growth is well demonstrated. Although the protocol was developed using this particular model of malignant brain tumour, it is believed that it will be possible to use it with other cell lines.

Endoscopic sinus surgery for the excision of nasal polyps: A systematic review of safety and effectiveness

BACKGROUND

Functional endoscopic sinus surgery (FESS) has been used for >20 years for the management of sinus disease including the excision of nasal polyps. Our objective was to perform a systematic review of safety and effectiveness of FESS for the removal of nasal polyps.

METHODS

The Cochrane Library, MEDLINE, Embase, Science Citation Index, other databases, and websites were searched in January and December 2005 using key words for nasal polyps and endoscopic surgery. All randomized controlled trials, nonrandomized comparative studies, and case series studies that described outcomes associated with FESS for the excision of nasal polyps were included. Forty-two publications were included from the 632 (6.6%) articles initially identified. Two reviewers assessed validity of included studies and extracted relevant data.

RESULTS

Three randomized controlled trials, 4 nonrandomized comparative studies, and 35 case series studies were included in the review. FESS was compared with endoscopic polypectomy, Caldwell-Luc, radical nasalization, and intranasal ethmoidectomy. In general, studies were of poor quality and lacked description of important variables influencing surgical outcome. Overall complications for FESS from case series studies ranged from 0.3 to 22.4% (median, 7.0%). Major complications ranged from 0 to 1.5% (median, 0%) and minor complications ranged from 1.1 to 20.8% (median, 7.5%). The potentially most serious complications were cerebrospinal fluid leaks, injury to the internal carotid artery, dural exposure, meningitis, bleeding requiring transfusion, periorbital/orbital fat exposure, and orbital penetration. Symptomatic improvement ranged from 78 to 88% for FESS compared with 43 to 84% for comparative procedures. From case series, symptomatic improvement ranged from 40 to 98% (median, 88%).

CONCLUSION

FESS may offer some advantages in safety and effectiveness over comparative techniques, but wide variation in reported results and methodological shortcomings of studies limit the certainty of these conclusions. Wide variation in complication rates suggests the need for audit of existing practice. Additional high-quality studies with a fuller description of potential confounding factors and effect modifiers will help to define the effectiveness of FESS more clearly.

Offspring birthweight is not associated with paternal insulin resistance

AIMS/HYPOTHESIS

Low birthweight is associated with insulin resistance and other insulin resistance-related phenotypes: diabetes, hypertension, and vascular disease in later life. The underlying mechanism is unclear. The foetal insulin hypothesis proposes that a single genetic predisposition to beta cell dysfunction/insulin resistance results in both reduced insulin-dependent foetal growth in utero, hence low birthweight, and predisposition to type 2 diabetes. The aim of this study was to test whether, as predicted by the foetal insulin hypothesis, there is an association between measures of paternal insulin resistance and offspring birthweight.

SUBJECTS AND METHODS

The Exeter Family Study of Childhood Health (EFSOCH) is a community-based study within central Exeter (UK), established to test the foetal insulin hypothesis prospectively. Associations were tested between offspring birthweight and paternal insulin resistance, calculated by homeostasis model assessment analysis in 986 families using data relating to singleton, non-diabetic, UK white pregnancies. Ethics approval was given by the North and East Devon local ethics committee.

RESULTS

Offspring birthweight was not significantly correlated with log paternal insulin resistance (r=0, p=0.91), log HDL cholesterol concentration (r=-0.02, p=0.47) or log triglyceride concentration (r=0, p=0.99) when corrected for paternal BMI and common confounders. Multiple linear regression analysis confirmed that paternal insulin resistance was not an independent predictor of offspring birthweight.

CONCLUSIONS/INTERPRETATION

Results from a young, adult, non-diabetic population do not support the foetal insulin hypothesis as an explanation for the association of low birthweight with insulin resistance.

An epidemiological study of head injuries in a UK population attending an emergency department

We aimed to identify the attendance rate for all head injuries, and for moderate to severe head injury (MSHI), in an emergency department (ED), and related risk factors for MSHI, including age, sex, area of residence, and socioeconomic status (SES). This was a retrospective descriptive epidemiological study of an ED database of head injury attendances over 6 years, carried out in an ED that serves both urban and mixed rural and urban areas, with a wide socioeconomic range, and a total population of 344,600. The main outcome measure was rates of attendance for head injury. Head injury presentations accounted for 3.4% of all attendances per year. An overall rate of 453 per 100,000 was found for all head injuries, of which 40 per 100,000 were moderate to severe (10.9%). Urban residents had significantly greater risk of presenting with MSHI compared with residents of mixed/rural areas. Males were more at risk than females, and children and adolescents had higher risk of MSHI. A high attendance rate of MSHI was found in the <5 year old age group in urban areas for both sexes. A gradient, with higher attendance in groups with lower SES, was observed for children in urban areas, while the gradient was reversed in mixed/rural areas. Head injuries are a relatively common cause of attendance at ED. There is significant variation in attendance with MSHI with regard to sex, age, socioeconomic factors, and type of area of residence. The planning and delivery of preventative and management services may be improved by such analyses.

Impact of discussion on preferences elicited in a group setting

BACKGROUND

The completeness of preferences is assumed as one of the axioms of expected utility theory but has been subject to little empirical study.

METHODS

Fifteen non-health professionals was recruited and familiarised with the standard gamble technique. The group then met five times over six months and preferences were elicited independently on 41 scenarios. After individual valuation, the group discussed the scenarios, following which preferences could be changed. Changes made were described and summary measures (mean and median) before and after discussion compared using paired t test and Wilcoxon Signed Rank Test. Semi-structured telephone interviews were carried out to explore attitudes to discussing preferences. These were transcribed, read by two investigators and emergent themes described.

RESULTS

Sixteen changes (3.6%) were made to preferences by seven (47%) of the fifteen members. The difference between individual preference values before and after discussion ranged from -0.025 to 0.45. The average effect on the group mean was 0.0053. No differences before and after discussion were statistically significant. The group valued discussion highly and suggested it brought four main benefits: reassurance; improved procedural performance; increased group cohesion; satisfying curiosity.

CONCLUSION

The hypothesis that preferences are incomplete cannot be rejected for a proportion of respondents. However, brief discussion did not result in substantial number of changes to preferences and these did not have significant impact on summary values for the group, suggesting that incompleteness, if present, may not have an important effect on cost-utility analyses.

Association between methodological characteristics and outcome in health technology assessments which included case series

OBJECTIVES

Case series constitute a weak form of evidence for effectiveness of health technologies. However, for a variety of reasons, such studies may be included in health technology assessments. There are no clear criteria for assessing the quality of case series. We carried out an empirical investigation of the association between outcome frequency and methodological characteristics in a sample of health technology assessments.

METHODS

Systematic reviews of functional endoscopic sinus surgery for nasal polyps, spinal cord stimulation for chronic back pain, and percutaneous transluminal coronary angioplasty and coronary artery bypass grafting for chronic stable angina were identified as containing more than forty case series. Data were extracted by one reviewer and checked by a second on population characteristics, outcomes, and the following methodological features: sample size, prospective/retrospective approach, consecutive recruitment, multi- or single-center organization, length of follow-up, independence of outcome measurement, and date of publication. Association between methodological features and outcome were explored in univariate and multivariate analyses using parametric and nonparametric tests and robust regression or analysis of variance/analysis of covariance, as appropriate.

RESULTS

Included reviews contained between forty-two and seventy-six case series studies, involving 5 to 172,283 participants. Reporting of methodological features was poor and limited the analyses. In general, we found little evidence of any association between methodological characteristics and outcome. Sample size is used as an inclusion criterion in many reviews of'case series but was consistently shown to have no relationship to outcome in all analyses. A prospective approach was not associated with outcome. Insufficient data were available to explore consecutive recruitment. Mixed results were shown for length of follow-up, independence of outcome measurement, and publication date.

CONCLUSIONS

We found little evidence to support the use of many of the factors included in tools used for quality assessment of case series. Importantly, we found no relationship between study size and outcome across the four examples studied. Isolated examples of a potentially important relationship between other methodological factors and outcome were shown, for example, blinding of outcome measurement, but these examples were not shown consistently across the small number of examples studied. Further research into the determinants of quality in case series studies is required to support health technology assessment.

What are the clinical features of lung cancer before the diagnosis is made? A population based case-control study

BACKGROUND

Over 38,000 new cases of lung cancer occur each year in the UK. Most are diagnosed after initial presentation to primary care, but the relative importance of the various clinical features is largely unknown.

METHODS

A population based case-control study was undertaken in all 21 general practices in Exeter, Devon, UK (population 128 700). 247 primary lung cancers were studied in subjects aged over 40 years diagnosed between 1998 and 2002 and 1235 controls matched by age, sex and general practice. The entire primary care record for 2 years before diagnosis was coded using the International Classification of Primary Care-2. Univariable and multivariable conditional logistic regression analyses were used to identify and quantify clinical features independently associated with lung cancer. The main outcome measures were odds ratios and positive predictive values for these variables.

RESULTS

Seven symptoms (haemoptysis, loss of weight, loss of appetite, dyspnoea, thoracic pain, fatigue and cough), one physical sign (finger clubbing), and two abnormal investigation results (thrombocytosis and abnormal spirometry) were associated with lung cancer in multivariable analyses, as was cigarette smoking. After excluding variables reported in the final 180 days before diagnosis, haemoptysis, dyspnoea and abnormal spirometry remained independently associated with cancer.

CONCLUSIONS

This study provides an evidence base for selection of patients for investigation of possible lung cancer, both for clinicians and for developers of guidelines.

Clinical features of colorectal cancer before diagnosis: a population-based case-control study

Most colorectal cancers are diagnosed after the onset of symptoms. However, the risk of colorectal cancer posed by particular symptoms is largely unknown, especially in unselected populations like primary care. This was a population-based case–control study in all 21 general practices in Exeter, Devon, UK, aiming to identify and quantify the prediagnostic features of colorectal cancer. In total, 349 patients with colorectal cancer, aged 40 years or more, and 1744 controls, matched by age, sex and general practice, were studied. The full medical record for 2 years before diagnosis was coded using the International Classification of Primary Care-2. We calculated odds ratios for variables independently associated with cancer, using multivariable conditional logistic regressions, and then calculated the positive predictive values of these variables, both individually and in combination. In total, 10 features were associated with colorectal cancer before diagnosis. The positive predictive values (95% confidence interval) of these were rectal bleeding 2.4% (1.9, 3.2); weight loss 1.2% (0.91, 1.6); abdominal pain 1.1% (0.86, 1.3); diarrhoea 0.94% (0.73, 1.1); constipation 0.42% (0.34, 0.52); abnormal rectal examination 4.0% (2.4, 7.4); abdominal tenderness 1.1% (0.77, 1.5); haemoglobin <10.0 g dl⁻¹ 2.3% (1.6, 3.1); positive faecal occult bloods 7.1% (5.1, 10); blood glucose>10 mmol l⁻¹ 0.78% (0.51, 1.1): all P<0.001. Earlier diagnosis of colorectal cancer may be possible using the predictive values for single or multiple symptoms, physical signs or test results.

Do the findings of case series studies vary significantly according to methodological characteristics?

OBJECTIVES

To review the use of case series in National Institute for Clinical Excellence (NICE) Health Technology Assessment (HTA) reports, to review systematically the methodological literature for papers relating to the validity of aspects of case series design, and to investigate characteristics and findings of case series using examples from the UK's Health Technology Assessment programme.

DATA SOURCES

Electronic databases. NICE website. Reports produced as part of the UK's HTA programme.

REVIEW METHODS

NICE HTAs that used information from case series studies were obtained from the NICE website and a range of quality criteria applied. Searches of electronic databases, handsearched journals and the bibliographies of papers were made in order to find studies that assessed aspects of case series design, analysis or quality in relation to study validity. Hypotheses relating to the design of case series studies were developed and empirically investigated using four case examples from existing reports produced as part of the UK's HTA programme (functional endoscopic sinus surgery for nasal polyps, spinal cord stimulation for chronic back pain, percutaneous transluminal coronary angioplasty and coronary artery bypass grafting for chronic angina). Analysis was undertaken comparing studies within each review.

RESULTS

There was no consensus on which case series to include in HTAs, how to use them or how to assess their quality, despite them being used in 30% of NICE HTAs. No previous studies empirically investigating methodological characteristics of case series were found. However, it is possible that the search strategy failed to find relevant studies. Poor reporting of case series characteristics severely constrained analysis and there were insufficient data to investigate all the hypotheses. Findings were not consistent across the different topics and were subject to considerable uncertainty. All the examples in our analysis were surgical interventions, which are prone to additional confounding factors due to difficulties of standardisation compared with drug treatment. Our findings may not be generalisable outside the interventions studied. The case series reports included generally exhibited poor reporting of methodological characteristics. This constrained our analysis. The use of several methods of analysis has led to apparently discrepant results. Given the number of analysis performed, the usual level of significance (p = 0.05) should be viewed with caution. The most important limitation of this study is the small number of cases on which the findings are based. The results are therefore tentative and should be viewed with caution.

CONCLUSIONS

Case series are incorporated in a significant proportion of health technology assessments. Quality criteria have been used to appraise the quality of case series and decide on their inclusion in reviews of studies using this design. In this small series of case studies drawn from HTAs carried out for the NHS HTA programme, little evidence was found to support the use of many of the factors included in quality assessment tools. Importantly, no relationship was found between study size and outcome across the four examples studied. Isolated examples of a potentially important relationship between other methodological factors and outcome were shown, such as blinding of outcome measurement, but these were not shown consistently across the small number of examples studied. This study is based on a very small sample of studies and should therefore be considered as exploratory. Further investigation of the relationship between methodological features and outcome is justified given the frequency of use of case series in health technology assessments. Further research into the methodological features of case series and their outcome is justified in a wider sample of technologies and larger sets of case series. Value of information analyses including case series could be explored. Further exploration of the differences between case series and randomised controlled trial results, preferably using registry or comprehensive case series data, would be valuable.

Microwave and thermal balloon ablation for heavy menstrual bleeding: a systematic review

OBJECTIVE

To compare the effectiveness of two second generation endometrial ablation techniques (microwave and thermal balloon endometrial ablation) with first generation techniques of endometrial ablation to treat heavy menstrual bleeding in women.

SEARCH STRATEGY

We searched the Cochrane Library (issue 3, 2002), the National Research Register, MEDLINE (1966 to August 2002), Embase (1980 to August 2002) and Web of Science Proceedings (all years). We also searched reference lists and contacted experts and manufacturers in the field.

SELECTION CRITERIA

Randomised controlled trials and controlled trials of microwave endometrial ablation and thermal balloon endometrial ablation versus transcervical resection and rollerball ablation, alone or in combination, to treat heavy menstrual bleeding were included.

DATA COLLECTION AND ANALYSIS

Two reviewers independently selected studies for inclusion and extracted data. As there was considerable clinical and methodological heterogeneity among the studies, meta-analysis was not undertaken and results are presented descriptively.

RESULTS

Two randomised controlled trials of microwave endometrial ablation and eight trials (six randomised controlled trials) of thermal balloon endometrial ablation were included in the review. No significant differences were found between first and second generation techniques in terms of amenorrhoea, bleeding patterns, pre-menstrual symptoms, patient satisfaction or quality of life. Microwave endometrial ablation and thermal balloon endometrial ablation had significantly shorter operating and theatre times than first generation techniques. Adverse effects were few with all techniques, but there were fewer peri-operative adverse effects with second generation techniques.

CONCLUSION

Microwave endometrial ablation and thermal balloon endometrial ablation are alternatives to first generation techniques for treating heavy menstrual bleeding. No head-to-head trials of microwave endometrial ablation and thermal balloon endometrial ablation have been undertaken and there is not yet enough evidence of differences in clinical effectiveness between these two techniques.

Cost effectiveness of imatinib compared with interferon-alpha or hydroxycarbamide for first-line treatment of chronic myeloid leukaemia

OBJECTIVE

To evaluate the cost utility of imatinib compared with interferon (IFN)-alpha or hydroxycarbamide (hydroxyurea) for first-line treatment of chronic myeloid leukaemia.

DESIGN AND SETTING

A cost-utility (Markov) model within the setting of the UK NHS and viewed from a health system perspective was adopted. Transition probabilities and relative risks were estimated from published literature. Costs of drug treatment, outpatient care, bone marrow biopsies, radiography, blood transfusions and inpatient care were obtained from the British National Formulary and local hospital databases. Costs (pound, year 2001-03 values) were discounted at 6%. Quality-of-life (QOL) data were obtained from the published literature and discounted at 1.5%. The main outcome measure was cost per QALY gained. Extensive one-way sensitivity analyses were performed along with probabilistic (stochastic) analysis.

RESULTS

The incremental cost-effectiveness ratio (ICER) of imatinib, compared with IFNalpha, was pound26,180 per QALY gained (one-way sensitivity analyses ranged from pound19,449 to pound51,870) and compared with hydroxycarbamide was pound86,934 per QALY (one-way sensitivity analyses ranged from pound69,701 to pound147,095) [ pound1=$US1.691=euro1.535 as at 31 December 2002].Based on the probabilistic sensitivity analysis, 50% of the ICERs for imatinib, compared with IFNalpha, fell below a threshold of approximately pound31,000 per QALY gained. Fifty percent of ICERs for imatinib, compared with hydroxycarbamide, fell below approximately pound95,000 per QALY gained.

CONCLUSIONS

This model suggests, given its underlying data and assumptions, that imatinib may be moderately cost effective when compared with IFNalpha but considerably less cost effective when compared with hydroxycarbamide. There are, however, many uncertainties due to the lack of long-term data.

What value health?: A review of health state values used in early technology assessments for NICE

The objective of this article was to review the methods used to obtain quality-of-life (utility) weights reported in assessments carried out for the National Institute for Health and Clinical Excellence (NICE).The design of the review was a cross-sectional survey. Health technology assessment (HTA) reports published on the NICE website up to May 2003 were reviewed. Data were extracted on the following: the approach to utility estimation (direct or indirect), how health states were described for indirect estimation, valuation techniques used (standard gamble [SG], time trade-off [TTO], visual analogue scale [VAS], etc.), whether uncertainty in utility estimates was explored in cost-utility analyses, and whether utility values were identified as a priority for further research by assessment authors.Fifty-six assessments were reviewed, of which 28 reported 45 cost-utility analyses. There was striking variation in the values used to describe different health states. Data from patients were used in 15 (33%) analyses, from the general public in 10 (22%) and from clinicians in 4 (9%). In 16 (36%) cases, the source for utility estimates was unclear. Health states were described using a range of generic and disease-specific measures, although the EQ-5D was used most frequently. In 25 analyses (56%), the valuation technique used was not reported. TTO was used in 11 (24%), SG in 3 (7%), magnitude estimation in 5 (11%) and VAS in 1 (2%). Sensitivity analyses based on utility values were reported in 25 cases (56%), more commonly in reports of analyses carried out by independent teams than technology sponsors although this may be subject to reporting bias. Further research into quality of life was recommended in 17 (61%) of the 28 assessment reports that contained at least one cost-utility analysis. Greater transparency and consistency are required in reporting the methods used to obtain quality-of-life weights in cost-utility analyses, and better sources of data are required. Methodological variation results in important differences in values. Therefore, caution must be exercised when comparing the results of different cost-utility analyses.

A cost-utility analysis of microwave and thermal balloon endometrial ablation techniques for the treatment of heavy menstrual bleeding

OBJECTIVE

To assess the cost effectiveness of the second-generation surgical treatments for heavy menstrual bleeding (microwave and thermal balloon endometrial ablation) compared with existing endometrial ablation techniques (transcervical resection and rollerball, alone or in combination) and hysterectomy.

DESIGN

A state transition (Markov) cost-utility economic model.

POPULATION

Women with heavy menstrual bleeding.

METHODS

A Markov model was developed using spreadsheet software. Transition probabilities, costs and quality of life data were obtained from a systematic review of effectiveness undertaken by the authors, from published sources, and expert opinion. Cost data were obtained from the literature and from a NHS trust hospital. Indirect comparison of thermal balloon endometrial ablation versus microwave endometrial ablation or either second-generation endometrial ablation method versus hysterectomy, and comparison of second-generation versus first-generation techniques were carried out from the perspective of health service payers. The effects of uncertainty were explored through extensive one-way sensitivity analyses and Monte Carlo simulation.

MAIN OUTCOME MEASURES

Incremental cost effectiveness ratios based on cost per quality adjusted life year (QALY) gained, and cost effectiveness acceptability curves.

RESULTS

Compared with first-generation techniques, both microwave and thermal balloon endometrial ablation cost less and accrued more QALYs. Hysterectomy was more expensive, but accrued more QALYs than all endometrial ablation methods. Baseline results showed that differences between microwave endometrial ablation and thermal balloon endometrial ablation were slight. Sensitivity analyses showed that small changes in values may have a marked effect on cost effectiveness. Probabilistic simulation highlighted the uncertainty in comparisons between different endometrial ablation options, particularly between second-generation techniques.

CONCLUSIONS

Despite limitations in available data, the analysis suggests that second-generation techniques are likely to be more cost effective than first-generation techniques in most cases. Hysterectomy, where a woman finds this option acceptable, continues to be a very cost effective procedure compared with all endometrial ablation methods.

Effectiveness and cost-effectiveness of imatinib for first-line treatment of chronic myeloid leukaemia in chronic phase: a systematic review and economic analysis

OBJECTIVES

To evaluate the effectiveness of imatinib as first-line treatment for chronic myeloid leukaemia (CML) compared with interferon-alpha (IFN-alpha), hydroxyurea and bone marrow transplantation (BMT), and the cost-effectiveness of imatinib compared with IFN-alpha and hydroxyurea.

DATA SOURCES

Electronic databases.

REVIEW METHODS

Selected studies and full-text articles were screened and rigorously selected. Survival was the key outcome measure. Surrogate outcome measures included haematological (blood) response and cytogenetic (bone marrow) response (CR). As no published cost-effectiveness studies were found that compared imatinib and IFN-alpha, an independent Markov model was constructed and this was compared with models submitted to the National Institute for Clinical Excellence by the manufacturer of imatinib.

RESULTS

Intention-to-treat analysis showed that imatinib was associated with complete CR at 12 months follow-up of 68% compared with 20% for the IFN-alpha plus Ara-C group. The estimated proportion of people taking imatinib who had not progressed to accelerated or blast phases at 12 months was 98.5%, and 93.1% for IFN-alpha plus Ara-C. Overall survival was not statistically significantly different. Withdrawal due to side-effects was 2% for imatinib and 5.6% for IFN-alpha plus Ara-C. Cross-over due to intolerance was 0.7% and 22.8% for imatinib and for IFN-alpha plus Ara-C, respectively. Quality of life was better in the imatinib group than the IFN-alpha group when assessed at 1, 3 and 6 months. Median survival across the four IFN-alpha versus hydroxyurea studies was 66 and 56.2 months, respectively. Median complete CR was 6% for IFN-alpha and 0 for hydroxyurea. Median withdrawal due to side-effects was 24% and 4% for IFN-alpha and hydroxyurea, respectively. Four out of the five studies comparing BMT and IFN-alpha showed a long-term survival advantage for BMT over IFN-alpha, but a short-term disadvantage. In four of the five studies comparing BMT and IFN-alpha, median survival had not yet been reached in the BMT groups in 6--10 years. Median survival in the IFN-alpha arms ranged from 5.2 to 7 years. The BMT group gained a survival advantage over IFN-alpha at 3--5.5 years. In the BMT group death due to transplant-related complications ranged from 36 to 45%. The incremental cost-effectiveness ratio (ICER) of imatinib compared with IFN-alpha from the independent model was GBP26,180 per quality-adjusted-life-years (QALY) gained and was relatively robust. Imatinib was less cost-effective than hydroxyurea with an ICER of GBP86,934.

CONCLUSIONS

Imatinib appears to be more effective than current standard drug treatments in terms of cytogenetic response and progression-free survival, with fewer side-effects. However, there is uncertainty concerning longer term outcomes, the development of resistance to imatinib, the duration of response and the place of imatinib relative to BMT. New issues are continually arising, such as optimal management pathways and combination therapies. Recommendations for research include: long-term follow-up data from the first- and second-line imatinib trials; investigation into specific subgroups, e.g. high-risk patients, the elderly, children or those eligible for BMT; long-term comparisons of imatinib with BMT performed in early stages of CML; the use of imatinib in combination with other therapies, and further detailed economic studies. Investigation of the impact of CML and imatinib on quality of life is also important.

The effectiveness and cost-effectiveness of microwave and thermal balloon endometrial ablation for heavy menstrual bleeding: a systematic review and economic modelling

OBJECTIVES

To estimate the clinical effectiveness and cost-effectiveness of microwave endometrial ablation (MEA) and thermal balloon endometrial ablation (TBEA) for heavy menstrual bleeding (HMB), compared with the existing (first-generation) endometrial ablation (EA) techniques of transcervical resection (TCRE) and rollerball (RB) ablation, and hysterectomy.

DATA SOURCES

Electronic databases, bibliographies of articles, and also experts in the field and relevant industry bodies were asked to provide information.

REVIEW METHODS

A detailed search strategy was carried out to identify systematic reviews and controlled trials of MEA and TBEA versus first-generation techniques for EA. In addition to electronic database searching, reference lists were hand-searched and information sought from manufacturers of EA devices and by experts in the field. A deterministic Markov model was developed to assess cost-effectiveness. Data for the model were taken from a range of sources.

RESULTS

The systematic review of first-generation EA techniques versus hysterectomy found that EA offered an alternative to hysterectomy for HMB, with fewer complications and a shorter recovery period. Satisfaction and effectiveness were high for both MEA and TBEA. Costs were lower with EA although the difference narrows over time. Second-generation EA techniques are an alternative treatment to first-generation techniques for HMB, and first-generation techniques are known to offer an alternative to hysterectomy. Although no trials of second-generation techniques and hysterectomy have been undertaken, it seems reasonable to assume that second-generation techniques also offer an alternative surgical treatment. Using the model to assess cost-effectiveness, costs were very slightly higher for MEA when compared to TBEA, and differences in quality-adjusted life-years (QALYs) were negligible. For MEA compared with transcervical resection of the endometrium (TCRE) and RB ablation, costs were slightly lower with MEA and MEA accrued very slightly more QALYs. Compared with hysterectomy, MEA costs less and accrues slightly fewer QALYs. For TBEA compared with TCRE and RB ablation, costs were lower with TBEA and TBEA accrued slightly more QALYs. Compared with hysterectomy, TBEA costs moderately less and accrues moderately fewer QALYs.

CONCLUSIONS

Overall, there were few significant differences between the outcomes of first- and second-generation techniques including bleeding, satisfaction and QoL measures and repeat surgery rates. Second-generation techniques had significantly shorter operating and theatre times and there appear to be fewer serious perioperative adverse effects with second-generation techniques and postoperative effects are similar. Compared with hysterectomy, TCRE and RB are quicker to perform and result in shorter hospitalisation and faster return to work. Hysterectomy results in more adverse effects and is more expensive, although the need for retreatment leads this difference to decrease over time. Satisfaction with hysterectomy is initially higher, but there is no significant difference after 2 years. The economic model suggests that second-generation techniques are more cost-effective than first-generation techniques of EA for HMB. Both TBEA and MEA appear to be less costly than hysterectomy, although the latter results in more QALYs. Further research is suggested to make direct comparisons of the cost-effectiveness of second-generation EA techniques, to carry out longer term follow-up for all methods of EA in RCTs, and to develop more sophisticated modelling studies. Further research is also recommended into HMB to establish health-state utility values, its surgical treatment, convalescence, complications of treatment, symptoms and patient satisfaction.

Systematic review of endoscopic sinus surgery for nasal polyps

OBJECTIVES

To provide a systematic review of the clinical effectiveness of endoscopic sinus surgery (ESS) for the removal of nasal polyps.

DATA SOURCES

Searches of electronic databases, websites and reference lists were made to identify relevant studies.

REVIEW METHODS

An extensive search was performed to identify all articles where FESS is used for the excision of nasal polyps. Two reviewers independently screened articles for inclusion according to predefined criteria. Comparative studies were included if they were primary research, focused on FESS for the removal of nasal polyps, reported patient relevant outcomes and were published in English. In addition, case series studies were included if they met the above criteria and enrolled more than 50 patients with polyps. Data were then extracted by one reviewer and checked by a second. A structured form was used to assess the internal and external validity of included studies. Comparative data were reported where available. Excluded case series and case reports were grouped and described. A group of nine ear, nose and throat (ENT) experts were selected, then using the literature and their own experience, they generated a list of priority research questions. Existing economic evaluations were sought and described.

RESULTS

Of the 33 studies included, the randomised controlled trials and controlled trials reported overall symptomatic improvement that ranged from 78 to 88% for FESS compared with 43 to 84% for similar techniques (including polypectomy, Caldwell-Luc and intranasal ethmoidectomy). Disease recurrence was 8% for FESS compared with 14% for Caldwell-Luc and polyp recurrence was 28% for endoscopic ethmoidectomy compared with 35% for polypectomy. Revision surgery was reported in one study only and was the same for FESS and Caldwell-Luc procedures. Percentage of overall complications was reported in only one comparative study and was 1.4% for FESS compared with 0.8% for conventional procedures. The case series studies reported overall symptomatic improvement for patients with nasal polyps ranging from 37 to 99% (median 89%). For the mixed patient groups (with and without polypoid disease) overall symptomatic improvement ranged from 40 to 98% (median 88%). Total complications in the case series studies ranged from 22.4 to 0.3% (median 6%).

CONCLUSIONS

The majority of studies report that symptoms improve following FESS with relatively few complications; however, only a small proportion of evidence is comparative. Results from non-comparative studies do not inform the choices that need to be made by ENT surgeons and commissioners. Health economics data are also lacking and therefore cannot inform these decisions. FESS may offer some advantages in effectiveness over comparative techniques, but there is enormous variation in the range of results reported and there are severe methodological limitations. There is a clear need for quality-controlled trials in order to answer questions regarding the effectiveness of FESS. A number of priority research questions from a selection of ENT surgeons within the UK are identified and presented.

Public health management of an outbreak of group C meningococcal disease in university campus residents

BACKGROUND

Increasing numbers of outbreaks of Group C meningococcal disease in teenagers and young adults led to a new policy in the UK in 1999 of vaccinating all new college students. The largest of these outbreaks involved seven students in one university, six of whom were from one hall of residence, and two of whom died.

METHODS

Control of the outbreak involved close medical surveillance of resident students, mass chemoprophylaxis and vaccination, and wide dissemination of daily information bulletins. Investigation of the epidemiology of the outbreak involved searching for the network of close contacts between cases, a prevalence survey of carriage of meningogocci and a case control study of risk factors for carriage.

RESULTS

Clinical cases could be linked by a discrete network of social contacts within the halls of residence, but the Group C epidemic strain (2a P1.5) was not detected in 454 students (upper 95% confidence interval 0.7%). Carriage of any meningococcal strain (19%) was associated with patronage of the campus bar (OR = 3.0, 0.99-9.1).

CONCLUSION

Important factors in the control of the outbreak were rapid institution of mass chemopropylaxis and immunisation of residents, and involvement of student organizations in the dissemination of information about the disease and its control. The role of campus bars in dissemination of the carriage of meningogocci deserves further investigation.

Effect on hospital attendance rates of giving patients a copy of their referral letter: randomised controlled trial

OBJECTIVES

To investigate whether sending patients a copy of their referral letter can reduce non-attendance at outpatient departments.

DESIGN

Blinded randomised controlled trial.

SETTING

13 general practices in Exeter, Devon.

SUBJECTS

2078 new consultant referrals from 26 doctors.

MAIN OUTCOME MEASURES

Non-attendance at outpatient departments.

RESULTS

The doctors excluded 117 (5.6%) referrals, and 100 (4.8%) received no appointment. Attendance data were available for 1857 of the 1861 patients sent an appointment (99.8%). The receipt of a copy letter had no effect on the non-attendance rate: copy 50/912 (5.5%) versus control 50/945 (5.3%).

CONCLUSION

Copy letters are ineffective in reducing non-attendance at outpatient departments.

Should we be doing more to prevent Group C meningococcal infection in school age children? How can we decide?

Meningococcal Group C infections are potentially preventable by vaccination in most cases. Population immunization has not been adopted because the disease is rare and the vaccine effective for only about three years. However, the recent rise in cases in school age children has prompted an assessment of the cost-effectiveness of alternative strategies for management of a case of Group C infection. Chemoprophylaxis and vaccination of close contacts is the most cost-effective strategy but will prevent relatively few cases. Population vaccination prevents considerably more cases, but at a much higher total and marginal cost. An intermediate strategy of giving antibiotics to and vaccinating the school population following a single case, in addition to contact tracing, has intermediate cost-effectiveness. Policy decisions will take into account other important factors but the approach we have taken makes explicit key assumptions so that wider debate including profession and public can be developed.

Atomic force microscopy of plant cell walls, plant cell wall polysaccharides and gels

Methods developed for the routine imaging of polysaccharides by atomic force microscopy (AFM) have been used to image plant polysaccharides from higher plants (pectin) and algae (carrageenan). These methods have been extended to image K-carrageenan association in hydrated films. Finally, AFM has been used to image polysaccharide architecture in moist plant cell walls. Simple experimental and image processing methods have been used to enhance molecular structure in 'rough' cell wall surfaces.

Emergency medical admissions to hospital--the influence of supply factors

A retrospective review of all adult medical in-patient hospital records in one health district (adult population 378,000) was performed over three consecutive years. Yearly age-standardised rates for emergency admissions were calculated and compared between sections of the population with differing access to hospital beds. Confounding and other explanatory variables were examined with a logistic regression model. Emergency medical admission rates were consistently higher in the population whose general practitioner had access to community hospital beds, as compared with those whose general practitioner had no access, (46.1 per thousand population vs 39.3 per thousand in the year 1994-95, difference significance, P < 0.05). Multivariable analysis suggests that in addition to supply factors, age, sex, morbidity and socio-economic circumstance influence admission rates.

Divergent views--patient, career and staff perceptions of diagnosis and reasons for psychiatric admission to a district general hospital

This study explores the differing perceptions of patients, carers, and professional staff in relation to psychiatric admission. There is poor to moderate agreement between lay people and professional beliefs about diagnosis or purpose of admission, although good agreement about the necessity of admission. The chronicity of symptoms in admitted patients and a rural-urban divide in rates of admissions are also noted.