Choline degradation in Paracoccus denitrificans: identification of sources of formaldehyde.

Paracoccus denitrificans is a facultative methylotroph that can grow on methanol and methylamine as sole sources of carbon and energy. Both are oxidized to formaldehyde and then to formate, so growth on C1 substrates induces the expression of genes encoding enzymes required for the oxidation of formaldehyde and formate. This induction involves a histidine kinase response regulator pair (FlhSR) that is likely triggered by formaldehyde. Catabolism of some complex organic substrates (e.g., choline and L-proline betaine) also generates formaldehyde. Thus, flhS and flhR mutants that fail to induce expression of the formaldehyde catabolic enzymes cannot grow on methanol, methylamine, and choline. Choline is oxidized to glycine via glycine betaine, dimethylglycine, and sarcosine. By exploring flhSR growth phenotypes and the activities of a promoter and enzyme known to be upregulated by formaldehyde, we identify the oxidative demethylations of glycine betaine, dimethylglycine, and sarcosine as sources of formaldehyde. Growth on glycine betaine, dimethylglycine, and sarcosine is accompanied by the production of up to three, two, and one equivalents of formaldehyde, respectively. Genetic evidence implicates two orthologous monooxygenases in the oxidation of glycine betaine. Interestingly, one of these appears to be a bifunctional enzyme that also oxidizes L-proline betaine (stachydrine). We present preliminary evidence to suggest that growth on L-proline betaine induces expression of a formaldehyde dehydrogenase distinct from the enzyme induced during growth on other formaldehyde-generating substrates.IMPORTANCEThe bacterial degradation of one-carbon compounds (methanol and methylamine) and some complex multi-carbon compounds (e.g., choline) generates formaldehyde. Formaldehyde is toxic and must be removed, which can be done by oxidation to formate and then to carbon dioxide. These oxidations provide a source of energy; in some species, the CO2 thus generated can be assimilated into biomass. Using the Gram-negative bacterium Paracoccus denitrificans as the experimental model, we infer that oxidation of choline to glycine generates up to three equivalents of formaldehyde, and we identify the three steps in the catabolic pathway that are responsible. Our work sheds further light on metabolic pathways that are likely important in a variety of environmental contexts.

DksA, ppGpp, and RegAB Regulate Nitrate Respiration in Paracoccus denitrificans.

The periplasmic (NAP) and membrane-associated (Nar) nitrate reductases of Paracoccus denitrificans are responsible for nitrate reduction under aerobic and anaerobic conditions, respectively. Expression of NAP is elevated in cells grown on a relatively reduced carbon and energy source (such as butyrate); it is believed that NAP contributes to redox homeostasis by coupling nitrate reduction to the disposal of excess reducing equivalents. Here, we show that deletion of either dksA1 (one of two dksA homologs in the P. denitrificans genome) or relA/spoT (encoding a bifunctional ppGpp synthetase and hydrolase) eliminates the butyrate-dependent increase in nap promoter and NAP enzyme activity. We conclude that ppGpp likely signals growth on a reduced substrate and, together with DksA1, mediates increased expression of the genes encoding NAP. Support for this model comes from the observation that nap promoter activity is increased in cultures exposed to a protein synthesis inhibitor that is known to trigger ppGpp synthesis in other organisms. We also show that, under anaerobic growth conditions, the redox-sensing RegAB two-component pair acts as a negative regulator of NAP expression and as a positive regulator of expression of the membrane-associated nitrate reductase Nar. The dksA1 and relA/spoT genes are conditionally synthetically lethal; the double mutant has a null phenotype for growth on butyrate and other reduced substrates while growing normally on succinate and citrate. We also show that the second dksA homolog (dksA2) and relA/spoT have roles in regulation of expression of the flavohemoglobin Hmp and in biofilm formation. IMPORTANCE Paracoccus denitrificans is a metabolically versatile Gram-negative bacterium that is used as a model for studies of respiratory metabolism. The organism can utilize nitrate as an electron acceptor for anaerobic respiration, reducing it to dinitrogen via nitrite, nitric oxide, and nitrous oxide. This pathway (known as denitrification) is important as a route for loss of fixed nitrogen from soil and as a source of the greenhouse gas nitrous oxide. Thus, it is important to understand those environmental and genetic factors that govern flux through the denitrification pathway. Here, we identify four proteins and a small molecule (ppGpp) which function as previously unknown regulators of expression of enzymes that reduce nitrate and oxidize nitric oxide.

Carer and staff perceptions of end-of-life care provision: case of a hospice-at-home service.

People requiring palliative care should have their needs met by services acting in accordance with their wishes. A hospice in the south of England provides such care via a 24/7 hospice at home service. This study aimed to establish how a nurse-led night service supported patients and family carers to remain at home and avoid hospital admissions. Semi-structured interviews were carried out with family carers (n=38) and hospice-at-home staff (n=9). Through night-time phone calls and visits, family carers felt supported by specialist hospice staff whereby only appropriate hospital admission was facilitated. Staff provided mediation between family carer and other services enabling more integrated care and support to remain at home. A hospice-at-home night service can prevent unnecessary hospital admissions and meet patient wishes through specialist care at home.

The Cost of Visit-based Home Care for up to Two Weeks in the Last Three Months of Life: APilot Study of Community Care Based at a Hospice-at-home Service in South East of England.

The cost of visit-based community care based around a 24/7 hospice-at-home (HatH) service in the last 3 months of life was assessed. Thirty families completed a health and social carediary of at-home visits over two-weeks following contact with the HatH night service. Diaries captured 333 days of care provision, averaging 11 diary days per family, 708 health care professional and carer visits, lasting 604 hours at a cost of £20,192 ($24,946). Hat H care, integrated with community support, seems an economic proposition but highlights the complexities of assessing cost of end of life care.

Sequential screening for lung cancer in a high-risk group: randomised controlled trial: LungSEARCH: a randomised controlled trial of Surveillance using sputum and imaging for the EARly detection of lung Cancer in a High-risk group.

BACKGROUND: Low-dose computed tomography (LDCT) screening detects early-stage lung cancer and reduces mortality. We proposed a sequential approach targeted to a high-risk group as a potentially efficient screening strategy. METHODS: LungSEARCH was a national multicentre randomised trial. Current/ex-smokers with mild/moderate chronic obstructive pulmonary disease (COPD) were allocated (1:1) to have 5 years surveillance or not. Screened participants provided annual sputum samples for cytology and cytometry, and if abnormal were offered annual LDCT and autofluorescence bronchoscopy (AFB). Those with normal sputum provided annual samples. The primary end-point was the percentage of lung cancers diagnosed at stage I/II (nonsmall cell) or limited disease (small cell). RESULTS: 1568 participants were randomised during 2007-2011 from 10 UK centres. 85.2% of those screened provided an adequate baseline sputum sample. There were 42 lung cancers among 785 screened individuals and 36 lung cancers among 783 controls. 54.8% (23 out of 42) of screened individuals versus 45.2% (14 out of 31) of controls with known staging were diagnosed with early-stage disease (one-sided p=0.24). Relative risk was 1.21 (95% CI 0.75-1.95) or 0.82 (95% CI 0.52-1.31) for early-stage or advanced cancers, respectively. Overall sensitivity for sputum (in those randomised to surveillance) was low (40.5%) with a cumulative false-positive rate (FPR) of 32.8%. 55% of cancers had normal sputum results throughout. Among sputum-positive individuals who had AFB, sensitivity was 45.5% and cumulative FPR was 39.5%; the corresponding measures for those who had LDCT were 100% and 16.1%, respectively. CONCLUSIONS: Our sequential strategy, using sputum cytology/cytometry to select high-risk individuals for AFB and LDCT, did not lead to a clear stage shift and did not improve the efficiency of lung cancer screening.

Environmental and Genetic Determinants of Biofilm Formation in Paracoccus denitrificans.

The genome of the denitrifying bacterium Paracoccus denitrificans predicts the expression of a small heme-containing nitric oxide (NO) binding protein, H-NOX. The genome organization and prior work in other bacteria suggest that H-NOX interacts with a diguanylate cyclase that cyclizes GTP to make cyclic di-GMP (cdGMP). Since cdGMP frequently regulates attached growth as a biofilm, we first established conditions for biofilm development by P. denitrificans. We found that adhesion to a polystyrene surface is strongly stimulated by the addition of 10 mM Ca2+ to rich media. The genome encodes at least 11 repeats-in-toxin family proteins that are predicted to be secreted by the type I secretion system (TISS). We deleted the genes encoding the TISS and found that the mutant is almost completely deficient for attached growth. Adjacent to the TISS genes there is a potential open reading frame encoding a 2,211-residue protein with 891 Asp-Ala repeats. This protein is also predicted to bind calcium and to be a TISS substrate, and a mutant specifically lacking this protein is deficient in biofilm formation. By analysis of mutants and promoter reporter fusions, we show that biofilm formation is stimulated by NO generated endogenously by the respiratory reduction of nitrite. A mutant lacking both predicted diguanylate cyclases encoded in the genome overproduces biofilm, implying that cdGMP is a negative regulator of attached growth. Our data are consistent with a model in which there are H-NOX-dependent and -independent pathways by which NO stimulates biofilm formation. IMPORTANCE The bacterium Paracoccus denitrificans is a model for the process of denitrification, by which nitrate is reduced to dinitrogen during anaerobic growth. Denitrification is important for soil fertility and greenhouse gas emission and in waste and water treatment processes. The ability of bacteria to grow as a biofilm attached to a solid surface is important in many different contexts. In this paper, we report that attached growth of P. denitrificans is stimulated by nitric oxide, an intermediate in the denitrification pathway. We also show that calcium ions stimulate attached growth, and we identify a large calcium binding protein that is required for growth on a polystyrene surface. We identify components of a signaling pathway through which nitric oxide may regulate biofilm formation. Our results point to an intimate link between metabolic processes and the ability of P. denitrificans to grow attached to a surface.

Research in progress--LungSEARCH: a randomised controlled trial of surveillance for the early detection of lung cancer in a high-risk group.

Low-dose CT screening for lung cancer is effective but expensive. Therefore, cheaper or more focused screening strategies may be required. LungSEARCH is a randomised prospective trial of 1568 high-risk individuals (ie, current or former moderate to heavy smokers with mild/moderate COPD) who undergo either annual sputum cytology/cytometry testing or no screening. Those with abnormal sputum then receive annual CT and fluorescent bronchoscopy for the remainder of 5 years, to identify early stage lung cancer. It is hoped that these simple initial tests could identify those requiring expensive CT scans, and the aim is to demonstrate a stage shift towards early stage cancers.Trial registration numbers ISRCTN: ISRCTN80745975, clinicaltrials.gov: NCT00512746.

Inefficient translation of nsrR constrains behaviour of the NsrR regulon in Escherichia coli.

The NsrR protein of Escherichia coli is a transcriptional repressor that contains an [Fe-S] cluster that is the binding site for nitric oxide (NO). Reaction of NsrR with NO leads to de-repression of its target genes, which include those encoding an NO scavenging flavohaemoglobin and the RIC (repair of iron centres) protein involved in the repair of NO-damaged [Fe-S] clusters. The nsrR gene is promoter proximal in a transcription unit with rnr, encoding the cold shock-inducible RNase R. Here, we show that nsrR is expressed from a strong promoter, but that its translation is extremely inefficient, leading to a low cellular NsrR concentration. Conversion of the nsrR start codon from the wild-type GUG to AUG increased the efficiency of translation (which, nevertheless, remained extremely low) and had measurable effects on the expression of some NsrR-regulated genes. We conclude that NsrR abundance in the cell is such that promoters with low-affinity NsrR binding sites may partially escape NsrR-mediated repression. Expression profiling confirmed that genes regulated by NsrR (whether directly or indirectly) tend to express lower mRNA levels when the nsrR start codon is AUG than when it is GUG. Transcriptomics data implicated the pyruvate oxidase gene poxB as a novel NsrR target, which we confirmed and showed to be due to read-through transcription from the upstream hcp-hcr genes. We also present evidence to suggest that NsrR is a regulator of the sufABCDSE genes, which encode the components of an [Fe-S] cluster biogenesis and repair system.

Lung cancer diagnosis and staging with endobronchial ultrasound-guided transbronchial needle aspiration compared with conventional approaches: an open-label, pragmatic, randomised controlled trial.

BACKGROUND: The diagnosis and staging of lung cancer is an important process that identifies treatment options and guides disease prognosis. We aimed to assess endobronchial ultrasound-guided transbronchial needle aspiration as an initial investigation technique for patients with suspected lung cancer. METHODS: In this open-label, multicentre, pragmatic, randomised controlled trial, we recruited patients who had undergone a CT scan and had suspected stage I to IIIA lung cancer, from six UK centres and randomly assigned them to either endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) or conventional diagnosis and staging (CDS), for further investigation and staging. If a target node could not be accessed by EBUS-TBNA, then endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) was allowed as an alternative procedure. Randomisation was stratified according to the presence of mediastinal lymph nodes measuring 1 cm or more in the short axis and by recruiting centre. We used a telephone randomisation method with permuted blocks of four generated by a computer. Because of the nature of the intervention, masking of participants and consenting investigators was not possible. The primary endpoint was the time-to-treatment decision after completion of the diagnostic and staging investigations and analysis was by intention-to-diagnose. This trial is registered with ClinicalTrials.gov, number NCT00652769. FINDINGS: Between June 10, 2008, and July 4, 2011, we randomly allocated 133 patients to treatment: 66 to EBUS-TBNA and 67 to CDS (one later withdrew consent). Two patients from the EBUS-TBNA group underwent EUS-FNA. The median time to treatment decision was shorter with EBUS-TBNA (14 days; 95% CI 14-15) than with CDS (29 days; 23-35) resulting in a hazard ratio of 1·98, (1·39-2·82, p<0·0001). One patient in each group had a pneumothorax from a CT-guided biopsy sample; the patient from the CDS group needed intercostal drainage and was admitted to hospital. INTERPRETATION: Transbronchial needle aspiration guided by endobronchial ultrasound should be considered as the initial investigation for patients with suspected lung cancer, because it reduces the time to treatment decision compared with conventional diagnosis and staging techniques. FUNDING: UK Medical Research Council.

Genome-wide analysis of the response to nitric oxide in uropathogenic Escherichia coli CFT073.

Uropathogenic Escherchia coli (UPEC) is the causative agent of urinary tract infections. Nitric oxide (NO) is a toxic water-soluble gas that is encountered by UPEC in the urinary tract. Therefore, UPEC probably requires mechanisms to detoxify NO in the host environment. Thus far, flavohaemoglobin (Hmp), an NO denitrosylase, is the only demonstrated NO detoxification system in UPEC. Here we show that, in E. coli strain CFT073, the NADH-dependent NO reductase flavorubredoxin (FlRd) also plays a major role in NO scavenging. We generated a mutant that lacks all known and candidate NO detoxification pathways (Hmp, FlRd and the respiratory nitrite reductase, NrfA). When grown and assayed anaerobically, this mutant expresses an NO-inducible NO scavenging activity, pointing to the existence of a novel detoxification mechanism. Expression of this activity is inducible by both NO and nitrate, and the enzyme is membrane-associated. Genome-wide transcriptional profiling of UPEC grown under anaerobic conditions in the presence of nitrate (as a source of NO) highlighted various aspects of the response of the pathogen to nitrate and NO. Several virulence-associated genes are upregulated, suggesting that host-derived NO is a potential regulator of UPEC virulence. Chromatin immunoprecipitation and sequencing was used to evaluate the NsrR regulon in CFT073. We identified 49 NsrR binding sites in promoter regions in the CFT073 genome, 29 of which were not previously identified in E. coli K-12. NsrR may regulate some CFT073 genes that do not have homologues in E. coli K-12.

The European initiative for quality management in lung cancer care.

Lung cancer is the commonest cause of cancer-related death worldwide and poses a significant respiratory disease burden. Little is known about the provision of lung cancer care across Europe. The overall aim of the Task Force was to investigate current practice in lung cancer care across Europe. The Task Force undertook four projects: 1) a narrative literature search on quality management of lung cancer; 2) a survey of national and local infrastructure for lung cancer care in Europe; 3) a benchmarking project on the quality of (inter)national lung cancer guidelines in Europe; and 4) a feasibility study of prospective data collection in a pan-European setting. There is little peer-reviewed literature on quality management in lung cancer care. The survey revealed important differences in the infrastructure of lung cancer care in Europe. The European guidelines that were assessed displayed wide variation in content and scope, as well as methodological quality but at the same time there was relevant duplication. The feasibility study demonstrated that it is, in principle, feasible to collect prospective demographic and clinical data on patients with lung cancer. Legal obligations vary among countries. The European Initiative for Quality Management in Lung Cancer Care has provided the first comprehensive snapshot of lung cancer care in Europe.

Finely tuned regulation of the aromatic amine degradation pathway in Escherichia coli.

FeaR is an AraC family regulator that activates transcription of the tynA and feaB genes in Escherichia coli. TynA is a periplasmic topaquinone- and copper-containing amine oxidase, and FeaB is a cytosolic NAD-linked aldehyde dehydrogenase. Phenylethylamine, tyramine, and dopamine are oxidized by TynA to the corresponding aldehydes, releasing one equivalent of H2O2 and NH3. The aldehydes can be oxidized to carboxylic acids by FeaB, and (in the case of phenylacetate) can be further degraded to enter central metabolism. Thus, phenylethylamine can be used as a carbon and nitrogen source, while tyramine and dopamine can be used only as sources of nitrogen. Using genetic, biochemical and computational approaches, we show that the FeaR binding site is a TGNCA-N8-AAA motif that occurs in 2 copies in the tynA and feaB promoters. We show that the coactivator for FeaR is the product rather than the substrate of the TynA reaction. The feaR gene is upregulated by carbon or nitrogen limitation, which we propose reflects regulation of feaR by the cyclic AMP receptor protein (CRP) and the nitrogen assimilation control protein (NAC), respectively. In carbon-limited cells grown in the presence of a TynA substrate, tynA and feaB are induced, whereas in nitrogen-limited cells, only the tynA promoter is induced. We propose that tynA and feaB expression is finely tuned to provide the FeaB activity that is required for carbon source utilization and the TynA activity required for nitrogen and carbon source utilization.

Cooperative and allosterically controlled nucleotide binding regulates the DNA binding activity of NrdR.

Ribonucleotide reductases (RNRs) are required for the synthesis of deoxyribonucleoside triphosphates (dNTPs) from ribonucleotides. In Escherichia coli, regulation of RNR expression is co-ordinated with the cell cycle, and involves several regulatory proteins. One of these, NrdR, has recently been shown to regulate all three nrd operons that encode RNR isoenzymes. Repression by NrdR is believed to be stimulated by elevated dNTPs, although there is no direct evidence for this model. Here, we sought to elucidate the mechanism by which NrdR regulates nrd expression according to the abundance of (d)NTPs. We determined that ATP and dATP bind to NrdR in a negatively cooperative fashion, such that neither can fully occupy the protein. Both nucleotides also appear to act as positive heterotropic effectors, since the binding of one stimulates binding of the other. Nucleotide binding stimulates self-association of NrdR, with tri- and diphosphates stimulating oligomerization more effectively than monophosphates. As-prepared NrdR contains (deoxy)nucleoside monophosphates, diphosphates and triphosphates, and its DNA binding activity is inhibited by triphosphates and diphosphates but not by monophosphates. We propose a model in which NrdR selectively binds (deoxy)nucleoside triphosphates, which are hydrolysed to their monophosphate counterparts in order to regulate DNA binding.

Genome-wide mapping of the binding sites of proteins that interact with DNA.

The coordinated regulation of the expression of a group of genes by a specific transcription factor frequently lies at the heart of the ability of a bacterium to respond to an environmental signal, or to progress through a developmental program. Thus, in many situations, it is of interest to identify all of the genes that are under the control of a particular regulatory protein. This chapter begins with a brief overview of some of the methods that have been used in attempts to identify some or all of the members of a regulon (i.e., those genes that are the targets for a transcriptional activator or repressor). Thereafter, the chapter will focus on one technique, chromatin immunoprecipitation and microarray analysis (ChIP-chip) and some of its variants. Design considerations and some protocols for ChIP-chip experiments are provided, along with some considerations related to downstream data analysis. ChIP-chip is a method for the genome-wide localization of protein-binding sites. In a typical ChIP-chip protocol, proteins are cross-linked nonspecifically to DNA in vivo. Chromatin is extracted and sheared, and specific protein-DNA complexes are immunoprecipitated with a suitable antibody. After purification, the DNA is hybridized to a microarray (after an amplification step in some protocols), together with a differentially labeled reference sample. Features on the microarray that show an elevated fluorescence ratio reveal DNA sequences that were enriched by immunoprecipitation. The corresponding genomic locations are those that were enriched, and are therefore close to sites of binding. The use of high-density tiled microarrays allows for binding site localization with quite high resolution. It is likely that ChIP-chip will soon be superseded by ChIP-seq, in which the immunoprecipitated DNA is analyzed directly by next-generation sequencing technologies. ChIP-chip and ChIP-seq applications are not confined to regulatory proteins, since they can be used with any protein that binds to DNA, either directly, or indirectly via an interaction with another protein. Thus, ChIP-chip has been used successfully to map binding sites for nucleoid proteins, and proteins involved in DNA replication.

Nitrous oxide production and consumption: regulation of gene expression by gas-sensitive transcription factors.

Several biochemical mechanisms contribute to the biological generation of nitrous oxide (N(2)O). N(2)O generating enzymes include the respiratory nitric oxide (NO) reductase, an enzyme from the flavo-diiron family, and flavohaemoglobin. On the other hand, there is only one enzyme that is known to use N(2)O as a substrate, which is the respiratory N(2)O reductase typically found in bacteria capable of denitrification (the respiratory reduction of nitrate and nitrite to dinitrogen). This article will briefly review the properties of the enzymes that make and consume N(2)O, together with the accessory proteins that have roles in the assembly and maturation of those enzymes. The expression of the genes encoding the enzymes that produce and consume N(2)O is regulated by environmental signals (typically oxygen and NO) acting through regulatory proteins, which, either directly or indirectly, control the frequency of transcription initiation. The roles and mechanisms of these proteins, and the structures of the regulatory networks in which they participate will also be reviewed.

Non-heme iron sensors of reactive oxygen and nitrogen species.

SIGNIFICANCE: In bacteria, transcriptional responses to reactive oxygen and nitrogen species (ROS and RNS, respectively) are typically coordinated by regulatory proteins that employ metal centers or reactive thiols to detect the presence of those species. This review is focused on the structure, function and mechanism of three regulatory proteins (Fur, PerR, and NorR) that contain non-heme iron and regulate the transcription of target genes in response to ROS and/or RNS. The targets for regulation include genes encoding detoxification activities, and genes encoding proteins involved in the repair of the damage caused by ROS and RNS. RECENT ADVANCES: Three-dimensional structures of several Fur proteins and of PerR are revealing important details of the metal binding sites of these proteins, showing a surprising degree of structural diversity in the Fur family. CRITICAL ISSUES: Discussion of the interaction of Fur with ROS and RNS will illustrate the difficulty that sometimes exists in distinguishing between true physiological responses and adventitious reactions of a regulatory protein with a reactive ligand. FUTURE DIRECTIONS: Consideration of these three sensor proteins illuminates some of the key questions that remain unanswered, for example, the nature of the biochemical determinants that dictate the sensitivity and specificity of the interaction of the sensor proteins with their cognate signals.

Attitudes to participation in a lung cancer screening trial: a qualitative study.

BACKGROUND: Earlier diagnosis of lung cancer is key to reducing mortality. New evidence suggests that smokers have negative attitudes to screening and participation in lung cancer screening trials is poor (<1 in 6 of those eligible). Understanding participation is important since uptake in screening trials is likely to predict uptake in screening programmes. A qualitative study of people accepting and declining participation in the Lung-SEARCH screening trial was conducted. Two questions were addressed: Are the screening methods offered acceptable to patients? Why do some people take part and others decline? METHODS: The qualitative study used semi-structured interviews with 60 respondents from three groups: (a) trial participants providing an annual sputum sample; (b) trial participants with a sputum sample showing abnormal cytology and thus undergoing annual CT scanning and bronchoscopy; and (c) those declining trial participation. RESULTS: Most respondents (48/60, 80%) viewed sputum provision, CT scanning and bronchoscopy as largely acceptable. Those declining trial participation described fear of bronchoscopy, inconvenience of travelling to hospitals for screening investigations and perceived themselves as having low susceptibility to lung cancer or being too old to benefit. Patients declining participation discounted their risk from smoking and considered negative family histories and good health to be protective. Four typological behaviours emerged within those declining: 'too old to be bothered', 'worriers', 'fatalists' and 'avoiders'. CONCLUSION: Sputum provision, CT scanning and bronchoscopy are largely acceptable to those participating in a screening trial. However, the decision to participate or decline reflects a complex balance of factors including acceptability and convenience of screening methods, risk perception, altruism and self-interest. Improving practical and changing cognitive aspects of participation will be key to improving uptake of lung cancer screening.

Screening for lung cancer: is this the way forward?

While low-dose CT scans have been shown to detect greater numbers of early lung cancers than conventional CXR, the first randomized trial of CT versus CXR screening in more than 50 000 subjects has shown a 20% reduction in mortality with CT. There are several other randomized trials in progress. CT scanning may be a useful technique for identifying lung cancer at an earlier stage and may reduce mortality. However, before it can be used on a wider scale, issues such as overdiagnosis bias, cost-effectiveness, false positive findings of multiple noncalcified nodules and the willingness of the relevant population to accept CT scanning need to be evaluated. There is still very little information on the cost per life-year saved as a result of CT scanning, as the data to date is very imprecise. There is no evidence that screening programs influence smoking rates despite the inclusion of cessation programs in many trials. Furthermore, if CT screening is adopted, much work is needed to persuade individuals at high risk, mostly current or former heavy smokers with some airflow obstruction, to participate in a screening program.