The prospective evaluation of the TB strain typing service in England: a mixed methods study.

BACKGROUND: In response to rising TB notification rates in England, universal strain typing was introduced in 2010. We evaluated the acceptability, effectiveness and cost-effectiveness of the TB strain typing service (TB-STS). METHODS: We conducted a mixed-methods evaluation using routine laboratory, clinic and public health data. We estimated the effect of the TB-STS on detection of false positive Mycobacterium tuberculosis diagnoses (2010-2012); contact tracing yield (number of infections or active disease per pulmonary TB case); and diagnostic delay. We developed a deterministic age-structured compartmental model to explore the effectiveness of the TB-STS, which informed a cost-effectiveness analysis. RESULTS: Semi-structured interviews explored user experience. Strain typing identified 17 additional false positive diagnoses. The TB-STS had no significant effect on contact tracing yield or diagnostic delay. Mathematical modelling suggested increasing the proportion of infections detected would have little value in reducing TB incidence in the white UK-born population. However, in the non-white UK-born and non-UK-born populations, over 20 years, if detection of latent infection increases from 3% to 13% per year, then TB incidence would decrease by 11%; reducing diagnostic delay by one week could lead to 25% reduction in incidence. The current TB-STS was not predicted to be cost-effective over 20 years (£95 628/quality-adjusted life-years). Interviews found people had mixed experiences, but identified broader benefits, of the TB-STS. CONCLUSIONS: To reduce costs, improve efficiency and increase effectiveness, we recommend changes to the TB-STS, including discontinuing routine cluster investigations and focusing on reducing diagnostic delay across the TB programme. This evaluation of a complex intervention informs the future of strain typing in the era of rapidly advancing technologies.

Toxicology study assessing efficacy and safety of repeated administration of lipid/DNA complexes to mouse lung.

For gene therapy to improve lung function in cystic fibrosis (CF) subjects, repeated administration of the gene transfer agent over the lifetime of patients is likely to be necessary. This requirement limits the utility of adenoviral and adeno-associated viral vectors (both previously evaluated in CF gene therapy trials) because of induced adaptive immune responses that render repeated dosing ineffective. For CF gene therapy trials, non-viral vectors are currently the only viable option. We previously showed that the cationic lipid formulation GL67A is the most efficient of several non-viral vectors analysed for airway gene transfer. Here, we assessed the efficacy and safety of administering 12 inhaled doses of GL67A complexed with pGM169, a CpG-free plasmid encoding human CFTR complementary DNA, into mice. We show that repeated administration of pGM169/GL67A to murine lungs is feasible, safe and achieves reproducible, dose-related and persistent gene expression (>140 days after each dose) using an aerosol generated by a clinically relevant nebuliser. This study supports progression into the first non-viral multidose lung trial in CF patients.

Lung clearance index: evidence for use in clinical trials in cystic fibrosis.

The ECFS-CTN Standardisation Committee has undertaken this review of lung clearance index as part of the group's work on evaluation of clinical endpoints with regard to their use in multicentre clinical trials in CF. The aims were 1) to review the literature on reliability, validity and responsiveness of LCI in patients with CF, 2) to gain consensus of the group on feasibility of LCI and 3) to gain consensus on answers to key questions regarding the promotion of LCI to surrogate endpoint status. It was concluded that LCI has an attractive feasibility and clinimetric properties profile and is particularly indicated for multicentre trials in young children with CF and patients with early or mild CF lung disease. This is the first article to collate the literature in this manner and support the use of LCI in clinical trials in CF.

Pre-clinical evaluation of three non-viral gene transfer agents for cystic fibrosis after aerosol delivery to the ovine lung.

We use both large and small animal models in our pre-clinical evaluation of gene transfer agents (GTAs) for cystic fibrosis (CF) gene therapy. Here, we report the use of a large animal model to assess three non-viral GTAs: 25 kDa-branched polyethyleneimine (PEI), the cationic liposome (GL67A) and compacted DNA nanoparticle formulated with polyethylene glycol-substituted lysine 30-mer. GTAs complexed with plasmids expressing human cystic fibrosis transmembrane conductance regulator (CFTR) complementary DNA were administered to the sheep lung (n=8 per group) by aerosol. All GTAs gave evidence of gene transfer and expression 1 day after treatment. Vector-derived mRNA was expressed in lung tissues, including epithelial cell-enriched bronchial brushing samples, with median group values reaching 1-10% of endogenous CFTR mRNA levels. GL67A gave the highest levels of expression. Human CFTR protein was detected in small airway epithelial cells in some animals treated with GL67A (two out of eight) and PEI (one out of eight). Bronchoalveolar lavage neutrophilia, lung histology and elevated serum haptoglobin levels indicated that gene delivery was associated with mild local and systemic inflammation. Our conclusion was that GL67A was the best non-viral GTA currently available for aerosol delivery to the sheep lung, led to the selection of GL67A as our lead GTA for clinical trials in CF patients.

Pneumothorax in cystic fibrosis: prevalence and outcomes in Scotland.

BACKGROUND: Pneumothorax is a feared complication of cystic fibrosis. With improved survival into adult life the incidence of pneumothorax is expected to increase. The optimal management of these patients is unclear. METHODS: Case review of patients from the three Scottish adult CF centres. RESULTS: A total of 22 episodes of pneumothorax occurred in 20 patients over a 12year period. 2 patients died as a result of the pneumothorax. 16 pneumothoraces were treated by insertion of an intercostal drain and 8 by observation. 8 patients suffered a prolonged air leak. 5 patients were treated with pleurodesis. Pneumothorax was associated with a small decline in lung function which persisted for at least 1year. CONCLUSION: Pneumothorax can present a challenge to treat in adult CF. However successful outcomes can be achieved even in cases of prolonged air leaks. Current national guidelines help in selecting optimal pleural interventions.

Sputum and serum calprotectin are useful biomarkers during CF exacerbation.

BACKGROUND: Adequate monitoring of cystic fibrosis lung disease is difficult. CF exacerbation offers a unique setting to test the utility of biomarkers in the assessment of changing airways inflammation. We hypothesised that levels of calprotectin in sputum (and serum) would change informatively following treatment of an exacerbation. METHODS: 27 patients with CF were recruited at onset of pulmonary exacerbation. Sputum and serum were collected at the start and end of anti-biotic therapy. Sputum calprotectin, interleukin-8 (IL8), and myeloperoxidase (MPO) were measured, as were serum calprotectin, CRP and vascular endothelial growth factor (VEGF). RESULTS: Sputum calprotectin decreased following treatment of an exacerbation (p<0.05), and was superior to other sputum markers. Serum calprotectin, CRP, and VEGF also decreased significantly (p=0.002, p=0.002, p=0.013 respectively). Serum calprotectin level following treatment had predictive value for time to next exacerbation (p=0.032). CONCLUSIONS: This study demonstrates the superiority of calprotectin (in sputum and serum) as a biomarker of CF exacerbation over better-established markers.

Ventilation heterogeneity in children with well controlled asthma with normal spirometry indicates residual airways disease.

BACKGROUND: In adults with asthma, ventilation heterogeneity, independent of inflammation, has been hypothesised to be associated with airway remodelling. Bronchial biopsy in preschool children with wheeze demonstrates early structural changes. Ventilation heterogeneity is sensitive to airway disease in other paediatric respiratory conditions such as cystic fibrosis, so may be sensitive to early airway disease in asthma. An observational study was performed in which it was hypothesised that ventilation heterogeneity (lung clearance index (LCI) and phase III slope indices (S(cond) and S(acin))) were more sensitive than conventional measurements (forced expiratory volume in 1 s (FEV(1)) and exhaled nitric oxide (Feno)) for detecting residual airways disease in children with well controlled asthma. METHODS: In 31 children with asthma of mean age 10.6 years (range 5-15), FEV(1), LCI, S(cond) and S(acin) were measured at two separate visits, before and after blinded salbutamol or placebo, with Feno measured once. 29 healthy volunteers of mean age 11.2 years (range 5-16) completed measurements at one visit only. RESULTS: Baseline mean (SD) LCI was significantly higher in children with asthma than in controls (6.69 (0.91) vs 6.24 (0.47), p = 0.02). There were no significant differences in FEV(1) or median Feno. Following salbutamol there was a small significant change in mean (SD) FEV(1) (from -1.26 (1.25) to -0.93 (0.23), p = 0.03) but not in LCI, S(cond) or S(acin). Importantly, LCI remained significantly higher after bronchodilator in children with asthma than in controls (6.64 (0.69), p = 0.01). CONCLUSION: This study identifies the presence of residual ventilation heterogeneity in children with well controlled asthma and normal FEV(1). The role of LCI in measuring early airway disease in children with asthma requires further exploration, possibly as a surrogate of structural remodelling.

Using laboratory measurements to predict in-flight desaturation in respiratory patients: are current guidelines appropriate?

In an attempt to guide physicians asked by respiratory patients for advice on flight fitness, the British Thoracic Society (BTS) have published guidelines on fitness to fly. The main potential hazard is hypobaric hypoxia, and efforts have focused on the prediction of hypoxia in individuals. The present study examines 10 years' experience of hypoxic challenge (HC) of respiratory patients to evaluate if the guidelines recommended by the BTS are appropriate. One hundred and eighteen patients (67 female, mean age 65.6+/-11.4 (SD) years) were referred for assessment. Patients underwent HC using a 40% Venturi mask supplied with 100% N(2) which lowered the F(i)O(2) to 15.1%. A further 13 patients on long-term oxygen therapy also underwent HC whilst receiving supplemental oxygen. In agreement with the BTS guidelines, all patients with a sea level SpO(2) of over 95% maintained their SpO(2) > or = 90% during HC. One third of patients with sea level SpO(2) of 92-95%, but no other risk factor (as defined by the guidelines) also desaturated below 90% during HC. Thirty-two patients were assessed as fit to fly with supplemental oxygen. Our results support the BTS guidelines for patients with a sea level SpO(2) > 95% but suggest that some revision is required for patients with a sea level SpO(2) of 92-95%. It was not possible to predict from either initial SpO(2) or spirometry which individuals were at risk of desaturation below 90% during hypoxic challenge.

Lung clearance index is a sensitive, repeatable and practical measure of airways disease in adults with cystic fibrosis.

BACKGROUND: Lung clearance index (LCI) is a sensitive marker of early lung disease in children but has not been assessed in adults. Measurement is hindered by the complexity of the equipment required. The aims of this study were to assess performance of a novel gas analyser (Innocor) and to use it as a clinical tool for the measurement of LCI in cystic fibrosis (CF). METHODS: LCI was measured in 48 healthy adults, 12 healthy school-age children and 33 adults with CF by performing an inert gas washout from 0.2% sulfur hexafluoride (SF6). SF6 signal:noise ratio and 10-90% rise time of Innocor were compared with a mass spectrometer used in similar studies in children. RESULTS: Compared with the mass spectrometer, Innocor had a superior signal:noise ratio but a slower rise time (150 ms vs 60 ms) which may limit its use in very young children. Mean (SD) LCI in healthy adults was significantly different from that in patients with CF: 6.7 (0.4) vs 13.1 (3.8), p<0.001. Ten of the patients with CF had forced expiratory volume in 1 s > or = 80% predicted but only one had a normal LCI. LCI repeats were reproducible in all three groups of subjects (mean intra-visit coefficient of variation ranged from 3.6% to 5.4%). CONCLUSIONS: Innocor can be adapted to measure LCI and affords a simpler alternative to a mass spectrometer. LCI is raised in adults with CF with normal spirometry, and may prove to be a more sensitive marker of the effects of treatment in this group.

Respiratory heat and moisture loss is associated with eosinophilic inflammation in asthma.

Increased mucosal vascularity is a hallmark of airway inflammation in asthma. It was hypothesised that this would lead to a detectable increase in respiratory heat and moisture loss (RHML), which would reflect the degree of airway inflammation present. A total of 23 subjects with asthma and 18 healthy controls had RHML measured in a cross-sectional study. The measurements were made using a device that combines temperature and humidity measurement during inspiration and expiration and allows precise control over inspirate conditions and ventilatory pattern. The subjects with asthma underwent parallel measurements of exhaled nitric oxide, sputum eosinophil percentage and exhaled breath condensate pH. Mean+/-SD RHML was elevated in patients with asthma (98.1+/-7.3 J.L(-1)) compared with control subjects (91.9+/-4.5 J.L(-1)). RHML measurement in asthma correlated with sputum eosinophil percentage. This novel correlation between thermal and cellular measurements in asthma suggests that both of these noninvasive indices are sensitive to the degree of underlying chronic airway inflammation.

Effects of breathing pattern and inspired air conditions on breath condensate volume, pH, nitrite, and protein concentrations.

BACKGROUND: The effects of breathing pattern and inspired air conditions on the volume and content of exhaled breath condensate (EBC) were investigated. METHODS: Total exhaled water (TEW), EBC volume, pH, nitrite and protein concentrations were measured in three groups of 10 healthy subjects breathing into a condenser at different target minute ventilations (Vm), tidal volumes (Vt), and inspired air conditions. RESULTS: The volumes of both TEW and EBC increased significantly with Vm. For Vm 7.5, 15 and 22.5 l/min, mean (SD) EBC was 627 (258) microl, 1019 (313) microl, and 1358 (364) microl, respectively (p<0.001) and TEW was 1879 (378) microl, 2986 (496) microl, and 4679 (700) microl, respectively (p<0.001). TEW was significantly higher than EBC, reflecting a condenser efficiency of 40% at a target Vm of 7.5 l/min which reduced to 29% at Vm 22.5 l/min. Lower Vt gave less TEW than higher Vt (26.6 v 30.7 microl/l, mean difference 4.1 (95% CI 2.6 to 5.6), p<0.001) and a smaller EBC volume (4.3 v 7.6 microl/l, mean difference 3.4 (95% CI 2.3 to 4.5), p<0.001). Cooler and drier inspired air yielded less water vapour and less breath condensate than standard conditions (p<0.05). Changes in the breathing pattern had no effect on EBC protein and nitrite concentrations and pH. CONCLUSION: These results show that condensate volume can be increased by using high Vt and increased Vm without compromising the dilution of the sample.

Seasonality of presentation of imported Plasmodium vivax malaria in Birmingham, UK.

Residents of the UK returning from northern Pakistan with Plasmodium vivax infection tend to develop symptoms and present to hospital in the summer months, irrespective of the month of return. Thus, infections acquired in the cooler months of November to April appear to have a longer latency before presentation. Experiments suggest that more hypnozoites arise from the liver when ambient temperatures fall, somehow 'programming' parasites within biting mosquitoes.

Chest physicians' and microbiologists' awareness and demand for drug monitoring in the treatment of TB.

There is a role for therapeutic drug monitoring (TDM) to achieve the optimum therapeutic concentration of anti-tuberculous drugs. This work aimed to determine the current awareness of TDM in TB control among chest physicians and to estimate the demand for this service. Responses from a sample of chest physicians in the West Midlands revealed that 60% were aware of TDM and 33% had used it. Responses were received from half of a UK group of microbiologists who reported a median of nine requests in the past year. It appeared that more was known about services for rifampicin and streptomycin than other first-line drugs. There appears to be a need for both increased awareness among potential service users and for coordination of assay services.

Airways in cystic fibrosis are acidified: detection by exhaled breath condensate.

BACKGROUND: The loss of cystic fibrosis transmembrane conductance regulator (CFTR) mediated chloride conductance does not fully explain the diverse pathologies evident in patients with cystic fibrosis (CF). Bicarbonate (HCO(3)(-)) secretion is also impaired in CFTR expressing tissues and CFTR is thought to regulate HCO(3)(-) secretion at the apical membrane of epithelial cells. We hypothesised that the epithelial lining fluid (ELF) of patients with CF would be acidified and that this may be worsened during an infective exacerbation due to the increased inflammatory burden. METHODS: pH and nitrite levels in exhaled breath condensate (EBC) from 12 healthy non-smoking controls and 30 patients with CF (11 of whom were in an infective exacerbation) were measured. A further nine patients were studied before and after intravenous antibiotic treatment for an exacerbation of CF. RESULTS: The pH of EBC was significantly lower in patients with stable CF than in controls (5.88 (0.32) v 6.15 (0.16), p=0.017), and was further reduced in CF patients with an exacerbation (5.32 (0.38), p=0.001) compared with stable CF patients. EBC pH increased significantly following antibiotic treatment from 5.27 (0.42) to 5.71 (0.42), p=0.049). Nitrite levels in EBC were increased in CF patients with an exacerbation compared with control subjects (4.4 (4.0) micro m v 1.6 (1.6) micro m p=0.047). No correlation was found between EBC pH and nitrite levels. CONCLUSIONS: These findings support the hypothesis that airway acidification occurs in CF. This acidity is in part a function of inflammation as the pH of the EBC of patients increased significantly with treatment of an exacerbation, although not to control levels. Acidic pH of the ELF may play a role in the pathophysiology of CF lung disease and requires further investigation.

Short term variability of single breath carbon monoxide transfer factor.

BACKGROUND: When monitoring patients with chronic lung disease it is important to distinguish genuine changes in gas transfer over time from natural variability. This study aims to define the coefficient of repeatability for routine measurements of single breath transfer factor (TCO) and transfer coefficient (KCO). METHODS: Sixty eight subjects (32 with emphysema, 36 healthy volunteers) had TCO measured twice at a mean (SD) interval of 7.5 (1.3) days. On each occasion a standard protocol (conforming to BTS guidelines) was followed, comprising duplicate measurements satisfying standard technical criteria. The mean of these duplicates was recorded. For the pooled data changes in TCO and KCO between study days were expressed as coefficient of repeatability. RESULTS: The coefficient of repeatability was +/-1.60 mmol/min/kPa for TCO and +/-0.24 mmol/min/kPa/l for KCO. Correcting TCO and KCO for prevailing barometric pressure or carboxyhaemoglobin level made no significant difference to the results. CONCLUSIONS: The quoted limits for variability in gas transfer over time are valid for a wide range of clinically relevant values. Changes in TCO and KCO greater than these limits are unlikely to arise from natural variation.

Atopy influences exhaled nitric oxide levels in adult asthmatics.

STUDY OBJECTIVE: To examine whether atopy influences exhaled nitric oxide (NO) levels in adults with established asthma. SETTING: Specialist respiratory unit in a university teaching hospital. PATIENTS: Twenty-eight asthmatics (mean FEV(1), 85.7%) receiving short-acting inhaled bronchodilators and a range of inhaled steroids (0 to 4,000 microg/d). INTERVENTIONS: Subjects were studied on two occasions, 5 to 7 days apart, between September and March. MEASUREMENTS AND RESULTS: On the first day, FEV(1), exhaled NO, and histamine challenge were performed. On the second day, exhaled NO, total IgE, and skin-prick testing to six common allergens were conducted. Exhaled NO was measured with the single exhalation method. We found exhaled NO levels to correlate positively with total IgE (r = 0.43, p = 0.02) and number of positive skin-prick tests (p = 0. 002). By contrast, there was no significant correlation between exhaled NO and FEV(1) or the provocative concentration causing a 20% fall in FEV(1). Subanalyses of steroid-treated and steroid-naive patients in this group revealed the same findings. CONCLUSION: Exhaled NO levels in asthmatics correlate more closely with atopy than with bronchial hyperreactivity and lung function.

Laboratory assessment of fitness to fly in patients with lung disease: a practical approach.

To identify patients with respiratory disease, who may be at risk of developing respiratory distress during commercial air travel, a hypoxia inhalation test (HIT) can be performed. This paper reports our experience of using such a test combined with an interpretation algorithm in a routine respiratory function laboratory. Twenty-eight patients were studied. Baseline oxygen saturation (Sa,O2) was measured using a pulse oximeter. If Sa,O2 was < 90% no HIT was performed and the patient was assessed as unfit for air travel. If baseline Sa,O2 was > or = 90% an HIT was performed by the patient breathing through a 35% Venturi mask supplied with 100% nitrogen which reduced inspiratory oxygen fraction to 15.1+/-0.2%. Results were interpreted using a locally derived algorithm, and validation was attempted using a questionnaire to investigate subsequent symptoms during travel. All patients tolerated the assessment well. Twenty-two patients were assessed as "fit to fly" with a further two patients "fit to fly with supplemental O2". Four patients were considered unfit to fly. Hypoxic response could not be predicted from either forced expiratory volume in one second, or pretest saturation. Validation of such protocols is difficult, but the hypoxia inhalation test may be a useful tool for predicting hypoxia during air travel in patients with chronic respiratory disease.