Khin M. Gyi

Lack of inducible nitric oxide synthase in bronchial epithelium: a possible mechanism of susceptibility to infection in cystic fibrosis

Cystic fibrosis (CF) is an inherited disorder associated with severe inflammation and repeated bacterial infection and colonization in the lung. Airway epithelium is involved in defence against bacteria, but this system may be defective in CF. Pro‐inflammatory cytokines can stimulate the expression of inducible nitric oxide synthase (iNOS), an enzyme generating nitric oxide, which functions as an important mediator in host defence mechanisms. To understand better the poor resistance to infections in the CF lung, the expression of the iNOS gene was investigated in explanted lungs from patients with cystic fibrosis (n‐13), bronchiectasis (n‐3), emphysema (n‐14), and in normal lungs (n‐8). In addition, bronchial epithelial cell lines were examined to study iNOS gene expression in vitro. Strong immunoreactivity for iNOS was seen in inflammatory cells and bronchial epithelium in all the diseased lungs, except for bronchial epithelium in CF. Quantitative analysis showed a significant reduction in the area of epithelium immunostained in CF [CF 6·8±1·6 (%±SEM); emphysema 18·2±2·8; normal 9·6±0·8, P<0·01], regardless of steroid treatment. These results were supported by in situ hybridization of iNOS mRNA, which showed a pattern of gene expression in CF, emphysema, and normal lung which paralleled that of protein immunoreactivity. Stimulation with cytokines (IL‐1β, TNF‐α, and IFN‐γ) increased the expression of iNOS mRNA detected by reverse transcriptase‐polymerase chain reaction (RT‐PCR) in cultures of normal (16HBE14o−), but not CF (CFBE41o−, with ΔF508 CFTR mutation) epithelial cells. Expression of iNOS in inflammatory cells suggests that the gene is normal in CF. Absence of iNOS from bronchial epithelium may be due to low expression of the gene resulting from abnormalities in the signalling system that normally causes induction, such as cytokine receptors, second messengers or transcription factors. The resulting deficiency of the nitric oxide defence system may be relevant to the susceptibility of CF patients to pulmonary bacterial colonization.

Variceal hemorrhage and cystic fibrosis: outcomes and implications for liver transplantation.

Autopsy and imaging studies show that liver involvement is common in cystic fibrosis. However, complications of chronic liver disease including portal hypertension and variceal bleeding are infrequently encountered, and the degree to which variceal hemorrhage affects prognosis in cystic fibrosis is unclear. This uncertainty has lead to debate as to whether liver transplantation is indicated in these patients. We describe a case series of 18 patients and compare their survival with a control group of cystic fibrosis patients without liver disease. The median age at first bleed was 20.0 years (range 9.7‐30.9). The median survival after first bleed was 8.4 years, compared to 13.0 years in the control group (P = 0.15). A total of 14 patients have died, 9 from respiratory disease with no discernable contribution from their liver disease. Liver disease contributed to 4 deaths. Only 1 patient suffered a fatal hemorrhage, which may have been either variceal or bronchial in origin. Long‐term survival is a frequent occurrence in patients with cystic fibrosis who suffer variceal hemorrhage, and age at death is comparable to the general cystic fibrosis population. In conclusion, this suggests that liver transplantation is not indicated in these patients without additional features of liver decompensation. (Liver Transpl 2005.)

Beyond postural drainage and percussion: Airway clearance in people with cystic fibrosis.

BACKGROUND Evidence indicates that there are no statistically significant differences in effectiveness among the airway clearance techniques (ACTs) of active cycle of breathing, autogenic drainage, positive expiratory pressure (PEP) or oscillating PEP in the short-term, but are there differences in the long-term (one year)? The objective of the study was to demonstrate non-inferiority in the long-term. METHODS Seventy-five people with cystic fibrosis entered the prospective, randomised controlled trial of these five different ACTs. The primary outcome measure was forced expiratory volume in one second (FEV(1)). Secondary outcome measures included exercise capacity and health related quality of life. RESULTS Using intention to treat, data were available on 65 subjects at the end of the study period. There were no statistically significant differences among the regimens in the primary outcome measurement of FEV(1) (p=0.35). CONCLUSION In different countries either one or several airway clearance regimens are used. This study provides evidence in support of current practices.

HbA1c as a screening tool for cystic fibrosis related diabetes

AIMS Early diagnosis of cystic fibrosis (CF) related diabetes (CFRD) is important to improve outcomes. International guidelines recommend an oral glucose tolerance test (OGTT) for all CF patients aged ≥10 years - this approach is controversial. The aim of this study was to develop an effective screening tool and reduce the need for a universal OGTT. METHODS Adult CF patients (without CFRD) attending an annual review assessment were recruited prospectively (March 2009-July 2012) into two sequential studies - a primary investigative study followed by validation study. All patients underwent an OGTT and were simultaneously screened by predetermined biochemical/clinical criteria to identify their risk of CFRD. A sensitivity/specificity analysis was performed using the World Health Organisation diabetes criteria as gold standard; modifications were made to improve the screening tools accuracy and determine the optimal screening thresholds. This was tested in the validation study. RESULTS 429 patients (primary, n=94; validation, n=335: mean age=31.7 ± 10.4(SD), 43% female, 77% on pancreatic supplements). Primary study: in predicting a positive OGTT, the test sensitivity was 66.7% and specificity 60%. HbA1c was carried over to the validation study as it was the most discriminative (optimal threshold ≥5.8% (40 mmol/mol); receiver operating curve, ROC, score 0.60). Validation study: the number of patients with a normal, impaired and diabetic OGTT was 268(80%), 51(15.2%) and 16(4.8%), respectively. HbA1c provided a test sensitivity, specificity and ROC score of 93.8%, 53.0% and 0.73, respectively. CONCLUSIONS The use of HbA1c ≥ 5.8%(40 mmol/mol) is an effective tool for CFRD screening and reduced the need for an OGTT by 50.7%.

Effect of acute exacerbations on skeletal muscle strength and physical activity in cystic fibrosis

BACKGROUND Skeletal muscle weakness is an important complication of chronic respiratory disease. The effect of acute exacerbations on strength in patients with cystic fibrosis is not known. METHODS Quadriceps (QMVC) and respiratory muscle strength were measured in patients at the time of acute admission, at discharge and one month later. Patients wore an activity monitor during admission and at one month. Convalescent values were compared to the stable clinic population. RESULTS Data were available for 13 acute admissions and 25 stable CF outpatients. Strength and other parameters including daily step count did not differ significantly between the stable and one month post-admission groups. At admission, QMVC was 16.7 (8.3)% lower than at convalescence, whereas inspiratory muscle strength did not change significantly. Reduction in QMVC did not correlate with activity levels or with markers of systemic inflammation. CONCLUSION Further research is needed to identify the mechanisms responsible for the reduction in QMVC.

Predicting survival in end-stage cystic fibrosis.

The natural history of cystic fibrosis (CF) is unpredictable and the optimal timing for lung transplantation in end-stage disease uncertain. Predicting survival based on FEV1 alone remains controversial and therefore the aim of this study was to assess the value of walk test performance in pre-transplant assessment. Retrospective review of adult patients with end-stage CF who underwent transplant assessment between 1988 and 2004 including a documented walk test on room air, but who died before transplant. The six-minute walk test (6MWT) was used between 1988 and 1993 and the shuttle walk test (SWT) thereafter, the two cohorts were therefore individually assessed. A total of 121 patients were identified. The median (IQR) survival in patients performing SWT (n=77) and 6MWT (n=44) was 363 days (226, 566) and 433 days (232, 844), respectively, with survival in both cohorts significantly associated with pre-test (resting) heart rate (HR) (p<0.03), but not distance walked, pre-test SpO2, FEV1 or BMI. It was predicted that 85% of patients performing SWT with a resting HR of 120 bpm, 70% of those with a HR of 109 bpm (cohort median) but only 25% with a HR of 72 bpm would die within 500 days. Distance walked in the SWT was significantly related to pre-test HR (p<0.01), SpO2 (p<0.01) and Borg score (p=0.016) when performing linear regression. Only pre-test HR remained significant when performing multiple regression. Resting heart rate was the only consistent parameter in this study at predicting a high risk of dying on the transplant waiting list.

A woman with cystic fibrosis, severe hypoxaemia, an atrial thrombus and a patent foramen ovale: a case report

IntroductionCystic fibrosis is usually associated with chronic pulmonary sepsis and frequent infective exacerbations. We report a very unusual cause of severe hypoxaemia in a woman with cystic fibrosis caused by thrombus formation in the right atrium.Case presentationA 21-year-old Caucasian woman with cystic fibrosis and a totally implantable venous access device presented with severe hypoxaemia. This was initially treated with antibiotics but her oxygen levels did not improve significantly. Subsequently, a transient ischaemic attack occurred. Further investigations, including a contrast echocardiogram and a cardiac magnetic resonance scan, revealed the presence of a large right atrial thrombus and right-to-left intracardiac shunt through a patent foramen ovale.ConclusionThis case highlights the need to consider a right-to-left shunt in chronic respiratory diseases when hypoxaemia is out of proportion to the degree of lung function impairment. Totally implantable venous access devices should always be considered as a source of thrombus formation.

Response to Letter to the Editor: HbA1c as a screening tool for cystic fibrosis related diabetes: Response to letters by Widger et al. and Schnyder et al.

a National Heart and Lung Institute, Imperial College, London, United Kingdom b Adult Cystic Fibrosis Centre, Royal Brompton Hospital, London, United Kingdom c Endocrinology and Diabetes Department, Chelsea Childrens Hospital, Chelsea and Westminster NHS Healthcare Trust, London, United Kingdom d Medical Statistician, Respiratory Biomedical Research Unit, Royal Brompton Hospital, London, United Kingdom

173 Validation of near patient testing blood capillary glucose for the oral glucose tolerance test in cystic fibrosis

Introduction Early diagnosis and treatment of CFRD is important to slow pulmonary function decline and improve outcomes. Oral glucose tolerance test (OGTT) using venous plasma samples (VPS) is the accepted method for diagnosis recommended by WHO. Near patient testing (NPT) by blood capillary sampling (BCS) provides real time results but this technique has not been validated in CF. Aim To validate the accuracy of NPT for an OGTT by BCS using HemoCue Glucose 201 RT™ (HG) by comparing this with standard laboratory VPS. Methods Prospective study of clinically stable patients undergoing OGTT (June 2013 to April 2014). All patients had simultaneous VPS and BCS at 0 min (fasting) and 120 min after a glucose 75 g solution drink. BCS was analysed immediately using HG (daily quality control, QC). VPS were analysed in an accredited laboratory by standard methods. Results 70 patients were recruited. QC for BCS and reproducibility from control material was excellent. WHO criteria for diabetes were used: Lab (VPS) at 120 min – normal glucose tolerance (NGT), n=53 (76%); impaired (IGT), n=9 (13%); and, diabetic (DGT), n=8 (11%). BCS at 120 min – NGT, n=54 (77%); IGT, n=9 (13%); and DGT, n=7 (10%). Sensitivity and specificity of BCS for DGT was 87.5% and 98.4%, respectively. The correlation coefficient(R 2 ) of the different sampling techniques was 0.47 and 0.95 for fasting and 120 min samples, respectively. Conclusion There was a consistent discrepancy between absolute values for BCS and VPS, particularly for fasting samples. Although this had limited impact on diagnostic categories, the sensitivity may not be acceptable for clinical implementation; this needs further evaluation.