Lung function decline in relation to diagnostic criteria for airflow obstruction in respiratory symptomatic subjects

Contains fulltext : 108583.pdf (publisher's version ) (Open Access)BACKGROUND: Current COPD guidelines advocate a fixed < 0.70 FEV1/FVC cutpoint to define airflow obstruction. We compared rate of lung function decline in respiratory symptomatic 40+ subjects who were 'obstructive' or 'non-obstructive' according to the fixed and/or age and gender specific lower limit of normal (LLN) FEV1/FVC cutpoints. METHODS: We studied 3,324 respiratory symptomatic subjects referred to primary care diagnostic centres for spirometry. The cohort was subdivided into four categories based on presence or absence of obstruction according to the fixed and LLN FEV1/FVC cutpoints. Postbronchodilator FEV1 decline served as primary outcome to compare subjects between the respective categories. RESULTS: 918 subjects were obstructive according to the fixed FEV1/FVC cutpoint; 389 (42%) of them were non-obstructive according to the LLN cutpoint. In smokers, postbronchodilator FEV1 decline was 21 (SE 3) ml/year in those non-obstructive according to both cutpoints, 21 (7) ml/year in those obstructive according to the fixed but not according to the LLN cutpoint, and 50 (5) ml/year in those obstructive according to both cutpoints (p = 0.004). CONCLUSION: This study showed that respiratory symptomatic 40+ smokers and non-smokers who show FEV1/FVC values below the fixed 0.70 cutpoint but above their age/gender specific LLN value did not show accelerated FEV1 decline, in contrast with those showing FEV1/FVC values below their LLN cutpoint

Abandoning FEV(1)/FVC < 0.70 to detect airway obstruction: an essential debate but with the right emphasis?

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Kan de diagnose COPD op één spirometrietest berusten?

Huisartsen stellen de diagnose COPD vaak op basis van één spirometrietest. Een te lage post-bronchodilatoire FEV1/FVC wijst dan op een luchtwegobstructie die kan passen bij COPD. In een onderzoek onder 2352 personen met verdenking op COPD, die door hun huisarts waren verwezen naar huisartsenlaboratoria, bleken aanvankelijk 758 personen (32%) luchtwegobstructie te vertonen. Na een jaar was dit bij 22% (168/758) en na twee jaar bij 32% (244/758) echter niet meer het geval. Van de 1594 personen zonder obstructie bij de eerste spirometrietest was na een jaar bij 90% wederom geen sprake van obstructie; na twee jaar bij 85%. Verschillende persoonskenmerken voorspelden de kans op verschuiving van obstructief naar niet-obstructief. De FEV1/FVC en het daarop gebaseerde oordeel wel/niet obstructief varieert dusdanig in de tijd dat eenmalige spirometrie leidt tot over- en onderdiagnostiek van COPD. (aut. ref.

Development of a real-time PCR assay and comparison to CHROMagarTM STEC to screen for Shiga toxin-producing Escherichia coli in stool, Cape Town, South Africa

Introduction: Shiga toxin-producing Escherichia coli (STEC) is an emerging infectious pathogen which could lead to haemolytic uremic syndrome. Even though previous studies have compared the performance of CHROMagarTMSTEC to real-time polymerase chain reaction (PCR) in Europe, no study has been done to assess its performance on African isolates. Objectives: This project aimed to validate and test an in-house-developed duplex real-time PCR and use it as a reference standard to determine the performance of CHROMagarTMSTEC on African isolates from diarrhoeic stool samples. Methods: This study evaluated STEC diagnostic technology on African isolates. An in-house-developed duplex real-time PCR assay for detection of stx1 and stx2 was validated and tested on diarrhoeic stool samples and then used as a reference standard to assess the performance of CHROMagarTMSTEC. Real-time PCR was used to screen for stx in tryptic soy broth and the suspected STEC isolates, while conventional PCR was used to detect the other virulence genes possessed by the isolates. Results: The real-time PCR limit of detection was 5.3 target copies/μL of broth. The mean melting temperature on melt-curve analysis for detection of stx1 was 58.2 °C and for stx2 was 65.3 °C. Of 226 specimens screened, real-time PCR detected stx in 14 specimens (6.2%, 95% confidence interval = 3.43% – 10.18%). The sensitivity, specificity, negative predictive value and positive predictive value of the CHROMagarTMSTEC were 33.3%, 77.4%, 95.3% and 11.3%. Conclusions: The in-house developed real-time PCR assay is a sensitive and specific option for laboratory detection of STEC as compared to CHROMagarTMSTEC in this setting

Should the diagnosis of COPD be based on a single spirometry test?

Clinical guidelines indicate that a chronic obstructive pulmonary disease (COPD) diagnosis is made from a single spirometry test. However, long-term stability of diagnosis based on forced expiratory volume in 1 s over forced vital capacity (FEV1/FVC) ratio has not been reported. In primary care subjects at risk for COPD, we investigated shifts in diagnostic category (obstructed/non-obstructed). The data were from symptomatic 40+ years (ex-)smokers referred for diagnostic spirometry, with three spirometry tests, each 12±2 months apart. The obstruction was based on post-bronchodilator FEV1/FVC < lower limit of normal (LLN) and <0.70 (fixed ratio). A total of 2,352 subjects (54% male, post-bronchodilator FEV1 76.5% predicted) were studied. By LLN definition, 32.2% were obstructed at baseline, but 32.2% of them were no longer obstructed at years 1 and/or 2. By fixed ratio, these figures were 46.6 and 23.8%, respectively. Overall, 14.3% of subjects changed diagnostic category by 1 year and 15.4% by 2 years when applying the LLN cut-off, and 15.1 and 14.6% by fixed ratio. Change from obstructed to non-obstructed was more likely for patients with higher body mass index (BMI) and baseline short-acting bronchodilator (SABA) users, and less likely for older subjects, those with lower FEV1% predicted, baseline inhaled steroid users, and current smokers or SABA users at year 1. Change from non-obstructed to obstructed was more likely for males, older subjects, current smokers and patients with lower baseline FEV1% predicted, and less likely for those with higher baseline BMI. Up to one-third of symptomatic (ex-)smokers with baseline obstruction on diagnostic spirometry had shifted to non-obstructed when routinely re-tested after 1 or 2 years. Given the implications for patients and health systems of a diagnosis of COPD, it should not be based on a single spirometry test

Predicting an accelerated lung function decline in smokers: is there a proper threshold?

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COPD prognosis in relation to diagnostic criteria for airflow obstruction in smokers

Item does not contain fulltextThe aim of this study was to establish which cut-off point for the forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) ratio (i.e. fixed 0.70 or lower limit of normal (LLN) cut-off point) best predicts accelerated lung function decline and exacerbations in middle-aged smokers. We performed secondary analyses on the Lung Health Study dataset. 4045 smokers aged 35-60 years with mild-to-moderate obstructive pulmonary disease were subdivided into categories based on presence or absence of obstruction according to both FEV1/FVC cut-off points. Post-bronchodilator FEV1 decline served as the primary outcome to compare subjects between the categories. 583 (14.4%) subjects were nonobstructed and 3230 (79.8%) subjects were obstructed according to both FEV1/FVC cut-off points. 173 (4.3%) subjects were obstructed according to the fixed cut-off point, but not according to the LLN cut-off point ("discordant" subjects). Mean+/-SE post-bronchodilator FEV1 decline was 41.8+/-2.0 mL.year(-1) in nonobstructed subjects, 43.8+/-3.8 mL.year(-1) in discordant subjects and 53.5+/-0.9 mL.year(-1) in obstructed subjects (p<0.001). Our study showed that FEV1 decline in subjects deemed obstructed according to a fixed criterion (FEV1/FVC <0.70), but non-obstructed by a sex- and age-specific criterion (LLN) closely resembles FEV1 decline in subjects designated as non-obstructed by both criteria. Sex and age should be taken into account when assessing airflow obstruction in middle-aged smokers

Prevalence and antibiotic susceptibility patterns of enteric bacterial pathogens in human and non-human sources in an urban informal settlement in Cape Town, South Africa

Abstract Background In light of rampant childhood diarrhoea, this study investigated bacterial pathogens from human and non-human sources in an urban informal settlement. Meat from informal abattoirs (n = 85), river water (n = 64), and diarrheic stool (n = 66) were collected between September 2015 and May 2016. A duplex real-time PCR, gel-based PCR, and CHROMagar™STEC were used to screen Tryptic Soy Broth (TSB) for diarrheic E. coli. Standard methods were used to screen for other selected food and waterborne bacterial pathogens. Results Pathogens isolated from stool, meat, and surface water included Salmonella enterica (6, 5, 0%), Plesiomonas shigelloides (9, 0, 17%), Aeromonas sobria (3, 3, 0%), Campylobacter jejuni (5, 5, 0%), Shigella flexneri (17, 5, 0%), Vibrio vulnificus (0, 0, 9%), and diarrheic E. coli (21, 3, 7%) respectively. All the isolates were resistant to trimethoprim–sulphamethoxazole. Conclusions There was a high burden of drug resistant diarrheal pathogens in the stool, surface water and meat from informal slaughter. Integrated control measures are needed to ensure food safety and to prevent the spread of drug resistant pathogens in similar settings