Correction: How Reliable Are Current Data for Assessing the Actual Prevalence of Chronic Obstructive Pulmonary Disease?

[This corrects the article DOI: 10.1371/journal.pone.0149302.].

How Reliable Are Current Data for Assessing the Actual Prevalence of Chronic Obstructive Pulmonary Disease?

BACKGROUND: Estimating COPD occurrence is perceived by the scientific community as a matter of increasing interest because of the worldwide diffusion of the disease. We aimed to estimate COPD prevalence by using administrative databases from a city in central Italy for 2002-2006, improving both the sensitivity and the reliability of the estimate. METHODS: Multiple sources were used, integrating the hospital discharge register (HDR), clinical charts, spirometry and the cause-specific mortality register (CMR) in a longitudinal algorithm, to reduce underestimation of COPD prevalence. Prevalence was also estimated on the basis of COPD cases confirmed through spirometry, to correct misclassification. Estimating such prevalence relied on using coefficients of validation, derived as the positive predictive value (PPV) for being an actual COPD case from clinical and spirometric data at the Institute of Clinical Physiology of the National Research Council. RESULTS: We found that sensitivity of COPD prevalence increased by 37%. The highest estimate (4.43 per 100 residents) was observed in the 5-year period, using a 3-year longitudinal approach and combined data from three sources. We found that 17% of COPD cases were misclassified. The above estimate of COPD prevalence decreased (3.66 per 100 residents) when coefficients of validation were applied. The PPV was 80% for the HDR, 82% for clinical diagnoses and 91% for the CMR. CONCLUSIONS: Adjusting the COPD prevalence for both underestimation and misclassification of the cases makes administrative data more reliable for epidemiological purposes.

Preliminary observations on the effect of hypoxic and hyperbaric stress on pulmonary gas exchange in breath-hold divers.

AIM: To evaluate pulmonary alveolar-capillary membrane integrity and ventilation/perfusion mismatch after breath-hold diving. METHODS: Pulmonary diffusing capacity to carbon monoxide (DLCO) and nitric oxide (DLNO), haemoglobin (Hb) and haematocrit (Hct) were measured in six elite divers before and at 2, 10 and 25 minutes after a maximal breath-hold dive to a depth of 10 metres' sea water. RESULTS: Compared to pre-dive, DLCO showed a slight increase at 2 minutes in five subjects and a tendency to decrease at 25 minutes (P < 0.001) in all subjects. DLNO showed an increase at 10 minutes in three divers and a slight decrease at 25 minutes in five subjects. There was a small but significant (P < 0.001) increase in Hb and Hct at 2 minutes, possibly affecting the DLCO measurements. CONCLUSIONS: An early but transient increase in DLCO in five divers may reflect the central shift in blood volume during a breath-hold dive. The late parallel decrease in DLCO and DLNO likely reflects alveolar-capillary distress (interstitial oedema). The DLNO increase in three subjects at 10 minutes may suggest ventilation/perfusion mismatch.

Soluble receptor for advanced glycation end products in COPD: relationship with emphysema and chronic cor pulmonale: a case-control study.

BACKGROUND: The receptor for advanced glycation end products (RAGE) is a multiligand signal transduction receptor that can initiate and perpetuate inflammation. Its soluble isoform (sRAGE) acts as a decoy receptor for RAGE ligands, and is thought to afford protection against inflammation. With the present study, we aimed at determining whether circulating sRAGE is correlated with emphysema and chronic cor pulmonale in chronic obstructive pulmonary disease (COPD). METHODS: In 200 COPD patients and 201 age- and sex-matched controls, we measured lung function by spirometry, and sRAGE by ELISA method. We also measured the plasma levels of two RAGE ligands, N-epsilon-carboxymethyl lysine and S100A12, by ELISA method. In the COPD patients, we assessed the prevalence and severity of emphysema by computed tomography (CT), and the prevalence of chronic cor pulmonale by echocardiography. Multiple quantile regression was used to assess the effects of emphysema, chronic cor pulmonale, smoking history, and comorbid conditions on the three quartiles of sRAGE. RESULTS: sRAGE was significantly lower (p = 0.007) in COPD patients (median 652 pg/mL, interquartile range 484 to 1076 pg/mL) than in controls (median 869 pg/mL, interquartile range 601 to 1240 pg/mL), and was correlated with the severity of emphysema (p < 0.001), the lower the level of sRAGE the greater the degree of emphysema on CT. The relationship remained statistically significant after adjusting for smoking history and comorbid conditions. In addition, sRAGE was significantly lower in COPD patients with chronic cor pulmonale than in those without (p = 0.002). Such difference remained statistically significant after adjusting for smoking history, comorbidities, and emphysema severity. There was no significant difference in the plasma levels of the two RAGE ligands between cases and controls. CONCLUSIONS: sRAGE is significantly lower in patients with COPD than in age- and sex-matched individuals without airflow obstruction. Emphysema and chronic cor pulmonale are independent predictors of reduced sRAGE in COPD.

Prognostic value of C-reactive protein in chronic obstructive pulmonary disease.

To establish whether C-reactive protein (CRP) is an independent predictor of all-cause mortality and hospitalization in chronic obstructive pulmonary disease (COPD), we followed 200 patients with COPD and 201 age- and gender -matched controls for a median time of 4.2 years (range, 0.2-5.1 years). Airflow obstruction was rated moderate if forced expiratory volume in one second (FEV(1)) was 50-69% of the predicted value, or severe if FEV(1) was <50%. The CRP level was categorized as low (≤3 mg/L) or high (>3 mg/L). The hazard of death was estimated by a proportional hazard regression model, using controls with low CRP as the reference category. Fifty subjects died: 41 (21%) among the COPD and 9 (4%) among the controls (p < 0.0001). The hazard of death in moderate COPD was not significantly higher than in the reference category, independently of the CRP level. In severe COPD with a low CRP, the hazard of death is 3.4 times higher than in the reference category (p = 0.008); in severe COPD and a high CRP it is 9.6 times higher (p < 0.0001). The rate of hospitalization in COPD patients with a high CRP is 1.9 times higher than in those with a low CRP [95% confidence interval (CI), 1.2-3.2]. In severe COPD, it is 6.9 times higher than in moderate COPD (95% CI, 3.8-12.7). A high CRP level is a significant amplifier of the risk of death only in severe COPD. The degree of airflow obstruction is a strong independent predictor of COPD-related outcomes.

Nicotine dependence, psychological distress and personality traits as possible predictors of smoking cessation. Results of a double-blind study with nicotine patch.

AIM: Nicotine replacement therapy (NRT) is an effective treatment for smokers who want to quit, however, the rates of successful quitting can be improved even more. In this context, nicotine dependence (assessed via the Fagerström Tolerance Questionnaire, FTQ), psychological distress (measured via the Symptom Rating Test, SRT), and personality traits (evaluated via the Adult Eysenck Personality Inventory, AEPI) were evaluated as possible predictors of smoking cessation. RESULTS: A total of 297 cigarette smokers were followed for one year as part of a NRT double-blind, parallel group, randomized trial. Baseline nicotine dependence (weeks 12 and 26: p<0.05), AEPI neuroticism (weeks 12 and 52: p<0.05), and AEPI psychoticism (weeks 12 and 52: p<0.05) scores significantly influenced the outcome of smoking cessation during one-year of follow-up. An increase in psychological distress during follow-up was associated with a lower probability of quitting smoking (p=0.000). CONCLUSIONS: Nicotine dependence, neuroticism, psychoticism and, over time, psychological distress were the main factors influencing the long-term outcome (i.e., up to 12 months) of smoking cessation under NRT.

Assessment of the alveolar volume when sampling exhaled gas at different expired volumes in the single breath diffusion test.

BACKGROUND: Alveolar volume measured according to the American Thoracic Society-European Respiratory Society (ATS-ERS) guidelines during the single breath diffusion test can be underestimated when there is maldistribution of ventilation. Therefore, the alveolar volume calculated by taking into account the ATS-ERS guidelines was compared to the alveolar volume measured from sequentiallly collected samples of the expired volume in two groups of individuals: COPD patients and healthy individuals. The aim of this study was to investigate the effects of the maldistribution of ventilation on the real estimate of alveolar volume and to evaluate some indicators suggestive of the presence of maldistribution of ventilation. METHODS: Thirty healthy individuals and fifty patients with moderate-severe COPD were studied. The alveolar volume was measured either according to the ATS-ERS guidelines or considering the whole expired volume subdivided into five quintiles. An index reflecting the non-uniformity of the distribution of ventilation was then derived (DeltaVA/VE). RESULTS: Significant differences were found when comparing the two measurements and the alveolar volume by quintiles appeared to have increased progressively towards residual volume in healthy individuals and much more in COPD patients. Therefore, DeltaVA/VE resulted in an abnormal increase in COPD. CONCLUSION: The results of our study suggest that the alveolar volume during the single breath diffusion test should be measured through the collection of a sample of expired volume which could be more representative of the overall gas composition, especially in the presence of uneven distribution of ventilation. Further studies aimed at clarifying the final effects of this way of calculating the alveolar volume on the measure of DLCO are needed. DeltaVA/VE is an index that can help assess the severity of inhomogeneity in COPD patients.