Persistent Empiric COPD Diagnosis and Treatment After Pulmonary Function Test Showed No Obstruction

BACKGROUND

Health-care providers often diagnose and empirically treat COPD without a confirmative pulmonary function test (PFT) or even despite a PFT that is not diagnostic of obstructive lung disease. We hypothesized that a portion of patients continue to carry a persistent empiric COPD diagnosis and receive treatment with bronchodilators and inhaled steroids after a PFT shows no obstruction.

METHODS

We retrospectively reviewed single PFT sessions with both spirometry and plethysmography in 1,805 subjects. We included subjects who had a normal PFT or a restrictive ventilatory defect. Persistent empiric COPD diagnosis and treatment were defined when subjects with normal PFTs or a restrictive ventilatory defect continued to carry a health-care provider COPD diagnosis or receive treatment with bronchodilators and/or inhaled glucocorticoids, respectively, after a PFT showed no obstruction.

RESULTS

One quarter of subjects with FEV1/FVC ≥ lower limit of the normal range had nonspecific PFT abnormalities. We included 473 subjects with normal PFTs and 382 with a restrictive ventilatory defect (n = 855). Persistent empiric COPD diagnosis (60 of 855, 7% prevalence) was associated with current (odds ratio [OR] = 44.7, P < .001) and former smoking (OR = 17.3, P < .001) and older age (OR = 1.03/y, P = .005). Persistent empiric treatment (208 of 855, 24%) was associated with empiric COPD diagnosis (OR = 24.6, P < .001), female sex (OR = 1.75, P = .002), current (OR = 2.04, P = 0.040) and former smoking (OR = 1.53, P = 0.029), interstitial lung disease (OR = 2.09, P = .001), other respiratory diagnosis (OR = 3.17, P < .001), and obstructive sleep apnea (OR = 1.79, P = .006).

CONCLUSIONS

Persistent empiric COPD diagnosis was 7%, but persistent empiric treatment was common.

The difference between slow and forced vital capacity increases with increasing body mass index: a paradoxical difference in low and normal body mass indices

BACKGROUND

Obesity reduces FVC, the most commonly used measurement of vital capacity (VC) and slow VC (SVC). It is unknown whether the difference between SVC and FVC is constant in different body mass indices (BMIs). We hypothesized that the difference between SVC and FVC increases as a function of BMI.

METHODS

We retrospectively reviewed pulmonary function tests (PFTs) that included spirometry and plethysmography and were performed in adults from January 2013 to August 2013. A total of 1,805 PFTs were enrolled. The non-parametric Wilcoxon signed-rank test was used to compare FVC with SVC, and to compare FEV1/FVC with FEV1/SVC ratio. Spearman correlation analysis was used to determine whether BMI has an effect on the discordance between FVC and SVC. Finally, we used the McNemar test for paired binary data to compare the prevalence rate of obstruction when using different measurements of VC.

RESULTS

In individuals with BMI < 25 kg/m(2) and no evidence of obstruction in the PFTs, FVC was larger than SVC (P = .03), whereas in overweight and obese individuals, SVC was significantly larger than FVC. The difference between SVC and FVC was positively correlated with BMI (P < .001). One hundred thirty-one patients had a normal FEV1/FVC but low FEV1/SVC ratio. Fifty of these 131 individuals also had a normal FVC; the majority of them (46 of 50) had the PFTs for investigation of respiratory symptoms and had BMI > 25 kg/m(2) (42 of 50).

CONCLUSIONS

Our results indicate that FVC is larger than SVC in patients with low and normal BMI and no evidence of obstruction in the PFTs, whereas FVC is smaller than SVC in overweight and obese individual. Our findings add to the existing literature that use of FEV1/FVC may lead to underdiagnosis of obstructive airway disease in overweight and obese individuals.

Complement in asthma: sensitivity to activation and generation of C3a and C5a via the different complement pathways

Studies in rodent models suggested that complement may play a critical role in susceptibility to airway hyperresponsiveness (AHR) and as a mediator of bronchial obstruction and inflammation in asthma. Complement may participate in susceptibility to asthma because of an intrinsic abnormality in complement activation and generation of C3a, C5a, or other products that affect cellular responses, resulting in T(H)2 predominance and asthma susceptibility. Alternatively, an intrinsic abnormality in the cellular response to complement activation products could determine susceptibility to asthma. In this study, the authors investigated whether complement in patients with atopic asthma versus nonatopic controls possesses an increased propensity to become activated. Despite reports that total complement plasma levels in unchallenged asthmatics are normal, an abnormal sensitivity of complement to activation may exist if an isoform or a polymorphic variant of a complement protein was present and resulted in gain or loss of function without associated changes in total complement levels. Therefore, complement activation was induced in vitro in plasma of asthmatics and controls using activators of the classical, alternative, and lectin pathways and measured C3a, other C3 fragments, and C5a. For each pathway, similar amounts of generated fragments, as well as C3a/C3 and C5a/C5 ratios, were found in asthmatics and controls. Also, similar basal plasma levels of C3a and C5a were found in both groups; however, mannan-binding lectin (MBL) levels were moderately elevated in asthmatics. In conclusion, the results suggest that, in asthmatic patients, complement activation does not exhibit an abnormal sensitivity to activation by any of the known activation pathways.