For this reason observational selleckbio studies were undertaken and these indirect data were used to support efficacy. For instance, the NIH registry  suggested that individuals who received therapy for at least 6 months had not just a reduction in mortality but also a modulation of the FEV1 decline for those with baseline values in the range 35-60% predicted. However, these data were likely influenced, at least in part, by availability of healthcare provision and social aspects of healthcare delivery in the USA. Nevertheless, other studies provided similar results by observing a greater decline in FEV1 in countries where augmentation was not available  and a reduction in decline after therapy was instigated .
Furthermore the former observation was also supported by a recent meta-analysis providing indirect evidence that spirometric decline is less where augmentation is available . Nevertheless it is recognised that these observations, though supportive, cannot replace formal clinical trials. Importantly the NIH study, where used to support augmentation, has been interpreted as suggesting no benefit outside the FEV1 limits of 35-60% predicted and in some countries augmentation is stopped below this lower limit and not usually started above these limits. However recent data has indicated that using other more specific and sensitive measures of emphysema, such as the alveolar gas transfer and/or the decrease in lung density, indicate that progression of lung disease occurs both above and below these FEV1 limits [13,14], even when FEV1 remains stable as indicated in data summarised in Figure 1 for an individual patient from the UK National Registry.
Figure 1 The decline in FEV1 and Kco expressed as a % predicted is shown over time for a 43 year old female from the UK registry who stopped smoking after diagnosis in 2005. A recent Cochrane review took the pragmatic approach of analysing the efficacy of augmentation therapy based on the results of decline in FEV1 of the Drug_discovery only 2 small placebo controlled trials available [15,16] and concluded that there was no convincing data to support the efficacy of augmentation therapy . However, both studies were just short of conventional statistical significance in favour of the efficacy of augmentation therapy using lung densitometry as the outcome. Combining the 2 studies and excluding all individuals who participated in the first (less robust study) from the second (more robust study) was however highly suggestive of efficacy in reducing the rate of decline in lung density , which is validated and has become accepted as the most specific and sensitive measurement of the progression of emphysema [13,19,20].