Letter to the Editor, International Journal of COPD [Letter]

Dear editor

We read the paper by Llordés et al¹ with some interest. The results from this small study are interesting but the analysis and conclusion seem to be at odds with the data. The authors consider a COPD diagnosis by both lower limit of normal (LLN) and the fixed ratio (FR), that is FEV1/FVC<0.7, as concordant (LLN+FR+) and subjects who are FR+LLN- as discordant. Their data show that the discordant group have lower CAT score and lower BODE index suggesting that this group likely has other co-morbidities. As expected, the discordant group is older, more male-dominated² and has fewer hospital admissions. Furthermore, the discordant group has a better overall survival and less respiratory mortality which highlights that the discordant group is quite dissimilar to the concordant group. It is not clear how these data clearly demonstrate that using the FR in the diagnosis COPD is superior to LLN.

The single piece of data the authors have to support their main conclusion, that the FR is better for diagnosing COPD than the LLN, is that the discordant group has a greater decline in FEV1/FVC than the concordant group. This is not an acceptable way to look at deterioration of airflow obstruction.³ In patients with a low FEV1/FVC the ratio can increase with severity since the FVC starts to reduce to a greater extent because of premature airway closure. Decline in FEV1 should be used to assess deterioration, and no significant difference in annualised decline in FEV1 was shown.

The authors strong conclusion that LLN is less useful than FR for diagnosing COPD in primary care seems to be a misinterpretation of the data presented.

Disclosure

The authors report no conflicts of interest in this communication.