To the Editor:
The joint statements on lung function testing by the American Thoracic Society (ATS)/European Respiratory Society (ERS) Task Force provided useful recommendations for standardisation of the tests in daily practice [1]. However, the equations for adjusting diffusing capacity of the lung for carbon monoxide (DL,CO) for the haemoglobin (Hb) level (equations 13 and 14 in the original document) may be confusing [1]. In daily clinical practice, instead of changing the predicted reference value, we tend to adjust the observed DL,CO value as if the patient had a normal Hb level [2–4]. Therefore, as suggested by most guidelines [2, 4], we suggest new equations for adjustment, as shown in table 1.
It is well known that anaemia decreases observed DL,CO by decreasing the area for diffusion due to a reduction in pulmonary capillary haemoglobin [1–4]. For example, in our suggested equation for adult males and adolescents, a Hb level <14.6 g·dL−1 makes (10.22+Hb)/(1.7×Hb)>1, making DL,COadjusted for Hb>DL,COobserved to eliminate the effect of anaemia. This adjustment makes DL,CO more standardised for assessing pulmonary conditions.
As the joints statements by the ATS/ERS Task Force are widely used as a guide for standardisation of clinical practice, we believe that clarifying this point is important.
Footnotes
Statement of Interest
None declared.
- ©ERS 2013