Piror studies have shown lung density to correlate with lung function. The effect that anemia has on CT density and how this affects correlation between lung attenuation and function as determined by PFTs has not been looked at. This investigation attempts to clarify the interaction between hemoglobin concentration and lung attenuation on chest CT scan.
We wrote software that uses density changes within the mediastinum on a CT chest to estimate the patients hemoglobin. The estimated Hb is correlated with a measured Hb obtained at a time proximal to that of the CT-scan. The software also calculates mean lung attenuations from the CT image and correlates this with lung function. Corrections are made to the mean lung attenuation based on hemoglobin concentration which is then correlated with lung function to assess whether this improves correlation between attenuation and lung function. Linear regression is used for the assessment of correlation.
31 CT scans were analyzed. A correlation coefficient between estimated hemoglobin and measured hemoglobin concentration is 0.6 (p = 0.0004, df = 29). Correlation of mean lung attenuation and FEV1/FVC is 0.45 (p = 0.01, df = 29), and that between corrected mean lung attenuation and FEV1/FVC was unchanged (r = 0.45, p = 0.01, df = 29).
Anemia does not play a significant role in the variations in lung attenuation to upset its ability to predict and track lung disease despite there being an effect on attenuation based on hemoglobin.
Lung densitometry is not widely utilized in the diagnosis or surveillance of lung disease despite studies showing correlation between lung function and changes in lung attenuation. This is attributable to several factors including lack of a clearly defined relationship between consequential changes in function as well as their clinical significance with the changes caused by disease in lung attenuation. We are in the process of evaluating potential confounders in order to enhance its predictive and surveillance value. This study suggests that densitometry from serial CT scans can be used to follow disease progression despite changes in patients Hb concentration.
Irtza Sharif, No Financial Disclosure Information; No Product/Research Disclosure Information