PURPOSE:Lung Diffusing Capacity for carbon monoxide (DLCO) is a pulmonary function test PFT that can be helpful in the diagnosis of PAH. Adjusted DLCO to alveolar volume DLCO/VA may offer an advantage as it controls for lung volume. We sought to evaluate the performance of DLCO and DLCO /VA as diagnostic and prognostic tools.
METHODS:This is a retrospective chart review study of all patients that had both PFT and echocardiography. Data collected included patient demographics, body mass index, smoking history, PFT findings and the presence of PAH with peak pulmonary arterial pressure PAP value estimated by echocardiography. Continuous variables were expressed as means or medians based on normality testing by K-S tests and compared using appropriate parametric or nonparametric testing. Categorical variables were expressed as percentages and compared using chi-square test.
RESULTS:We analyzed data from 398 patients. Baseline characteristics are shown in table 1. We found that 257 (64.6%) patients had PAH and 141(35.4%) had normal PAP and were classified as controls. Only 19.8% had connective tissue disease. Compared to controls, PAH patients were older, had lower forced vital capacity FVC, lower DLCO, and lower DLCO/VA. Multi-variate analysis demonstrated only age and FVC as independent predictors for PAH [Odds Ratios 1.038 (1.02–1.056); p<0..001 and 0.972 (0.955–0.988); p=0.001 respectively]. We found significant correlation between DLCO and PAP though it was weak (r=-0.205; p=0.001). DLCO/VA did not statistically correlate with PAP (r=-0.086; p=0.160). Receiver operative characteristics ROC analysis (Figure1) revealed the best cutoff value for DLCO was 62.5% with an area under the curve of 0.618 (0.562–0.675).
CONCLUSION:DLCO is not an independent predictor for PAH. While DLCO inversely correlated with PAP, DLCO /VA did not. FVC and age were the only independent predictors for PAH.
CLINICAL IMPLICATIONS:DLCO neither predicted nor was helpful in determining the severity of PAH . DLCO/VA did not offer any additional advantage for diagnosis or severity. According to our findings we do not recommend relying on DLCO or DLCO/VA as predictors for PAH.
DISCLOSURE:Kimberly Delcour, No Financial Disclosure Information; No Product/Research Disclosure Information