BO, a serious manifestation of graft-versus-host disease after HSCT, is a disease of the small airways and usually not identified by spirometry and conventional pulmonary function tests (cPFTs). Forced oscillometry (FO) is a new diagnostic test that measures small airway function with sensitivity and specificity, providing potential for early detection of BO.
To compare the sensitivity of FO with spirometry in early detection of lung function decline post HSCT.
All patients undergoing HSCT at our centre, who have consented, are prospectively enrolled and undergo paired FO and spirometry testing in our PFT Laboratory at baseline, 2, 4, 6, 9, 12 and 18 months post-HSCT.
To-date, 26 patients (13F:13M, mean age=55.6 yrs, range 22.5-74.6 yrs) underwent 28 paired FO-spirometry testing. Mean %predicted FEV1 (%predFEV1) was 88% (range 53-112%). Mean FEV1/FVC (forced vital capacity) was 77% (range 40-99%). Of the FO parameters, the reactance at 5 Hz (X5) and integrated area of low-frequency reactance (AX) were most highly correlated with %predFEV1 and FEV1/FVC ratio, as well as forced expiratory flow at 50% and 75% of FVC. In patients with spirometric airflow obstruction (FEV1/FVC=65.5±3.2%, n=6), X5 and AX showed a 2-fold change (-2.8±1.1 and 19.7±9.7 kPa s L-1, respectively) compared to those with normal FEV1/FVC ratio.
In screening pulmonary function studies prior to HSCT in 26 subjects and testing at 2 months post-HSCT in 2 patients, we observed significant correlation of spirometric airflow obstruction with X5 and AX, suggesting that X5 and AX hold promise for early detection of airflow obstruction post-HSCT.