Validity and reliability of assessing diaphragmatic mobility by area on X-rays of healthy subjects

ABSTRACT

Objective:

To investigate the concurrent validity, as well as the intra- and inter-rater reliability, of assessing diaphragmatic mobility by area (DM_area) on chest X-rays of healthy adults.

Methods:

We evaluated anthropometric parameters, pulmonary function, and diaphragmatic mobility in 43 participants. Two observers (rater A and rater B) determined diaphragmatic mobility at two time points. We used Pearson’s correlation coefficient to evaluate the correlation between DM_area and the assessment of diaphragmatic mobility by distance (DM_dist). To evaluate intra- and inter-rater reliability, we used the intraclass correlation coefficient (ICC [2,1]), 95% CI, and Bland-Altman analysis.

Results:

A significant correlation was found between the DM_area and DM_dist methods (r = 0.743; p < 0.0001). For DM_area, the intra-rater reliability was found to be quite high for the right hemidiaphragm (RHD)-ICC (2,1) = 0.92 (95% CI: 0.86-0.95) for rater A and ICC (2,1) = 0.90 (95% CI: 0.84-0.94) for rater B-and the left hemidiaphragm (LHD)-ICC (2,1) = 0.96 (95% CI: 0.93-0.97) for rater A and ICC (2,1) = 0.91 (95% CI: 0.81-0.95) for rater B-(p < 0.0001 for all). Also for DM_area, the inter-rater reliability was found to be quite high for the first and second evaluations of the RHD-ICC (2,1) = 0.99 (95% CI: 0.98-0.99) and ICC (2,1) = 0.95 (95% CI: 0.86-0.97), respectively-and the LHD-ICC (2,1) = 0.99 (95% CI: 0.98-0.99) and ICC (2,1) = 0.94 (95% CI: 0.87-0.97)-(p < 0.0001 for both). The Bland-Altman analysis showed good agreement between the mobility of the RHD and that of the LHD.

Conclusions:

The DM_area method proved to be a valid, reliable measure of diaphragmatic mobility.

Keywords:
Diaphragm/physiology; Validation studies; Reproducibility of results; Radiography