Repeatability of PDA diameter measurements on echocardiography

Diameter of the patent ductus arteriosus (PDA) on transthoracic echocardiography (TTE) is used as a marker of haemodynamic significance. We aimed to assess the intra- and inter-observer variability in PDA diameter in babies born at ≤ 30 weeks' gestation. TTEs for 56 infants were performed by a single neonatologist. Cineloops were stored without measurement annotations. PDAs were measured on 2-dimensional (2D) and Colour Doppler. A second, blinded neonatologist repeated measurements on the same cineloops. The scanning neonatologist repeated measurements at a later date, blinded to original measurements. Inter-observer results showed repeatability coefficients of 1.57 (2D) and 2.18 (Colour), and repeatability index of 73% (2D) and 91% (Colour). Intra-observer results showed repeatability coefficients of 0.99 (2D) and 1.32 (Colour), and repeatability index of 43% (2D) and 49% (Colour).Conclusion: There is significant inter- and intra-observer variability in measurements of PDA diameter, even on the same cineloops. We advise caution when using diameter alone as a marker of haemodynamic significance, and recommend using multiple parameters to determine haemodynamic significance of PDA. What is Known: • PDA is associated with numerous comorbidities such as bronchopulmonary dysplasia, necrotising enterocolitis, intraventricular haemorrhage and mortality. • PDA diameter is commonly measured on transthoracic echocardiography and used as a marker of haemodynamic significance. • A previous, smaller study has shown there may be poor repeatability of PDA diameter measurements in serial echocardiograms. What is New: • There is significant inter-observer variability in 2D and Colour Doppler measurements of PDA internal diameter on TTE in preterm infants. • There is moderate intra-observer correlation of repeated measurements on the same imaging in both 2D and Colour Doppler imaging.