Low false positive rate of perfusion index as a screening tool for neonatal aortic coarctation

AIM Adding perfusion index (PI) to pulse oximetry screening (POS) may increase neonatal detection of CoA (aortic coarctation). A cut-off <0.7% has been suggested but is associated with a high rate of false positives. We aimed to evaluate the specificity of PI when using repeated instead of single measurements. METHODS A pilot study was conducted in 50 neonates. PI was recorded in right hand and a foot by pulse oximeter. If PI was <0.7%, the measurement was immediately repeated up to 3 times. If all three measurements were <0.7% in hand and/or foot the screen was positive and echocardiography was performed. There were 3/50 false positive screens. The protocol was therefore modified requiring 30 minutes intervals between measurements. RESULTS An additional 463 neonates were included using the modified protocol at a median age of 18 hours. There were no false positives. The only neonate with CoA had a negative screen (PI hand 1.2% and foot 0.8%). The measurement required on average an extra 3 minutes and 30 seconds compared to POS only. CONCLUSION The false positive rate of PI was reduced by using repeated PI-measurements. The sensitivity for CoA using this protocol should be evaluated in large-scale prospective studies.