Perfusion Index as a Diagnostic Tool for Patent Ductus Arteriosus in Preterm Infants

Background: Patent ductus arteriosus (PDA) is common among preterm infants. Preterm infants with patent ductus arteriosus have left-to-right shunt across PDA causing less blood flow to the lower legs. Echocardiogram is the gold standard for diagnosing PDA but is not available in all NICU. Perfusion index (PI) reflects the peripheral circulation which can be measured using a pulse oximeter and it could aid in diagnosing PDA. Objective: To evaluate the accuracy of Delta perfusion index (Delta PI; pre ductal – post ductal PI) in diagnosing PDA in preterm babies. Methods: Preterm infants with gestational age <37 weeks were assessed for pre and post ductal perfusion index on days 1 and 3 of life and difference between pre and post ductal perfusion index (Delta PI) were calculated. All the patients were undergone echocardiographic examination on day 3. Based on echocardiography, each infant was categorized into PDA and no-PDA group. Mean delta perfusion index were compared between two group. Receiver operating characteristic (ROC) curve analysis with associated area under the curve (AUC) was conducted to explore the discriminative ability of delta perfusion index level in predicting PDA with selection of the most suitable cut-off point. Results: Seventy infants with median age 32.84 ± 2.230 weeks and weight 1613 ± 420 grams were analyzed. The baseline characteristics did not differ significantly between the groups. The mean delta perfusion index in the PDA group was significantly higher than the mean delta perfusion index of non-PDA group in Day 1 (0.680 ± 0.