Perfusion Index as a Diagnostic Tool for Patent Ductus Arteriosus in Preterm Infants
Author(s): Nazmus Sihan, Sharmin Reza Suchi, Mahboba Akther, Tareq Rahman, Humayra Akter, Mosammad Alpana Jahan, Arif Hossain, Shahidullah, Abdul Mannan
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 ± 0.164 vs 0.414 ± 0.129). Also, on day 3 the significantly higher mean delta perfusion index in the PDA group was observed than the mean delta perfusion index of the non-PDA group (0.820 ± 0.216 vs 0.516 ± 0.255). The mean delta perfusion index on both days 1 and 3 showed that HsPDA group had significantly higher mean delta perfusion index than in the non HsPDA group (Day 1: 0.754 ± 0.175, Day 3: 0.890 ± 0.246) vs. (Day 1: 0.440 ± 0.139, Day 3: 0.549 ± 0.253), indicating the more steal occurring in the HsPDA group. The area under the receiver operating characteristic curve was significant for delta perfusion index on both Days 1 and 3. The delta Perfusion Index cutoff of 0.5 on Day 1 offered a good sensitivity (85%) and specificity (89%). While the delta Perfusion Index cutoff 0.7 had good specificity (90%) but less sensitivity (50%) on Day 3.
Conclusion: Assessment of the difference between pre-ductal perfusion index and post-ductal perfusion index (Delta Perfusion Index -∆PI) can be a diagnostic tool to identify patent ductus arteriosus in preterm infants.