Improved prediction of twin anemia–polycythemia sequence by delta middle cerebral artery peak systolic velocity: new antenatal classification system

OBJECTIVES: To investigate the diagnostic accuracy of delta middle cerebral artery peak systolic velocity (MCA‐PSV) > 0.5 multiples of the median (MoM) and compare its predictive value with that of the current MCA‐PSV cut‐off values of > 1.5 MoM in the donor and < 1.0 MoM in the recipient, for the diagnosis of twin anemia–polycythemia sequence (TAPS) in monochorionic twin pregnancy. METHODS: This was a retrospective consecutive cohort study comprising all uncomplicated monochorionic twin pregnancies and twin pregnancies with a postnatal diagnosis of TAPS managed between 2003 and 2017 in the Dutch national referral center for fetal therapy. Cases with incomplete MCA‐PSV Doppler measurements 1 week prior to delivery or with incomplete hemoglobin measurements within 1 day after birth were excluded. The postnatal diagnosis of TAPS was based on an intertwin hemoglobin difference > 8 g/dL and at least one of the following: reticulocyte count ratio > 1.7 or presence of minuscule anastomoses on the placental surface. We compared the predictive accuracy of the current diagnostic method using MCA‐PSV cut‐off values of > 1.5 MoM in the donor and < 1.0 MoM in the recipient with that of a new method based on intertwin difference in MCA‐PSV > 0.5 MoM for prediction of TAPS. RESULTS: In total, 45 uncomplicated and 35 TAPS monochorionic twin pregnancies were analyzed. The sensitivity and specificity of the cut‐off MCA‐PSV values (donor > 1.5 MoM, recipient < 1.0 MoM) to predict TAPS was 46% (95% CI, 30–62%) and 100% (95% CI, 92–100%), respectively; positive predictive value was 100% (95% CI, 81–100%) and negative predictive value 70% (95% CI, 58–80%). Delta MCA‐PSV showed a sensitivity of 83% (95% CI, 67–92%) and a specificity of 100% (95% CI, 92–100%); the positive and negative predictive values were 100% (95% CI, 88–100%) and 88% (95% CI, 77–94%), respectively. Of the 35 cases with TAPS diagnosed postnatally, 13 twin pairs showed a delta MCA‐PSV > 0.5 MoM but did not fulfill the cut‐off MCA‐PSV criteria. Of these 13 TAPS twins, nine donors and four recipients had normal MCA‐PSV values. There was a high correlation between delta MCA‐PSV and intertwin difference in hemoglobin level (R = 0.725, P < 0.01). CONCLUSION: Delta MCA‐PSV > 0.5 MoM has a greater diagnostic accuracy for predicting TAPS compared to the current MCA‐PSV cut‐off criteria. We therefore propose a new antenatal classification system for TAPS. In monochorionic twin pregnancies with delta MCA‐PSV > 0.5 MoM on Doppler ultrasound, but normal MCA‐PSV values in the donor or recipient, obstetricians should be aware of the therapeutic implications and neonatal morbidities associated with TAPS. © 2018 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology.