858 Secondary sonographic markers for diagnosis of twin anemia polycythemia sequence (TAPS)

Objective: TAPS is a complication of monochorionic-diamniotic (MCDA) twins diagnosed by middle cerebral artery peak systolic velocity (MCA-PSV) measurements using either absolute (MCA-PSV > 1.5 and MCA-PSV < 1.0 MoMs) or relative (difference in MCA-PSV > 0.5 MoMs) criteria. “Starry sky” liver in the plethoric twin, placental echogenicity discordance, and cardiomegaly in the anemic twin are proposed secondary markers for TAPS. We sought to determine the diagnostic performance of these markers’ in the absolute vs. relative criteria. Study Design: This is a case-control study of MCDA pregnancies followed between 2011 to 2020. Patients diagnosed with TAPS with or without twin to twin transfusion syndrome (TTTS) were identified from ultrasound reports. Controls were matched to cases by gestational age of TAPS diagnosis randomly in a 1:2 ratio. Controls were selected from a cohort with no complications of MCDA twinning (including TAPS) throughout their pregnancies. Ultrasound images were systematically reviewed for the presence of each of the three secondary markers. Cardiothoracic ratio (CTCR) was assessed for cardiomegaly. Results: TAPS was diagnosed in 69 cases by relative criteria; 18 of these cases also met absolute criteria. We matched 140 control patients. Characteristics were similar between patients diagnosed by each criterion (Table 1). Starry sky liver occurred in 77.8%, 57.4%, and 3.6% of the absolute TAPS, relative TAPS, and control groups, respectively (p<0.01). Placental discordance occurred in 44.4%, 40.3%, and 4.3% of patients in these groups, respectively (p<0.01). There was no difference in the CTCRs among the three groups (0.53 ± 0.05, 0.51 ± 0.05, and 0.51 ± 0.03, NS). Placental discordance was more common with greater differences in MCA-PSV between twins and Stage II or higher TAPS (Figure). Conclusion: Placental discordance is associated with greater differences in the MCA-PSV between twins and more severe TAPS (Stage II+). Absolute criteria for TAPS coupled with the presence of secondary markers may help improve diagnostic accuracy. [Formula presented] [Formula presented]