The variability in the interpretation of prenatal diagnostic ultrasound

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Abstract
Although prenatal ultrasound is broadly used to detect abnormal fetuses, the variability in the interpretation of second-trimester prenatal ultrasound examinations is unknown. We sought to evaluate the consistency of the interpretation of prenatal ultrasound examinations. Physicians who perform prenatal ultrasound and who participate in the California Maternal Serum Expanded AFP program were asked to interpret a series of test ultrasound examinations. The series of cases was selected to include a random sample of fetal structural abnormalities, ultrasound markers that have been associated with chromosomal abnormalities, and normal cases. Interobserver agreement was evaluated using a kappa statistic for each organ system. The sensitivity and false-positive rate were calculated for detecting specific anatomic abnormalities within each organ system. Of the 210 sonologists eligible for inclusion in the study, completed responses were received from 148 (70%). There was moderate to substantial agreement between physicians in reporting the presence of fetal abnormalities for all organ systems (kappa range 0.40-0.88, P < 0.001). The consistency was highest for the central nervous system (CNS), neck, and face. Within each organ system, the consistency was similar for major structural abnormalities and ultrasound markers of chromosomal abnormalities. The sensitivity ranged from 62% (95% confidence interval (CI) 58-66%) for major renal abnormalities to 91% (95% CI 88-94%) for CNS abnormalities, with corresponding false-positive rates of 7% (95% CI 6-9%) for renal abnormalities and 9% (95% CI 7-11%) for CNS abnormalities. For most organ systems, the sensitivity for detecting ultrasound markers of chromosomal abnormalities was similar to the sensitivity for detecting structural abnormalities. There is moderate to substantial agreement in the interpretation of second-trimester prenatal ultrasound examinations. Whether the identification of specific ultrasound abnormalities and markers is overall beneficial to patients remains to be determined.