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Analysis of Z ‐score distribution for the quality control of fetal ultrasound measurements at 20–24 weeks
Author(s) -
Salomon L. J.,
Bernard J. P.,
Ville Y.
Publication year - 2005
Publication title -
ultrasound in obstetrics and gynecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.202
H-Index - 141
eISSN - 1469-0705
pISSN - 0960-7692
DOI - 10.1002/uog.2640
Subject(s) - medicine , sonographer , ultrasound , youden's j statistic , gestational age , nuclear medicine , standard score , fetus , biparietal diameter , population , obstetrics , pregnancy , head circumference , radiology , statistics , receiver operating characteristic , mathematics , genetics , environmental health , biology
Objectives To develop and evaluate the feasibility of Z ‐score distribution‐based quality assessment for fetal biometry at 20–24 gestational weeks. Methods Four sonographers measured fetal biparietal diameter, head circumference, abdominal circumference and femur length in unselected pregnancies undergoing routine sonography at 20–24 weeks in our center between June 2001 and January 2004. All measurements were transformed into Z ‐scores. Distributions of Z ‐scores were compared with the expected standard normal distribution based on mean, SD and the Kolmogorov–Smirnov test. Modelling was performed to assess the sensitivity, specificity and Youden's index (sensitivity + specificity − 1) of each sonographer, reflecting their ability to detect fetuses with abnormal biometry in our population. Results A total of 5241 ultrasound examinations were included. None of the Z ‐score distributions could be considered similar to the standard normal distribution: means of Z ‐scores ranged from −0.604 to 0.73 and the SD ranged from 0.726 to 0.896. Sensitivity and specificity ranged from 25.31% to 68.67% and 93.44% to 100%, respectively; Youden's index ranged from 0.25 to 0.69. Conclusion Analysis of Z ‐score distribution can be used to assess the quality of fetal measurements. Several indices can be extracted from this analysis in order to improve quality assessment of fetal biometry measured by ultrasound. Copyright © 2005 ISUOG. Published by John Wiley & Sons, Ltd.