Multivariable analysis of tests for the diagnosis of intrauterine growth restriction

• Published in: Ultrasound in obstetrics & gynecology Vol. 21; no. 4; pp. 370 - 374
• Main Authors: Bachmann, L. M., Khan, K. S., Ogah, J., Owen, P.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01-04-2003; Wiley
• Subjects: accuracy; Amniotic Fluid - chemistry; Biological and medical sciences; Cohort Studies; diagnosis; Diseases of mother, fetus and pregnancy; Female; Fetal Growth Retardation - diagnostic imaging; Fetal Growth Retardation - physiopathology; Gynecology. Andrology. Obstetrics; Humans; intrauterine growth restriction; Laser-Doppler Flowmetry - methods; Medical sciences; Multivariate Analysis; Predictive Value of Tests; Pregnancy; Pregnancy. Fetus. Placenta; Prospective Studies; regression analysis; ROC Curve; Ultrasonography, Prenatal; Umbilical Arteries - physiology; Sonography; Fetal diseases; Intrauterine growth retardation; Pregnancy disorders; Gynecology; Echography; Diagnosis; Obstetrics
• ISSN: 0960-7692; 1469-0705
• DOI: 10.1002/uog.77

Objectives
To describe how data from antenatal fetal ultrasound biometry, amniotic fluid index and umbilical artery Doppler can be appropriately combined using multivariable models and to investigate how the addition of these ultrasound parameters influences the ability to predict intrauterine growth restriction (IUGR).
Methods
This was a prospective cohort study involving 274 low‐risk pregnancies undergoing serial ultrasound examination at predetermined intervals. Standard deviation (Z) scores of the last values for fetal abdominal area (FAA), growth velocity of the FAA, amniotic fluid index (AFI) and umbilical artery Doppler pulsatility index prior to delivery were calculated for 260 fetuses. Customized estimated fetal weight (cEFW) centiles were also calculated using the last EFW before delivery after adjustment for fetal gender, gestational age, birth order and maternal weight, height and ethnic origin. Following delivery the neonatal ponderal index was calculated and centile position obtained. A neonatal ponderal index <25th centile served as the main outcome measure for diagnosis of IUGR. Logistic regression analysis was used to delineate the predictive value of the three fetal growth tests FAA, FAA growth velocity and cEFW and the additional values of AFI and pulsatility index of the umbilical artery.
Results
The areas under the receiver–operating characteristics (ROC) curves (95% confidence interval) for FAA, FAA growth velocity and cEFW alone were 0.819 (0.748–0.891), 0.784 (0.699–0.869) and 0.74 (0.643–0.837), respectively, in the prediction of a neonatal ponderal index <25th centile. The addition of both the AFI and pulsatility index to FAA, FAA growth velocity and cEFW generated small increases in the areas, to 0.831 (0.758–0.904), 0.817 (0.735–0.899) and 0.766 (0.672–0.859), respectively. These improvements in diagnostic prediction were not statistically significant.
Conclusions
The addition of AFI and umbilical artery pulsatility index to the fetal biometry parameters did not significantly increase the ROC areas in the study population. The approach applied in this study is useful in the context of hypothesis generation. Further studies using larger data sets and other predictors should be carried out using the analytical techniques outlined in this paper to determine the contribution of various antenatal tests in the prediction of IUGR. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.