This prospective observational study was performed at the Department of Obstetrics and Gynecology, Faculty of Medicine, Chulalongkorn University, King Chulalongkorn Memorial Hospital, Bangkok, Thailand, between April 2020 and July 2021. The study was approved by the Institutional Review Board of the Faculty of Medicine, Chulalongkorn University. This study has been performed in accordance with the Declaration of Helsinki. All women received information about the study protocol and provided written informed consent prior to any procedures.
The inclusion criteria were singleton pregnant women aged 20–45 years old and gestational age of 11–13+6 weeks. The exclusion criteria were pregnant women who carried an abnormal fetus (structural or chromosomal) and those who took aspirin prior to enrollment in the study. If there is an indication for using prophylactic aspirin, aspirin has been started after the sampling and sonographic evaluation.
Sample size calculation was based upon the expected sensitivity of the test at 80%, with 20% allowable error and α error at 0.05. Prevalence was based on the preeclampsia incidence at King Chulalongkorn Memorial Hospital in the past five years, which was 4.99%. We need 16 preeclamptic cases to test this hypothesis. A minimum of 368 women were required in this study, for adjustments of 4.99% incidence of preeclampsia at our institute and a loss to follow-up rate of 15%,
Preeclampsia is defined by a new onset hypertension (an elevated systolic blood pressure (SBP) of at least 140 mmHg or diastolic blood pressure (DBP) of at least 90 mmHg), measured on two occasions at least 6 h apart, combined with proteinuria (at least 1 + on urine dipstick test or 300 mg/24 h or urine protein/creatinine ratio index ≥ 0.3) after 20 weeks of gestation. In the absence of proteinuria, the presence of headache, visual disturbance, epigastric pain, pulmonary edema, increased creatinine level, thrombocytopenia, and transaminitis was also considered preeclampsia8.
The primary aim was to investigate the predictive value of first-trimester serum HtrA4 combined with UtA-PI in predicting preeclampsia. The secondary aim was to identify the predictive value of this combination to detect adverse pregnancy outcomes, such as preterm delivery, gestational diabetes, and fetal growth restriction.
Maternal demographic data, UtA-PI, the presence of uterine artery notching, and maternal and neonatal outcomes were recorded. Blood pressure was measured by validated automated devices (Microlife AG, 9443 Widnau, Switzerland) after resting in a sitting position for 5 min. The SBP, DBP, and mean arterial pressure (MAP) were recorded.
Transabdominal ultrasound was performed by a single investigator to assess uterine artery Doppler using ultrasonographic machines with a convex probe AB 2–7 MHz (GE Voluson E10, GE Medical Systems, Zipf, Austria). After the mid-sagittal plane of the uterus and cervix was obtained, the probe was then tilted laterally to demonstrate uterine artery along both sides. A 2 mm gate pulse-wave Doppler was positioned on the uterine artery at the level of the internal os of the cervix, with an insonation angle of less than 30°. Three waveforms with a peak systolic velocity > 60 cm/s were obtained. Each side was measured three times, and the mean of the UtA-PI was calculated and recorded. The presence or absence of the uterine artery notch was recorded for each side15.
Blood for serum HtrA4 was drawn via venipuncture and collected in non-heparinized tubes before centrifugation at 2,500 rpm for 10 min and stored at -80 °C until assayed. Serum samples were collected at 8.00–10.00 a.m. All the samples were analyzed in the same period after finishing patient enrollment by ELISA Kit test for HtrA4 (Cloud-Clone Corp, China), which is a sandwich enzyme immunoassay. It was used to measure maternal serum HtrA4 levels, with the ranges of intra- and inter-assay < 10%.
Statistical analysis was performed using SPSS software version 22.0 (IBM, New York, USA). Data were presented in mean, standard deviation (SD), median, interquartile range (IQR), sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) with a 95% confidence interval (CI). The cut-off value of serum HtrA4 level was calculated by using the receiver operating characteristic (ROC) curve. The chi-square test was used for comparing categorical data, while the independent t-test and Mann Whitney U test were used for comparing continuous data. A p value < 0.05 was considered statistically significant.