title: Longitudinal discriminant analysis of hemoglobin level for predicting preeclampsia.
abstract: BACKGROUND
  Preeclampsia is one of the most serious complications during pregnancy with important effects on health of mother and fetus that causes maternal and fetal morbidity and mortality. This study was performed to evaluate whether high levels of hemoglobin may increase the risk of preeclampsia.
  
  
  OBJECTIVE
  The present study aimed to predict preeclampsia by the hemoglobin profiles through longitudinal discriminant analysis and comparing the error rate of discrimination in longitudinal and cross sectional data.
  
  
  METHODS
  In a prospective cohort study from October 2010 to July 2011, 650 pregnant women referred to the prenatal clinic of Milad Hospital in Tehran were evaluated in 3 stages. The hemoglobin level of each woman was measured in the first, second, and third trimester of pregnancy by an expert technician. The subjects were followed up to delivery and preeclampsia was the main outcome under study. The covariance pattern and linear-mixed effects models are common methods that were applied for discriminant analysis of longitudinal data. Also Student t, Mann-Whitney U, and chi-square tests were used for comparing the demographic and clinical characteristics between two groups. Statistical analyses were performed using the SAS software version 9.1.
  
  
  RESULTS
  The prevalence rate of preeclampsia was 7.2% (47 women). The women with preeclampsia had a higher mean of hemoglobin values and the difference was 0.46 g/dL (P = 0.003). Also the mean of hemoglobin in the first trimester was higher than that of the second trimester, and was lower than that of the third trimester and the differences were significant (P = 0.015 and P < 0.001, respectively). The sensitivity for longitudinal data and cross-sectional data in three trimesters was 90%, 67%, 72%, and 54% and the specificity was 88%, 55%, 63%, and 50%, respectively.
  
  
  CONCLUSIONS
  The levels of hemoglobin can be used to predict preeclampsia and monitoring the pregnant women and its regular measure in 3 trimesters help us to identify women at risk for preeclampsia.
authors.affiliation: Department of Biostatistics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, IR Iran.
authors.forename: Malihe
authors.initials: M
authors.lastname: Nasiri
authors.affiliation: Department of Biostatistics, Faculty of Medical Sciences, Zanjan University of Medical Sciences, Zanjan, IR Iran.
authors.forename: Soghrat
authors.initials: S
authors.lastname: Faghihzadeh
authors.affiliation: Department of Biostatistics, Faculty of Paramedical, Shahid Beheshti University of Medical Sciences, Tehran, IR Iran.
authors.forename: Hamid
authors.initials: H
authors.lastname: Alavi Majd
authors.affiliation: Department of Biostatistics, Faculty of Paramedical, Shahid Beheshti University of Medical Sciences, Tehran, IR Iran.
authors.forename: Farid
authors.initials: F
authors.lastname: Zayeri
authors.affiliation: Department of Midwifery, Faculty of Nursing and Midwifery, Shahid Beheshti University of Medical Sciences, Tehran, IR Iran.
authors.forename: Noorosadat
authors.initials: N
authors.lastname: Kariman
authors.affiliation: Department of Midwifery, Faculty of Medical Sciences, Islamic Azad University, Ardabil, IR Iran.
authors.forename: Nastaran
authors.initials: N
authors.lastname: Safavi Ardebili
keywords: Discriminant Analysis; Hemoglobin; Preeclampsia