Individual longitudinal patterns in biochemical and hematological markers for the early prediction of pre-eclampsia.

OBJECTIVE

To analyze the individual longitudinal patterns of maternal biochemical and hematological tests performed throughout gestation in order to predict at the 20th week of pregnancy the later development of pre-eclampsia.

STUDY

DESIGN

A longitudinal study was conducted on 187 white normotensive pregnant women all with a history of pre-eclampsia. Blood samples were performed at the 8th week of gestation and then every 4 weeks until the 36th week. The longitudinal patterns of urea, creatinine, uric acid, total proteins, hematocrit, red blood cells, hemoglobin, mean red cell volume, ferritin and iron were derived. By means of regression analysis, for each woman and each significant marker, a 'theoretical physiological pattern', from the 8th to the 20th week, was constructed. By comparing the observed values of each marker for each woman with her 'theoretical physiological pattern', variables indicating the match or mismatch to it were derived. Such variables were used, together with other maternal characteristics, in a logit regression for the probability of developing pre-eclampsia later in pregnancy.

RESULTS

In 140 cases, pregnancies followed a physiological course, while 47 women developed pre-eclampsia during the third trimester. In the physiological gestations, the weekly mean values of creatinine, hematocrit, total proteins, uric acid and urea showed patterns that were significantly different from those of the pathological group. The logit model was able to classify correctly 96% of the physiological and 87% of the pathological pregnancies, with a negative predictive value of 96% and a positive predictive value of 89% (area under the receiver operator characteristics (ROC) curve 0.98). The ability of the model to predict later complications at the 20th week was confirmed by a validation procedure.

CONCLUSION

The simultaneous use of individual longitudinal patterns of parameters, achieved non-invasively as part of the standard methods of antenatal care that provide a global evaluation of plasma volume expansion, showed a high ability to predict, early in pregnancy, the later development of pre-eclampsia.