Abstract
Background. An altered renal function is an essential component of the patho-physiology of pre-eclampsia. The plasma levels of low molecular mass proteins, e.g. β-trace protein, β-2-microglobulin and cystatin C, are increased in the third trimester of normal pregnancy. The plasma levels of cystatin C and β-2-microglobulin are further increased in pre-eclampsia, and the cystatin C level has been reported to be a reliable marker for the disease. The aim of this investigation was to study the plasma levels of β-trace protein, β-2-microglobulin and cystatin C in pre-eclampsia, and to determine the diagnostic performance of these proteins compared to that of urate and creatinine. Methods. A case-control study of 57 women diagnosed with pre-eclampsia, and 218 healthy women with uncomplicated singleton pregnancies in the third trimester. Women in the catchment area of Lund, Sweden, were included during an 18-month period from October 2003 to April 2005. Venous blood samples were drawn upon inclusion when diagnosis was made. The maternal plasma concentrations of the 3proteins were analysed by automated particle-enhanced immunoturbidimetric assays. Results. The plasma levels of the 3 proteins were significantly higher in the third trimester of pre-eclamptic patients compared to healthy pregnant women in the third trimester. The upper reference limits (parametric 97.5 percentile) were 2.57mg/l for β-2-microglobulin, 0.72mg/l for β-trace protein and 1.37mg/l for cystatin C. ROC analysis showed similar diagnostic performance for the 3 proteins, with β-trace protein displaying the best diagnostic performance of all the analytes. Conclusions. In this study, the maternal plasma levels of β2-microglobulin, β-trace protein and cystatin C were all significantly elevated in pre-eclampsia compared to those of healthy pregnant women, and displayed similar diagnostic performance for diagnosing pre-eclampsia. The results indicate that low molecular mass proteins are useful as markers of renal impairment in pre-eclampsia.