Study on the cut-off values of urinary microalbumin, transferrin and α1-microglobulin during pregnancy in pre-eclampsia with proteinuria

Abstract

Objective: To study the cut-off values of urinary microalbumin (mAlb), transferrin (TRF) and α1-microglobulin (α1-MG) during pregnancy in pre-eclampsia (PE) with proteinuria. Methods: A total of 210 pregnant women were enrolled in Renji Hospital from January 2016 to December 2019, including 92 (43.8%) cases of PE pregnant women and 118 (56.2%) cases of normal pregnant women. According to the diagnostic test evaluation method, the positive predictive values, negative predictive values and accuracy of non-pregnant cut-off values of urinary mAlb, TRF and α1-MG for the quantitative determination of 24-hour proteinuria were analyzed. The receiver operating characteristic (ROC) curve was applied to determine the optimal cut-point values of urinary mAlb, TRF and α1-MG during pregnancy. Results: (1) The diagnostic study of non-pregnant adults urinary mAlb, TRF and α1-MG cut-off values for the determination of 24-hour proteinuria value: when urinary mAlb was 30.0 mg/L, TRF was 2.5 mg/L, α1-MG was 12.5 mg/L as the cut-off value, the positive predictive values of the corresponding 24-hour proteinuria value≥ 300 mg were 88.1% (89/101), 88.2% (90/102) and 78.9% (75/95), its negative predictive values were 97.2% (106/109), 98.1% (106/108) and 85.2% (98/115), its diagnostic accuracy were 92.9% (195/210), 93.3% (196/210) and 82.4% (173/210), respectively. As the 24-hour proteinuria value≥ 300 mg was the golden standard, there were significant differences between the diagnostic method of the non-pregnant cut-off value of urinary mAlb, TRF and the golden standard (P<0.05). There was no significant difference between the diagnostic method of the non-pregnant cut-off value of urinary α1-MG and the golden standard (P>0.05). (2) Research on the ROC curve and the optimal cut-point value of urinary mAlb, TRF and α1-MG value: as the 24-hour proteinuria value≥ 300 mg as the criterion, the ROC curve of urinary mAlb, TRF and α1-MG were 0.992, 0.984 and 0.907, respectively. The optimal cut-point values of urinary mAlb, TRF and α1-MG were 86.5 mg/L (Youden index=0.927), 5.5 mg/L (Youden index=0.923), and 15.4 mg/L (Youden index=0.687). (3) The diagnostic study of the optimal cut-point value of urinary mAlb, TRF and α1-MG for the determination of 24-hour proteinuria value: according to the ROC results, when urinary mAlb was 86.5 mg/L, urinary TRF was 5.5 mg/L, and urinary α1-MG was 15.4 mg/L as the cut-off value, the positive predictive values of the corresponding 24-hour proteinuria value≥300 mg were 98.9% (86/87), 95.7% (88/92), 87.7% (71/81), and its negative predictive values were 95.1% (117/123), 96.6% (114/118), 83.7% (108/129), and its accuracy were 96.7% (203/210), 96.2% (202/210), 85.2% (179/210). As the 24-hour proteinuria value≥ 300 mg was the golden standard, there was no significant difference between the diagnostic method of the best cut-off values of urinary mAlb, TRF, α1-MG and the golden standard (P>0.05). Conclusion: It is recommended to define the cut-off values of mAlb, TRF and α1-MG as 86.5 mg/L, 5.5 mg/L and 15.4 mg/L, respectively, during pregnancy.