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Serum complement values (C3 and C4) to differentiate between systemic lupus activity and pre-eclampsia
Insights
Serum C3 and C4 levels can help differentiate between systemic lupus erythematosus (SLE) exacerbations and pre-eclampsia in pregnant patients. Lower C3 and C4 levels indicate SLE activity, while normal or elevated levels suggest pre-eclampsia.
Area of Science:
- Immunology
- Nephrology
- Obstetrics
Background:
- Differentiating between systemic lupus erythematosus (SLE) exacerbations and pre-eclampsia is challenging due to overlapping symptoms like proteinuria and hypertension.
- Systemic lupus erythematosus (SLE) is an autoimmune disease that can affect multiple organs, including the kidneys.
- Pre-eclampsia is a pregnancy-specific condition characterized by new-onset hypertension and proteinuria.
Purpose of the Study:
- To investigate the utility of serum C3 and C4 complement levels in distinguishing SLE activity from pre-eclampsia in pregnant women.
- To establish reference ranges for serum C3 and C4 in nonpregnant women, normal pregnant women, and women with pre-eclampsia.
Main Methods:
- Serum C3 and C4 levels were measured in three groups: nonpregnant women of childbearing age, normal pregnant women in their third trimester, and pregnant women with documented pre-eclampsia.
- Complement levels were also assessed in pregnant women with SLE during their third trimester.
- Serial complement measurements were performed in a subset of women with SLE.
Main Results:
- Serum C3 and C4 levels were significantly lower in pregnant women with SLE compared to both normal pregnant women and those with pre-eclampsia.
- In normal pregnancy and pre-eclampsia, C3 and C4 levels were generally elevated or comparable to nonpregnant levels.
- Falling C3 or C4 levels in women with SLE correlated with disease flares, while rising levels did not, though one patient with rising C3 developed pre-eclampsia.
Conclusions:
- Serum C3 and C4 measurements are valuable tools for differentiating SLE activity from pre-eclampsia in pregnant patients.
- Significantly lower C3 and C4 levels during pregnancy are indicative of SLE activity.
- Complement levels may provide prognostic information regarding SLE flares during or after pregnancy.
Abstract:
It is often difficult to differentiate between an exacerbation of systemic lupus erythematosus (SLE) and intercurrent pre-eclampsia in a patient with SLE since the manifestations of both entities include proteinuria and hypertension. This study was undertaken to determine wether serum C3 and C4 values can help distinguish SLE activity from pre-eclampsia. In 21 nonpregnant women of child-bearing age, the mean C3 level was 124 +/- 5 mg/dl and the mean C4 was 31 +/- 1 mg/dl. In 24 normal women in the third trimester of pregnancy, the C3 and C4 levels were elevated (165 +/- 4 mg/dl, p less than 0.001 versus nonpregnant control women; 37 +/- 2 mg/dl, p less than 0.01 versus nonpregnant control women, respectively). In 17 women in the third trimester of pregnancy with documented pre-eclampsia, the mean C3 level was 162 +/- 4 mg/dl, no different from that in normal pregnant women (p less than 0.001 versus nonpregnant control women; p = NS versus normal pregnant women), and the mean C4 was 29 +/- 3 mg/dl, lower than that found in normal pregnant women (p less than 0.02 versus normal pregnant women). Antinuclear antibody was absent at titers of less than 1:20 in all of these pre-eclamptic patients. In contrast, pregnant women with SLE has significantly lower C3 (103 +/- 13 mg/dl) and C4 (15.3 +/- 3.6 mg/dl) values during the third trimester of pregnancy than either normal pregnant women (p less than 0.001 for C3 and C4) or women with pre-eclampsia (p less than 0.001 for C3 and p less than 0.004 for C4) during the third trimester of pregnancy. Of the eight women with SLE in whom serial complement values were determined, three had falling C3 or C4 levels, and in each, there was a flare of SLE activity either during or immediately after pregnancy. None of the five patients with a rising C3 concentration had a flare of disease activity; however, pre-eclampsia developed in one of these patients, characterized by hypertension and proteinuria. Thus, measurement of serum C3 and C4 can help differentiate between SLE activity and pre-eclampsia, since both C3 and C4 are significantly lower in women with SLE than women with pre-eclampsia, and serum C3 and C4 concentrations rise during uncomplicated or pre-eclamptic pregnancy in women with SLE.