Abstract
Objective: The association between increased amniotic fluid interleukin-6 (IL-6) concentrations and preterm labor has received increasing attention. Several research groups have evaluated this association using commercial IL-6 kits, which principally use the sandwich-enzyme-immunoassay method, and were originally created to measure IL-6 in plasma, serum, or culture media. We evaluated commercial kits for the determination of IL-6 in amniotic fluid. Methods: Seven commercial kits were used to determine IL-6 concentrations in three amniotic fluid samples which were obtained from patients with clinical chorioamnionitis during labor and five from normal pregnancies at mid-trimester. Results: Amniotic fluid IL-6 values differed significantly with some having over a 50-fold discrepancy and the recovery of known IL-6 added to amniotic fluid ranged from 12 to 123%. However, by all kits we were able to identify that amniotic fluid from patients with chorioamnionitis contained significantly higher IL-6 concentrations than those from normal mid-trimester pregnancies. Conclusion: Our data indicate that standardization of the method for measuring IL-6 in amniotic fluid is desirable for the comparison of values from various laboratories.
Highlights
Our data indicate that standardization of the method for measuring IL-6 in amniotic fluid is desirable for the comparison of values from various laboratories
Amniotic fluid; assay kits; chorioamnionitis; interleukin-6 nterleukin-6 (IL-6) is a multifunctional protein and an inducer of the acute-phase response. It is produced by a variety of cells, and its production is stimulated by infections. 1,2 Increasing information has become available on the association between amniotic fluid IL-6 concentrations and pregnancy outcome.[3,4,5,6,7,8,9,10,11,12,13,14]
The recovery of known IL-6 added to the amniotic fluid samples varied from 12 to 123% depending on the kits used (Table 2)
Summary
Seven commercial kits were used to determine IL-6 concentrations in three amniotic fluid samples which were obtained from patients with clinical chorioamnionitis during labor and five from normal pregnancies at mid-trimester. Amniotic fluid samples were obtained during labor using a transcervical intrauterine pressure catheter from three women with clinical chorioamnionitis. Five amniotic fluids were collected during genetic amniocentesis at about 17 weeks of gestation. These amniotic fluid samples were originally collected for various clinical evaluations and would have been discarded, if not used in this investigation. Amniotic fluid samples were centrifuged (900g for 10 rain), separated into aliquots, and stored at-70C until analyses
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