Journal of Perinatology (2015), 1–3 © 2015 Nature America, Inc. All rights reserved 0743-8346/15 www.nature.com/jp
ORIGINAL ARTICLE
Evaluation of the performance of the insulin-like growth factor-binding protein-1/alpha-fetoprotein test in diagnosing ruptured fetal membranes in pregnant women P Ruanphoo and V Phupong OBJECTIVE: The objective of this study was to evaluate the efficacy of IGFBP-1/AFP (insulin-like growth factor-binding protein-1/ alpha-fetoprotein) immunoassay (Amnioquick Duo+) in diagnosing rupture of membranes (ROM). STUDY DESIGN: A prospective, observational study was performed in pregnant women with a history of fluid leakage from the vagina. The IGFBP-1/AFP immunoassay and conventional methods were used to diagnose ROM. The obstetricians were blinded to the results of the IGFBP-1/AFP immunoassay. The diagnosis of ROM was finally confirmed by reviewing the medical records after delivery. RESULT: One hundred patients were recruited into this study. The mean gestational age was 37.6 weeks (range 25 to 41 weeks). Twenty-six percent were preterm and 74% were at term. IGFBP-1/AFP immunoassay had a sensitivity of 94.1%, specificity of 87.5%, positive predictive value of 97.5%, negative predictive value of 73.7% and accuracy of 93% in diagnosing ROM. CONCLUSION: IGFBP-1/AFP immunoassay is a rapid immunoassay test for diagnosing ROM with a high sensitivity and specificity. This test can be used as an alternative method for diagnosis of ROM. Journal of Perinatology advance online publication, 26 February 2015; doi:10.1038/jp.2015.6
INTRODUCTION Premature rupture of membranes (PROM) is defined as the rupture of fetal membranes at any gestational age before the onset of labor.1,2 PROM is a common complication in pregnant women resulting in high morbidity and mortality in both the mother and the neonate, especially in preterm PROM less than 34 weeks.3 The prevalence of PROM is ~ 2 to 18% of all pregnancies.1,4 Preterm PROM (PPROM), defined as PROM before 37 weeks, is less common and occurs in 0.7 to 4% of pregnancies.1 Management of PROM depends on the gestational age. If in term pregnancy, then the labor should be induced, whereas for preterm PROM, management should be treated as expectant. Accurate diagnosis of rupture of membranes (ROM) is an important factor that can affect the management of pregnant women with signs and symptoms of ROM. It is easy to diagnose ROM when there is an obvious rupture and gross leakage; however, in some cases, it is far more difficult to diagnose ROM when the hallmark symptoms are not present. The gold standard for diagnosing ROM is the dye injection test that utilizes an indigo carmine dye solution.1,2 However, the instillation process is too invasive to be used routinely; therefore, a noninvasive procedure is much preferred. Unfortunately, there is no noninvasive, gold standard for diagnosing ROM. The common clinical evaluations of ROM are the presence of a gross leakage and collection of the fluid in the posterior fornix. Other evaluations utilize the laboratory bedside tests such as the fern test and nitrazine paper test. When there are no conspicuous leakages of the amniotic fluid, it cannot be diagnosed with these clinical examinations and conventional laboratory tests.5
As a result of this, there are many new bedside biological tests that were developed to detect certain biochemical markers that are highly present in the amniotic fluid but not in the vaginal fluid. Some of the biochemical markers that are used to detect membranes leakage such as alpha-fetoprotein (AFP), insulin-like growth factor-binding protein-1 (IGFBP-1), placental alphamicroglobulin-1 and fibronectin6–9 are targeted. Recently, a new, noninvasive, rapid immunochromatographic test known as the Amnioquick Duo+ (Biosynex, Strasbourg, France) became available. This immunochromatographic test can detect two biological markers, AFP and IGFBP-1, that are present in the amniotic fluid. The test has been set up with IGFBP-1 (10 ng ml − 1) and AFP (5 ng ml − 1) threshold. The objective of this study is to evaluate the performance of IGFBP-1/AFP immunoassay in diagnosing ROM in pregnant women who have a history of fluid leakage from the vagina. METHODS This prospective, observational study was performed at the Department of Obstetrics and Gynecology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand, from November 2013 to April 2014. This study was approved by the Research Ethics Committee of Faculty of Medicine, Chulalongkorn University, and written informed consent was obtained from all subjects. Pregnant women with symptoms or signs of ROM were invited to participate in the study. Patients with active vaginal bleeding, multiple pregnancies, fetal anomalies and fetal deaths were excluded. All patients were evaluated for ROM by collecting a detailed medical history of ROM, physical examination (including sterile vaginal speculum examinations) and transabdominal ultrasonogram. At the initial sterile speculum examination, all patients were assessed with the conventional standard
Department of Obstetrics and Gynecology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand. Correspondence: Professor V Phupong, Department of Obstetrics and Gynecology, Faculty of Medicine, Chulalongkorn University, Rama IV Road, Pathumwan, Bangkok 10330, Thailand. E-mail: [email protected] Received 20 October 2014; revised 12 January 2015; accepted 20 January 2015
IGFBP-1/AFP and rupture of membranes P Ruanphoo and V Phupong
2 methods (visual evaluation for fluid leakage or pooling of the amniotic fluid in the posterior fornix, nitrazine test and ferning test). After that, the IGFBP-1/AFP test was performed according to the manufacturer’s instructions. In brief, for IGFBP-1/AFP immunoassay (Amnioquick Duo+), the fluid from the posterior fornix of the vagina was collected by placing a sterile Nylon swab in the posterior fornix of the vagina for 1 min to ensure saturation of the swab. Then, the swab was removed and put into a unit dose vial containing solvent. The vial containing the swab and the solvent was rotated for 10 s. Next, three drops of the vial containing the substance extracted from the swab by the solvent was dispensed into a round sample well of the test device. The result was interpreted in 10 min. There are three distinct zones on the cassette for AFP (A), IGFBP-1(B) and control (C). Interpretation of these results was carried out according to the manufacturer’s algorithm, classified as positive, negative and doubtful for ROM. The test was positive when the C and the B lines were both present or when the A and the C lines were both present for cases with GA ⩾ 39 weeks. The test was negative when both the A and the B lines were absent. The test was doubtful when the A and the C lines were both present for cases with GAo39 weeks (line A for AFP, line B for IGFBP-1 and line C for control; Figure 1). Obstetricians who were caregivers to the patients were blinded to the results from the IGFBP-1/AFP immunoassay tests. An initial diagnosis for ROM was made from the conventional standard methods from sterile speculum examination of all patients using the following clinical criteria: (1) amniotic fluid was seen leaking from the cervical opening during the speculum examination, or (2) two of the three clinical signs were present (pooling of amniotic fluid in the posterior fornix, positive nitrazine test and positive ferning test). After the initial diagnosis of ROM, all patients were managed according to the standard gestational age-specific clinical management guideline.2 Women with PROM at initial diagnosis were admitted for close monitoring. PROMo34 weeks was managed expectantly. Expectant management included the administration of prophylactic antibiotics, corticosteroids and monitoring for infection. A final diagnosis of whether or not the patients had ROM at the initial presentation was made after the patient had delivered and the medical record was reviewed. This determination was made by the co-investigator who was blinded to the IGFBP-1/AFP results. The criteria used to determine the membrane status included results of sterile speculum examination, ultrasound assessment of amniotic fluid, presence or absence of chorioamnionitis, whether artificial ROM was performed in labor and whether spontaneous ROM occurred during labor.10 The sensitivity, specificity, positive predictive value, negative predictive value, accuracy, false-positive rate and false-negative rate for the IGFBP-1/ AFP immunoassay with 95% confidence interval were calculated.
RESULTS A total of 100 consecutive women were enrolled into the study. All women had followed the protocol. The study was able to perform all procedures and collect all data form all of the
participants. The mean age ± s.d. was 28.9 ± 5.7 years. Mean ± s.d. of the gestational age was 37.6 ± 2.3 weeks (range 25 to 41 weeks). Twenty-six percent (26 of 100) were preterm, and 74% (74 of the 100) were at term. Mean ± s.d. of gestational age at the time of delivery was 38.1 ± 1.7 weeks (range 33 to 41 weeks). The median time interval from having a history of fluid leakage to initial assessment was 1.8 h (range 0.2 to 188.3 h) and the median time interval from having a history of fluid leakage to delivery (latency period) was 9.7 h (range 1.2 to 3359.7 h). The pregnancy outcome was good. There were no maternal and neonatal deaths. Chorioamnionitis occurred in two cases. A total of 75 (75%) women were initially diagnosed with ROM using the conventional standard methods and 81 (81%) using the IGFBP-1/AFP immunoassay. Subsequent review of the medical records after delivery confirmed that 84 out of the 100 (84%) had ROM at their initial presentation, whereas 16 (16%) had intact membranes (Table 1). The mean birth weight ± s.d. was 3017.56 ± 593.5 g. Apgar scores at 1 and 5 min were 8.8 ± 0.8 (range 4 to 9) and 9.9 ± 0.3 (range 8 to 10), respectively. The diagnostic value of IGFBP-1, AFP, Amnioquick Duo+ and conventional standard methods are shown in Table 2. The diagnostic values for the IGFBP-1/AFP immunoassay were as follows: sensitivity was 94.1%, specificity was 87.5%, positive predictive value was 97.5%, negative predictive value was 73.7%, accuracy was 93% and false-positive rate was 12.5% for the diagnosis of ROM at the initial presentation (Table 2). The sensitivity, negative predictive value and accuracy of the IGFBP-1/AFP test were higher than the individual IGFBP-1 and AFP test. The specificity, positive predictive value and false-positive were comparable between the IGFBP-1/AFP test and individual IGFBP-1 and AFP test. The false-negative of the IGFBP-1/AFP test was lower than the individual IGFBP-1 and AFP test. DISCUSSION This study is the to report on the diagnostic values for IGFBP-1 (10 ng ml − 1)/AFP (5 ng ml − 1; Amnioquick Duo+), which is a new, noninvasive, rapid, immunoassay test used to detect ROM. The IGFBP-1/AFP immunoassay had a high sensitivity (94.1%) for the detection of ROM. This is because the test can detect a combination of IGFBP-1 and AFP. Concentrations of IGFBP-1 and AFP in the amniotic fluid are high when compared with the blood and the cervicovaginal secretion. However, the sensitivity of the IGFBP-1/AFP test in this study was lower than the previous study by Thomasino et al.10 They evaluated the diagnostic values for monoclonal/polyclonal immunoglobulin to detect IGFBP-1/AFP (ROM plus). The sensitivity and specificity were 99% and 91%, respectively. This difference may be because of the lower detection threshold of IGFBP-1 (5 ng ml − 1) of the ROM plus compared with the Amnioquick Duo+ (10 ng ml − 1), which was used in this study. When other tests for PROM/ROM were reviewed, the sensitivity of the Amnioquick Duo+ used in this study (94.1%) was higher Table 1.
Summary of patients tested with IGFBP-1/AFP test and final diagnosis of ROM Final diagnosis
IGFBP-1/AFP test
Figure 1.
Positive Negative Total
ROM
No ROM
Total
79 5 84
2 14 16
81 19 100
Abbreviations: AFP, alpha-fetoprotein; IGFBP-1, insulin-like growth factorbinding protein-1; ROM, rupture of membranes.
Test interpretation.
Journal of Perinatology (2015), 1 – 3
© 2015 Nature America, Inc.
IGFBP-1/AFP and rupture of membranes P Ruanphoo and V Phupong
3 Table 2.
Diagnostic value of IGFBP-1, AFP, Amnioquick Duo+ and conventional standard methods
Diagnostic value Sensitivity Specificity PPV NPV Accuracy False-positive False-negative
IGFBP-1 91.7 87.5 97.5 66.7 91 12.5 8.3
(86.3, 97.1) (81.0, 93.9) (94.4, 100) (57.5, 75.9) (85.4, 96.6) (6.0, 18.9) (2.9, 13.7)
AFP 67.9 75.0 93.4 30.8 69 25.0 32.1
(58.7, (66.5, (88.5, (21.8, (59.9, (16.5, (22.9,
Amnioquick Duo+ 77.0) 83.4) 98.3) 39.9) 78.1) 33.5) 41.3)
94.1 87.5 97.5 73.7 93 12.5 5.9
(89.5, 98.7) (81.0, 93.9) (94.4, 100) (65.1, 82.3) (88, 98) (6.0, 18.9) (1.3, 10.5)
Conventional standard methods 89.3 100.0 100.0 64.0 91
(83.2, 95.4) (100.0, 100.0) (100.0, 100.0) (54.6, 73.4) (85.4, 96.6) 0 10.7 (4.6, 16.8)
Abbreviations: AFP, alpha-fetoprotein; CI, confidence interval; IGFBP-1, insulin-like growth factor-binding protein-1; NPV, negative predictive value; PPV, positive predictive value. Data presented as percentage (95% CI).
than those that used only IGFBP-1 tests.11–14 The higher sensitivity in this study may be because of the combination of detecting both IGFBP-1 and AFP in Amnioquick Duo+ tests. The IGFBP-1/AFP had a false-positive rate of 12.5% in present study. This false-positive rate was seen to be comparable to some studies,11,12 whereas in others it was poorer.13,14 It is unclear what factors contribute to these false-positives. It is possible that there was a microleakage of the amniotic fluid in the vagina that could not be detected with a physical examination, bedside laboratories and ultrasonography. The sensitivity of the IGFBP-1/AFP test was higher than the conventional standard methods (94.1% versus 89.3%) in detecting ROM. The reason for this is because the IGFBP-1/AFP test can detect low levels of both IGFBP-1 (10 ng ml − 1) and AFP (5 ng ml − 1). Patients with intact membranes will not have any IGFBP-1/AFP in the cervicovaginal secretions.11,12 However, the specificity of the IGFBP-1/AFP test was lower (87.5%) than the conventional methods (100%). The sensitivity, negative predictive value and accuracy of the IGFBP-1/AFP test were higher than the individual IGFBP-1 and AFP test. The false-negative of the IGFBP-1/AFP test was lower than the individual IGFBP-1 and AFP test. The specificity, positive predictive value and false-positive were comparable between the IGFBP-1/ AFP test and individual IGFBP-1 and AFP test. This result confirmed the benefit of this combined two biomarkers in the test. The uniqueness of this study is to evaluate the diagnostic value of a new test for detection of ROM (IGFBP-1 (10 ng ml − 1)/AFP (5 ng ml − 1; Amnioquick Duo+)). Limitation of this study is the small size of control. The small size of control cases makes the calculated values for sensitivity, specificity, positive predictive value, negative predictive value and accuracy less reliable. In conclusions, IGFBP-1/AFP immunoassay (Amnioquick Duo+) is a rapid immunoassay test for diagnosis of ROM with a high sensitivity and specificity. This test can be used as an alternative method for diagnosis of ROM. CONFLICT OF INTEREST The authors declare no conflict of interests.
ACKNOWLEDGEMENTS We wish to thank Dr Thierry Paper, CEO and President of Biosynex SA, France for his kind support and free supply of the Amnioquick Duo+ tests.
© 2015 Nature America, Inc.
DISCLAIMER Biosynex SA, which supplied the Amnioquick Duo+ tests, did not get involved or participate in the study design, collection, analysis and manuscript development.
REFERENCES 1 Phupong V, Taneepanichskul S. Prelabour rupture of membranes. J Paediatr Obstet Gynaecol 2003; 29: 25–32. 2 ACOG Practice Bulletin No. 80: premature rupture of membranes. Clinical management guidelines for obstetrician-gynecologists. Obstet Gynecol 2007; 109: 1007–1019. 3 Phupong V, Taneepanichskul S. Outcome of preterm premature rupture of membranes. J Med Assoc Thai 2000; 83: 640–645. 4 Alexander JM, Cox SM. Clinical course of premature rupture of the membranes. Semin Perinatol 1996; 20: 369–374. 5 Friedman ML, McElin TW. Diagnosis of ruptured fetal membranes. Clinical study and review of the literature. Am J Obstet Gynecol 1969; 104: 544–550. 6 Guibourdenche J, Luton D, Andre E, Noel M, Porquet D. Rapid detection of insulinlike growth factor-binding protein-1 and foetal fibronectin in cervico-vaginal secretions to diagnose premature membrane rupture. Ann Clin Biochem 1999; 36: 388–390. 7 Cousins LM, Smok DP, Lovett SM, Poeltler DM. AmniSure placental alpha microglobulin-1 rapid immunoassay versus standard diagnostic methods for detection of rupture of membranes. Am J Perinatol 2005; 22: 317–320. 8 Kishida T, Hirao A, Matsuura T, Katamine T, Yamada H, Sagawa T et al. Diagnosis of premature rupture of membranes with an improved alpha-fetoprotein monoclonal antibody kit. Clin Chem 1995; 41: 1500–1503. 9 Sukchaya K, Phupong V. A comparative study of positive rate of placental alphamicroglobulin-1 test in pre-term pregnant women with and without uterine contraction. J Obstet Gynaecol 2013; 33: 566–568. 10 Thomasino T, Levi C, Draper M, Neubert AG. Diagnosing rupture of membranes using combination monoclonal/polyclonal immunologic protein detection. J Reprod Med 2013; 58: 187–194. 11 Jeurgens-Borst AJ, Bekkers RL, Sporken JM, van den Berg PP. Use of insulin like growth factor binding protein-1 in the diagnosis of ruptured fetal membranes. Eur J Obstet Gynecol Reprod Biol 2002; 102: 11–14. 12 Martinez de Tejada B, Boulvain M, Dumps P, Bischof P, Meisser A, Irion O. Can we improve the diagnosis of rupture of membranes? The value of insulin-like growth factor binding protein-1. BJOG 2006; 113: 1096–1099. 13 Wang T, Zhou R, Xiong W, Wang Y, Zhu C, Song C et al. Clinical evaluation of soluble intercellular adhesion molecule-1 and insulin like growth factor-binding protein-1-based rapid immunoassays for the diagnosis of prelabor rupture of membranes. J Perinat Med 2013; 41: 181–185. 14 Tagore S, Kwek K. Comparative analysis of insulin-like growth factor binding protein-1 (IGFBP-1), placental alpha-microglobulin-1 (PAMG-1) and nitrazine test to diagnose premature rupture of membranes in pregnancy. J Perinat Med 2010; 38: 609–612.
Journal of Perinatology (2015), 1 – 3
ORIGINAL ARTICLE
Evaluation of the performance of the insulin-like growth factor-binding protein-1/alpha-fetoprotein test in diagnosing ruptured fetal membranes in pregnant women P Ruanphoo and V Phupong OBJECTIVE: The objective of this study was to evaluate the efficacy of IGFBP-1/AFP (insulin-like growth factor-binding protein-1/ alpha-fetoprotein) immunoassay (Amnioquick Duo+) in diagnosing rupture of membranes (ROM). STUDY DESIGN: A prospective, observational study was performed in pregnant women with a history of fluid leakage from the vagina. The IGFBP-1/AFP immunoassay and conventional methods were used to diagnose ROM. The obstetricians were blinded to the results of the IGFBP-1/AFP immunoassay. The diagnosis of ROM was finally confirmed by reviewing the medical records after delivery. RESULT: One hundred patients were recruited into this study. The mean gestational age was 37.6 weeks (range 25 to 41 weeks). Twenty-six percent were preterm and 74% were at term. IGFBP-1/AFP immunoassay had a sensitivity of 94.1%, specificity of 87.5%, positive predictive value of 97.5%, negative predictive value of 73.7% and accuracy of 93% in diagnosing ROM. CONCLUSION: IGFBP-1/AFP immunoassay is a rapid immunoassay test for diagnosing ROM with a high sensitivity and specificity. This test can be used as an alternative method for diagnosis of ROM. Journal of Perinatology advance online publication, 26 February 2015; doi:10.1038/jp.2015.6
INTRODUCTION Premature rupture of membranes (PROM) is defined as the rupture of fetal membranes at any gestational age before the onset of labor.1,2 PROM is a common complication in pregnant women resulting in high morbidity and mortality in both the mother and the neonate, especially in preterm PROM less than 34 weeks.3 The prevalence of PROM is ~ 2 to 18% of all pregnancies.1,4 Preterm PROM (PPROM), defined as PROM before 37 weeks, is less common and occurs in 0.7 to 4% of pregnancies.1 Management of PROM depends on the gestational age. If in term pregnancy, then the labor should be induced, whereas for preterm PROM, management should be treated as expectant. Accurate diagnosis of rupture of membranes (ROM) is an important factor that can affect the management of pregnant women with signs and symptoms of ROM. It is easy to diagnose ROM when there is an obvious rupture and gross leakage; however, in some cases, it is far more difficult to diagnose ROM when the hallmark symptoms are not present. The gold standard for diagnosing ROM is the dye injection test that utilizes an indigo carmine dye solution.1,2 However, the instillation process is too invasive to be used routinely; therefore, a noninvasive procedure is much preferred. Unfortunately, there is no noninvasive, gold standard for diagnosing ROM. The common clinical evaluations of ROM are the presence of a gross leakage and collection of the fluid in the posterior fornix. Other evaluations utilize the laboratory bedside tests such as the fern test and nitrazine paper test. When there are no conspicuous leakages of the amniotic fluid, it cannot be diagnosed with these clinical examinations and conventional laboratory tests.5
As a result of this, there are many new bedside biological tests that were developed to detect certain biochemical markers that are highly present in the amniotic fluid but not in the vaginal fluid. Some of the biochemical markers that are used to detect membranes leakage such as alpha-fetoprotein (AFP), insulin-like growth factor-binding protein-1 (IGFBP-1), placental alphamicroglobulin-1 and fibronectin6–9 are targeted. Recently, a new, noninvasive, rapid immunochromatographic test known as the Amnioquick Duo+ (Biosynex, Strasbourg, France) became available. This immunochromatographic test can detect two biological markers, AFP and IGFBP-1, that are present in the amniotic fluid. The test has been set up with IGFBP-1 (10 ng ml − 1) and AFP (5 ng ml − 1) threshold. The objective of this study is to evaluate the performance of IGFBP-1/AFP immunoassay in diagnosing ROM in pregnant women who have a history of fluid leakage from the vagina. METHODS This prospective, observational study was performed at the Department of Obstetrics and Gynecology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand, from November 2013 to April 2014. This study was approved by the Research Ethics Committee of Faculty of Medicine, Chulalongkorn University, and written informed consent was obtained from all subjects. Pregnant women with symptoms or signs of ROM were invited to participate in the study. Patients with active vaginal bleeding, multiple pregnancies, fetal anomalies and fetal deaths were excluded. All patients were evaluated for ROM by collecting a detailed medical history of ROM, physical examination (including sterile vaginal speculum examinations) and transabdominal ultrasonogram. At the initial sterile speculum examination, all patients were assessed with the conventional standard
Department of Obstetrics and Gynecology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand. Correspondence: Professor V Phupong, Department of Obstetrics and Gynecology, Faculty of Medicine, Chulalongkorn University, Rama IV Road, Pathumwan, Bangkok 10330, Thailand. E-mail: [email protected] Received 20 October 2014; revised 12 January 2015; accepted 20 January 2015
IGFBP-1/AFP and rupture of membranes P Ruanphoo and V Phupong
2 methods (visual evaluation for fluid leakage or pooling of the amniotic fluid in the posterior fornix, nitrazine test and ferning test). After that, the IGFBP-1/AFP test was performed according to the manufacturer’s instructions. In brief, for IGFBP-1/AFP immunoassay (Amnioquick Duo+), the fluid from the posterior fornix of the vagina was collected by placing a sterile Nylon swab in the posterior fornix of the vagina for 1 min to ensure saturation of the swab. Then, the swab was removed and put into a unit dose vial containing solvent. The vial containing the swab and the solvent was rotated for 10 s. Next, three drops of the vial containing the substance extracted from the swab by the solvent was dispensed into a round sample well of the test device. The result was interpreted in 10 min. There are three distinct zones on the cassette for AFP (A), IGFBP-1(B) and control (C). Interpretation of these results was carried out according to the manufacturer’s algorithm, classified as positive, negative and doubtful for ROM. The test was positive when the C and the B lines were both present or when the A and the C lines were both present for cases with GA ⩾ 39 weeks. The test was negative when both the A and the B lines were absent. The test was doubtful when the A and the C lines were both present for cases with GAo39 weeks (line A for AFP, line B for IGFBP-1 and line C for control; Figure 1). Obstetricians who were caregivers to the patients were blinded to the results from the IGFBP-1/AFP immunoassay tests. An initial diagnosis for ROM was made from the conventional standard methods from sterile speculum examination of all patients using the following clinical criteria: (1) amniotic fluid was seen leaking from the cervical opening during the speculum examination, or (2) two of the three clinical signs were present (pooling of amniotic fluid in the posterior fornix, positive nitrazine test and positive ferning test). After the initial diagnosis of ROM, all patients were managed according to the standard gestational age-specific clinical management guideline.2 Women with PROM at initial diagnosis were admitted for close monitoring. PROMo34 weeks was managed expectantly. Expectant management included the administration of prophylactic antibiotics, corticosteroids and monitoring for infection. A final diagnosis of whether or not the patients had ROM at the initial presentation was made after the patient had delivered and the medical record was reviewed. This determination was made by the co-investigator who was blinded to the IGFBP-1/AFP results. The criteria used to determine the membrane status included results of sterile speculum examination, ultrasound assessment of amniotic fluid, presence or absence of chorioamnionitis, whether artificial ROM was performed in labor and whether spontaneous ROM occurred during labor.10 The sensitivity, specificity, positive predictive value, negative predictive value, accuracy, false-positive rate and false-negative rate for the IGFBP-1/ AFP immunoassay with 95% confidence interval were calculated.
RESULTS A total of 100 consecutive women were enrolled into the study. All women had followed the protocol. The study was able to perform all procedures and collect all data form all of the
participants. The mean age ± s.d. was 28.9 ± 5.7 years. Mean ± s.d. of the gestational age was 37.6 ± 2.3 weeks (range 25 to 41 weeks). Twenty-six percent (26 of 100) were preterm, and 74% (74 of the 100) were at term. Mean ± s.d. of gestational age at the time of delivery was 38.1 ± 1.7 weeks (range 33 to 41 weeks). The median time interval from having a history of fluid leakage to initial assessment was 1.8 h (range 0.2 to 188.3 h) and the median time interval from having a history of fluid leakage to delivery (latency period) was 9.7 h (range 1.2 to 3359.7 h). The pregnancy outcome was good. There were no maternal and neonatal deaths. Chorioamnionitis occurred in two cases. A total of 75 (75%) women were initially diagnosed with ROM using the conventional standard methods and 81 (81%) using the IGFBP-1/AFP immunoassay. Subsequent review of the medical records after delivery confirmed that 84 out of the 100 (84%) had ROM at their initial presentation, whereas 16 (16%) had intact membranes (Table 1). The mean birth weight ± s.d. was 3017.56 ± 593.5 g. Apgar scores at 1 and 5 min were 8.8 ± 0.8 (range 4 to 9) and 9.9 ± 0.3 (range 8 to 10), respectively. The diagnostic value of IGFBP-1, AFP, Amnioquick Duo+ and conventional standard methods are shown in Table 2. The diagnostic values for the IGFBP-1/AFP immunoassay were as follows: sensitivity was 94.1%, specificity was 87.5%, positive predictive value was 97.5%, negative predictive value was 73.7%, accuracy was 93% and false-positive rate was 12.5% for the diagnosis of ROM at the initial presentation (Table 2). The sensitivity, negative predictive value and accuracy of the IGFBP-1/AFP test were higher than the individual IGFBP-1 and AFP test. The specificity, positive predictive value and false-positive were comparable between the IGFBP-1/AFP test and individual IGFBP-1 and AFP test. The false-negative of the IGFBP-1/AFP test was lower than the individual IGFBP-1 and AFP test. DISCUSSION This study is the to report on the diagnostic values for IGFBP-1 (10 ng ml − 1)/AFP (5 ng ml − 1; Amnioquick Duo+), which is a new, noninvasive, rapid, immunoassay test used to detect ROM. The IGFBP-1/AFP immunoassay had a high sensitivity (94.1%) for the detection of ROM. This is because the test can detect a combination of IGFBP-1 and AFP. Concentrations of IGFBP-1 and AFP in the amniotic fluid are high when compared with the blood and the cervicovaginal secretion. However, the sensitivity of the IGFBP-1/AFP test in this study was lower than the previous study by Thomasino et al.10 They evaluated the diagnostic values for monoclonal/polyclonal immunoglobulin to detect IGFBP-1/AFP (ROM plus). The sensitivity and specificity were 99% and 91%, respectively. This difference may be because of the lower detection threshold of IGFBP-1 (5 ng ml − 1) of the ROM plus compared with the Amnioquick Duo+ (10 ng ml − 1), which was used in this study. When other tests for PROM/ROM were reviewed, the sensitivity of the Amnioquick Duo+ used in this study (94.1%) was higher Table 1.
Summary of patients tested with IGFBP-1/AFP test and final diagnosis of ROM Final diagnosis
IGFBP-1/AFP test
Figure 1.
Positive Negative Total
ROM
No ROM
Total
79 5 84
2 14 16
81 19 100
Abbreviations: AFP, alpha-fetoprotein; IGFBP-1, insulin-like growth factorbinding protein-1; ROM, rupture of membranes.
Test interpretation.
Journal of Perinatology (2015), 1 – 3
© 2015 Nature America, Inc.
IGFBP-1/AFP and rupture of membranes P Ruanphoo and V Phupong
3 Table 2.
Diagnostic value of IGFBP-1, AFP, Amnioquick Duo+ and conventional standard methods
Diagnostic value Sensitivity Specificity PPV NPV Accuracy False-positive False-negative
IGFBP-1 91.7 87.5 97.5 66.7 91 12.5 8.3
(86.3, 97.1) (81.0, 93.9) (94.4, 100) (57.5, 75.9) (85.4, 96.6) (6.0, 18.9) (2.9, 13.7)
AFP 67.9 75.0 93.4 30.8 69 25.0 32.1
(58.7, (66.5, (88.5, (21.8, (59.9, (16.5, (22.9,
Amnioquick Duo+ 77.0) 83.4) 98.3) 39.9) 78.1) 33.5) 41.3)
94.1 87.5 97.5 73.7 93 12.5 5.9
(89.5, 98.7) (81.0, 93.9) (94.4, 100) (65.1, 82.3) (88, 98) (6.0, 18.9) (1.3, 10.5)
Conventional standard methods 89.3 100.0 100.0 64.0 91
(83.2, 95.4) (100.0, 100.0) (100.0, 100.0) (54.6, 73.4) (85.4, 96.6) 0 10.7 (4.6, 16.8)
Abbreviations: AFP, alpha-fetoprotein; CI, confidence interval; IGFBP-1, insulin-like growth factor-binding protein-1; NPV, negative predictive value; PPV, positive predictive value. Data presented as percentage (95% CI).
than those that used only IGFBP-1 tests.11–14 The higher sensitivity in this study may be because of the combination of detecting both IGFBP-1 and AFP in Amnioquick Duo+ tests. The IGFBP-1/AFP had a false-positive rate of 12.5% in present study. This false-positive rate was seen to be comparable to some studies,11,12 whereas in others it was poorer.13,14 It is unclear what factors contribute to these false-positives. It is possible that there was a microleakage of the amniotic fluid in the vagina that could not be detected with a physical examination, bedside laboratories and ultrasonography. The sensitivity of the IGFBP-1/AFP test was higher than the conventional standard methods (94.1% versus 89.3%) in detecting ROM. The reason for this is because the IGFBP-1/AFP test can detect low levels of both IGFBP-1 (10 ng ml − 1) and AFP (5 ng ml − 1). Patients with intact membranes will not have any IGFBP-1/AFP in the cervicovaginal secretions.11,12 However, the specificity of the IGFBP-1/AFP test was lower (87.5%) than the conventional methods (100%). The sensitivity, negative predictive value and accuracy of the IGFBP-1/AFP test were higher than the individual IGFBP-1 and AFP test. The false-negative of the IGFBP-1/AFP test was lower than the individual IGFBP-1 and AFP test. The specificity, positive predictive value and false-positive were comparable between the IGFBP-1/ AFP test and individual IGFBP-1 and AFP test. This result confirmed the benefit of this combined two biomarkers in the test. The uniqueness of this study is to evaluate the diagnostic value of a new test for detection of ROM (IGFBP-1 (10 ng ml − 1)/AFP (5 ng ml − 1; Amnioquick Duo+)). Limitation of this study is the small size of control. The small size of control cases makes the calculated values for sensitivity, specificity, positive predictive value, negative predictive value and accuracy less reliable. In conclusions, IGFBP-1/AFP immunoassay (Amnioquick Duo+) is a rapid immunoassay test for diagnosis of ROM with a high sensitivity and specificity. This test can be used as an alternative method for diagnosis of ROM. CONFLICT OF INTEREST The authors declare no conflict of interests.
ACKNOWLEDGEMENTS We wish to thank Dr Thierry Paper, CEO and President of Biosynex SA, France for his kind support and free supply of the Amnioquick Duo+ tests.
© 2015 Nature America, Inc.
DISCLAIMER Biosynex SA, which supplied the Amnioquick Duo+ tests, did not get involved or participate in the study design, collection, analysis and manuscript development.
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