A C TA Obstetricia et Gynecologica
AOGS B R I E F C O M M E N T A R Y
Scarce scientific evidence for the use of cardiotocography plus fetal ECG ST interval analysis (STAN) P AL ØIAN1,2 & ELLEN BLIX1,3 1
Women’s Health and Perinatology Research Group, University of Tromsø, 2Department of Obstetrics and Gynecology, and 3Department of Clinical Research, University Hospital of Northern Norway, Tromsø, Norway
DOI: 10.1111/aogs.12414
Cardiotocography (CTG) has been recommended for fetal surveillance of high-risk pregnancies in labor in many countries for decades. The test has a high sensitivity, but a low specificity (1), which might have contributed to an increase in cesarean section rate for fetal distress. Therefore, we need a test to identify the truly hypoxic fetuses. The introduction of CTG plus electrocardiotocography (ECG) ST interval analysis (STAN) was thought to have solved this problem. Extensive basic and clinical research by K.G. Rosen and co-workers (2) led to the development of the STAN monitoring technology, and it is now routinely used for fetal monitoring in labor in many countries (63% of all delivery units in Denmark, 53% in Norway). In this issue of Acta Obstetricia et Gynecologica Scandinavica, Per Olofsson et al. present a critical appraisal of the five randomized controlled trials (RCTs; Plymouth, Swedish, Finnish, French, Dutch studies) comparing CTG plus ECG ST interval analysis against CTG alone (3). The aim of the study was to address the quality of the RCTs published between 1993 and 2010 with 799–5681 laboring women included. It is not clear what criteria were used for quality assessment. The article is detailed and in some ways difficult to follow. It is often unclear if the results reported are from the original studies or the authors’ interpretations. They find considerable differences in study design, inclusion criteria, intrapartum management protocols, and outcome parameters. Many of these studies were underpowered. The authors’ key message is that the Plymouth, Swedish and Dutch trials have the most similar design and therefore should be the main source of information. They argue that the French study comprised important violations of the STAN guidelines and should be omitted from meta-analysis, but they do not discuss if this could be the case in other studies too. They also argue that base deficit (BD) from measured pH and PCO2 values should be calculated in extracellular fluid, but not in blood. We agree with this, since the fetus/newborn has a relatively much larger extracellular volume than later in life. However, they do not discuss the individual variations in extracellular fluid, and the cut-off levels used for BD. Three of the five RCTs have published revised results. The Swedish study was alleged to contain irregularities in
570
reporting, and errors in data analysis were confirmed, although these did not influence the reduction in metabolic acidosis rates (4). An RCT is the gold standard for clinical trials. The setting for such studies can vary from simple interventions, like administering a drug, to more multi-faceted interventions, such as those used in the STAN studies. The setting in RCTs is often one of more selected patients and highly controlled conditions. Rare, but serious complications are often not observed in such studies. The STAN technology is not just a machine, it is a concept. A strong focus is on education, training, and interpretation. There are pitfalls with the concept, including poor signal control, too late application of STAN, subjectivity of CTG interpretation and classification, and inter-professional communication. Many of the authors of this critical appraisal are pioneers in introducing the STAN technology in Sweden, Norway, USA, and Portugal. Two of the authors are medical advisors for Neoventa, a company that produces and sells the STAN machines. It can be argued that use of STAN in addition to continuous CTG monitoring in labor is not associated with significant perinatal benefits. We are surprised that they do not discuss in more detail the limited evidence from the five RCTs regarding beneficial effects on hard endpoints and the lack of long-term outcome data. References 1. Nelson KB, Dambrosia JM, Ting TY, Grether JK. Uncertain value of electronic fetal monitoring in predicting cerebral palsy. N Engl J Med. 1996;334:613–18. 2. Rosen KG. Fetal electrocardiogram waveform analysis in labour. Curr Opin Obstet Gynecol. 2005;17:147–50. 3. Olofsson P, Ayres-de-Campos D, Kessler J, Tendal B, Yli BM, Devoe L. A critical appraisal of the evidence for using cardiotocography plus ECG ST interval analysis for fetal surveillance in labor. Part I: the randomized controlled trials. Acta Obstet Gynecol Scand. 2014;93:556–68. 4. Steer P, Hvidman LE. Scientific and clinical evidence for the use of fetal ECG ST segment analysis (STAN). Acta Obstet Gynecol Scand 2014;93:533–38.
ª 2014 Nordic Federation of Societies of Obstetrics and Gynecology, Acta Obstetricia et Gynecologica Scandinavica 93 (2014) 570
AOGS B R I E F C O M M E N T A R Y
Scarce scientific evidence for the use of cardiotocography plus fetal ECG ST interval analysis (STAN) P AL ØIAN1,2 & ELLEN BLIX1,3 1
Women’s Health and Perinatology Research Group, University of Tromsø, 2Department of Obstetrics and Gynecology, and 3Department of Clinical Research, University Hospital of Northern Norway, Tromsø, Norway
DOI: 10.1111/aogs.12414
Cardiotocography (CTG) has been recommended for fetal surveillance of high-risk pregnancies in labor in many countries for decades. The test has a high sensitivity, but a low specificity (1), which might have contributed to an increase in cesarean section rate for fetal distress. Therefore, we need a test to identify the truly hypoxic fetuses. The introduction of CTG plus electrocardiotocography (ECG) ST interval analysis (STAN) was thought to have solved this problem. Extensive basic and clinical research by K.G. Rosen and co-workers (2) led to the development of the STAN monitoring technology, and it is now routinely used for fetal monitoring in labor in many countries (63% of all delivery units in Denmark, 53% in Norway). In this issue of Acta Obstetricia et Gynecologica Scandinavica, Per Olofsson et al. present a critical appraisal of the five randomized controlled trials (RCTs; Plymouth, Swedish, Finnish, French, Dutch studies) comparing CTG plus ECG ST interval analysis against CTG alone (3). The aim of the study was to address the quality of the RCTs published between 1993 and 2010 with 799–5681 laboring women included. It is not clear what criteria were used for quality assessment. The article is detailed and in some ways difficult to follow. It is often unclear if the results reported are from the original studies or the authors’ interpretations. They find considerable differences in study design, inclusion criteria, intrapartum management protocols, and outcome parameters. Many of these studies were underpowered. The authors’ key message is that the Plymouth, Swedish and Dutch trials have the most similar design and therefore should be the main source of information. They argue that the French study comprised important violations of the STAN guidelines and should be omitted from meta-analysis, but they do not discuss if this could be the case in other studies too. They also argue that base deficit (BD) from measured pH and PCO2 values should be calculated in extracellular fluid, but not in blood. We agree with this, since the fetus/newborn has a relatively much larger extracellular volume than later in life. However, they do not discuss the individual variations in extracellular fluid, and the cut-off levels used for BD. Three of the five RCTs have published revised results. The Swedish study was alleged to contain irregularities in
570
reporting, and errors in data analysis were confirmed, although these did not influence the reduction in metabolic acidosis rates (4). An RCT is the gold standard for clinical trials. The setting for such studies can vary from simple interventions, like administering a drug, to more multi-faceted interventions, such as those used in the STAN studies. The setting in RCTs is often one of more selected patients and highly controlled conditions. Rare, but serious complications are often not observed in such studies. The STAN technology is not just a machine, it is a concept. A strong focus is on education, training, and interpretation. There are pitfalls with the concept, including poor signal control, too late application of STAN, subjectivity of CTG interpretation and classification, and inter-professional communication. Many of the authors of this critical appraisal are pioneers in introducing the STAN technology in Sweden, Norway, USA, and Portugal. Two of the authors are medical advisors for Neoventa, a company that produces and sells the STAN machines. It can be argued that use of STAN in addition to continuous CTG monitoring in labor is not associated with significant perinatal benefits. We are surprised that they do not discuss in more detail the limited evidence from the five RCTs regarding beneficial effects on hard endpoints and the lack of long-term outcome data. References 1. Nelson KB, Dambrosia JM, Ting TY, Grether JK. Uncertain value of electronic fetal monitoring in predicting cerebral palsy. N Engl J Med. 1996;334:613–18. 2. Rosen KG. Fetal electrocardiogram waveform analysis in labour. Curr Opin Obstet Gynecol. 2005;17:147–50. 3. Olofsson P, Ayres-de-Campos D, Kessler J, Tendal B, Yli BM, Devoe L. A critical appraisal of the evidence for using cardiotocography plus ECG ST interval analysis for fetal surveillance in labor. Part I: the randomized controlled trials. Acta Obstet Gynecol Scand. 2014;93:556–68. 4. Steer P, Hvidman LE. Scientific and clinical evidence for the use of fetal ECG ST segment analysis (STAN). Acta Obstet Gynecol Scand 2014;93:533–38.
ª 2014 Nordic Federation of Societies of Obstetrics and Gynecology, Acta Obstetricia et Gynecologica Scandinavica 93 (2014) 570
