- Email: [email protected]
Cardiotocography and ST analysis for intrapartum fetal monitoring – Author's reply
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Correspondence
See Online for webappendix
applied quality control. The specified criteria were “According to the study protocol, blood samples from both the cord artery and cord vein were required (minimum difference in pH 0·03 and in pCO2 1·0 kPa)“. Those criteria are not mentioned in the original article. In the reanalysis, Maršál does not consider that, if the same criteria are applied for the originally included 46 cases of metabolic acidosis, another ten patients do not comply with the inclusion criteria. In the reanalysis, now published,2 there is a completely new and quite different definition of valid data. Implementation of those two different criteria will give large differences in participants with valid data in the total study. I and another reviewer have earlier recommended a complete reanalysis of the data. Such a control was not done by the Swedish Research Council. I hope that Maršál will take the responsibility, and, according to the decision of the Vice-Chancellor of Lund University, present a reanalysis based on validated data according to the prespecified criteria. Finally, inconsistent application of prespecified rules is a major concern. I declare that I have no conflicts of interest.
Ulf Hanson [email protected] Department of Obstetrics and Gynecology, Uppsala University, 75643 Uppsala, Sweden 1
2
Amer-Wåhlin I, Hellsten C, Norén H, et al. Cardiotocography only versus cardiotocography plus ST analysis of fetal electrocardiogram for intrapartum fetal monitoring: a Swedish randomised controlled trial. Lancet 2001; 358: 534–38. Amer-Wåhlin I, Kjellmer I, Maršál K, Olofsson P, Rosén KG. Swedish randomized controlled trial of cardiotocography only versus cardiotocography plus ST analysis of fetal ECG revisited: analysis of data according to standard versus modified intention-to-treat principle. Acta Obstet Gynecol Scand 2011; 90: 990–96.
Author’s reply To improve the identification of fetuses at risk of asphyxia in labour, an automatic analyser of the ST waveform of the fetal electrocardiogram (STAN) for use in combination with cardiotocography (CTG) was 1138
introduced in the 1990s. During 1998–2000, we did a randomised controlled trial to compare CTG only with CTG+ST in 4966 labouring women at three Swedish labour wards.1 The rate of metabolic acidosis in the umbilical arterial blood was found to be significantly lower in the CTG+ST group than in the CTG group (see webappendix). Subsequently, the STAN method became commercially available and used in clinical practice around Europe. From Sweden, some cases of adverse neonatal outcome were reported when using ST waveform analysis. This initiated a debate regarding the validity of data on metabolic acidosis in our trial. Three subsequent investigations of the study were undertaken by external experts: one initiated by the research group and two by Lund University. In September, 2010, the Vice-Chancellor of Lund University concluded that there were errors in a few cases, but that no misconduct in research had taken place.2 The original data have been scrutinised by the STAN research group and two cases of misclassification were identified (one case of erroneous rounding of the third decimal of a pH value and one with acid-base data missing in the study database). Furthermore, six cases of metabolic acidosis in the CTG group and four in the CTG+ST group should not have been considered since too small an arteriovenous gradient in pH or pCO2 made the acid-base data invalid. The statistical analysis after corrections showed slightly changed relative risks and 95% CIs; however, the level of significance remained unchanged in favour of the CTG+ST group (webappendix). Thus, the results of renewed analysis did not change the conclusion of the original study that intrapartum monitoring with CTG+ST waveform analysis resulted in an improved perinatal outcome as reflected in a decreased rate of metabolic acidosis at birth. The
details of the reanalysis and discussion of various types of data analysis when assessing medical devices in a randomised controlled trial have been published elsewhere.3 During the past decade, substantial experience in the use of the STAN method in labour has been gained, confirming its clinical usefulness,4 and international guidelines for users have been developed.5 I declare that I have no conflicts of interest.
Karel Maršál, on behalf of all authors [email protected] Department of Obstetrics and Gynecology, Skåne University Hospital Lund, 22185 Lund, Sweden 1
2
3
4
5
Amer-Wåhlin I, Hellsten C, Norén H, et al. Cardiotocography only versus cardiotocography plus ST analysis of fetal electrocardiogram for intrapartum fetal monitoring: a Swedish randomised controlled trial. Lancet 2001; 358: 534–38. Lunds Universitet. Utredning av forskningsoredlighet— fosterövervakningstekniken STAN. http:// www.med.lu.se/nyheter/utredning_av_ forskningsoredlighet (accessed May 24, 2011). Amer-Wåhlin I, Kjellmer I, Maršál K, Olofsson P, Rosén KG. Swedish randomized controlled trial of cardiotocography only versus cardiotocography plus ST analysis of fetal ECG revisited: analysis of data according to standard versus modified intention-to-treat principle. Acta Obstet Gynecol Scand 2011; 90: 990–96. Norén H, Carlsson A. Reduced prevalence of metabolic acidosis at birth: an analysis of established STAN usage in the total population of deliveries in a Swedish district hospital. Am J Obstet Gynecol 2010; 202: 546.e1–7. Amer-Wåhlin I, Arulkumaran SS, Hagberg H, Maršál K, Visser GHA. Fetal electrocardiogram: ST waveform analysis in intrapartum surveillance. BJOG 2007; 114: 1191–93.
www.thelancet.com Vol 378 September 24, 2011
Correspondence
See Online for webappendix
applied quality control. The specified criteria were “According to the study protocol, blood samples from both the cord artery and cord vein were required (minimum difference in pH 0·03 and in pCO2 1·0 kPa)“. Those criteria are not mentioned in the original article. In the reanalysis, Maršál does not consider that, if the same criteria are applied for the originally included 46 cases of metabolic acidosis, another ten patients do not comply with the inclusion criteria. In the reanalysis, now published,2 there is a completely new and quite different definition of valid data. Implementation of those two different criteria will give large differences in participants with valid data in the total study. I and another reviewer have earlier recommended a complete reanalysis of the data. Such a control was not done by the Swedish Research Council. I hope that Maršál will take the responsibility, and, according to the decision of the Vice-Chancellor of Lund University, present a reanalysis based on validated data according to the prespecified criteria. Finally, inconsistent application of prespecified rules is a major concern. I declare that I have no conflicts of interest.
Ulf Hanson [email protected] Department of Obstetrics and Gynecology, Uppsala University, 75643 Uppsala, Sweden 1
2
Amer-Wåhlin I, Hellsten C, Norén H, et al. Cardiotocography only versus cardiotocography plus ST analysis of fetal electrocardiogram for intrapartum fetal monitoring: a Swedish randomised controlled trial. Lancet 2001; 358: 534–38. Amer-Wåhlin I, Kjellmer I, Maršál K, Olofsson P, Rosén KG. Swedish randomized controlled trial of cardiotocography only versus cardiotocography plus ST analysis of fetal ECG revisited: analysis of data according to standard versus modified intention-to-treat principle. Acta Obstet Gynecol Scand 2011; 90: 990–96.
Author’s reply To improve the identification of fetuses at risk of asphyxia in labour, an automatic analyser of the ST waveform of the fetal electrocardiogram (STAN) for use in combination with cardiotocography (CTG) was 1138
introduced in the 1990s. During 1998–2000, we did a randomised controlled trial to compare CTG only with CTG+ST in 4966 labouring women at three Swedish labour wards.1 The rate of metabolic acidosis in the umbilical arterial blood was found to be significantly lower in the CTG+ST group than in the CTG group (see webappendix). Subsequently, the STAN method became commercially available and used in clinical practice around Europe. From Sweden, some cases of adverse neonatal outcome were reported when using ST waveform analysis. This initiated a debate regarding the validity of data on metabolic acidosis in our trial. Three subsequent investigations of the study were undertaken by external experts: one initiated by the research group and two by Lund University. In September, 2010, the Vice-Chancellor of Lund University concluded that there were errors in a few cases, but that no misconduct in research had taken place.2 The original data have been scrutinised by the STAN research group and two cases of misclassification were identified (one case of erroneous rounding of the third decimal of a pH value and one with acid-base data missing in the study database). Furthermore, six cases of metabolic acidosis in the CTG group and four in the CTG+ST group should not have been considered since too small an arteriovenous gradient in pH or pCO2 made the acid-base data invalid. The statistical analysis after corrections showed slightly changed relative risks and 95% CIs; however, the level of significance remained unchanged in favour of the CTG+ST group (webappendix). Thus, the results of renewed analysis did not change the conclusion of the original study that intrapartum monitoring with CTG+ST waveform analysis resulted in an improved perinatal outcome as reflected in a decreased rate of metabolic acidosis at birth. The
details of the reanalysis and discussion of various types of data analysis when assessing medical devices in a randomised controlled trial have been published elsewhere.3 During the past decade, substantial experience in the use of the STAN method in labour has been gained, confirming its clinical usefulness,4 and international guidelines for users have been developed.5 I declare that I have no conflicts of interest.
Karel Maršál, on behalf of all authors [email protected] Department of Obstetrics and Gynecology, Skåne University Hospital Lund, 22185 Lund, Sweden 1
2
3
4
5
Amer-Wåhlin I, Hellsten C, Norén H, et al. Cardiotocography only versus cardiotocography plus ST analysis of fetal electrocardiogram for intrapartum fetal monitoring: a Swedish randomised controlled trial. Lancet 2001; 358: 534–38. Lunds Universitet. Utredning av forskningsoredlighet— fosterövervakningstekniken STAN. http:// www.med.lu.se/nyheter/utredning_av_ forskningsoredlighet (accessed May 24, 2011). Amer-Wåhlin I, Kjellmer I, Maršál K, Olofsson P, Rosén KG. Swedish randomized controlled trial of cardiotocography only versus cardiotocography plus ST analysis of fetal ECG revisited: analysis of data according to standard versus modified intention-to-treat principle. Acta Obstet Gynecol Scand 2011; 90: 990–96. Norén H, Carlsson A. Reduced prevalence of metabolic acidosis at birth: an analysis of established STAN usage in the total population of deliveries in a Swedish district hospital. Am J Obstet Gynecol 2010; 202: 546.e1–7. Amer-Wåhlin I, Arulkumaran SS, Hagberg H, Maršál K, Visser GHA. Fetal electrocardiogram: ST waveform analysis in intrapartum surveillance. BJOG 2007; 114: 1191–93.
www.thelancet.com Vol 378 September 24, 2011