Learning curve for fetoscopic laser surgery using cumulative sum analysis
Suzanne H P Peeters1, Erik W Van Zwet, Dick Oepkes
1Department of Obstetrics, Leiden University Medical Center, Leiden, the Netherlands.
Objective:
To identify a learning curve and monitor operator performance for fetoscopic laser surgery for twin-to-twin transfusion syndrome using cumulative sum analysis.
Design:
Retrospective cohort study.
Setting:
National tertiary referral center for invasive fetal therapy.
Population:
A total of 340 consecutive monochorionic pregnancies with twin-to-twin transfusion syndrome treated with fetoscopic laser coagulation between August 2000 and December 2010.
Methods:
A learning curve was generated using learning curve cumulative sum analysis and cumulative sum methodology to assess changes in double survival across the case sequence. Laser surgery was initially performed by two operators, joined by a third and fourth operator after 1 and 2 years, respectively.
Main Outcome Measures:
Individual operator performance, double perinatal survival at 4 weeks.
Results:
Overall survival of both twins occurred in 59% (201/340), median gestational age at birth was 32.0 weeks. Cumulative sum graphs showed that level of competence for double survival for the operators was reached after 26, 25, 26, and 35 procedures, respectively. Two operators kept their competence level and continued to improve after completing the initial learning process; two others went out of control at one point in time, according to the cumulative sum boundaries. A difference in learning effect was associated with number of procedures performed annually and previous experience with other ultrasound-guided invasive procedures.
Conclusions:
This study shows that all operators reached a level of competence after at least 25 fetoscopic laser procedures and confirms the value of using the cumulative sum method both for learning curve assessment and for ongoing quality control.
