Interobserver agreement in CTG classification and clinical decision during labour: a comparison between STAN2007 and STAN2022 classifications

ST analysis during labour requires the classification of CTG traces in order to help clinical decisions. The usual STAN classification is based on the FIGO 1987 classification, modified in 2007. New STAN guidelines adapted to physiology-based interpretation have been proposed in 2022. This study compares the interobserver agreement of CTG classification and clinical decisions making, and the ease of use following the 2022 and 2007 STAN guidelines.

Material and Methods

Thirty CTG traces from STAN monitors were selected from a local French database and analysed (CTG classification, clinical decision making) by six observers with different levels of experience in two sessions three months apart. Observers followed the STAN2007 and the STAN2022 guidelines in the first and in the second sessions respectively. Weighted kappa (primary outcome), proportion of complete agreement within the 6 observers, and percent agreement (secondary outcomes) were estimated. At the end of the second session observers rated their satisfaction, ease of use and which guidelines they preferred.

Results

The interobserver agreement for CTG classification were comparable when following STAN2007 and STAN2022 guidelines (weighted kappa 0.57 versus 0.58, P = 0.91, moderate agreement), but a higher proportion of complete agreement within the 6 observers and a higher percent agreement were obtained when following STAN2022 compared to STAN2007 guidelines (complete agreement 50 % versus 20 % respectively, P = 0.01; percentage of agreement 72 % vs 55 %, P = 0.006). Interobserver agreement for clinical decisions did not differ when following STAN2007 or STAN2022 guidelines. Satisfaction scores were higher with STAN2022 guidelines, but not significantly (P = 0.052). All 6 observers stated that they preferred to use the STAN2022 guidelines.

Conclusion

Interobserver agreement is comparable between STAN2022 and STAN2007 for CTG classification in labour and clinical decision making. However, complete agreement and percent agreement are in favour of STAN 2022 for CTG classification.