Inter-observer Variation in Assessment of 845 Labor Admission Tests: Comparison Between Midwives and Obstetricians in the Clinical Setting and Two Experts

Abstract

The labor admission tests entails 20-30 minutes of cardiotocographic (CTG) recording on entry to the maternity ward. Because observer variability reflects the reliability of any clinical test, this study was done to determine the degree of agreement between midwives and obstetricians in evaluating labor admission tests. Two expert consultant obstetricians from other centers also participated. The study group included 845 high- and low-risk women who were admitted in labor and gave birth within 24 hours of the test. Test findings were rated as reactive, equivocal, or ominous. The kappa (κ) value is the difference between observed and expected agreement, or the proportion of potential agreement beyond change. Values exceeding 0.75 reflect excellent agreement, and values between 0.4 and 0.75 reflect fair to good agreement. Weighted kappa (κW) was used in this analysis. The proportion of agreement (Pa) also was calculated. Agreement between the two experts was κw 0.38; Pa for a reactive labor admission test, 0.86; and Pa for an equivocal or ominous test, 0.33. The respective values for agreement between one expert and midwives/obstetricians were 0.25, 0.89, and 0.18. For the other expert, the respective figures were 0.28, 0.85, and 0.20. Nearly 6% of newborn infants had fetal distress. At a cutoff of an equivocal test, sensitivity values for the 2 expert observers were 0.22 and 0.31. Positive predictive values were 0.13 and 0.11. The likelihood ratios for a positive test were 2.3 and 1.92, and for a negative test, 0.86 and 0.83. Despite little evidence that it is beneficial, labor admission testing remains routine practice in most obstetrical units in the Western world. The present findings should prompt reconsideration of this practice, and they suggest the relevance of educational programs for maternity ward staff so that they will more accurately interpret CTG recordings.