ABSTRACT
Objective: Interest in an inexpensive, easyโtoโadminister antenatal screening test that did not rely on the use of electronic fetal monitoring led to development of the fetoscope administered auscultated acceleration test (AAT) in the late 1980s. More recent efforts have been directed toward providing those who may use the AAT with important information about the most effective and clinically appropriate AAT procedures. The purpose of this study was to determine the screening test validity performance of two AAT time intervalsโ6 minutes and 10 minutes.
Methods: Two auscultated acceleration tests (AAT6 and AAT10) were simultaneously performed using different time intervals on 205 women with highโrisk pregnancies undergoing simultaneous nonstress tests (NSTS) who were referred to a tertiary care unit for antepartum testing. Standard measurements of screening test validity were calculated for each test in the prediction of selected perinatal outcomes. NST findings were included for comparative purposes.
Results: The AAT6 yielded an overall higher specificity as compared with the AAT10 at the expense of a slightly lower sensitivity for most perinatal outcomes; these differences were not significant at the .05 level. Relative risk ratios were similar for the AAT6 and AAT10 for both fetal distress and neonatal morbidity, with both AAT being a more effective predictor of neonatal morbidity than for fetal distress. Both tests yielded better sensitivity when compared with NST.
Conclusions: Even though there was a nonsignificant trend toward higher sensitivities and lower specificities for the 10โminute AAT, this study showed that the differences in prediction of perinatal outcomes between the 6โminute and 10โminute AAT were minimal. In view of the added labor required for the 10โminute AAT in the absence of enhanced screening test validity, the 6โminute AAT is clinically preferred. This study has prompted new research questions for the continued development of the AAT as a lowโtechnology fetal assessment technique with potential usefulness by midwives and their colleagues in a variety of settings worldwide.