A comparison of two time intervals for the auscultated acceleration test

Objective: Interest in an inexpensive, easy-to-administer antenatal screeni ng test that did not rely on the use of electronic fetal monitoring led to development of the fetoscope administered auscultated acceleration test (AA T) in the late 1980s. More recent efforts have been directed toward providi ng those who may use the AAT with important information about the most effe ctive and clinically appropriate AAT procedure:;. Thr purpose of this stud: was to determine the screening test validity performance of two AAT time i ntervals-6 minutes and 10 minutes. Methods: Two auscultated acceleration tests (AAT6 and AAT10) were simultane ously performed using different time intervals on 205 women with high-risk pregnancies undergoing simultaneous nonstress tests (NSTS) who were referre d 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 pu rposes. Results: The AAT6 yielded an overall higher specificity as compared with th e AAT10 at the expense of a slightly lower sensitivity for most perinatal o utcomes; 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 neon atal morbidity than fetal distress. Both tests yielded better sensitivity w hen compared with SST. Conclusions: Even though there was a nonsignificant tl end toward higher se nsitivities and lower specificities for the Ill-minute AAT this study showe d that the differences in prediction of perinatal outcomes between the 6-mi nute and 10-minute AAT were minimal. In view of the added labor required fo r the 10-minute AAT in the absence of enhanced screening test validity, the 6-minute AAT is clinically preferred. This study has prompted new research questions for the continued development of the AAT as a low-technology fet al assessment technique with potential usefulness by midwives and their col leagues in a variety of settings worldwide. (C) 2001 by the American Colleg e of Nurse-Midwives.