Learning curve for lung area to head circumference ratio measurement in fetuses with congenital diaphragmatic hernia

Abstract

Objective To assess the learning curve for the fetal lungarea to head circumference ratio (LHR) calculation infetuses with congenital diaphragmatic hernia (CDH). Methods Three trainees with the theoretical knowledge, but without prior experience in the LHR measurement, were selected. Each trainee and one experienced examinermeasured the observed to expected (O/E)-LHR inthe lung contralateral to the side of the hernia bytwo methods - manual tracing of lung borders andmultiplication of the longest diameters - in a cohort of95 consecutive CDH fetuses. The average differencebetween the three trainees and the expert in the O/E-LHRmeasurement was calculated. A difference below 10%was considered to indicate an accurate measurement. Theaverage learning curve was delineated using cumulativesum analysis (CUSUM). Results The CUSUM plots demonstrate that the learningcurve was achieved by 77 and 72 tests performed for thearea obtained by the manual-tracing and multiplicationof-the-longest- diameter methods, respectively. Conclusion The minimum number of scans requiredfor an inexperienced trainee to become competent inexamining the LHR is on average 70. Copyright © 2010 ISUOG. Published by John Wiley & Sons, Ltd.