SHORT-TERM AND LONG-TERM REPRODUCIBILITY OF THE 1-H 50-G GLUCOSE CHALLENGE TEST

A study was undertaken to assess the short-term (intrapregnancy) and l ong-term (interpregnancy) variability of the 1-h 50-g oral glucose cha llenge test (GCT). Two groups of pregnant women had GCTs in consecutiv e pregnancies, 1 (n = 77) and 2 (n = 43) years apart. Their results we re compared with published results for a group (n = 53) who had GCTs o n consecutive days. Robust estimates of the mean error variance (sigma (error)(2) = sigma(within-individual)(2) + sigma(2analytical)) were ca lculated on log(10)-transformed data and were for the three groups 0.0 03995, 0.002603, and 0.0026249 (mg/dL)(2), respectively. There was no significant difference between the group variances, establishing that the short- and long-term reliability of the GCT is comparable. sigma(b etween-individuals)(2) was estimated from the GCT values for 2695 preg nant women tested during the same period and was the main component (6 7.1%) of the total sample variation gma(between-individuals)(2)/sigma( population)(2)). Estimates of the population mean, sigma(between-indiv iduals)(2), and sigma(error)(2) were used to compute the probability t hat an observed GCT value had a true value equal to or greater than th e consensus threshold of 7.8 mmol/L (140 mg/dL).