Accuracy of portable glucose meters for the determination of amniotic fluid glucose levels

OBJECTIVE: To evaluate the accuracy of three commercially available blood glucose meters to measure amniotic fluid glucose levels as compared to an accepted laboratory standard. METHODS: A prospective study of amniotic fluid from 104 consecutive amniocenteses was performed. Glucose concentration in this fluid was determined by glucose oxidase measurement (control) and by using three portable meters: Advantage (ADV) (Boehringer Mannheim), Glucometer Elite (ELT) (Bayer) and One Touch II Hospital (OT2) (Lifescan). Twenty amniotic fluid samples were sent for glucose oxidase assay to assess the effect of cellular activity and time delay on amniotic fluid glucose concentrations. Data are reported and mean ±SE and were assessed by 1-way ANOVA. RESULTS: Of the 104 patients studied, 75 were of gestational age <20 weeks. All 3 ambulatory meters demonstrated a linear relationship with control (all p<0.001). Given a slope of almost 1 (m=0.93) and a y intercept approaching zero (b=0.93) the OT2 proved to correlate best with control. ELT: (ra=0.53, m=0.71, b=26.8) and ADV: (r=0.70, m=1.36, b=21.2) both overestimated fluid glucose in the lower ranges. When the glucose oxidase was <30mg/dL, OT2: (p<0.0002, r=0.78, m=1.0l and b=1.75) performed better than ADV (p=0.11, r'2 = .016, m = 0.60, b=13.8.) The correlation between the delayed samples with and without metabolic inhibitors was excellent; (r2=0.92, rn=0.9 and b-4.0) compared to control. CONCLUSION: The One Touch II most accurately predicted amniotic fluid glucose at the bedside with excellent correlation including glucose levels <SOmg/dL. ADV and ELT proved too inaccurate for clinical use. The control sample was not effected by additives or time delay. These finds allow immediate amniotic fluid glucose determinations using the OT2 with suspected chorioamnionitis.