A comparison of chromogen test strip (Chemstrip bG) and serum glucose values in newborns

Although glucose oxidase-peroxidase chromogen test strips are frequently used to estimate serum glucose values in newborns, previous studies have not evaluated multiobserver variability of test strip readings and have included few infants with hypoglycemia. We compared values of 272 samples of serum glucose with values simultaneously obtained by chromogen test strips (Chemstrip bG) in newborns. The diagnostic sensitivity of a chromogen test strip less than 2.2 mmol/L for predicting a serum glucose level less than 1.9 mmol/L was 86% (95% confidence interval [CI], 75% to 94%), with 78% specificity (95% CI, 73% to 84%). The positive predictive value in our specimens, with a 21% prevalence of serum glucose levels less than 1.9 mmol/L, was 52% (95% CI, 41% to 62%), with a negative predictive value of 95% (95% CI, 91% to 100%). Fifty-eight of our serum glucose values were less than 1.9 mmol/L and the levels obtained by chromogen test strip were greater than or equal to 2.2 mmol/L in 8 of these cases. Review of these 8 cases showed that a delay in performing the laboratory glucose oxidase serum glucose could account for the discrepancy in 2 cases. Chromogen test strips are readily available and easy to use, but more sensitive, specific, accurate, and precise methods of serum glucose screening in newborns are needed.