Stability of reacted Chemstrip bG

Reacted Chemstrip bG glucose reagent strips have been reported to retain their color changes for up to 7 days. Thus, patients could theoretically measure their blood glucose and mail their reacted test strips to their physicians for reanalysis. To test the stability of reacted Chemstrip bG blood glucose measurements, 268 Chemstrip bG test strips were reacted with blood obtained from 67 insulin-dependent diabetic patients, stored in desiccator vials, and read daily for 5 consecutive days with an Accu-Chek II blood glucose meter. Although Chemstrip bG blood glucose values significantly correlated with initial reference Beckman glucose analyzer glucose determinations for all 5 days, a steady significant decay in blood glucose readings over time was observed, and clinically accurate strip readings declined from 94% to 68%. Because this decay appeared consistent, correction factors were calculated with regression analyses. The correction factor for day 5 Accu-Chek II readings reduced measurement error by 77%. When applied to a different validation sample, this correction factor decreased day 5 error by 73%. Hence, it seems that correction factors may be applied to delayed readings of Chemstrips obtained with Accu-Chek II that would correct for the observed reduction in blood glucose readings. From these results, we conclude that delayed readings of Chemstrip bG test strips with the Accu-Chek II are not sufficiently accurate for clinical decision making or research purposes unless mathematically corrected.