Correction of an unexpected increasing trend in glucose measurements during 7 years recruitment to a cohort study

To study an unexpected, significant increase in glucose measurements during 7 year recruitment to a cohort study. Measurements of quality control solutions and blood glucose in pregnant women were done by Accu-Chek Sensor glucometer. Time-trends were analysed by regression models and control charts. Cohort measurements were de-trended by weighted linear regressions based on independent control values. Biologically implausible trends in data can be corrected by using independent control values. ► Glucose values increased unexpectedly during a 7 year study. ► Data from quality controls, BMI and insulin pointed to the point-of-care glucometer. ► Blood glucose measurements were de-trended by statistical regression techniques. ► Regular quality controls and control charts should be used.