Examination of Accuracy of Self-Reported Blood Glucose Using mHealth Data Collection

Introduction: Daily self-monitoring of blood glucose (SMBG) is essential for type 1 diabetes (T1D) management. Adherence to SMBG is often suboptimal during adolescence. SMBG paper diaries are often inaccurate compared to glucometer readings. The current study aimed to compare self-reported SMBG values gathered using ecological momentary assessment via smartphones to glucometer readings.

Methods: Youth (n=54, 11-21 years, 59.3% male) with T1D received 3 text messages/day for 10 consecutive days containing REDCap surveys inquiring to SMBG values. SMBG values from glucometers were obtained during the same period. Based on a previously developed system, paired values were compared and categorized as accurate or discrepant. A discrepancy was categorized as: omission (i.e., glucometer reading with no self-reported SMBG value), addition (i.e., self-reported SMBG value with no glucometer reading), alteration (i.e., self-reported SMBG value different by >10 mg/dL from glucometer value), or digit transformation (i.e., 164 instead of 146). Self-reported values were categorized further to reflect whether patients reported a more clinically favorable or unfavorable profile.

Results: A significant positive correlation was found between glucometer and self-reported SMBG values for all matched pairs (r=.628, p<.001). Out of 817 pairings, 39.3% of the self-reported values were congruent to glucometer readings and 60.7% were discrepant. Of the discrepant, 45% were alterations, 40.9% were additions, 13% were omissions, and .01% were digit transformations. Also, 54.5% of self-reported SMBG appeared clinically favorable, while 45.5% appeared clinically unfavorable.

Conclusions: These findings are consistent with previous studies comparing paper SMBG diaries to glucometers in a pediatric population. Self-reported mHealth data is likely to produce discrepant SMBG values compared to glucometers. Providers are urged to use objective blood glucose devices for clinical decisions.