Preterm Glycosuria - New Data from a Continuous Glucose Monitoring System

Careful control of glucose homeostasis is essential for infants with very low birth weight (VLBW). In clinical practice, blood and urine glucose levels are monitored; however, their correlation has not been fully investigated in VLBW infants.

To evaluate the correlation between interstitial fluid glucose concentration (ISFG), glycosuria, and urine output among VLBW infants through continuous glucose monitoring (CGM).

A prospective, single-center, open cohort study enrolled 74 VLBW infants with a mean birth weight of 1,066 g. CGM (Guardian Real-Time CGM®; Medtronic, Northridge, CA, USA) was used to measure glucose. The urine output was calculated using 4-hour intervals. Reagent strips were used for semiquantitative measurement of glycosuria.

The CGM delivered 102,334 glucose measurements. 2,684 urine samples were checked for glycosuria, of which 92.06% remained negative. Corresponding glycemia in samples without glycosuria remained normoglycemic (median 103 mg/dL; 10-90th percentile 80-144 mg/dL). The median glucose concentrations for samples in ascending glycosuria categories 1+, 2+, 3+, and 4+ were 152, 181, 214, and 222 mg/dL, respectively. A moderate correlation between ISFG and urine output was found for categories ≥1+ (rs = 0.56; 95% confidence interval 0.42-0.68; p < 0.001). The urine output was significantly lower when glycosuria was absent (p < 0.05). Polyuria was observed only in glycosuria 4+ (median urine output 9.9; interquartile range 7.4-12.2 mL/kg/h).

The renal glucose threshold in VLBW infants is between 150 and 180 mg/dL. A negative result for glycosuria is a reliable screening test to exclude hyperglycemia. Occurrence of glycosuria ≥1+ is an indication to test blood glucose.