Biological variation of capillary blood glucose: A systematic review

Biological variation (BV) refers to changes in biochemical constituents in the blood or other biological fluids, indicative of body regulation via homeostatic processes. Intra- and interindividual BV data are essential for establishing analytical performance specifications and evaluating the significance between consecutive measurements of an analyte. Given this context, the present study conducted a systematic review of the intra- and interindividual BV of capillary blood glucose. Out of 461 initial studies identified, only 4 met the inclusion criteria for detailed analysis after excluding 419 for title irrelevance, 10 for duplication, 21 based on abstract content and 7 based on article content. Notably, none of the studies primarily focused on the intra- and interindividual BV of capillary blood glucose; rather, they reported it as a secondary outcome. Regarding fasting, data analyses revealed intra-individual BVs of 4.5 and 31.1% for healthy and diabetic individuals, respectively, and interindividual coefficient of variations of 4.7-5.8 and 12.9-16.3% for healthy and diabetic individuals, respectively. Only one study provided the analytical coefficient of variation, corroborating the recommended practices. Additionally, the fasting duration, meal standardization before sampling, and number and interval between collections varied among the studies. Hence, the results suggest that there are no reliable data on intra- and interindividual BVs for capillary blood glucose in the literature.