Analytical validation of a portable human Accu-Chek glucometer in honeybee hemolymph

Abstract

Glucose and trehalose are the main energy sources used by honeybees ( Apis mellifera) for daily activities. However, there is no validated point-of-care method to reliably measure both sugars. We performed an analytical validation of a portable human glucometer (Accu-Chek; Roche) for glucose measurement in honeybee hemolymph compared to a reference method (GluCH, UniCel DxC 600; Beckman Coulter). We used 30 pooled hemolymph samples collected from the antennae of anesthetized honeybees and diluted 1:4 in 0.9% saline. We evaluated dilution linearity, spike recovery, and inter- and intra-assay imprecision. Glucose concentration was measured over time (2 h, 4 h, 8 h, 12 h, 1 d, 2 d, 3 d, 7 d, 21 d, 28 d) at various storage temperature (25°C, 4°C, −20°C, −80°C). The trehalose concentration was measured indirectly by trehalase hydrolyzation. Glucose concentrations measured by both instruments had a strong correlation (0.985, p < 0.0001) and a bias of −7.33 mmol/L (±1.96SD: 13.70 to −28.36), with linear agreement at <20 mmol/L (physiologic value: 100 mmol/L). The accuracy of the glucometer decreased at >20 mmol/L. Recovery of 115–130% of diluted spikes indicated good specificity. Inter- and intra-assay imprecision were 2.50% and 2.21%, respectively. Glucose concentrations fluctuated in stored samples dependent on time and temperature; however, glucose concentrations were constant with storage at −80°C for ≥28 d. The Accu-Chek glucometer is an adequate instrument to measure honeybee glucose concentration in hemolymph diluted with 0.9% NaCl, with good accuracy and precision at <20 mmol/L. Hemolymph storage at −80°C is suitable for long-term conservation of glucose.

Effects of Varroa destructor on Hemolymph Sugars and Secondary Infections in Honeybees (Apis mellifera)

“…Sugar concentrations in hemolymph were assessed at three time points (on 19 June, 2 August, and 18 September 2019), where 10 µL of pooled hemolymph was mixed with saline solution (0.9% NaCl) (1:4 dilution). The glucose concentration in hemolymph was measured five times with a human Accu-Chek glucometer, previously validated for honeybee hemolymph [31]. Trehalose concentrations were indirectly measured five times by the glucometer following trehalase hydrolyzation, which consisted of adding commercial trehalase (Millipore Sigma, T8778, Burlington, MA, USA) to samples, followed by 3 h incubation at 30 • C [31].…”

“…The glucose concentration in hemolymph was measured five times with a human Accu-Chek glucometer, previously validated for honeybee hemolymph [31]. Trehalose concentrations were indirectly measured five times by the glucometer following trehalase hydrolyzation, which consisted of adding commercial trehalase (Millipore Sigma, T8778, Burlington, MA, USA) to samples, followed by 3 h incubation at 30 • C [31].…”

Special section on honey bee health and disease

“…Most of the usual laboratory techniques (e.g., PCR, bacterial culture, histopathology) can be adapted for honey bees, although some require adjustments specific to this species. 5,6,11 The scientific and general population have expressed concerns about human, livestock, and pollinator exposure to potentially harmful pesticides, especially neonicotinoids. 3,8 For this reason, much research has aimed at detecting residues and studying their effects in different species, 2,3,8 and the use of several pesticides has been prohibited in various countries over the last decade, particularly in the European Union.…”

“…Most of the usual laboratory techniques (e.g., PCR, bacterial culture, histopathology) can be adapted for honey bees, although some require adjustments specific to this species. 5 , 6 , 11 …”