Retrospective analysis of insulin responses to standard dosed oral glucose tests (OGTs) via naso-gastric tubing towards definition of an objective cut-off value

Abstract

BackgroundInsulin dysregulation (ID) with basal or postprandial hyperinsulinemia is one of the key findings in horses and ponies suffering from the equine metabolic syndrome (EMS). Assessment of ID can easily be performed in clinical settings by the use of oral glucose challenge tests. Oral glucose test (OGT) performed with 1 g/kg bodyweight (BW) glucose administered via naso-gastric tube allows the exact administration of a defined glucose dosage in a short time. However, reliable cut-off values have not been available so far. Therefore, the aim of the study was to describe variations in insulin response to OGT via naso-gastric tubing and to provide a clinical useful cut-off value for ID when using the insulin quantification performed with an equine-optimized insulin enzyme-linked immunosorbent assay.ResultsData visualization revealed no clear separation in the serum insulin concentration of insulin sensitive and insulin dysregulated horses during OGT. Therefore, a model based clustering method was used to circumvent the use of an arbitrary limit for categorization. This method considered all data-points for the classification, taking into account the individual insulin trajectory during the OGT. With this method two clusters were differentiated, one with low and one with high insulin responses during OGT. The cluster of individuals with low insulin response was consistently detected, independently of the initialization parameters of the algorithm. In this cluster the 97.5% quantile of insulin is 110 µLU/mL at 120 min. We suggest using this insulin concentration of 110 µLU/mL as a cut-off value for samples obtained at 120 min in OGT.ConclusionOGT performed with 1 g/kg BW glucose and administration via naso-gastric tubing can easily be performed under clinical settings. Application of the cut-off value of 110 µLU/mL at 120 min allows assessment of ID in horses.

ECEIM consensus statement on equine metabolic syndrome

“…As an alternative, the OGT can be performed with 1.0 g/kg BM glucose dissolved in 2 L of water and administered via nasogastric tube as long as sedation or stressful restraint are not required . The suggested cutoff value for this test protocol is 110 μIU/mL insulin at 120 minutes, using the equine optimized insulin ELISA …”

Comparison of endocrine and metabolic responses to oral glucose test and combined glucose-insulin tests in horses

“…The AUCinsulin OGT differed, whereas the AUCglucose OGT did not differ between HR and LR animals, suggesting that HR horses secrete more insulin to maintain their glucose homeostasis after the oral glucose challenge. According to recently published reference ranges for OGT procedures performed by nasogastric intubation and quantification of equine insulin with the ELISA used in the present study, insulin concentrations above 110 µIU/mL insulin at 120 minutes are indicative for ID (Warnken et al 2018). If this cut-off is supplied to the oral sugar test (OGT) data only one horse (horse 10) has slightly elevated insulin response in OGT with 114 µIU/mL.…”

“…If this cut-off is supplied to the oral sugar test (OGT) data only one horse (horse 10) has slightly elevated insulin response in OGT with 114 µIU/mL. It has been reported that insulin responses after OGT show wide variation and fluent transition from IS to ID (Warnken et al 2018). However, it remains unclear whether these clear differences between horses were normal physiological variation or already indicative of subclinical abnormalities which may predispose these four individuals to develop metabolic pathologies.…”

Neuraminidase characterisation reveals very low levels of antiviral resistance and the presence of mutations associated with reduced antibody effectiveness in the Irish influenza 2018/2019 season

“…Current Irish guidelines for the use of antivirals recommend antivirals for the treatment of uncomplicated influenza in at-risk groups i.e. those ≥65 years of age, pregnant women, residential care facilities residents, immunosuppressed individuals, individuals with chronic medical conditions and for treatment of clinically complicated influenza [ 14 ]. Targeted use of antivirals for post-exposure prophylaxis is also recommended for those in these at-risk groups.…”