Foals are at risk for development of gastric ulcer syndrome (GUS), and while incidence ranges from 22-57%, not all affected foals are symptomatic. Gastroscopy is a definitive tool to aid in diagnosis. A study looked at the use of sucrose permeability testing as a different and relatively minimally invasive means of screening for GUS in foals [Hewetson, et al., Diagnostic accuracy of blood sucrose as a screening test for equine gastric ulcer syndrome (EGUS) in weanling foals, Acta Vet Scand (2018) 60:24].
Examination was done on 45 foals, aged approximately six months old, with both gastroscopy and sucrose permeability testing one week prior to and two weeks after weaning. The two tests were compared in their sensitivity and specificity to identify gastric lesions, glandular lesions and squamous lesions. After gastroscopy, the foals were intubated with a nasogastric tube and administered 1g/kg of sucrose as a 10-20% solution. Blood was taken at 45 and 90 minutes following sucrose administration.
Prior to weaning, 21% of foals had gastric ulcers, with 9% glandular and 7% squamous lesions. Following weaning, 98% of foals had gastric lesions with 97% squamous and 59% glandular. Severity of lesions was more pronounced after weaning.
Sensitivity of the sucrose permeability test was 85-95% for both 45- and 90-minute blood samples. With this result, the researchers state that a high sensitivity correctly identifies most foals with gastric ulcers, and if the test is negative, then it reliably rules out gastric ulcers. Those identified at risk of GUS via blood sucrose can then be scoped to determine location and severity of lesions.
Specificity was not as useful, ranging from 41-71%, with a high false positive rate. This could result in unnecessary scoping, but because many weanling foals with GUS are mostly asymptomatic, this enables clinicians to more accurately identify foals in need of treatment.
The sucrose given to fasted foals was well tolerated without any occurrence of diarrhea. Older foals have sucrase activity in the small intestine, whereas neonates do not, so this test works best after six months of age. By six months of age, foals have increased gastric permeability to sucrose due to changes in gastric mucosal epithelium.
The study concluded, “Due to its poor specificity, it is not expected that the sucrose blood test would replace gastroscopy; however, it may represent a clinically useful screening test that can be used to identify foals that may benefit from gastroscopy.”