Comparative analysis of hydrogen breath test devices for the diagnosis of carbohydrate malabsorption: fructose tests...

Hydrogen breath tests are commonly used to diagnose lactose and fructose malabsorption. While lactose breath tests are reliable, the utility of fructose tests is debated due to inconsistent results. This study aimed to compare the performance of two hydrogen breath test devices - handheld and stationary - in diagnosing lactose and fructose malabsorption in paediatric patients.

Seventy-eight lactose and 53 fructose breath tests were performed in children (mean age: 11.4 ± 3.1 years) using both a handheld electrochemical detector and a stationary gas chromatograph. Malabsorption was defined as a rise in hydrogen ≥20 ppm over baseline. Device performance was compared using Pearson correlation, McNemar's test, and Bland-Altman analysis.

For lactose, 28 (35.9%) tested positive with the handheld device and 31 (39.7%) with the stationary device, showing 93.6% agreement ( P  = 0.38). For fructose, 16 (30.2%) tested positive with the handheld device and 26 (49.1%) with the stationary device, with only 81.1% agreement ( P  = 0.002). McNemar's test for marginal homogeneity suggested equivalence of the two instruments for the lactose breath tests ( P  = 0.38), but there was strong evidence of inequality between the two instruments for the fructose breath tests ( P  = 0.002). Bland-Altman analysis showed a bias toward higher hydrogen levels with the stationary device, especially in fructose tests.

Lactose breath tests were reliable across both devices, but significant discrepancies in fructose testing, particularly higher hydrogen levels with the stationary device, raise concerns about the diagnostic reliability of fructose tests. These findings suggest the need for caution when using fructose breath tests in clinical practice.