Hydrogen breath tests in the diagnosis of primary lactase deficiency

: The H2 breath test as an indirect method of detecting lactase deficiency was evaluated in 55 patients referred because of abdominal complaints. The patients underwent both jejunal biopsy with determination of enzyme activities and the H2 breath test. 19 patients had lactase deficiency defined as a lactase/sucrase ratio less than 0.33. A rise in breath H2 of more than 20 ppm above base-line at two hours following 50 g lactose given orally was used as the cut off point indirectly suggesting lactase deficiency. The specificity of the H2 breath test in detecting lactase deficiency was 89%. The sensitivity was 74%.