Serum Diamine Oxidase Values, Indicating Histamine Intolerance, Influence Lactose Tolerance Breath Test Results.

Lactose intolerance (LIT) is one of the major causes of irritable bowel syndrome (IBS) spectrum complaints. Differences in inadequate lactose digestion are described as various LIT phenotypes with basically unknown pathophysiology. In LIT patients, we retrospectively assessed the effect of histamine intolerance (HIT) on expiratory hydrogen (H₂) during H₂ lactose breath tests. In a retrospective evaluation of charts from 402 LIT patients, 200 patients were identified as having only LIT. The other 202 LIT patients were found to additionally have diamine oxidase (DAO) values of <10 U/mL, which indicates histamine intolerance (HIT). To identify HIT, standardized questionnaires, low serum DAO values and responses to a histamine-reduced diet were used. Patients were separated into three diagnostic groups according to the result of H₂ breath tests: (1) LIT, with an H₂ increase of >20 parts per million (ppm), but a blood glucose (BG) increase of >20 mg/dL, (2) LIT with an H₂ increase of 20 ppm in combination with a BG increase of <20 mg/dL, and (3) LIT with an exhaled H₂ increase of <20 ppm and BG increase of <20 mg/dL. Pairwise comparison with the Kruskal Wallis test was used to compare the areas under the curve (AUC) of LIT and LIT with HIT patients. Exhaled H₂ values were significantly higher in H₂ > 20 ppm and BG < 20 mg/dL patients with LIT and HIT (p = 0.007). This diagnostic group also showed a significant higher number of patients (p = 0.012) and a significant higher number of patients with gastrointestinal (GI) symptoms during H₂ breath tests (p < 0.001). Therefore, low serum DAO values, indicating HIT, influence results of lactose tolerance breath tests. [ABSTRACT FROM AUTHOR]