Are there differences between patients with and without the homozygous--13910CC genetic variant in the MCM-6 gene upstream from the lactase gene?--A non-randomised, two armed intervention study without control group.

BACKGROUND: Patients with chronic abdominal complaints are a diagnostic challenge for general practitioners (GP). Lactose intolerance (LI) often remains undiagnosed in these patients. Genetic testing for the homozygous -13910CC variant of the MCM-6 gene (LI+) combined with a lactose-restricted diet (LRD) seems to be an acceptable approach. The primary aim of the study was to determine the effect of a LRD in patients with chronic abdominal complaints without a definite diagnosis, with or without the homozygous -13910CC variant. The secondary aim was to determine in family practices the prevalence of undiagnosed LI in these patients.

METHODS: In 25 practices around Düsseldorf (Germany) all patients presenting with chronic abdominal complaints for at least 12 months without definite diagnosis were identified by their GPs. Patients participating underwent a MCM-6 gene test and all, including those not genetically predisposed, were asked to keep a LRD for eight weeks. Symptoms were evaluated three times over two months using a standardized gastrointestinal Questionnaire (GIQLI, max. score 144).

RESULTS: 210 patients were included. The gene test revealed 29.5% genetically positive for the homozygous T-13910-C mutation (LI+). All patients showed a significant increase in GIQLI scores (improvement) during the observation period, i.e. after four and eight weeks on the diet (p = 0.001, two-way repeated measures ANOVA). There was no significant difference between both groups (LI+/LI-) at any point of symptom measurement.

CONCLUSIONS: A lactose-restricted diet showed an unspecific positive effect for patients with chronic abdominal pain without a defined diagnosis. For the LI-group, this could be explained by an unspecific effect of a diet in general, e.g., getting special attention. This can be important for a group of patients probably having psychosomatic complaints focussed on the abdomen.