Time Course of H2 Production Following Oral Lactose Load in Childrenwith and without Lactose Intolerance

Aims: To evaluate whether orocoecal transit time (OCTT) might improve the correct allocation (lactose absorb- ers vs malabsorbers) of subjects with "borderline" H2 Breath test (H2BT) values ranging 10-20 ppm, and to determine among malabsorbers if OCTT can aid to discern lactose intolerant from tolerant individuals. Patients and Methods: OCTT and increment of H2 levels in breath following a dose of lactose were assessed in 49 chil- dren (mean age 3.3 years; range 0.6-11.0) suspected of lactose malabsorption. A rise > 20 ppm was used as the criterion to separate malabsorbers from absorbers. Results: OCTT averaged 177 ± 40 minutes (mean ± SD) in 14 H2 producing lactose absorbers and 78 ± 39 minutes in 22 lactose malabsorbers (p 75 minutes and no lactose tolerant subject had an OCTT < 75 minutes (sensitivity and specificity 100%; PPV and NPV 100%). Values between 105 and 175 minutes represented a gray area including both absorbers (21%) and all tolerant malabsorb- ers (100%). OCTT longer than 175 minutes excluded lactose malabsorption (sensitivity 100%; specificity 69%; PPV 84%; NPV 100%). In 6 out of 8 cases with borderline H2BT results, OCTT clear cut values were useful to reach the cor- rect diagnostic allocation. Conclusions: OCTT evaluation in addition to considering only H2 concentration is a methodological improvement of H2BT procedure. Although it does not represent an absolute gold standard, OCTT testing may aid in reaching a diagnostic conclusion in some patients where clinical and laboratory features after lactose ingestion remains unclear.