Lactose Breath Test and Genotyping Showed Higher Concordance Than the Urine Gaxilose Test for the Diagnosis of Lactose Malabsorption in Adults.

BACKGROUND

Lactose malabsorption (LM) is a common condition that occurs when undigested lactose reaches the colon, often causing symptoms such as diarrhea, flatulence, and abdominal pain. Diagnosis can be obtained by performing several tests, each with advantages and disadvantages. This study aims to compare three of the five available methods-the genetic, the urine gaxilose, and the lactose breath tests (LBT) - to evaluate their concordance and assess patient preferences.

METHODS

This is an observational and prospective study from two Spanish hospitals, including 73 adult patients with digestive symptoms and LM suspicion. Alongside the three evaluated methods, the lactose intolerance quick test was performed on duodenal samples in a subgroup of patients. Interpretation of LM was determined based on test concordance. Patient questionnaires were completed once all the tests had been performed.

RESULTS

There were 71% of female patients, the mean age was 37.6 years, and 52% showed LM. The patients with LM more commonly displayed nausea or vomiting (p = 0.039), avoidance of dairy products (p = 0.023), and use of analgesic and/or anti-inflammatory drugs (p = 0.016). Higher concordance among tests was found in patients without LM (83%), compared to 53% in patients with LM, due to false negatives (32%) for the gaxilose test. All tests showed over 90% sensitivity, with LBT displaying the highest (97%). Genetic testing showed the highest specificity (95%) and the gaxilose test the lowest (68%). Among the three tests, 72% of patients preferred the genetic test.

CONCLUSIONS

The LBT and genetic tests showed higher concordance than gaxilose for detecting LM.