Lactose tolerance test shortened to 30 minutes: An exploratory study of its feasibility and impact

Lactose malabsorption (LM) is a very common condition with a high prevalence in our setting. Lactose tolerance test (LTT) is a basic, affordable test for diagnosis that requires no complex technology. It has been recently shown that this test can be shortened to 3 measurements (baseline, 30 min, 60 min) with no impact on final results. The purpose of our study was to assess the feasibility and benefits of LTT simplification and shortening to 30 min, as well as the financial impact entailed.

A multicenter, observational study of consecutive patients undergoing LTT for LM suspicion. Patients received 50 g of lactose following a fasting period of 12 h, and had blood collected from a vein at all 3 time points for the measurement of blood glucose (mg/dl). Differences between the shortened and complete test forms were analyzed using McNemar´s test. A comparison of blood glucose levels between patients with normal and abnormal results was performed using Student´s T-test for independent mean values. Consistency was assessed using the kappa index. A p < 0.05 was considered to be statistically significant.

A total of 270 patients (69.6 % females) were included, with a mean age of 39.9 ± 16 years. LTT was abnormal for 151 patients (55.9 %). We observed no statistically significant differences in baseline blood glucose levels between patients with normal and abnormal LTT results (p = 0.13); however, as was to be expected, such differences were obvious for the remaining time points (p < 0.01). Deleting blood glucose measurements at 60 minutes only led to overdiagnose LM (false positive results) in 6 patients (2.22 %), with a kappa index of 0.95 (95 % CI: 0.92-0.99) (p < 0.001) versus the complete test. Suppressing measurements at 60 min would have saved at least € 7,726.

The shortening of LTT to only 2 measurements (baseline and 30-min) hardly leads to any differences in final results, and would entail savings in time, materials, and personnel.