Diagnóstico de Intolerancia a la Lactosa en Adultos: Rendimiento Comparativo de la Clínica, Test Espiratorio y Test Genético

Resumen

COMPARATIVE PERFORMANCE OF SYMPTOMS QUESTIONNAIRE, HYDROGEN TEST AND GENETIC TEST FOR LACTOSE INTOLERANCE

Background: Genetically programmed adult-type hypolactasia affects 56% of Chilean population. Ideally, diagnosis should be confirmed. Aim: To compare diagnostic yield of genetic test, hydrogen (H₂) expiratory test and a validated symptomatic structured survey (SS). Material and methods: Patients submitted to H₂ test answered a historic (anamnestic) and current SS (after the ingestion of 25 g of lactose). A blood sample was obtained for determination of genetic polymorphisms C/T_13910, C/G_13907 and G/A_22018 by polymerase chain reaction. The gold standard for diagnosis of lactose intolerance was the agreement of at least two of three tests. Results: Sixty-one participants aged 39 ± 12 years (21 males), were studied. Anamnestic SS was diagnostic of LI in all cases (score ?7), while current SS detected LI in 27/61(46%). H₂ test (an increase ? 15 ppm after ingestion of 25 g of lactose ) showed LI in 31/61 (51%). The locus C/G_13907 showed no polymorphism and locus G/A_22018 was in complete linkage disequilibrium with C/T_13910. Genotype C/C_13910, associated to hypolactasia, was present in 30/58(52%). According to the gold-standard, 32/61(52.5%) patients were diagnosed as LI. Sensitivity and specificity were, respectively, 79% and 69% for current SS, 93% and 93% for H2 test  and 97% and 93% for the genetic test. The last two showed a positive  likelihood ratio (LR) > 10 and a negative LR < 0.1, figures within the range considered clinically useful. Conclusions: Genotype C/C_13910 is responsible for hypolactasia in this population. Anamnestic report of symptoms after milk ingestion and symptoms after lactose ingestion, are not accurate enough. H₂ and genetic tests are simple and similarly accurate to diagnose lactose intolerance in adults.