Concordance of genetic and breath tests for lactose intolerance in a tertiary referral centre.
OBJECTIVE
Lactase non-persistence causes gastrointestinal symptoms after milk ingestion. Hydrogen breath test (BTH) and genotyping of a single nucleotide polymorphism (SNP) C >T 13,910 base pairs upstream of the lactase gene represent potential methods for diagnosis of this autosomal-recessive trait. The aim of the study was to compare the results of both tests in detecting lactose non-persistence in a tertiary referral centre.


METHODS
A group of 58 patients admitted to a German university hospital for symptoms suggesting lactose intolerance.


METHODS
BTH after lactose ingestion (50 g) and SNP -13,910C>T genotyping using single nucleotide primer extension (SNaPshot) technology (CC genotype--lactase non-persistence; TC/TT genotypes--lactase persistence).


RESULTS
Overall, 17 (29%) patients had a positive and 41 (71%) had a negative BTH result; 15 (26%) patients were CC-positive and 43 (74%) were CC-negative [28 (48%) TC; 15 (26%) TT]. The genotype frequencies did not deviate from the Hardy-Weinberg equilibrium. In the CC-positive group, concordance between both tests was 100%. In contrast, in the CC-negative group concordance was 95%, and positive BTH results could be attributed to other gastrointestinal pathologies in two patients. BTH had 100% negative predictive value, 88% positive predictive value, 100% sensitivity and 95% specificity, as compared to genetic testing.


CONCLUSIONS
In carriers of the CC-genotype, BTH and genotyping correlate perfectly, and the genetic test provides an unambiguous result. In BTH-positive individuals with a negative genetic test there is good reason to suspect secondary causes of lactase deficiency.
Krawczyk
Marcin
M
Medical University of Lublin, Poland.
Wolska
Malgorzata
M
Schwartz
Stephanie
S
Gruenhage
Frank
F
Terjung
Birgit
B
Portincasa
Piero
P
Sauerbruch
Tilman
T
Lammert
Frank
F
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000388:Air / Q000032:analysis; D001944:Breath Tests / Q000379:methods; D004247:DNA / Q000235:genetics*; D005260:Female; D005787:Gene Frequency; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006801:Humans; D006859:Hydrogen / Q000032:analysis*; D043322:Lactase / Q000235:genetics* / Q000378:metabolism; D007787:Lactose Intolerance / Q000175:diagnosis* / Q000235:genetics / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D011446:Prospective Studies
D006859:Hydrogen; D004247:DNA; D043322:Lactase