Evaluation of breath, plasma, and urinary markers of lactose malabsorption to diagnose lactase non-persistence following lactose or milk ingestion

Table 3 Accuracy of diagnostic measures and substrates for lactose malabsorption

Measure^a and substrate^b	AUC^c	95% CI	p value^d	Cut-off^e	Sensitivity(%)	Specificity (%)
*Breath H*₂
Lactose	1.000	1	< 0.001	79 ppm	100	100
CON	0.942	0.828–1	< 0.001	21 ppm	92	100
A2M	0.994	0.981–1	< 0.001	13 ppm	92	100
*Plasma glucose*
Lactose	0.755^a	0.603–0.907	0.008	1.77 mmol/L	61	100
CON	0.535^b	0.271–0.645	0.671	NA	NA	NA
A2M	0.458^b	0.348–0.723	0.712	NA	NA	NA
*Urinary galactose/creatinine ratio*
Lactose	0.758	0.611–0.905	0.008	0.03 mg/mg	53	100
CON	0.653	0.480–0.838	0.112	NA	NA	NA
A2M	0.618	0.433–0.803	0.223	NA	NA	NA

^aMaximal increase in breath H₂ and plasma glucose over baseline for 3 h, urinary galactose/creatinine ratio at 3 h post lactose and milk challenge
^b Lactose: 50 g lactose in 250 mL water; CON and A2M: 750 mL milk
^c Values are area under the receiver operating characteristics (ROC) curve (AUC)
Different letters (a, b) represent a significant difference in the AUCs of the ROC curve between substrates calculated by ROC test
^dp value between calculated ROC AUC and AUC of 0.5 (no discrimination between true positives (TP; LNP) and true negatives (TN; LP)) was computed using the Mann-Whitney U test
^e Cut offs (calculated by the Youden Index) are presented, unless AUC > 0.7 and P value < 0.05
A2M a2 milk, CON conventional milk, CI confidence interval

ISSN: 1471-230X