Table 3.
Accuracy of diagnostic measures and substrates for lactose malabsorption
| Measurea and substrateb | AUCc | 95% CI | p valued | Cut-offe | Sensitivity(%) | Specificity (%) |
|---|---|---|---|---|---|---|
| Breath H2 | ||||||
| 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 | 0.755a | 0.603–0.907 | 0.008 | 1.77 mmol/L | 61 | 100 |
| CON | 0.535b | 0.271–0.645 | 0.671 | NA | NA | NA |
| A2M | 0.458b | 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