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

Table 4 Performance of diagnostic measures of lactose malabsorption for detection of lactase non-persistence

Measure^a and substrate^b	Cut-off used^c	Sensitivity (%)	Specificity (%)	FP (n)	FN (n)	TP (n)	TN (n)	PPV (%)	NPV (%)	κ index^d
*Breath H2*
Lactose	20 ppm	100.0	96.2	1	0	14	25	93.3	100	0.9***
CON - unadjusted	20 ppm	92.9	100.0	0	1	13	26	100	96.3	0.9**
CON - adjusted	15 ppm	92.9	96.2	1	1	13	25	82.9	96.2	0.9***
A2M - unadjusted	20 ppm	78.6	100.0	0	3	11	26	100	89.6	0.8***
A2M - adjusted	15 ppm	85.7	100.0	0	2	12	26	100	89.7	0.8***
*Plasma glucose*
Lactose	1.11 mmol/L	64.3	69.2	8	5	9	18	52.9	78.2	0.3*
CON - unadjusted	1.11 mmol/L	92.9	26.9	19	1	13	7	40.6	87.5	0.2
CON - adjusted	0.83 mmol/L	78.6	57.7	15	3	11	11	42.4	78.6	0.2
A2M - unadjusted	1.11 mmol/L	64.3	38.5	16	5	9	10	36	66.7	0.02
A2M - adjusted	0.83 mmol/L	57.1	46.2	14	6	8	12	36.4	77.8	0.02.
*Urinary galactose/creatinine ratio*^e
Lactose	0.10 mg/mg	100.0	NA	26	0	14	0	35	NA	0
CON- unadjusted	0.10 mg/mg	100.0	NA	26	0	14	0	35	NA	0
CON - adjusted	0.08 mg/mg	100.0	NA	26	0	14	0	35	NA	0
A2M- unadjusted	0.10 mg/mg	100.0	NA	26	0	14	0	35	NA	0
A2M- adjusted	0.08 mg/mg	100.0	NA	26	0	14	0	35	NA	0

Classification was based on the genotype reference standard for lactase non-persistence (LNP; n = 14) relative to lactase persistent (LP; n = 26)
^a Breath H₂, plasma glucose indicates maximal increase in breath H₂ and plasma glucose over baseline for 3 h post lactose and milk ingestion and urinary galactose/creatinine ratio at 3 h post lactose and milk ingestion
^b Lactose: 50 g lactose in 250 mL water; CON and A2M: 750 mL of milk
^cCut-off values for lactose and unadjusted (CON and A2M) were based on ingestion of 50 g lactose. Adjusted cut-off values were calculated based on ingestion of 750 mL of milk ~ 37.5 g of lactose
^dκ represents the Cohen’s kappa index indicating the agreement between lactose malabsorption and genotype
Significance indicated as * p value < 0.05, ** p value < 0.01, *** p value < 0.001
^e Galactose/creatinine ratio concentration range was lower than the threshold of 0.10 mg/mg; no lactose malabsorption was detected by the method using the literature threshold of 0.10 mg/mg [28] for both CON and A2M
A2M a2 milk, CON conventional milk, FN false negative, FP false positive, NPV negative predictive value, PPV positive predictive value, TN true negative, TP true positive. FN and FP represent the total number of false negativeand false positive, respectively out of total (N = 40) participants

ISSN: 1471-230X