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

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

Measurea and substrateb Cut-off usedc Sensitivity (%) Specificity (%) FP (n) FN (n) TP (n) TN (n) PPV (%) NPV (%) κ indexd
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 ratioe
 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
  1. Classification was based on the genotype reference standard for lactase non-persistence (LNP; n = 14) relative to lactase persistent (LP; n = 26)
  2. 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
  3. b Lactose: 50 g lactose in 250 mL water; CON and A2M: 750 mL of milk
  4. 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
  5. dκ represents the Cohen’s kappa index indicating the agreement between lactose malabsorption and genotype
  6. Significance indicated as * p value < 0.05, ** p value < 0.01, *** p value < 0.001
  7. 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
  8. 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