. 2014 Oct 21;3(1):12–21. doi: 10.1093/gastro/gou068

Table 2.

Principal studies investigating gastric emptying of liquids and solids by breath tests using carbon ¹⁴C and ¹³C

Author (year)	Subjects/patients	Isotope	Test meal (kcal)	Main diagnostic outcomes
Ghoos et al. (1993) [55]	16 healthy subjects 20 functional dyspepsia	¹⁴C-OA in egg yolk	Solid (320 kcal)	Validation studies of OA incorporation into egg yolk Validation with scintigraphy Non-linear regression model Subtraction of 66 min from ‘real' BT T1/2 calculated by mathematical model^a Tlag and GEC (Normal GEC = 3.1)
	5 healthy individuals	¹⁴C-OA and ¹³C-OA in egg yolk	Solid (320 kcal)	Repeated studies (3 times) Inter-individual variability NS Day-to-day variability NS Coefficient variation mean 27%
	41 healthy individuals	^aC-OA in egg yolk	Solid (320 kcal)	Studies for normal range 72 ± 22SD min 83 min (75^th percentile)
Maes et al. (1994) [73, 74]	9 healthy subjects: accelerated emptying (i.v. 200 mg erythromycin); delayed emptying (i.v. 30 mg propantheline) 36 healthy subjects 20 dyspeptic patients	¹⁴C-OA and ¹³C-OA in egg yolk	Solid (250 kcal)	Validation with scintigraphy Non-linear regression model T1/2 Normal 71 ± 27SD min Accelerated 37 ± 21 min Delayed 141 ± 88 min
Braden et al. (1995) [64]	20 healthy subjects 16 functional dyspepsia	¹³C-acetate in 100 mL water	Liquid (0 kcal)	Validation with scintigraphy Normal T1/2: 78 ± 14 min Dyspepsia T1/2: 100 ± 21 min
Duan et al. (1995) [63]	6 healthy subjects 6 dyspeptic patients With or without cisapride (10 mg x 2) 12 healthy subjects (day-to-day variability)	¹³C-acetate in water ¹³C-OA in egg yolk	Liquid (0 kcal) Solid (250 kcal)	Liquid T1/2 83 ± 6SD min (control); 96 ± 21 min (dyspepsia) Solid T1/2 148 ± 35 min (control); 203 ± 41 min (dyspeptic) Cisapride T1/2 117 ± 27 min (control); 166 ± 58 min (dyspeptic) In healthy controls, T1/2 for liquids and solids were reproducible on the two different days
Choi et al. (1997) [62]	15 healthy subjects	¹³C-OA in egg yolk	Solid (240 kcal)	Validation with scintigraphy Non-linear linear regression model High intra-individual variability, dependent also on collection periods (4, 5, 6 hours, delta 43-63 min) Low intra-individual variability (on 3 different days) T1/2 median (range) 186–191 min (167–210)
Choi et al. (1998) [76]	30 healthy subjects	¹³C-OA in egg yolk	Solid (240 kcal)	Validation with scintigraphy T1/2: different between subjects but highly reproducible within subjects Normal T1/2 median 191 min (range 120–386)
Lee et al. (2000) [60]	30 healthy subjects	¹³C-S. Platensis	Solid (220 kcal) or Pre-packed biscuit	Validation with scintigraphy General linear regression model Normal T1/2 100 ± 20SD min (solid meal) T1/2 91 ± 15 min (biscuit)
Lee et al. (2000) [67]	6 healthy subjects 50 healthy subjects (additional) 22 symptomatic diabetic patients	¹³C-OA in egg yolk	Solid (420 kcal)	Validation with scintigraphy Non-linear regression model: high variability and T1/2 BT longer than T1/2 scintigraphy General linear regression models: more accurate results Normal T1/2 median 118 min (range 72–188) Diabetic gastroparesis in 3 patients (1 misclassified according to scintigraphy)
Viramontes et al. (2001) [68]	50 healthy subjects Accelerated emptying (i.v. erythromycin) Delayed emptying (i.v. atropine)	¹³C-S. Platensis	Solid (220 kcal)	Validation with scintigraphy General linear regression model T1/2 ‘Normal' range 70–150 min
Hellmig et al. (2006) [65]	90 healthy subjects	¹³C-acetate in water ¹³C-OA in egg yolk	Liquid (250 mL apple juice) Solid (310 kcal)	Liquid T1/2 81 ± 22SD min (range 43–51) Solid T1/2 144 ± 55 (median 127 min; 25–75% percentiles: 112.0–168 min) No influence of age, sex or BMI
Szarka et al. (2008) [69]	38 healthy subjects 5 healthy subjects (i.v. atropine) 124 patients (suspicion of delayed gastric emptying)	¹³C-S. Platensis	Solid (238 kcal)	Validation with scintigraphy Normal T1/2 68 ± 15SD Accelerated if <10^th percentile (52 min) Delayed if >90^th percentile (86 min)
Perri et al. (2010) [57]	131 healthy subjects 8 diabetic gastroparesis 11 untreated celiac patients	¹³C-OA	Solid (378 kcal) (EXPIROGer®) pre-packed muffin	T1/2 Normal 88 ± 29SD min Normal upper cut-off value 146 min Gastroparesis 179 ± 50 min Celiac disease 151 ± 20 min

^aProbably dependent on the observed half-time for absorption and oxidation of OA after intraduodenal instillation (i.e. 62 min).

BMI = body mass index; BT = breath test; GEC = gastric emptying coefficient; NS = not significant; OA = octanoic acid; SD = standard deviation; T1/2 = half-emptying; Tlag = calculation of lag phase time (min).