Table 2. Stepwise multiple regression for L-[1-¹³C]phenylalanine breath test indices as dependent variables.

Dependant variable	Predictor variablea	β	Adjusted r2	P
Cmax	Body weight (kg)	−0.458	0.273	0.002
	Diagnostic statusb	−0.281		0.047
AUC	Body weight (kg)	−0.503	0.396	<0.001
	Age (year)	0.295		0.023
	Diagnostic status	−0.261		0.044
CRR0−120	Body weight (kg)	−0.318	0.282	0.025
	Age (year)	0.346		0.015
	Diagnostic status	−0.304		0.032

Abbreviations: AUC, area under the Δ¹³CO₂-time curve; C_max, the maximal Δ¹³CO₂ (‰); CRR₀₋₁₂₀, the cumulative recovery rate during the 120 min test.

^aPossible predictor variables included diagnostic status, sex, age and body weight.

^bDiagnostic status was measured on a nominal scale: 1=healthy control; 2=schizophrenia.