Table 1.

Validation of initial cut-off values by CDC proficiency samples.

Analytes	Cut-off (μmol/L)	Positive samples (n)	Negative samples (n)	Analytical PPV (%)	NPV (%)	Sensitivity (%)	Accuracy (%)
Valine	<174	5	25	100	100	100	100
Leucine/Isoleucine	<281	5	25	100	100	100	100
Methionine	<70	5	25	100	100	100	100
Phenylalanine	<165	5	25	100	100	100	100
Citrulline	<49	5	25	100	100	100	100
Tyrosine	<217	5	25	100	100	100	100
Arginine	<99	5	25	100	100	100	100
C0	<57	5	25	100	96	80	96
C3	<6.0	5	25	100	100	100	100
C4	<0.95	5	25	100	100	100	100
C5	<0.56	5	25	100	100	100	100
C5DC	<0.47	5	25	100	100	100	100
C5OH	<0.5	5	25	100	100	100	100
C6	<0.13	5	25	100	100	100	100
C8	<0.14	5	25	100	100	100	100
C10	<0.17	5	25	100	100	100	100
C14	<0.6	5	25	100	100	100	100
C14:1	<0.39	5	25	100	100	100	100
C16	<9.30	5	25	100	100	100	100
C18	<2.00	5	25	83	100	100	96

For abbreviations, see footnote Table 2. PPV: positive predictive value, NPV: negative predictive value.