Table 1.

Reference and diagnostic amino acid variables.

Disorder (no. of cases)Diagnostic mass (m/z)aRatio componentsReference concn., μmol/L2Abnormal concn., μmol/L, mean (range)
Mean (SD)Lower cutoff (0.5 pctl.)Upper cutoff (99.5 pctl.)
PKU (19)3222 /227Phenylalanine/IS71.7 (20.9)NA129(0.0000000>877 (497–1566)
TYR (2)238 /242Tyrosine/IS100 (46.1)NA275376, 331
206 /209Methionine/IS27.7 (9.52)9.0758.81026
MSUD (14)174 /182Valine/IS116 (36.1)52.8234281 (28.5–674)
188 /191(Leucine+Ile)/IS103 (32.7)43.42051058 (319–3650)
HCYS (11)206 /209Methionine/IS27.7 (9.52)9.0758.8378 (79.0–614)
NKG (2)132 /134Glycine/IS402 (111)NA7372460, 1162
ASD (9)215 /222Citrulline4 /phenylalanine0.01 (0.01)5NA0.050.65 (0.23–1.70)
232 /238Citrulline/tyrosine0.14 (0.13)5NA0.7721.1 (1.57–50.5)
ALD (6)232 /238Citrulline/tyrosine0.14 (0.13)5NA0.771.97 (1.08–3.37)
PYG/PIP (3)186 /222pyroglutamic0.21 (0.18)5NA1.221.81 (1.30–2.50)
(pipecolic)/phenylalanine
PRO (2)172 /222Proline/phenylalanine2.38 (0.79)5NA5.6222.7, 43.1