Table 1.
Metabolite descriptive information and results from proficiency test specimens distributed in 2019.
| Metabolite (Abbreviation) | Specimen Identifier | Expected Value | CDC PT | Raw PT | Harmonized PT | Number of Labs | Number of Methods |
|---|---|---|---|---|---|---|---|
| Arginine (Arg) | 11,954 | 130.2 | 125.4 | 103.9 [65.5–120] | 119.32 [96.38–133.95] | 21 | 3 |
| Free Carnitine (C0) | 41,964 | 32.52 | 30.43 | 26.92 [19.3–36.15] | 33.47 [19.69–50.19] | 30 | 5 |
| Acetylcarnitine (C2) | 41,964 | 17.15 | 15.42 | 14.54 [11.1–19.58] | 16.51 [14.3–17.91] | 8 | 4 |
| Propionylcarnitine (C3) | 31,964 | 11.04 | 10.84 | 9.49 [7.9–15.01] | 11.41 [8.38–19.03] | 30 | 5 |
| Malonylcarnitine (C3DC) | 31,965 | 25.03 | 21.82 | 24.48 [7.02–41.78] | 26.8 [23.1–32.55] | 6 | 2 |
| Butyrylcarnitine (C4) | 31,965 | 3.04 | 2.55 | 2.56 [2.21–4.09] | 2.91 [2.21–3.37] | 25 | 5 |
| Hydroxybutyrylcarnitine (C4OH) | 41,961 | 3.04 | 2.68 | 2.27 [1.65–3.63] | 2.96 [2.41–3.9] | 6 | 2 |
| Isovalerylcarnitine (C5) | 41,965 | 1.55 | 1.59 | 1.4 [1.06–2.48] | 1.68 [1.44–1.99] | 30 | 5 |
| Tiglylcarnitine (C5:1) | 31,965 | 0.76 | 0.62 | 0.48 [0.34–0.8] | 0.68 [0.52–1] | 24 | 5 |
| Hydroxyisovalerylcarnitine (C5OH) | 41,964 | 1.91 | 1.71 | 1.41 [1.1–2.22] | 1.89 [1.37–2.29] | 29 | 5 |
| Glutarylcarnitine (C5DC) | 31,962 | 1.82 | 2.10 | 1.89 [0.51–2.4] | 2.26 [1.73–3.13] | 29 | 5 |
| Hexanoylcarnitine (C6) | 31,963 | 2.71 | 2.28 | 2.35 [1.99–2.73] | 2.62 [2.09–4.37] | 27 | 5 |
| Octanoylcarnitine (C8) | 11,962 | 0.68 | 0.69 | 0.8 [0.64–1.09] | 0.78 [0.64–0.95] | 27 | 4 |
| Decanoylcarnitine (C10) | 31,963 | 1.95 | 1.80 | 1.78 [1.49–2.9] | 1.97 [1.63–2.72] | 26 | 5 |
| Myristoylcarnitine (C14) | 41,962 | 1.59 | 1.42 | 1.55 [1.17–2.08] | 1.65 [1.42–1.96] | 26 | 5 |
| Tetradecenoylcarnitine (C14:1) | 41,962 | 1.75 | 1.29 | 1.27 [0.93–1.95] | 1.45 [1.16–1.72] | 26 | 5 |
| Palmitoylcarnitine (C16) | 31,965 | 15.52 | 11.44 | 12.12 [10.43–14.34] | 12.62 [10.58–15.68] | 27 | 5 |
| Hydroxypalmitoylcarnitine (C16OH) | 41,963 | 1.01 | 0.81 | 0.69 [0.52–1.08] | 1.01 [0.77–1.24] | 29 | 5 |
| Stearoylcarnitine (C18) | 11,965 | 3.77 | 4.22 | 3.36 [2.8–3.74] | 3.42 [3.12–3.77] | 23 | 4 |
| Hydroxystearoylcarnitine (C18OH) | 41,963 | 0.80 | 0.44 | 0.55 [0.47–0.74] | 0.57 [0.43–0.72] | 21 | 5 |
| Citrulline (Cit) | 11,951 | 181.3 | 190.3 | 180.7 [117.4–214] | 187.1 [130.9–254.3] | 27 | 4 |
| Leucine (Leu) | 41,951 | 450.0 | 521.3 | 498.8 [338.9–621.1] | 496.4 [436–571] | 30 | 5 |
| Methionine (Met) | 41,955 | 185.0 | 140.6 | 149.2 [116–188] | 176.4 [129.43–215.83] | 30 | 5 |
| Phenylalanine (Phe) | 11,952 | 311.4 | 296 | 295.9 [32–1685.4] | 338.42 [23.8–1743.5] | 268 | 16 |
| Succinylacetone (SUAC) | 41,953 | 50.0 | 28.2 | 17.6 [10.1–53.4] | 26.6 [12.5–49.9] | 26 | 4 |
| Tyrosine (Tyr) | 41,953 | 900.0 | 930.8 | 859.6 [558.3–1228] | 894.3 [749.7–1046.4] | 27 | 5 |
| Valine (Val) | 41,951 | 450.0 | 473.8 | 492.7 [266.9–639.3] | 463.6 [369.8–540.4] | 20 | 5 |
Amino acid and acylcarnitine metabolites and the corresponding specimen identifier used in this study are presented from the 2019 proficiency test (PT). Each metabolite’s expected value and CDC PT value are presented in µM units. The CDC PT values reported in 2019 were from our derivatized method. Raw and harmonized PT values are presented in µM units in the format of mean (minimum–maximum). All data are from US public health newborn screening (NBS) laboratories, except phenylalanine data which also includes US non-public health and international NBS laboratories.