title: Urinary concentrations of gamma-hydroxybutyric acid and related compounds in pregnancy.
abstract: Endogenous production complicates the interpretation when gamma-hydroxybutyric acid (GHB) is measured in urine for forensic purposes. We performed a cross-sectional study to test the hypothesis that pregnant women have higher levels of urinary GHB than non-pregnant controls, and thus increased risk of false-positive GHB tests. GHB, gamma-butyrolactone (GBL) and beta-hydroxybutyric acid (BHB) concentrations in urine from 66 pregnant women and 69 non-pregnant controls were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS-MS). The mean GHB, GBL, and BHB concentrations were 0.36, 0.34 and 1.92 mg/L in the pregnant women, and 0.24, 0.08 and 0.40 mg/L in the control group. The pregnant women had significantly higher levels of GHB (1.5-fold), GBL (4.3-fold), and BHB (4.8-fold). Creatinine-adjusted GHB concentrations were similar in both groups. Pregnant women have higher urinary levels of GHB, GBL, and BHB. In LC-MS-MS assays not distinguishing between GHB and BHB, there is a significantly increased risk of false-positive GHB tests in pregnant women. This false-positive rate can be reduced by correcting for creatinine concentration, by using GHB-specific assays or by introducing higher interpretative cut-off levels for pregnant women in assays that do not discriminate between GHB and GBL or BHB.
authors.affiliation: Department of Clinical Pharmacology, University Hospital of North Norway Trust, NO-903B Tromsø, Norway.
authors.forename: Guttorm
authors.initials: G
authors.lastname: Raknes
authors.forename: Lena
authors.initials: L
authors.lastname: Aronsen
authors.forename: Ole Martin
authors.initials: OM
authors.lastname: Fuskevåg
mesh_terms: D020155:3-Hydroxybutyric Acid / Q000652:urine*; D015107:4-Butyrolactone / Q000652:urine*; D002853:Chromatography, Liquid; D003430:Cross-Sectional Studies; D005189:False Positive Reactions; D005260:Female; D053593:Forensic Toxicology; D006801:Humans; D006885:Hydroxybutyrates / Q000652:urine*; D011247:Pregnancy / Q000652:urine*; D012016:Reference Values; D015203:Reproducibility of Results; D053719:Tandem Mass Spectrometry
chemical_list: D006885:Hydroxybutyrates; C111420:4-hydroxybutyric acid; D015107:4-Butyrolactone; D020155:3-Hydroxybutyric Acid