While earlier studies have attempted to resolve the challenges encountered when interpreting gamma-hydroxybutyric acid (GHB) concentrations in hair (primarily due to its endogenous presence), few have had large sample sizes. The first objective of this study was to evaluate the inter-individual variation of endogenous GHB concentrations. The second objective, to be detailed in another report, was to assess intra-individual variation and the impact on exogenous GHB discrimination. Over 2,000 hair segments from 141 women and 73 men (all processed hair 3–12 cm long) were analyzed in this study. The raw calculated range of endogenous GHB concentrations was <0.40–5.47 ng/mg with 97.5% of the segmental results calculated less than 2.00 ng/mg. Imputation, assuming a lognormal distribution, was applied to the data to include non-detect (ND) data (<LOQ), which led to an estimated endogenous GHB range of 0.16–5.47 ng/mg. Kruskal–Wallis tests were employed on a segmental basis for group comparisons. This test was applied to the male and female segmental medians and subsequently indicated that these groups were different at the α = 0.05 level of significance. Additionally, female hair samples appeared to have a trend comprising higher endogenous GHB concentrations close to the scalp and a mean net decrease of ~0.2–0.3 ng/mg distally. Male hair samples displayed the opposite trend, with a mean net increase of ~0.5–0.6 ng/mg from the proximal to the distal end of the hair shaft. It was also concluded that differences exist between the median GHB concentrations of the ‘treated’ and ‘untreated’ hair in the female group at the α = 0.05 level of significance. Age groups and races were analyzed, but none of the observed differences in median concentration were significant at α = 0.05. This is the largest endogenous GHB hair population study to date and provides substantial new data on inter-individual variation and chronological trends of GHB concentrations in hair.

中文翻译：

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分段头发中的内源性GHB第一部分：组间个体差异。

尽管较早的研究试图解决解释头发中的γ-羟基丁酸（GHB）浓度时遇到的挑战（主要是由于其内源性存在），但很少有大样本量。这项研究的第一个目标是评估内源性GHB浓度的个体差异。第二个目标（将在另一份报告中详细介绍）是评估个体内部差异及其对外源性GHB歧视的影响。在这项研究中，分析了来自141名女性和73名男性（全部处理过的3–12 cm长）的2,000多个发束。内源性GHB浓度的原始计算范围为<0.40–5.47 ng / mg，其中97.5％的分割结果计算得出的值小于2.00 ng / mg。假设对数正态分布，将插补应用于数据以包括非检测（ND）数据（< LOQ），这导致估计的内源性GHB范围为0.16-5.47 ng / mg。群体比较采用Kruskal–Wallis检验进行分段。该测试应用于男性和女性分段中位数，随后表明这些组在α= 0.05的显着性水平上有所不同。此外，女性头发样本的趋势似乎包括靠近头皮的内源性GHB浓度更高，远端平均净减少〜0.2-0.3 ng / mg。男性头发样本显示相反的趋势，从发干的近端到远端平均净增加〜0.5–0.6 ng / mg。还得出结论，女性组中“处理过的”和“未处理过的”头发的中值GHB浓度之间存在差异，其显着性水平为α= 0.05。对年龄段和种族进行了分析，但在α= 0.05时，观察到的中位浓度差异均无显着性。这是迄今为止最大的内源性GHB头发种群研究，它提供了有关头发中GHB浓度的个体差异和时间趋势的大量新数据。