The dim light melatonin onset (DLMO) is the current gold standard biomarker of the timing of the central circadian clock in humans and is often assessed from saliva samples. To date, only one commercially available salivary melatonin assay is considered accurate at the low daytime levels required to accurately detect the DLMO (Novolytix RIA RK-DSM2). The aim of this study was to conduct the first independent evaluation of a newly improved enzyme-linked immunosorbent assay (ELISA; Novolytix MLTN-96) and compare it with the recommended radioimmunoassay (RIA)—both in terms of melatonin concentrations and derived DLMOs. Twenty participants (15 females, 18–59 years old) provided saliva samples every 30 min in dim light starting 6 h before their habitual bedtime, yielding a total of 260 saliva samples. Both the RIA and ELISA yielded daytime melatonin concentrations <2 pg/mL, indicating adequate accuracy to detect the DLMO. The melatonin concentrations from the two assays were highly correlated (r = .94, p < .001), although the RIA yielded lower levels of melatonin concentration than the ELISA, on average by 0.70 pg/mL (p = .006). Seventeen DLMOs were calculated from the melatonin profiles and the DLMOs from both assays were not statistically different (p = .36) and were highly correlated (r = .97, p < .001). Two DLMOs derived from the RIA occurred more than 30 min earlier than the DLMO derived from the ELISA. These results indicate that the new Novolytix ELISA is an appropriate assay to use if the Novolytix RIA is not feasible or available.

中文翻译：

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Novolytix 唾液褪黑素放射免疫测定法与新型 Novolytix 唾液褪黑素酶联免疫吸附测定法的独立比较

弱光褪黑激素起始（DLMO）是目前人类中央生物钟计时的金标准生物标志物，通常通过唾液样本进行评估。迄今为止，只有一种市售唾液褪黑激素测定被认为在准确检测 DLMO 所需的低日间水平上是准确的（Novolytix RIA RK-DSM2）。本研究的目的是对新改进的酶联免疫吸附测定（ELISA；Novolytix MLTN-96）进行首次独立评估，并将其与推荐的放射免疫测定（RIA）进行比较——无论是在褪黑激素浓度还是衍生的 DLMO 方面。20 名参与者（15 名女性，18-59 岁）从习惯性就寝时间前 6 小时开始，在昏暗光线下每 30 分钟提供一次唾液样本，总共产生了 260 个唾液样本。RIA 和 ELISA 产生的日间褪黑激素浓度均<2 pg/mL，表明检测 DLMO 具有足够的准确性。两种测定的褪黑激素浓度高度相关 ( r  = .94，p  < .001)，尽管 RIA 产生的褪黑激素浓度水平低于 ELISA，平均低 0.70 pg/mL ( p  = .006)。根据褪黑激素谱计算了 17 个 DLMO，两次测定的 DLMO 没有统计学差异 ( p  = .36)，并且高度相关 ( r  = .97，p  < .001)。来自 RIA 的两个 DLMO 比来自 ELISA 的 DLMO 早 30 分钟以上。这些结果表明，如果 Novolytix RIA 不可行或不可用，则新的 Novolytix ELISA 是一种合适的检测方法。