Dried blood spot (DBS) metabolite analysis is a central tool for the clinic, e.g., newborn screening. Instead of applying multiple analytical methods, a single liquid chromatography-mass spectrometry (LC–MS) method was developed for metabolites spanning from highly polar glucose to hydrophobic long-chain acylcarnitines. For liquid chromatography, a diphenyl column and a multi-linear solvent gradient operated at elevated flow rates allowed for an even-spread resolution of diverse metabolites. Injecting moderate volumes of DBS organic extracts directly, in contrast to evaporation and reconstitution, provided substantial increases in analyte recovery. Q Exactive MS settings were also tailored for sensitivity increases, and the method allowed for analyte retention time and peak area repeatabilities of 0.1–0.4 and 2–10%, respectively, for a wide polarity range of metabolites (log P −4.4 to 8.8). The method’s performance was suited for both untargeted analysis and targeted approaches evaluated in clinically relevant experiments.

The neurotoxin 3‐nitropropionic acid (3‐NPA) is an inhibitor of succinate dehydrogenase, an enzyme participating both in the citric acid cycle and the mitochondrial respiratory chain. In human intoxications, it produces symptoms such as vomiting and stomach ache in mild cases, and dystonia, coma, and sometimes death in severe cases. We report the results from a liquid chromatography‐Orbitrap mass spectrometry metabolomics study mapping the metabolic impacts of 3‐NPA intoxication in plasma, urine, and cerebrospinal fluid (CSF) samples of a Norwegian boy initially suspected to suffer from a mitochondrial disease. In addition to the identification of 3‐NPA, our findings included a large number of annotated/identified altered metabolites (80, 160, and 62 in plasma, urine, and CSF samples, respectively) belonging to different compound classes, for example, amino acids, fatty acids, and purines and pyrimidines. Our findings indicated protective mechanisms to attenuate the toxic effects of 3‐NPA (e.g., decreased oleamide), occurrence of increased oxidative stress in the patient (such as increased free fatty acids and hypoxanthine) and energy turbulence caused by the intoxication (e.g., increased succinate). To our knowledge, this is the first case of 3‐NPA intoxication reported in Norway and the first published metabolomics study of human 3‐NPA intoxication worldwide. The unexpected identification of 3‐NPA illustrates the importance for health care providers to consider intake‐related intoxications during diagnostic evaluations, treatment and follow‐up examinations for neurotoxicity and a wide range of metabolic derangements.

Dried blood spot samples are simple to prepare and transport, enabling safe and accessible diagnostics, both locally and globally. We review dried blood spot samples for clinical analysis, focusing on liquid chromatography‐mass spectrometry as a versatile measurement tool for these samples. Dried blood spot samples can provide information for, for example, metabolomics, xenobiotic analysis, and proteomics. Targeted analyses of small molecules are the main application of dried blood spot samples and liquid chromatography‐mass spectrometry, but emerging applications include untargeted metabolomics and proteomics. Applications are highly varied, including analyses related to newborn screening, diagnostics and monitoring of disease progression and treatment effects of virtually any disease, as well as studies into the physiology and effects of diet, exercise, xenobiotics, and doping. A range of dried blood spot products and methods are available, and applied liquid chromatography‐mass spectrometry instrumentation is varied with regard to liquid chromatography column formats and selectivity. In addition, novel approaches such as on‐paper sample preparation (e.g., selective trapping of analytes with paper‐immobilized antibodies) are described. We focus on research papers published in the last 5 years.