Simultaneous determination of cystathionine, total homocysteine, and methionine in dried blood spots by liquid chromatography/tandem mass spectrometry and its utility for the management of patients with homocystinuria

• A method for determination of 3 amino acids in dried blood spots was developed.
• Concentrations of analytes in blood are 3.8%–42.2% lower than in plasma.
• Twelve patients with homocystinurias were clearly distinguished from controls.
• Methionine/cystathionine ratio differentiates two types of homocystinurias.
• This method may facilitate management of patients with hyperhomocysteinemias.

BackgroundDisorders of homocysteine and B-vitamin metabolism represent a significant problem in clinical practice. Establishing the diagnosis requires specialized tests with demanding preanalytical requirements. To advance the detection of patients with these disorders, we developed a method for the simultaneous determination of cystathionine (Cysta), methionine (Met) and total homocysteine (tHcy) in dried blood spots (DBSs).MethodsA punch from a DBS sample was mixed with a solution of isotopically labeled internal standards, and analytes were extracted using methanol/0.1% formic acid/0.5 mol/L dithiothreitol. The extract was injected into an LC–MS/MS system operating in MRM mode.ResultsThe analytical performance of the method employing DBS is adequate for its purpose and the type of sample. Compared with Cysta, tHcy and Met plasma levels, our method exhibited a negative bias between − 3.8% and − 42.2% due to the lower concentrations of these analytes in erythrocytes. The tHcy level and the Met/Cysta ratio in DBS enabled the clear detection of 12 patients with disorders of transsulfuration and with genetic and nutritional remethylation defects.ConclusionsThe ease of collecting and transporting DBS samples may advance diagnostic procedures in patients with neuropsychiatric disorders and thromboembolism. Consequently, this approach may facilitate detection and simplify the monitoring of patients with homocystinuria.