Direct analysis of sterols from dried plasma/blood spots by an atmospheric pressure thermal desorption chemical ionization mass spectrometry (APTDCI-MS) method for a rapid screening of Smith–Lemli–Opitz syndrome

摘要

Here is proposed a rapid and sensitive method involving atmospheric pressure thermal desorption chemical ionization mass spectrometry (APTDCI-MS) for specific laboratory screening of the Smith– Lemli–Opitz syndrome (SLOS), an inherited defect of cholesterol biosynthesis. Biochemical findings in the blood of SLOS patients are low cholesterol (Chol), high 7- and 8-dehydrocholesterol (DHCs) levels and high DHCs/Chol ratios. The APTDCI proposed method is able to ionize sterols for qualitative and quantitative analysis directly from dried plasma/blood spots. Critical APTDCI parameters – desolvation gas flow and temperature – were optimized analyzing Chol, 7-DHC and cholesteryl stearate standards spotted onto a glass slide acquiring the full scan spectra in positive ion mode. Chol levels in dried plasma spots of unaffected controls (n 23) obtained by the proposed method were compared with those of the enzymatic method (y 0.9166x + 0.3811; r 0.8831) while Chol and DHCs of SLOS patients (n 9) were compared with the gas chromatography flame ionization detection (GC-FID) method (y 0.8214x + 0.7388; r 0.8288). The APTDCI-MS method is also able to differentiate normal from SLOS samples directly analyzing whole blood and washed red cells spotted on paper. In conclusion, the intrinsic analytical high-throughput of APTDCI-MS method for sterol analysis could be useful to screen SLO syndrome.