Mass spectrometry (MS) is now an essential technology for laboratory medicine. The most successful application of MS in laboratory medicine is the rapid identification of microorganisms using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) MS. However, the adoption of MS-based assays for routine testing in clinical chemistry is very slow in Japan. In this review, we summarize the current status of clinical mass spectrometry in the US, Europe, and Japan, and discuss the possible reasons why Japan is behind in this regard.

Liquid chromatography-tandem mass spectrometry (LC/MS/MS) is a highly accurate and reproducible analytical technique, but a number of challenges and pitfalls remain for routine use in clinical laboratories, such as the effects of various pre-analytical factors. Indeed, we observed a significant noise peak during routine measurements of vitamin D metabolites, most likely due to a separating gel in blood collection tubes used for particular specimens sent by another hospital. Ion suppression due to matrix effects and problems associated with stable isotope labeled internal standards should also be considered.

MS assays are typically laboratory developed tests at present. As LC/MS/MS procedures become more automated and more MS-related in vitro diagnostics become commercially available, the application of LC/MS/MS to laboratory medicine will be significantly accelerated.

Metabolomics is an essential tool for not only understanding the pathophysiology of various diseases but also for searching for initial clues to unknown toxic effects of drugs. Mass spectrometry-based metabolomics has achieved highly sensitive and selective analysis of metabolites, and gas chromatography mass spectrometry remains a gold standard because of its robustness and usability. However, it is tedious to annotate metabolites with electron ionization (EI)-based mass spectra; thus, gas chromatography tandem mass spectrometry (GC/MS/MS)-based metabolome analysis has played an important role in metabolomics. In particular, the selected reaction monitoring (SRM) mode achieves higher selectivity and an improved signal-to-noise ratio, which leads to easier metabolite identification. In this mini review, we concisely outline the pros and cons of GC/MS/MS-based metabolome analysis and provide its applications to pathophysiological analysis of disease and drug-induced toxicity in animal models based on our previous studies. Finally, future perspectives for newly developed high-throughput metabolome analysis are briefly described.

Application of liquid chromatography tandem mass spectrometry (LC-MS/MS) in clinical chemistry has been increasing worldwide, especially in large institution and reference laboratories. Although immunoassays are often used for measurement of serum estradiol (E2) when fast turnaround time is required, more sensitive and specific measurements are needed for determination of menopausal status, estrogen deficiency and in the diagnosis of sex hormone related disorders. Furthermore, simultaneous measurement of estrone (E1) and E2 is often requested particularly from gynecologic oncologists. Indeed, increased risk of endometrial cancers has been shown in subjects with high serum estrogen levels. The aim of this study is to develop and validate LC-MS/MS method for simultaneous measurement of E1 and E2 in human serum. Serum samples were first prepared in a 96-well supported liquid extraction plate and the eluate was derivatized by the dansyl chloride acetone solution. The derivatized samples were subjected to LC-MS/MS, and detected by selected reaction monitoring. The lower limits of quantification for E1 and E2 were 6.2 and 7.3 pg/mL, respectively. The 60 female sera values obtained by the LC-MS/MS method were compared with those obtained by two commercially available immunoassays. The both of values obtained by the two immunoassays exhibited positive bias particularly at low E2 levels. Various preanalytical factors, such as long sample sitting prior to serum separation, repeated freeze–thaw cycles, and the presence of anticoagulants, had no significant effects on these determinations. This method will aid further understanding of low-abundance estrogen, as well as the accurate determination of E1 and E2.

In this study, a new quantification method was developed for analysis of ethanol in whole blood samples by needle extraction (NeedlEx^®) and gas chromatography/mass spectrometry (GC/MS). Whole blood samples (0.1 mL) containing ethanol and ethanol-d₆ (internal standard) were incubated at room temperature in a 10-mL headspace vial. The NeedlEx^® for alcohols with a gas aspirating pump was exposed to the headspace of vial to allow adsorption alcohols before GC/MS. The GC separation of the compounds was achieved on a fused-silica capillary column Rtx-5 ms (30 m × 0.25 mm i.d.; 0.25-μm film thickness) with MS detection operated in electron impact ionization ion source mode. The regression equations showed good linearity (r>0.998) from 0.1 to 5.0 mg/mL for whole blood. The accuracies and precisions were 99.0–112% and 3.0–7.0%, respectively. The method was successfully applied to actual analyses of autopsy samples. The present results on the analysis of ethanol by NeedlEx^®-GC/MS suggest its applicability to a number of other volatile compounds in clinical and forensic toxicology.

Lipids and lipoqualities are important for skin barrier function. In previous reports, repeated irritation by sodium lauryl sulfate (SLS) was found to reduce epidermal barrier function and epidermal water content. Imaging mass spectrometry (IMS) can reveal not only the identity and localization of lipids in organs but also the distribution of administered drugs. Here, we attempted to visualize the distribution of SLS and changes in lipid composition in the epidermis of the skin. Initially, we histologically examined micro damage of the skin using trypan blue in the foot-pad of mice treated with SLS. Subsequently, we assessed the invasion of SLS and the effect of SLS on the lipid composition of the skin using IMS. We found that, relative to the foot-pad of mice treated with saline, the foot-pad of mice treated with SLS exhibited a significant change in m/z 817.71 associated with sphingomyelin despite the fact that no noticeable damage was observed in the layer structure dyed with trypan blue. Furthermore, we proved the penetration of SLS to the epidermis and dermis. The results suggest that SLS penetrates the skin tissue and alters the lipid composition on the skin surface.

Together with 2-methyl-3-hydroxybutyrylcarnitine, 2-methylacetoacetylcarnitine has been newly identified in significantly increased amounts in serum and dried blood spot of patients with β-ketothiolase deficiency. In patients with HSD10 disease, however, the amounts of 2-methylacetoacetylcarnitine were considerably low as compared with those in patients with β-ketothiolase deficiency, and the decreased ratio of 2-methylacetoacetylcarnitine to 2-methyl-3-hydroxybutyrylcarnitine in dried blood spot could be an additional index to discriminate HSD10 disease from β-ketothiolase deficiency.