The recognized index of vitamin D (VTD) status is the measurement of circulating concentrations of 25-OH VTD (25VTD). A concentration of 30 ng/ml 25VTD (75 nM) is considered by many experts as the minimum optimal concentration.(1) There is currently a growing interest in VTD far beyond bone and calcium metabolism, (2) including cancer, immunology, and hypertension, which has caused a recent upsurge in requests for 25VTD evaluation, (3) necessitating the need for accurate measurement.We report here the case of a 60-yr-old woman diagnosed as having VTD deficiency (serum 25VTD measured with the automated Roche Elecsys method at 12 ng/ml). She was given a single 600,000U VTD 2 oral dose. Because serum 25VTD measured with the same assay 2 wk later was still low (11 ng/ml), she was referred to our unit for extensive laboratory testing. All biochemical parameters were normal, including 25VTD (50 ng/ml), but this time the Diasorin radioimmunoassay (RIA) was used to quantify 25VTD. To study the cause for these discrepant results further, we conducted measurements of 25VTD by a specific liquid chromatography-mass spectrometry (LC/MS/MS) method. The LC/MS/MS method separates and quantifies 25-hydroxylated metabolites of both VTD 2 and VTD 3 , which are summed to get the total 25VTD concentration. The LC/MS/MS is considered by many as the candidate reference method for 25(OH)D measurement, (4) although drawbacks because of the recognition of other compounds such as epimers have been highlighted, especially in pediatric subjects. (5,6) In addition to the index case, all three methods were used to measure 25VTD in serum collected from 11 healthy subjects (5 men and 6 women; age, 21-62 yr) before (D0) and 7 and 28 days after a single 600,000U VTD 2 dose to mimic the above-mentioned case. Pooling the results from the three time-points, we found that the LC/MS/MS results were highly correlated with the RIA values (Spearman's ס 0.94; p < 0.0001) but not with the Elecsys values ( ס 0.16; not significant).On day 0, the mean concentration [SD] was similar with the three assays (Diasorin RIA: 29.3 [6.8] 4] ng/ ml) with the Roche Elecsys assay. All subjects had a 25VTD concentration >30 ng/ml with LC/MS/MS and the Diasorin RIA, whereas this was the case in only two of them with the Elecsys. At day 28, 25VTD remained >30 ng/ml in all subjects when measurements were conducted by Diasorin RIA (52.0 [20.3] ng/ml) and LC/MS/MS (52.8 [8.5] ng/ml), whereas it was <30 ng/ml (21.4 [4.9] ng/ml) in all subjects with the Elecsys assay (Fig. 1). The LC/MS/MS data confirmed that the increases observed were solely caused by an increase in the 25VTD 2 metabolite.The supplementation with 600,000 IU of VTD 2 did not produce a significant rise in calcium and phosphorus levels (2.35, 2.35, and 2.39 mM, respectively, for day 0, 7, and 28 median calcium levels and 1.07, 1.05, and 1.06 mM, respectively, for phosphorus concentrations at the same times). We did not observe any significant variation in parathormone levels (41 versus 44 pg/ml before and a...
Azole antifungals are a group of fungistatic agents that can be administered orally or parenterally. The determination of the concentrations of these antifungals (miconazole, fluconazole, ketoconazole, posaconazole, voriconazole, itraconazole, and its major active metabolite, hydroxy-itraconazole) in serum can be useful to adapt the doses to pharmacological ranges because of large variability in the absorption and metabolism of the drugs, multiple drug interactions, but also potential resistance or toxicity. A method was developed and validated for the simultaneous determination of these drugs in serum utilizing ultra-high pressure liquid chromatography and diode array detection (UHPLC-DAD). After a simple and rapid liquid-liquid extraction, the pre-treated sample was analysed on an UHPLC-DAD system (Waters Corporation(®)). The chromatographic separation was carried out on an Acquity BEH C18 column (Waters Corporation) with a gradient mode of mobile phase composed of acetonitrile and aqueous ammonium bicarbonate 10·0 M pH10. The flow rate was 0·4 ml/min and the injection volume was 5 μl. The identification wavelength varied according to the drug from 210 to 260 nm. The method was validated by the total error method approach by using an analytical validation software (e•noval V3·0 Arlenda(®)). The seven azole antifungals were identified by retention time and specific UV spectra, over a 13-minute run time. All calibration curves showed good linearity (r(2)>0·99) in ranges considered clinically adequate. The assay was linear from 0·05 to 10 mg/l for voriconazole, posaconazole, itraconazole, hydroxy-itraconazole, and ketoconazole, from 0·3 to 10 mg/l for fluconazole, and from 0·1 to 10 mg/l for miconazole. The bias and imprecision values for intra- and inter-assays were lower than 10% and than 15%, respectively. In conclusion, a simple, sensitive, and selective UHPLC-DAD method was developed and validated to determine seven azole antifungal drugs in human serum. This method is applicable to patient samples, and can be applied successfully to clinical applications and therapeutic drug monitoring.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.