Ultra high performance liquid chromatography-tandem mass spectrometry vs. commercial immunoassay for determination of vancomycin plasma concentration in children. Possible implications for everyday clinical practice.

BACKGROUND: Vancomycin therapeutic drug monitoring (TDM) is necessary for effective and safetherapy. The aim of the this paper was to develop a specific and robust ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method for vancomycin quantification starting from low plasma volumes to be applied for the routine TDM in children. METHODS: Samples from children receiving intravenous vancomycin were analysed using a TSQ Quantum Access MAX Triple Quadrupole system coupled with an Accela 1250 UHPLC system after a rapid protein precipitation. Gradient separation chromatography was carried out using a Hypersil GOLD aQ C18 column (50 × 2.1 mm, particle size 1.9 µm). Method performance was validated following international guidelines. RESULTS: UHPLC-MS/MS allowed a rapid and specific quantification of vancomycin over the range 0.1-128 µg/mL from 50 µL of plasma with high reproducibility and accuracy in the absence of matrix effect. The comparison with the commercial immunoassay performed on 138 samples demonstrated the presence of a proportional bias. The concentrations of vancomycin measured with immunoassay were found to be 4.5% (95% CI: 1.3-7.7) higher than those determined with UHPLC-MS/MS. Importantly, a clinical discordance was found in about 10% of samples analysed. CONCLUSIONS: This new UHPLC-MS/MS method is accurate and specific for the measurement of vancomycin starting from small (50 µL) plasma volumes. The use of UHPLC-MS/MS is recommended to prevent a misclassification of therapeutic or toxic vancomycin levels in paediatrics.

Plasma cardiac troponin I concentrations in healthy neonates, children and adolescents measured with a high sensitive immunoassay method: High sensitive troponin I in pediatric age.

Over the past 10years cardiac troponin (cTn) immunoassays have been improved in analytical sensitivity and precision thereby allowing the measurement of cTn in adult healthy subjects. However, there are currently substantial gaps in our knowledge on circulating levels of cTn in healthy children. The aim of this study is to evaluate the distribution of plasma troponin concentration in apparently healthy pediatric subjects using a high sensitive immunoassay for cTnI measurement (hs-cTnI). Blood samples were obtained from 357 healthy pediatric subjects [204 males; age range 0-18years; mean (SD): 8.7(6) years], including 36 subjects aged <1month (neonates), 57 between 1 and 12months (infants), 65 between 1 and 10years (toddlers), and 223 between 10 and 18years (adolescents). The percentages of healthy population with cTnI values equal or less than the calculated and LOD value were 13.1%. cTnI plasma levels were highest in the first month of life with a progressive decline in the next years and were lower in female. At multivariate analysis, only age was predictor of hs-cTnI plasma levels. The age and sex of children influence normal and physiologically released circulating concentrations of hs-cTnI, suggesting the need of reference intervals specific for age and sex.

DBS-LC-MS/MS assay for caffeine: validation and neonatal application.

AIM: DBS might be an appropriate microsampling technique for therapeutic drug monitoring of caffeine in infants. Nevertheless, its application presents several issues that still limit its use. This paper describes a validated DBS-LC-MS/MS method for caffeine. RESULTS: The results of the method validation showed an hematocrit dependence. In the analysis of 96 paired plasma and DBS clinical samples, caffeine levels measured in DBS were statistically significantly lower than in plasma but the observed differences were independent from hematocrit. CONCLUSION: These results clearly showed the need for extensive validation with real-life samples for DBS-based methods. DBS-LC-MS/MS can be considered to be a good alternative to traditional methods for therapeutic drug monitoring or PK studies in preterm infants.

Urinary homovanillic and vanillylmandelic acid in the diagnosis of neuroblastoma: report from the Italian Cooperative Group for Neuroblastoma.

BACKGROUND: Urinary homovanillic and vanillylmandelic acid (HVA and VMA) are well known biomarkers for the management of neuroblastoma (NB). Very few and contradictory publications on their diagnostic performance are present in the literature. The aim of this study is to review the results of HVA/Cr and VMA/Cr obtained by the reference laboratory of the Italian Cooperative Group for NB within a 7-year period using HPLC-EC. PROCEDURE: Updated reference intervals based on age as a continuous variable were calculated by using a multivariate statistical analysis. The diagnostic performance of the two biomarkers has been established by calculating their specificity and sensitivity and by receiver operating characteristics (ROC) curves for different ages and stages of disease. RESULTS: Accurate age-related reference intervals were obtained from 648 HVA/Cr and 671 VMA/Cr results derived from patients in which the diagnosis of neuroendocrine tumors was excluded. Sensitivity, specificity and ROC curves were obtained from 169 HVA/Cr and 179 VMA/Cr results from confirmed NB patients. The best diagnostic performance was obtained in stage 4S tumors and in children <18months. CONCLUSIONS: This is the first report, to our knowledge, that analyzes in depth the diagnostic performance of HVA/Cr and VMA/Cr for NB in different stages and age subgroups. In addition, the present work provides cut-off points able to discriminate between NB patients and negative subjects suspected to have NB and could be of help in taking medical decisions.