Background Vitamin D supplementation is common practice for neonates and infants due to limited stores of vitamin D at birth. Although not commonly encountered, vitamin D toxicity can occur due to over-supplementation. However, toxic concentrations are often not included in method validation experiments, and assays often are not validated in the neonatal population. Methods We compared serial 25 hydroxy vitamin D [25(OH)D] measurements in pre-term neonates receiving 25(OH)D supplementation and identified 12 patients wherein concentrations of 25(OH)D were above 50 ng/mL (125 nM) that required additional investigations as the 25(OH)D results did not match the clinical picture. Available samples were compared across 4 immunoassay platforms (LIAISON XL, Roche Cobas e602, Abbott Alinity i, and Siemens Centaur XP) and LC–MS/MS. Results Concentrations of 25(OH)D observed on one individual immunoassay platform (LIAISON XL) fluctuated substantially between subsequent blood draws in select neonates with elevated concentrations. Serum samples from these patients showed variable agreement between LC–MS/MS and other immunoassay platforms. These fluctuations were not explained by the presence of 3-epimer-25(OH)D or 24,25(OH)2D. Conclusions Although we were unable to identify a cause for the variable elevated results, our findings suggest that neonatal 25(OH)D measurements alone should not be used for assessment of nutritional monitoring, and that clinical correlation and other laboratory parameters including ionized calcium should be considered.
Objectives Monitoring estradiol (E2) is important for determining the onset of pubertal development as well as in the evaluation of girls with precocious puberty. However, E2 measurement remains an analytical challenge in children, who have lower circulating levels. We developed and evaluated a simple and sensitive LC-MS/MS procedure for serum E2 quantification in pediatric populations and established age- and sex-specific pediatric reference intervals. Methods Residual patient serum samples were used to evaluate the analytical performance of our in-house LC-MS/MS E2 assay. The evaluation included accuracy, precision, linearity, functional sensitivity (LLoQ), and method comparison. Age- and sex-specific pediatric E2 reference intervals were also established from a cohort of 405 healthy children (birth to 18 years) recruited with informed consent. Age- and sex-specific differences were assessed, and outliers were removed. Reference intervals were established using the robust method. Results The assay imprecision was <5.3 %. Assay linearity ranged from 13.7 to 1923.3 pmol/L. The LLoQ corresponding to a CV of 20 % was determined to be 8.9 pmol/L. Bland-Altman analysis revealed a mean bias of 29.3 pmol/L or 9.1 % between our LC-MS/MS E2 assay and an external reference laboratory measuring E2 by LC-MS/MS. Conclusions Our LC-MS/MS E2 assay shows acceptable accuracy, precision, functional sensitivity (LLoQ), and linearity for E2 quantification. Our LC-MS/MS E2 assay also showed good agreement with an external reference laboratory measuring E2 by LC-MS/MS. In addition, using CALIPER samples, we established robust age- and sex-specific pediatric E2 reference intervals to improve accuracy of test result interpretation and clinical decision making.
Introduction A patient presented to hospital with chest pain and shortness of breath on 2 occasions 4 weeks apart. Clinical examination revealed an elevated jugular venous pressure consistent with heart failure or elevated filling pressures. Methods The patient was investigated through various modalities including electrocardiogram (ECG), transthoracic echocardiogram, coronary angiography, MRI, cardiac catheterization, positron emission tomography, and an extensive laboratory workup. Results Serial hs TnI measurements consistently revealed grossly elevated troponin I (>10 000 ng/L). In-lab investigation of increased high sensitivity troponin I (hsTnI) showed evidence of falsely increased troponin due to the presence of heterophilic antibodies. Discussion This case demonstrates a complex patient presentation and the value of involving the laboratory medicine team when dealing with potentially discrepant results. This is a rare report of grossly elevated troponin due to heterophilic antibodies for high-sensitivity troponin Abbott assay.
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