Comprehensive characterization and resolution of discrepant spectrophotometric bilirubin results in patients on eltrombopag therapy.

Background Eltrombopag is a thrombopoietin receptor agonist used for the treatment of thrombocytopenic conditions. It can cause pH-dependent discoloration of plasma/serum. Eltrombopag is potentially hepatotoxic. It can affect the assessment of hyperbilirubinemia because of its (i) absorbance at ~450 nm (bilirubin), (ii) absorbance at ~550 nm (diazo-bilirubin) and (iii) it can cause yellowish discoloration of the eyes at normal circulating bilirubin levels. Methods We collected 66 samples from patients on a range of eltrombopag dosages up to 150 mg daily. Bilirubin was measured using multiple routine spectrophotometric analyzers, the Doumas reference method and high-performance liquid chromatography (HPLC). Plasma/serum eltrombopag concentrations were determined using liquid chromatography tandem mass spectrometry (LC-MS/MS). Spike-in and admixture experiments delineated the effects of eltrombopag and its metabolites. Results Forty-nine of 52 samples from patients on ≥50 mg daily eltrombopag therapy showed significantly discrepant inter-analyzer total bilirubin results, a difference up to 64 µmol/L (3.7 mg/dL). In one sample, total bilirubin varied from 8 to 65 µmol/L (0.4-3.8 mg/dL) by different routine analyzers, with direct bilirubin ≤4 µmol/L (0.2 mg/dL). There was a positive correlation between total bilirubin difference and plasma eltrombopag concentration (r = 0.679), and spike-in experiments demonstrated that Beckman AU and Doumas reference methods were susceptible to positive interference. HPLC can quantify bilirubin after separating eltrombopag, and results suggest different analyzers are affected to varying degrees by eltrombopag and its metabolites. Conclusions Eltrombopag and its metabolites can cause positive interference to the spectrophotometric measurements of total bilirubin. Accurate measurements of total bilirubin may improve our understanding of the prevalence of hyperbilirubinemia in patients on eltrombopag therapy.

High sensitivity troponin T concentrations in patients undergoing noncardiac surgery: a prospective cohort study.

OBJECTIVES: To determine the proportion of noncardiac surgery patients exceeding the published 99th percentile or change criteria with the high sensitivity Troponin T (hs-TnT) assay. DESIGN AND METHODS: We measured hs-TnT preoperatively and postoperatively on days 1, 2 and 3 in 325 adults. RESULTS: Postoperatively 45% (95% CI: 39-50%) of patients had hs-TnT≥14ng/L and 22% (95% CI:17-26%) had an elevation (≥14ng/L) and change (>85%) in hs-TnT. CONCLUSION: Further research is needed to inform the optimal hs-TnT threshold and change in this setting.

Stability of serum thyroid hormones following 8-11 years of cold storage.

BACKGROUND: Ethnic differences necessitate a need for local reference intervals (RI), but establishing these can be challenging in some cultures that are reluctant to donate blood. Frozen sera are an alternative, but results can be questionable. Between 1998 and 2001, we collected blood samples from 343 healthy pregnant Chinese women (5-41 weeks' gestation), and in 2001 published gestational RI for thyrotropin thyroid stimulating hormone (TSH), free thyroxine (FT4) and free triiodothyronine (FT3) using the ACS180, now obsolete. As a pilot to re-establishing RI, TSH, FT4 and FT3 were re-assayed in archived specimens using contemporary assays. METHODS: Thirty archived specimens (-80 degrees C) with ACS180 TSH concentrations ranging from 0.25 to 3.7 mIU/L were measured using the Roche E170, Advia Centaur and Architect i2000 TSH, FT4 and FT3 assays, along with 10 newer contemporary samples. Results were compared to the original, and examined in context of past and present methodological performances in an external quality assurance (EQA) program. RESULTS: All contemporary assays detected significantly lower TSH and increased FT4 and FT3 concentrations in the stored samples. CONCLUSIONS: With reference to methodological performances in EQA, the results obtained with contemporary assays suggest analyte deterioration in specimens and thus their unsuitability for re-establishing RI.

Steroid-induced osteonecrosis in severe acute respiratory syndrome: a retrospective analysis of biochemical markers of bone metabolism and corticosteroid therapy.

AIM: We investigated the effect of massive doses of corticosteroid therapy on bone metabolism using specific biochemical markers of bone metabolism, and the prevalence of osteonecrosis in severe acute respiratory syndrome (SARS) patients at a university teaching hospital in Hong Kong. METHODS: Seventy-one patients with a clinical diagnosis of SARS were studied according to the modified World Health Organization case definition of SARS who were involved in the SARS epidemic between 10 March and 20 June 2003. The clinical diagnosis was confirmed by serological test and/or molecular analysis. Biochemical markers of bone metabolism were analysed retrospectively using serial clotted blood samples collected from each patient during the course of hospital admission to discharge and subsequent follow-up at out-patient clinic using the arbitrary time periods: (i) Day <10; (ii) Day 28-44; (iii) Day 51-84; and (iv) Day >90 after the onset of fever. Magnetic resonance imaging of the knee and hip joints were performed post-admission to evaluate the prevalence of osteonecrosis amongst these SARS patients. Various risk factors for the development of osteonecrosis were assessed using receiver operating characteristics curve comparison with appropriate test statistics and Spearman's coefficients of rank correlation with biochemical bone markers. RESULTS: Biochemical markers of bone metabolism showed significant bone resorption as evidenced by a marked increase in serum C-terminal telopeptide concentration (CTx) from Day 28-44 after the onset of fever. With tapering down of corticosteroid dosage, CTx started to return to previous baseline level from Day 51 onwards, while other bone formation markers, serum osteocalcin and bone-specific alkaline phosphatase concentrations (OC and BALP, respectively), started to increase. The latter effect was even more marked after Day >90. Seven patients developed radiological evidence of osteonecrosis. The prevalence of osteonecrosis in this cohort was 9.9%. A total corticosteroid dosage of >1900 mg hydrocortisone, >2000 mg methylprednisolone, >13 340 mg hydrocortisone-equivalent corticosteroid therapy, and >18 days on corticosteroid therapy were found to be significant risk factors for the subsequent development of osteonecrosis. There were also significant positive correlations amongst various biochemical bone markers in this patient cohort. CONCLUSIONS: Both bone resorption and formation markers were unable to predict the subsequent development of osteonecrosis. The use of high dose of hydrocortisone or methylprednisolone for an extended duration was shown to be a significant risk factor for osteonecrosis. Its prevalence in this cohort is comparable to those reported in the literature for SARS patients with high-dose corticosteroid therapy. The Day 28-44 increase in the serum CTx coincided with the timing of corticosteroid use. The Day >51 increase in serum OC and BALP coincided with the timing of corticosteroid withdrawal.

Effect of a compensated Jaffe creatinine method on the estimation of glomerular filtration rate.

BACKGROUND: Roche Diagnostics has issued new c-fas calibrators for its automated systems. These produce creatinine values that are more comparable with those obtained by high-performance liquid chromatography. However, this results in an underestimation of measured creatinine at concentrations below 155 micromol/L and an overestimation at concentrations above this value. METHODS: Serum and urine creatinine concentrations were prospectively determined on samples from 60 patients using the new (compensated) and old (uncompensated) c-fas calibrators, and Passing-Bablok regression analysis was performed. The regression equations thus determined were then used retrospectively to determine the compensated creatinine results (i.e. those results that would have been obtained using the new calibrator) in those serum and urine samples analysed in the previous year using the old uncompensated c-fas calibrator. The compensated creatinine results were then used to estimate the glomerular filtration rate (GFR) by calculating creatinine clearance. This was done by using the formula: UV/Pt, in which U represents the urinary creatinine concentration (micromol/L), V the urinary collection volume (mL), P the serum creatinine concentration (micromol/L) and t the urinary collection time (min). It was also calculated using the abbreviated Modification of Diet in Renal Disease study group (MDRD) formula. RESULTS: The creatinine clearance as determined using either the UV/Pt calculation or the MDRD formula overestimated GFR by approximately 30% and approximately 50%, respectively, in normal individuals with a serum creatinine concentration below 155 micromol/L. However, in patients with mild to moderate renal failure (serum creatinine from 155 to 500 micromol/L), changes in creatinine clearances determined by the two procedures were minimal. CONCLUSION: When laboratories introduce this new, compensated calibrator into practice, it may be appropriate to discuss its potential impact with clinical staff who monitor patients using creatinine clearance.

mRNA of placental origin is readily detectable in maternal plasma.

The discovery of circulating fetal nucleic acid in maternal plasma has opened up new possibilities for noninvasive prenatal diagnosis. Thus far, a gender- and polymorphism-independent fetal-specific target that can be used for prenatal screening and monitoring in all pregnant women has not been reported. In addition, the origin of such circulating nucleic acid has remained unclear. Here we provide direct evidence that the placenta is an important source of fetal nucleic acid release into maternal plasma by demonstrating that mRNA transcripts from placenta-expressed genes are readily detectable in maternal plasma. The surprising stability of such placental mRNA species in maternal plasma and their rapid clearance after delivery demonstrate that such circulating mRNA molecules are practical markers for clinical use. The measurement of such plasma mRNA markers has provided a gender-independent approach for noninvasive prenatal gene expression profiling and has opened up numerous research and diagnostic possibilities.