Agreement Between a Colorimetric Assay and Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry for Quantifying Paracetamol Plasma Concentrations

Special populations, like geriatric patients, experience altered paracetamol pharmacokinetics (PK), complicating pain management. More PK research is essential to optimize paracetamol (acetaminophen) dosing. Yet, the reference method ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) is not readily available. Therefore, we aimed to evaluate the agreement between UPLC-MS/MS and the more accessible colorimetric Roche acetaminophen (ACETA) assay in quantifying paracetamol plasma concentrations, to facilitate PK studies and therapeutic drug monitoring for pain management. Patient data and plasma samples were obtained from a prospective study including geriatric patients admitted to the geriatric wards. ACETA and UPLC-MS/MS assays were performed in two separate laboratories. Bland-Altman plot and Passing-Bablok regression were used to assess agreement. Accuracy was evaluated using the McNemar test for a threshold value of 10 mg/L. Population PK modeling was employed to bridge PK data obtained from both methods (NONMEM 7.5). A total of 242 plasma sample pairs were available from 40 geriatric patients (age range, 80-95 years). Paracetamol plasma concentrations from ACETA (median 9.8 [interquartile range 6.1-14.4] mg/L) and UPLC-MS/MS (9.5 [6.2-14.8] mg/L) did not differ significantly (P > 0.05). No significant proportional nor additive bias was observed between both assay methods. The classification accuracy (at threshold 10 mg/L) was 85% (P = 0.414). The conversion factor between ACETA and UPLC-MS/MS was estimated at 1.06 (relative standard error 5%), yet with a 13.4% (relative standard error 23%) interindividual variability. ACETA assay showed no systematic bias in comparison with the UPLC-MS/MS assay in determining paracetamol exposure in geriatric blood samples despite the imprecision.

A False-Positive Gamma-Hydroxy Butyric Acid Urine Screening in a Patient with High Anion Gap Metabolic Acidosis Due to Ethylene Glycol Poisoning

A young woman with a history of several suicide attempts was admitted to the hospital after suspicion of a new intoxication without definite identification of the causing agent. The patient had a high anion gap metabolic acidosis (HAGMA) with respiratory compensation, a lactate gap and an osmolar gap at admission. Initial toxicological screening showed no abnormalities except for a weak positive gamma-hydroxy butyric acid (GHB) enzymatic screen in urine. This finding could not be confirmed using chromatographic analysis nor be explained by the presence of known cross-reacting substances like ethanol. In this case, falsely elevated urinary GHB screening was caused by the ingestion of ethylene glycol. To confirm that the interference was due to ethylene glycol or its metabolites, we performed a spiking experiment. Cross reactivity was linked to ethylene glycol and was low in our experiments (0.1-0.2%). Substantial amounts of ethylene glycol are required to slightly elevated GHB results, depending on the endogenous cutoff used. We can conclude that ethylene glycol can give rise to falsely elevated urinary GHB levels at ethylene glycol concentrations that are typically found in intoxications.

The influence of proteoforms: assessing the accuracy of total vitamin D-binding protein quantification by proteolysis and LC-MS/MS

OBJECTIVES

Vitamin D-binding protein (VDBP), a serum transport protein for 25-hydroxyvitamin D [25(OH)D], has three common proteoforms which have co-localized amino acid variations and glycosylation. A monoclonal immunoassay was found to differentially detect VDBP proteoforms and methods using liquid chromatography-tandem mass spectrometry (LC-MS/MS) might be able to overcome this limitation. Previously developed multiple reaction monitoring LC-MS/MS methods for total VDBP quantification represent an opportunity to probe the potential effects of proteoforms on proteolysis, instrument response and quantification accuracy.

METHODS

VDBP was purified from homozygous human donors and quantified using proteolysis or acid hydrolysis and LC-MS/MS. An interlaboratory comparison was performed using pooled human plasma [Standard Reference Material^® 1950 (SRM 1950) Metabolites in Frozen Human Plasma] and analyses with different LC-MS/MS methods in two laboratories.

RESULTS

Several shared peptides from purified proteoforms were found to give reproducible concentrations [≤2.7% coefficient of variation (CV)] and linear instrument responses (R²≥0.9971) when added to human serum. Total VDBP concentrations from proteolysis or amino acid analysis (AAA) of purified proteoforms had ≤1.92% CV. SRM 1950, containing multiple proteoforms, quantified in two laboratories resulted in total VDBP concentrations with 7.05% CV.

CONCLUSIONS

VDBP proteoforms were not found to cause bias during quantification by LC-MS/MS, thus demonstrating that a family of proteins can be accurately quantified using shared peptides. A reference value was assigned for total VDBP in SRM 1950, which may be used to standardize methods and improve the accuracy of VDBP quantification in research and clinical samples.

Measurable Serum Estradiol and Estrone in Women 36-56 Years During Adjuvant Treatment With Aromatase Inhibitors for a Hormone Receptor-Positive Breast Cancer. Case Studies and Cross-sectional Study Using an Ultra-sensitive LC-MS/MS-Method

BACKGROUND AND PURPOSE

Ovarian function recovery (OFR) during adjuvant use of an aromatase inhibitor (AI) negatively impacts breast cancer outcome. We measured serum FSH and estrogen levels in consecutive AI-users with an uncertain menopausal status during follow-up and report associated risk factors of OFR METHODS: A retrospective cross sectional observational monocentric study including breast cancer patients in follow-up using an adjuvant AI, age 36 to 56 years, with at least one serum estradiol (E2) and estrone (E1) measurement between 2013 and 2020. Estrogens were quantified using a sensitive liquid chromatography-tandem mass spectrometry method (LC-MS/MS). Women on LHRH agonist were included while those with a bilateral oophorectomy or ovarian irradiation were not. We aimed to identify risk factors of OFR considering age, body mass index (BMI), previous chemotherapy and duration of AI use. Univariable analysis was used to evaluate risk factors of OFR.

RESULTS

E2/E1 levels were assessed in 207 patients with a median age of 50 years (range 36-56). 17 of 159 on AI (10.7%) and 3 of 48 on AI + LHRH (6.3%) had OFR. Seven out of 17 patients (41,2%) with OFR in the AI only group and 2 out of 3 patients (66,7%) in the AI+LHRH agonist group were in amenorrhea. Age <50 y and adjuvant chemotherapy were statistically significantly different between the OFR group and the group with postmenopausal estrogen levels.

CONCLUSION

Breast cancer patients aged 36 to56 years need to be monitored closely during adjuvant treatment with aromatase inhibitors: to confirm menopausal status, to evaluate compliance and to ensure ovarian activity remains adequately suppressed. Estrone might be a better marker then estradiol to detect ovarian reactivation.

Vitamin D metabolites and the gut microbiome in older men

The vitamin D receptor is highly expressed in the gastrointestinal tract where it transacts gene expression. With current limited understanding of the interactions between the gut microbiome and vitamin D, we conduct a cross-sectional analysis of 567 older men quantifying serum vitamin D metabolites using LC-MSMS and defining stool sub-Operational Taxonomic Units from16S ribosomal RNA gene sequencing data. Faith's Phylogenetic Diversity and non-redundant covariate analyses reveal that the serum 1,25(OH)2D level explains 5% of variance in α-diversity. In β-diversity analyses using unweighted UniFrac, 1,25(OH)2D is the strongest factor assessed, explaining 2% of variance. Random forest analyses identify 12 taxa, 11 in the phylum Firmicutes, eight of which are positively associated with either 1,25(OH)2D and/or the hormone-to-prohormone [1,25(OH)2D/25(OH)D] "activation ratio." Men with higher levels of 1,25(OH)2D and higher activation ratios, but not 25(OH)D itself, are more likely to possess butyrate producing bacteria that are associated with better gut microbial health.

Field evaluation of a mobile biosafety laboratory in Senegal to strengthen rapid disease outbreak response and monitoring

Background

Past and recent outbreaks have highlighted the vulnerability of humans to infectious diseases, which represent serious economic and health security threats. A paradigm shift in the management of sanitary crises is urgently needed. Based on lessons from the 2014 Ebola outbreak, the Praesens Foundation has developed an all-terrain mobile biosafety laboratory (MBS-Lab) for effective field diagnostics capabilities.

Objective

The aim of the study was to train African teams and run a field evaluation of the MBS-Lab, including robustness, technical and operational sustainability, biosafety, connectivity, turn-around times for testing and result delivery.

Methods

The MBS-Lab was deployed in Senegal in October 2017 for a six-month field assessment under various ecological conditions and was mobilised during the dengue outbreaks in 2017 and 2018.

Results

The MBS-Lab can be considered an off-grid solution that addresses field challenges with regard to working conditions, mobility, deployment, environment and personnel safety. Blood (n = 398) and nasal swab (n = 113) samples were collected from 460 study participants for molecular screening for acute febrile illnesses and respiratory infections. The results showed that malaria (particularly in Kédougou) and upper respiratory tract infections remain problematic. Suspected dengue samples were tested on board during the dengue outbreaks in 2017 (882 tests; 128 confirmed cases) and 2018 (1736 tests; 202 confirmed cases).

Conclusion

The MBS-Lab is an innovative solution for outbreak response, even in remote areas. The study demonstrated successful local ownership and community engagement. The MBS-Lab can also be considered an open mobile healthcare platform that offers various opportunities for field-deployable, point-of-care technologies for surveillance programmes.

An unconscious man with profound drug-induced hypoglycaemia

Introduction

Hypoglycaemia has been reported as an unusual complication of tramadol use and in a few cases of tramadol poisoning, but the exact mechanism is not known.

Case description

An ambulance crew was dispatched to an unconscious 46-year old man. A glucometer point-of-care measurement revealed a profound hypoglycaemia (1.9 mmol/L). Treatment with intravenous glucose was started and the patient was transported to the hospital. The patient had several episodes of pulseless electrical activity requiring cardiopulmonary resuscitation in the ambulance and upon arrival in the hospital. Despite continuous glucose infusion the hypoglycaemia was difficult to correct during the next few hours and the patient developed hypokalaemia. Further investigation to identify the cause of hypoglycaemia revealed that insulin and C-peptide were inappropriately raised. A toxicological investigation revealed the presence of tramadol and its metabolites in lethal concentrations. Also acetaminophen, ibuprofen and lormetazepam were present. Ethanol screening was negative (< 0.1 g/L) and no sulfonylurea were detected. The patient developed multiple organ failure, but eventually recovered.

What happened

The hypoglycaemia was caused by inappropriate stimulation of insulin secretion in a patient intoxicated with tramadol. The sudden hypokalaemia was caused by a massive intracellular shift of potassium in response to the hyperinsulinemia, triggered by the intravenous administration of glucose.

Main lesson

To our knowledge, we are the first to document a significant rise in endogenous insulin production in a hypoglycaemic patient presenting with tramadol intoxication. Our observation suggests that hyperinsulinemia could be the cause of the hypoglycaemia associated with tramadol use.

Preanalytical considerations in therapeutic drug monitoring of immunosuppressants with dried blood spots

Background

Dried blood spots (DBSs) could allow patients to prepare their own samples at home and send them to the laboratory for therapeutic drug monitoring (TDM) of immunosuppressants. The purpose of this review is to provide an overview of the current knowledge about the impact of DBS-related preanalytical factors on TDM of tacrolimus, sirolimus and everolimus.

Content

Blood spot volume, blood spot inhomogeneity, stability of analytes in DBS and hematocrit (Hct) effects are considered important DBS-related preanalytical factors. In addition, the influence of drying time has recently been identified as a noteworthy preanalytical factor. Tacrolimus is not significantly influenced by these factors. Sirolimus and everolimus are more prone to heat degradation and exhibited variations in recovery which were dependent on Hct and drying time.

Summary and outlook

DBS-related preanalytical factors can have a significant impact on TDM for immunosuppressants. Tacrolimus is not significantly influenced by the studied preanalytical factors and is a viable candidate for DBS sampling. For sirolimus and everolimus more validation of preanalytical factors is needed. In particular, drying conditions need to be examined further, as current protocols may mask Hct-dependent effects on recovery. Further validation is also necessary for home-based self-sampling of immunosuppressants as the sampling quality is variable.

Free Testosterone Reflects Metabolic as well as Ovarian Disturbances in Subfertile Oligomenorrheic Women

BACKGROUND

Diagnosing polycystic ovary syndrome (PCOS) is based on ovulatory dysfunction, ovarian ultrasound data, and androgen excess. Total testosterone is frequently used to identify androgen excess, but testosterone is mainly bound to sex hormone-binding globulin (SHBG) and albumin. Only 1-2% of nonprotein-bound testosterone (so-called free testosterone) is biologically active and responsible for androgen action. Moreover, automated immunoassays which are frequently used for female testosterone measurements are inaccurate.

OBJECTIVE

To assess the clinical usefulness of liquid chromatography-tandem mass spectrometry measured testosterone and calculated free testosterone in subfertile women attending a fertility clinic with oligomenorrhea and suspected PCOS.

METHODS

Hormonal and metabolic parameters were evaluated, and ovarian ultrasound was performed. Total testosterone was measured by liquid chromatography-tandem mass spectrometry. Free testosterone was calculated from total testosterone and SHBG.

RESULTS

Sixty-six women were included in the study. Total testosterone was associated with ovarian volume and antral follicle count but not with metabolic parameters. However, SHBG and calculated free testosterone were associated with both ovarian ultrasound and metabolic parameters, such as BMI and insulin resistance.

CONCLUSIONS

Assessing SHBG and free testosterone is important in evaluating androgen excess in subfertile women with ovulatory dysfunction and suspected PCOS, as it reflects both ovarian and metabolic disturbances.

Estimating glomerular filtration rate for the full age spectrum from serum creatinine and cystatin C

Background

We recently published and validated the new serum creatinine (Scr)-based full-age-spectrum equation (FAS crea ) for estimating the glomerular filtration rate (GFR) for healthy and kidney-diseased subjects of all ages. The equation was based on the concept of normalized Scr and shows equivalent to superior prediction performance to the currently recommended equations for children, adolescents, adults and older adults.

Methods

Based on an evaluation of the serum cystatin C (ScysC) distribution, we defined normalization constants for ScysC ( Q cysC  =   0.82 mg/L for ages <70 years and Q cysC  =   0.95 mg/L for ages ≥70 years). By replacing Scr/ Q crea in the FAS crea equation with ScysC/ Q cysC , or with the average of both normalized biomarkers, we obtained new ScysC-based (FAS cysC ) and combined Scr-/ScysC-based FAS equations (FAS combi ). To validate the new FAS cysC and FAS combi we collected data on measured GFR, Scr, ScysC, age, gender, height and weight from 11 different cohorts including n  = 6132 unique white subjects (368 children, aged ≤18 years, 4295 adults and 1469 older adults, aged ≥70 years).

Results

In children and adolescents, the new FAS cysC equation showed significantly better performance [percentage of patients within 30% of mGFR (P30) = 86.1%] than the Caucasian Asian Paediatric Adult Cohort equation (P30 = 76.6%; P < 0.0001), or the ScysC-based Schwartz equation (P30 = 68.8%; P < 0.0001) and the FAS combi equation outperformed all equations with P30 = 92.1% (P < 0.0001). In adults, the FAS cysC equation (P30 = 82.6%) performed equally as well as the Chronic Kidney Disease Epidemiology Collaboration equation (CKD-EPI cysC ) (P30 = 80.4%) and the FAS combi equation (P30 = 89.9%) was also equal to the combined CKD-EPI equation (P30 = 88.2%). In older adults, FAS cysC was superior (P30 = 88.2%) to CKD-EPI cysC (P30 = 84.4%; P < 0.0001) and the FAS combi equation (P30 = 91.2%) showed significantly higher performance than the combined CKD-EPI equation (P30 = 85.6%) (P < 0.0001).

Conclusion

The FAS equation is not only applicable to all ages, but also for all recommended renal biomarkers and their combinations.

1β,25-Dihydroxyvitamin D3: A new vitamin D metabolite in human serum

BACKGROUND

The measurement of 1α,25(OH)₂D₃ in human serum poses a true challenge as concentrations are very low and structurally similar metabolites can interfere.

MATERIALS AND METHODS

During optimization of our in-house LC-MSMS method for serum 1α,25(OH)₂D₃ a previously co-eluting isobaric interference was separated. The isobar was identified as 1β,25(OH)₂D₃ by comparing retention time and fragmentation spectra to standards (other isobaric dihydroxylated vitamin D₃ analogs). 1β,25(OH)₂D₃ showed specific cluster formation (water), not present in 1α,25(OH)₂D₃. 1β,25(OH)₂D₃ was measured in serum of apparently healthy human volunteers (n=20), patients with high serum 25-hydroxyvitamin D [25(OH)D] concentrations (>50ng/mL) (n=33 among which 4 with very high levels (>150ng/mL)) and patients with kidney failure (n=68; 39 stage 1-3, 29 stage 4-5). Pearson's r was calculated for correlations and Mann-Whitney statistic to compare group medians.

RESULTS

Median serum 1β,25(OH)₂D₃ was 11pg/mL in apparently healthy volunteers and increased to 20pg/mL for serum 25(OH)D concentrations above 80ng/mL (n=22) (p<0.0001). 1β,25(OH)₂D₃ concentrations were significantly correlated to serum 25(OH)D concentrations (r=0.85) for the combined results from healthy volunteers and patient sera (n=53) (p<0.0001). For patients with kidney failure, median serum 1β,25(OH)₂D₃ was 7pg/mL and not different from the median level in healthy volunteers (p=0.06). The median concentration did not vary with different stages.

CONCLUSIONS

We present evidence for the widespread presence of 1β,25(OH)₂D₃, a new vitamin D metabolite, in human serum. The level increases with rising serum 25(OH)D concentrations and is particularly high in patients with very high 25(OH)D levels. We previously demonstrated that 1β,25(OH)₂D₃ is a poor genomic agonist but a potent non-genomic antagonist of 1α,25(OH)₂D_3. The clinical implications of the presence of this analog therefore require further exploration.

Data on the relation between renal biomarkers and measured glomerular filtration rate

The data presented in this article are related to the research article entitled "The Diagnostic Value of Rescaled Renal Biomarkers Serum Creatinine and Serum Cystatin C and their Relation with Measured Glomerular Filtration Rate" (Pottel et al. (2017) [1]). Data are presented demonstrating the rationale for the normalization or rescaling of serum cystatin C, equivalent to the rescaling of serum creatinine. Rescaling biomarkers brings them to a notionally common scale with reference interval [0.67-1.33]. This article illustrates the correlation between rescaled biomarkers serum creatinine and serum cystatin C by plotting them in a 2-dimensional graph. The diagnostic value in terms of sensitivity and specificity with measured Glomerular Filtration Rate as the reference method is calculated per age-decade for both rescaled biomarkers. Finally, the interchangeability between detecting impaired kidney function from renal biomarkers and from the Full Age Spectrum FAS-estimating GFR-equation and measured GFR using a fixed and an age-dependent threshold is shown.

The diagnostic value of rescaled renal biomarkers serum creatinine and serum cystatin C and their relation with measured glomerular filtration rate

BACKGROUND

Serum creatinine (Scr) is the major contributing variable in glomerular filtration rate (GFR) estimating equations. Serum cystatin C (ScysC) based GFR estimating (eGFR)-equations have also been developed. The present study investigates the relation between 'rescaled' levels of these renal biomarkers (with reference interval of [0.67-1.33]) and measured GFR (mGFR).

METHODS

We evaluated the diagnostic ability to detect impaired kidney function of the rescaled renal biomarkers in 8584 subjects from 12 cohorts with measured GFR, standardized Scr and ScysC. We calculated sensitivity and specificity of the rescaled biomarkers to identify kidney disease, with reference to a fixed (60mL/min/1.73m²) as well as an age-dependent threshold for mGFR.

RESULTS

The upper reference limit of 1.33 for rescaled renal biomarkers is closely related to the age-dependent threshold for defining kidney status by mGFR with sensitivity and specificity for the rescaled biomarkers close to 90% for all ages. If the fixed threshold of 60mL/min/1.73m² for mGFR is used, then lower specificity in children and sensitivity in older adults are observed.

CONCLUSIONS

Impaired kidney function can be diagnosed by rescaled renal biomarkers instead of eGFR-equations using the fixed threshold of 1.33 for all ages, consistent with an age-dependent threshold of mGFR.

The effect of paternal methyl-group donor intake on offspring DNA methylation and birth weight

Most nutritional studies on the development of children focus on mother-infant interactions. Maternal nutrition is critically involved in the growth and development of the fetus, but what about the father? The aim is to investigate the effects of paternal methyl-group donor intake (methionine, folate, betaine, choline) on paternal and offspring global DNA (hydroxy)methylation, offspring IGF2 DMR DNA methylation, and birth weight. Questionnaires, 7-day estimated dietary records, whole blood samples, and anthropometric measurements from 74 fathers were obtained. A total of 51 cord blood samples were collected and birth weight was obtained. DNA methylation status was measured using liquid chromatography-tandem mass spectrometry (global DNA (hydroxy)methylation) and pyrosequencing (IGF2 DMR methylation). Paternal betaine intake was positively associated with paternal global DNA hydroxymethylation (0.028% per 100 mg betaine increase, 95% CI: 0.003, 0.053, P=0.03) and cord blood global DNA methylation (0.679% per 100 mg betaine increase, 95% CI: 0.057, 1.302, P=0.03). Paternal methionine intake was positively associated with CpG1 (0.336% per 100 mg methionine increase, 95% CI: 0.103, 0.569, P=0.006), and mean CpG (0.201% per 100 mg methionine increase, 95% CI: 0.001, 0.402, P=0.049) methylation of the IGF2 DMR in cord blood. Further, a negative association between birth weight/birth weight-for-gestational age z-score and paternal betaine/methionine intake was found. In addition, a positive association between choline and birth weight/birth weight-for-gestational age z-score was also observed. Our data indicate a potential impact of paternal methyl-group donor intake on paternal global DNA hydroxymethylation, offspring global and IGF2 DMR DNA methylation, and prenatal growth.

Does Extremely Low Birth Weight Predispose to Low-Renin Hypertension?

Low birth weight and prematurity are risk factors for hypertension in adulthood. Few studies in preterm or full-term born children reported on plasma renin activity (PRA). We tested the hypothesis that renin might modulate the incidence of hypertension associated with prematurity. We enrolled 93 prematurely born children with birth weight <1000 g and 87 healthy controls born at term, who were all examined at ≈11 years. Renal length and glomerular filtration rate derived from serum cystatin C were 0.28 cm (95% confidence interval, 0.09–0.47) and 11.5 mL/min per 1.73 m 2 (6.4–16.6) lower in cases, whereas their systolic/diastolic blood pressure (BP) was 7.5 mm Hg (4.8–10.3)/4.0 mm Hg (2.1–5.8) higher ( P <0.001 for all). The odds of having systolic prehypertension or systolic hypertension associated with extreme low birth weight were 6.43 (2.52–16.4; P <0.001) and 10.9 (2.46–48.4; P =0.002). Twenty-four hours of urinary sodium excretion was similar in cases and controls (102.1 versus 106.8 mmol; P =0.47). Sodium load per nephron was estimated as sodium excretion divided by kidney length (mmol/cm). PRA was 0.54 ng/mL per hour (0.23–0.85; P =0.001) lower in cases. PRA, systolic BP, and sodium load were available in 43 cases and 56 controls. PRA decreased with systolic BP (slope −0.022 ng/mL per hour/ − mm Hg ; P =0.048), but was unrelated to sodium load (slope +0.13 mmol/cm − mm Hg ; P =0.54). The slope of PRA on systolic BP was similar ( P =0.17) in cases and controls. In conclusion, extremely low birth weight predisposes young adolescents to low-renin hypertension, but does not affect the inverse association between PRA and BP.

Clinical Trial Registration—

URL: https://www.clinicaltrials.gov . Unique identifier: NCT02147457.

Determination of human reference values for serum total 1,25-dihydroxyvitamin D using an extensively validated 2D ID-UPLC-MS/MS method

BACKGROUND

To assess a patient's vitamin D status the precursor metabolite 25-hydroxyvitamin D can be determined. However, measurement of 1,25-dihydroxyvitamin D is required when disorders of 1a-hydroxylation, extrarenal 1a-hydroxylation, or vitamin D receptor defects are suspected.

METHODS

The aim of this study was to determine reference values for 1,25-dihydroxyvitamin D₃ and D₂ using a 2D ID-UPLC-MS/MS method.

RESULTS

The LC-MS/MS method, able to measure picomolar concentrations of both 1,25-dihydroxyvitamin D₃ and D₂ in human serum, was extensively validated. Intra-assay variations were <5% and 8.5% and <7.5% and 11%, for 1,25-dihydroxyvitamin D₃ and D₂, respectively, over the whole dynamic range (3.1-376 and 3.1-652pmol/L). Limit of quantitation was 3.4pmol/L for both compounds. Our method correlated well with a published LC-MS/MS method (r=0.87) and with the average 1,25-dihydroxyvitamin D₃ results of the vitamin D External Quality Assessment Scheme (DEQAS) determined with LC-MS/MS (r=0.93). Reference ranges, determined in 96 plasma samples of healthy volunteers were 59-159pmol/L and <17pmol/L for respectively 1,25-dihydroxyvitamin D₃ and D₂. The female part of the reference group showed a statistically significant decrease of 1,25-dihydroxyvitamin D₃ concentrations with age. The presence of significantly higher average 1,25-dihydroxyvitamin D₃ levels in premenopausal women taking oral contraceptive pills compared to postmenopausal women suggests that this effect is estrogen-related, as estrogens lead to a higher vitamin D binding protein.

CONCLUSIONS

The major finding of the present study is a reference interval of 59-159pmol/L for 1,25-dihydroxyvitamin D₃ determined with a highly sensitive and precise LC-MS/MS method.

Free 25-Hydroxyvitamin D: Impact of Vitamin D Binding Protein Assays on Racial-Genotypic Associations

CONTEXT

Total 25-hydroxyvitamin D (25OHD) is a marker of vitamin D status and is lower in African Americans than in whites. Whether this difference holds for free 25OHOD (f25OHD) is unclear, considering reported genetic-racial differences in vitamin D binding protein (DBP) used to calculate f25OHD.

OBJECTIVES

Our objective was to assess racial-geographic differences in f25OHD and to understand inconsistencies in racial associations with DBP and calculated f25OHD.

DESIGN

This study used a cross-sectional design.

SETTING

The general community in the United States, United Kingdom, and The Gambia were included in this study.

PARTICIPANTS

Men in Osteoporotic Fractures in Men and Medical Research Council studies (N = 1057) were included.

EXPOSURES

Total 25OHD concentration, race, and DBP (GC) genotype exposures were included.

OUTCOME MEASURES

Directly measured f25OHD, DBP assessed by proteomics, monoclonal and polyclonal immunoassays, and calculated f25OHD were the outcome measures.

RESULTS

Total 25OHD correlated strongly with directly measured f25OHD (Spearman r = 0.84). Measured by monoclonal assay, mean DBP in African-ancestry subjects was approximately 50% lower than in whites, whereas DBP measured by polyclonal DBP antibodies or proteomic methods was not lower in African-ancestry. Calculated f25OHD (using polyclonal DBP assays) correlated strongly with directly measured f25OHD (r = 0.80-0.83). Free 25OHD, measured or calculated from polyclonal DBP assays, reflected total 25OHD concentration irrespective of race and was lower in African Americans than in US whites.

CONCLUSIONS

Previously reported racial differences in DBP concentration are likely from monoclonal assay bias, as there was no racial difference in DBP concentration by other methods. This confirms the poor vitamin D status of many African-Americans and the utility of total 25OHD in assessing vitamin D in the general population.

Therapeutic drug monitoring in neonates

Therapeutic drug monitoring (TDM) aims to integrate drug measurement results into clinical decision making. The basic rules apply when using TDM in neonates (aminoglycosides, vancomycin, phenobarbital, digoxin), but additional factors should also be taken into account. First, due to both pharmacokinetic variability and non-pharmacokinetic factors, the correlation between dosage and concentration is poor in neonates, but can be overcome with the use of more complex, validated dosing regimens. Second, the time to reach steady state is prolonged, especially when no loading dose is used. Consequently, the timing of TDM sampling is important in this population. Third, the target concentration may be uncertain (vancomycin) or depend on specific factors (phenobarbital during whole body cooling). Finally, because of differences in matrix composition (eg, protein, bilirubin), assay-related inaccuracies may be different in neonates. We anticipate that complex validated dosing regimens, with subsequent TDM sampling and Bayesian forecasting, are the next step in tailoring pharmacotherapy to individual neonates.

Comparison of molecular responses based on BCR-ABL1% (IS) results from an in-house TaqMan-based qPCR versus Xpert(®) assay in CML patients on tyrosine kinase inhibitor therapy

OBJECTIVES

Tyrosine kinase inhibitors (TKIs) have drastically changed the prospects for chronic myeloid leukemia (CML) patients. The European LeukemiaNet (ELN) recommends molecular monitoring of BCR-ABL1 mRNA levels at distinct time points to define an optimal response, warning, or failure of treatment.

METHODS

Sixty-four follow-up peripheral blood samples from CML patients on TKI were tested by two methods. Molecular responses based on BCR-ABL1% (IS) from an Xpert(®) BCR-ABL1 Monitor assay were compared with TaqMan-based qPCR.

RESULTS

Seven samples showed 'molecularly undetectable leukaemia' by both methods (11%). In-house qPCR showed 57 BCR-ABL1+ samples; 45/57 samples (79%) were concordant for 'major molecular response' (MMR, n = 32) and 'no MMR' (n = 13) by both assays, whereas nine were BCR-ABL1 negative by Xpert(®). Identical molecular responses (i.e. 'optimal') were defined in 41 samples. Discordances seen in patients < 10 months on TKI (n = 2) had no impact on clinical management, whereas for patients >12 months on TKI, a different molecular response was defined ('warning' versus 'optimal'). Thirteen samples had 'no MMR' by both methods. 10/13 showed identical intervals (>10%(IS), 1-10%(IS) or 0·1-1%(IS)), corresponding to seven 'failures' and three 'warnings'. Discordant intervals were seen in 3/13 samples (all defined as 'failures'). Deep molecular responses (MR(4·0) or MR(5·0)) with detectable BCR-ABL1 showed some fluctuations between both methods, nevertheless, all had 'optimal' responses. 'Molecularly undetectable leukaemia' was observed more frequently by Xpert(®) (n = 16) as by our in-house assay (n = 7).

DISCUSSION

Based on current ELN recommendations, Xpert(®) BCR-ABL1 assay defines identical molecular responses as TaqMan-based qPCR BCR-ABL1% (IS) data in 98% (63/64) of samples.

Aberrant glycated haemoglobin (HbA1c) results leading to haemoglobinopathy diagnosis in four Belgian patients

INTRODUCTION

We report four cases in which haemoglobinopathy screening was triggered following aberrant HbA1c analysis. Either the HbA1c assay was unable to produce a quantifiable result or it showed the presence of an extra fraction and/or the result was discordant with the clinical context.

CASE REPORT

In the reported four patients, all from Caucasian, Belgian descent, Hb analysis was performed using cation-exchange high performance liquid chromatography. If necessary, additional Hb electrophoresis was carried out to establish a preliminary (biochemical) diagnosis. Definitive diagnosis was obtained for every sample through DNA-analysis. Three patients were carriers of Hb J-Toronto and one of Hb Stanleyville-II.

DISCUSSION

This report underlines the importance of correct interpretation of HbA1c results to avoid mismanagement of (diabetic) patients. Since neither the RBC indices, the clinical context, nor the ethnicity of these patients was suspicious for an underlying haemoglobinopathy, the aberrant HbA1c result was the only indicator for further investigation. Laboratory personnel and clinicians should be aware of the possibility of uncommon, sometimes clinically unsuspected, Hb variants to cause aberrant HbA1c values, even in populations with low prevalence for haemoglobinopathies. Further analysis should be prompted to obtain definitive diagnosis. Alternative methods for monitoring glycaemic control should be used.

Evaluation of the Sebia Minicap Flex Piercing capillary electrophoresis for hemoglobinopathy testing

INTRODUCTION

Capillary zone electrophoresis (CZE) at alkaline pH is one of the techniques used for hemoglobinopathy screening. In this study, an evaluation of the performance of a lower throughput CZE instrument, the Sebia Minicap Flex Piercing system, for this purpose is reported for the first time.

METHODS

The analytical performance of the Sebia Minicap Flex Piercing system was evaluated. Furthermore, a method comparison between the Sebia Minicap Flex Piercing and two HPLC methods, that is, the Bio-Rad Variant Classic(™) and the Bio-Rad D-10(™) systems was performed by measuring samples with and without clinically relevant hemoglobin disorders.

RESULTS

The analytical performance was acceptable for the determination of HbA, HbA2, HbS, and HbF, with an imprecision ≤2.0%. Method comparison showed a linear correlation for HbA2, HbF, and HbS measurements. Clinical concordance was acceptable when comparing CZE and HPLC.

CONCLUSIONS

Lower throughput CZE using the Sebia Minicap Flex Piercing can be used for precise and accurate first line screening and follow-up of hemoglobinopathies.

Deproteination of whole blood for LC-MS/MS using paramagnetic micro-particles

OBJECTIVES

Liquid chromatography tandem mass spectrometry has become increasingly popular in clinical laboratories over the last decade due to the inherent sensitivity and specificity of the technology. Nevertheless, full automation and hence application in routine laboratories is still hampered by laborious and difficult-to-automate sample pre-treatment protocols. Functionalized paramagnetic micro-particles could simplify sample pre-treatment and ease automation. We evaluated the applicability of a pre-commercial, straightforward paramagnetic micro-particle based kit for the lysis and deproteination of whole blood for the LC-MS/MS analysis of everolimus and compared the performance to our routine protein precipitation method.

DESIGN AND METHODS

Samples were prepared for LC-MS/MS everolimus analysis on an Acquity UPLC chromatographic system coupled to a TQD mass spectrometer (both Waters Ltd.) using a pre-commercial MagSi-TDMprep kit and a routine protein precipitation respectively. Both pre-treatment methods were validated for imprecision, accuracy, linearity, limit of quantification, matrix effect, recovery and process efficiency. A method comparison (n=63) between both pre-treatment methods was performed.

RESULTS

Imprecision and bias were within pre-defined criteria (15%) for both pre-treatment methods. Both methods were linear from 1.2 to 14.8μg/L with a limit of quantification of 0.6μg/L. Process efficiency was on average 65% for protein precipitation pre-treatment and was substantially higher for the MagSi-TDMprep method (85%). A Passing-Bablok regression showed no significant difference between the two pre-treatment methods.

CONCLUSION

For everolimus in whole blood, the MagSi-TDMprep sample pre-treatment was applicable and comparable to protein precipitation for LC-MS/MS with the possible advantage of easier automation.

Paired measurement of urinary creatinine in neonates based on a Jaffe and an enzymatic IDMS-traceable assay

Background

Urinary creatinine can be quantified by Jaffe or enzymatic assays and is commonly used as denominator of urinary excretion of electrolytes or protein. Paired analysis in pediatric and adult samples documented inter-assay differences (up to 80%). We verified the interchangeability of two IDMS-traceable assays (Jaffe and enzymatic) for neonatal urine and report on neonatal urinary creatinine values using these IDMS-traceable methods.

Methods

Creatinine was measured in 84 neonatal urine samples from 46 neonates by an IDMS traceable Jaffe and enzymatic assay (Roche Diagnostics, Cobas c702 module). Creatinine values, differences in urinary creatinine and clinical characteristics were described and covariates of between assay difference were explored (Wilcoxon, Bland-Altman, correlation, multiple regression).

Results

Median Jaffe and enzymatic urinary creatinine concentrations were 9.25 (range 3.7-42.2) and 9.15 (range 3.8-42.9) mg/dL respectively, resulting in a median difference of 0.08 (SD 0.6, range −2.4 to 0.96) mg/dL. In a multiple regression model, urinary enzymatic creatinine concentration (r = 0.45) and postnatal age (r = −0.59) remained independent variables of the difference between both assays (r² adj = 0.45).

Conclusions

The tested IDMS-traceable assays showed interchangeable in heterogeneous neonatal urine samples. Using these assays, neonatal urinary creatinine showed 5–20 fold lower values than those observed in children or adults with a significant negative correlation with postnatal age.

Abstract P1-13-09: Sensitive liquid chromatography-tandem mass spectrometry method for serum estradiol and estrone assessment without derivatisation, overcoming cross reactivity with exemestane

Objective Measuring serum estrogen levels in postmenopausal women on oral aromatase inhibitors is important but challenging. Direct immunoassays are the most widely used techniques for measuring serum estradiol (E2) in research and clinical laboratories. Unfortunately, commercially available immunoassays for E2 lack precision and accuracy in the low range (&lt;20 ng/l) and are susceptible to interference. In addition, particularly in exemestane users biochemical monitoring of E2 is problematic because exemestane metabolites cross react in most immunoassays for E2. We developed a sensitive, routinely applicable liquid chromatography-tandem mass spectrometry (LC-MSMS) method for E2 and estrone (E1) quantification in human serum without the need for derivatization or an extended extraction protocol.

Materials and methods Serum E2 levels, assessed with LC-MSMS and electrochemiluminescence estradiol assay (ECLIA) on Modular E170 from Roche Diagnostics, of 10 breast cancer patients treated with exemestane were compared. Limit of quantification (LOQ) was 1.3 ng/l for LC-MSMS (coefficient of variation &lt;20% and signal-to-noise ratio &gt; 10, own validation) and 5 pg/ml for ECLIA (Roche, according to manufacturer).

Results Patients treated with exemestane showed much higher E2 levels when measured by ECLIA compared to E2 levels determined by LC-MSMS (Table 1). All patients, but one, had E2 values below LOQ when assessed with LC-MSMS whereas ECLIA measurements showed higher levels with a large variety (mean: 16.5 ng/l; range: 7-33 ng/l).

Results for E2 via ECLIA and LC-MSMS for patients treated with exemestanePatientE2 LC-MSMS ng/lE2 ECLIA ng/l1&lt;1.3212&lt;1.373&lt;1.3124&lt;1.3335&lt;1.3156&lt;1.3227&lt;1.398&lt;1.32692.51010&lt;1.310

Conclusion E2 levels in exemestane users measured with ECLIA from Roche are overestimated, probably due to cross reactivity of its metabolites. Therefore, this assay can not be used in these patients. Here, we demonstrate that this hurdle can be overcome by assessment of estrogen values with LC-MSMS. Our group was able to develop such a sensitive method, without derivatization.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-13-09.

Ecstasy intoxication as an unusual cause of epileptic seizures in young children

In light of the widespread use of ecstasy, it is surprising that only few cases of intoxicated young children have been reported. Patients almost invariably present with convulsions accompanied by sympathetic signs and symptoms such as hyperthermia. Two new cases of toddlers intoxicated with ecstasy are described. The first patient, a 19-month-old boy, presented with convulsions but no sympathetic signs. The pediatrician's suspicion was raised because of the absence of a postictal state. The second patient, a 20-month-old girl, had a more typical presentation with convulsions and hyperthermia. Her story illustrates the fact that immunoassays for toxicological screening can easily miss traces of additional illicit drugs present in the urine such as cocaine. The presence of other illicit drugs provides clues to the child's risky environment and should lead to further investigation. Finally, we review the available literature on ecstasy intoxication to summarize the key presenting manifestations.

Sensitive routine liquid chromatography-tandem mass spectrometry method for serum estradiol and estrone without derivatization

The need for a routinely applicable assay to measure low estradiol levels in adult men, postmenopausal women, and young adolescents was recently discussed in an Endocrine Society position statement. Our aim was to develop a sensitive liquid chromatography-tandem mass spectrometry method for estradiol and estrone in human serum without the need for derivatization or extended extraction protocols. After protein precipitation of serum with a mixture of methanol/acetonitrile (85/15) (v/v) containing isotopic internal standards (17β-estradiol-16,16,17-d 3 and estrone-2,3,4-(13)C), we quantified estradiol and estrone by two-dimensional liquid chromatography-tandem mass spectrometry with electrospray ionization in the negative mode monitoring 5 × 271.20→145.00 (17β-estradiol) and 269.20→145.00 (estrone). Sensitivity was increased by using fluoride and summation of 5 identical transitions for estradiol. Our method was analytically validated, compared against direct immunoassays using serum of 25 adult men, and clinically tested by measuring samples of 3 men at baseline and after chemical castration, 30 postmenopausal women and 15 patients receiving aromatase inhibitors. Total imprecision was below 20% for the low quality controls. Limit of quantification was 1.3 ng/L (4.8 pmol/L) for estradiol and 1.2 ng/L (4.4 pmol/L) for estrone. Estradiol in Certified Reference Material BCR-576 was within specified uncertainty limits. No significant ion suppression or interference was observed. Our method showed modest correlation with direct immunoassay for estradiol (r(2) = 0.64) but no correlation for estrone (r(2) = 0.12). Patient sample results were within expected ranges. In conclusion, we developed a routinely applicable liquid chromatography-tandem mass spectrometry method for estradiol and estrone measurement which is sensitive enough for use in men, postmenopausal women, and young adolescents.

Lifestyle after bariatric surgery: a multicenter, prospective cohort study in pregnant women

BACKGROUND

To ensure a good pregnancy outcome after bariatric surgery, a healthy life-style and a multidisciplinary prenatal follow-up is recommended. The aim of this prospective multicenter trial was to compare diet quality and physical activity (PA) of pregnant women with bariatric surgery with current lifestyle recommendations.

METHODS

Pregnant women (>18 years, prepregnancy BMI 28 ± 6 kg/m², 39 % nulliparae, 25 % smokers) with a history of bariatric surgery were recruited and allocated to two groups according to surgery type: restrictive (N = 18) and bypass group (N = 31). One 7-day dietary record and one Kaiser questionnaire on PA were collected during the first and second trimester. Dietary quality was assessed using the Healthy Eating Index.

RESULTS

The diet quality did not change during pregnancy (restrictive group p = 0.050; bypass group p = 0.975) and was comparable between groups (first trimester p = 0.426; second trimester p = 0.937). During the first trimester, 15 % of the pregnant women had a healthy diet quality, 82 % had a diet that needed improvement, and 3 % had a poor diet quality. This was independent of surgery type and was comparable in the second trimester (p = 0.525). No difference between groups was observed for the PA level, but the PA level in the bypass group significantly decreased from the first to the second trimester (p = 0.033).

CONCLUSIONS

Nutritional advice and lifestyle coaching in this high-risk population seems recommendable since only 15 % of the pregnant women had a healthy diet quality, 25 % was smoking at the beginning of pregnancy, and the reported PA levels were low.

Coxsackievirus B1 peritonitis in a patient treated with continuous ambulatory peritoneal dialysis: a case report and brief review of the literature

We report a case of viral peritonitis caused by coxsackievirus B1 in a 79-year-old male undergoing continuous ambulatory peritoneal dialysis (CAPD), and review the English language literature. Clinicians should be aware of viral peritonitis in patients on CAPD presenting with a viral syndrome and mononuclear peritoneal dialysis effluent. Currently, viral diagnostic tests are available to confirm the diagnosis and avoid unnecessary treatment with antibiotics.

The role of surgery and transplantation in neuroendocrine tumours

Surgery represents the only chance of cure for a patient with a neuroendocrine tumour (NET). The main indications for surgery lie in the risk of developing metastatic disease with increasing tumour diameter and for a functioning NET also in control of the hormonal syndrome. However, only a small minority of patients presents with a potentially resectable primary NET without metastatic disease. An R0-resection is mandatory, which may be achieved in selected cases by tissue sparing surgical techniques. Most patients unfortunately present with a locally advanced or metastatic disease. For patients with an advanced functioning NET, control of the hormonal syndrome may also represent a surgical indication. Various cytoreductive techniques or, in highly selected cases, liver transplantation can be applied. For locally advanced non-functioning tumours, there is an indication for surgery in large tumours which tend to create local complications because of bleeding or bowel obstruction. Especially in ileal NETs aggressive surgical therapy is recommended because of prevention of long-term complications, which may improve survival.

Role of chemotherapy in gastro-entero-pancreatic neuroendocrine tumors: the end of a story?

Gastroenteropancreatic Neuroendocrine Tumours (GEP NET) are heterogeneous and rare malignancies although their prevalence is increasing. Multiple therapeutic approaches are available to date for their management, including surgery, hormonal and immune radionucleide therapies and chemotherapy. The purpose of this review is to collect, examine, and analyze data available regarding contemporary chemotherapeutic management of GEP NET in order to determine whether or not chemotherapy still takes place in the therapeutic arsenal of GEP NET. We therefore performed a systematic search of all the English-spoken literature regarding GEP NET. Anthracyclins, 5-fluorouracil (5-FU), DTIC and streptozotocin are amongst the most commonly used chemotherapeutic agents, usually prescribed in combination. Their efficiency in reducing tumor burden is not always associated with better survival, perhaps due to severe toxicity. Chemotherapy in GEP NET is mainly devoted to poorly differentiated tumours, but also in well differentiated carcinomas either not eligible or resistant to other therapies. Chemotherapy remains therefore useful in specific cases of GEP NET management. However, a new era of antitumoral agents, such as targeted therapies, could eventually replace these old recipes in the near future.

Diagnostic pitfalls in digestive neuroendocrine tumours

Gastro-entero-pancreatic neuroendocrine tumours (GEP NET) represent a rare and highly heterogeneous entity that often is revealed by vague and non-specific symptoms, leading to a delayed diagnosis. Here we will review some of the most regularly observed false positive and false negative cases and provide clues to recognize and manage them properly. Particularly, the value of chromogranin-A as a serum tumour marker and Somatostatin receptor scintigraphy as an imaging test, are reviewed. Indeed, chromogranin-A and other hormones, such as gastrin, as well as urinary 5-hydroxy-indolic acetic acid (5-HIAA) are often tested to diagnose NET without appraising the clinical situation, leading to extensive work-up on false bases. On the other hand, some tests are performed in situations where they do not add additional information (e.g. 5-HIAA in pancreatic or rectal NET) because invariably negative. Somatostatin receptor scintigraphy is an expensive examination, still not reimbursed in Belgium, for which indications must be carefully assessed, knowing its specificity and sensitivity.

Carcinoid heart disease--a hidden complication of neuroendocrine tumours

Carcinoid heart disease (CHD) develops in serotonin-producing neuroendocrine tumours (NET) due to fibrotic endocardial plaques with associated valve dysfunction leading most often to right-sided heart failure. The classical carcinoid syndrome usually occurs when serotonin-producing NET metastasize to the liver. Up to 50% of those patients will exhibit carcinoid heart disease. The pathophysiological process is not yet completely understood: serotonin is considered to be a major initiator of the fibrotic process, but other tumour secreted factors may contribute to the pathogenesis. Histopathology reveals intact valvular cusps with superimposed fibrotic plaques, leading to thickening and retraction of the valves, causing valvular dysfunction. A high index of clinical suspicion to diagnose CHD is needed since symptoms can be rather non-specific. Transthoracic echocardiography is the gold standard for diagnosis and should probably be performed at the time of diagnosing serotonin-producing NET and then repeated annually. On the other hand, when diagnosing right-heart failure, the presence of CHD and underlying serotonin-producing NET should be taken into account. Therapeutic options include pharmacotherapy for heart failure, control of the systemic carcinoid disease and in selected individuals cardiac valve replacement. The elucidation of the pathologic process is necessary to develop targeted antifibrotic therapeutic agents since CHD seems to be irreversible and associated with poor prognosis.