Comparison of the Japan Society of Clinical Chemistry reference method and CDC method for HDL and LDL cholesterol measurements using fresh sera

Objectives

In 2009, the Japan Society of Clinical Chemistry (JSCC) recommended a reference method for the measurement of serum high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) levels. This automated method uses cholesterol esterase-cholesterol dehydrogenase to measure cholesterol levels in fractions obtained after ultracentrifugation and dextran sulfate/magnesium chloride precipitation. In the present study, using fresh samples, we compared the LDL-C and HDL-C levels measured using this method with those measured using the traditional Centers for Disease Control and Prevention (CDC)-beta-quantification (BQ) method.

Design

and methods: Using both the JSCC and CDC-BQ methods, LDL-C/HDL-C levels were measured in 47 non-diseased and 126 diseased subjects, whose triglyceride levels were lower than 11.29 ​mmol/L (1000 ​mg/dL).

Results

For LDL-C, the equation of the line representing the correlation between the two methods was y ​= ​0.991x + 0.009 ​mmol/L; r ​= ​0.999; and Sy/x ​= ​0.025 ​mmol/L, where x is the mean LDL-C level measured using the CDC-BQ method. Similarly, for HDL-C, the equation of the line representing the correlation between the two methods was y ​= ​0.988x + 0.041 ​mmol/L, r ​= ​0.999, and Sy/x ​= ​0.019 ​mmol/L, where x is the mean HDL-C level measured using the CDC-BQ method.

Conclusions

The JSCC method agreed with the CDC-BQ method in cases of both non-diseased and diseased subjects, including those with dyslipidemia.

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Using both the JSCC and BQ methods, LDL-C/HDL-C levels were measured.

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The JSCC method agrees with the BQ method.

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The JSCC reference method is an accurate, simple, and automatable method.

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The JSCC method is suitable for quantitative analysis of LDL-C and HDL-C levels.

Development of a CDC-certified total testosterone assay for adult and pediatric samples using LC-MS/MS

BACKGROUND

Highly accurate and sensitive method to measure testosterone in hypogonadal male, female and children is vital for proper diagnosis of hormone-related conditions and their treatment.

OBJECTIVE

To develop an accurate and robust total testosterone ESI-LC-MS/MS quantification method with a simple sample preparation workflow and sufficient sensitivity for serum or plasma samples of all gender and age groups, via ketone functional group derivatization (using Amplifex™ Keto Reagent).

METHOD

A simple sample preparation method to accommodate both low and high numbers of samples was developed using simultaneous protein precipitation and derivatization with Amplifex™ Keto reagent, followed by centrifugation and direct injection of supernatant into an LC-MS/MS system (SCIEX Topaz™ IVD LC-MS/MS, in which MS is equivalent to a SCIEX 4500MD Mass Spectrometer). Total testosterone in human serum or plasma samples was quantified using an external calibration curve generated by calibrators spanning a broad concentration range of ∼1-2000 ng/dL (10-20,000 pg/mL), traceable to NIST 971 SRM. 13C3-enriched testosterone was used as an internal standard to correct for both analyte loss during sample preparation and matrix effect during analysis (Supplementary Information: SI Fig. 4C). Two methods, one using a 96-well filter plate and another using Eppendorf tubes, were developed. Both methods were certified by the Centers for Disease Control (CDC) hormone standardization (HoSt) program for total serum testosterone. The feasibility of implementing the method for plasma and serum samples was tested via a small-scale method comparison study between matched pediatric serum and plasma samples derived from the same donor. In addition, plasma samples originating from the same donor collected in two different anticoagulant tube types (Li-heparin and K2EDTA) were compared.

RESULTS

Using in-house formulated NIST 971-traceable calibrators, the method was linear (r2 > 0.999) between 1 and 2000 ng/dL (10 and 20,000 pg/mL) with a limit of detection of approximately 1 ng/dL (10 pg/mL). The testosterone concentration bias against 40 reference samples from the HoSt certification program was absolute <3% with an average %CV of ∼3-4%. More than 78% of samples passed the CDC bias criterion of ±6.4%. Comparison between pediatric matched serum and plasma samples resulted in high correlation (r2 = 0.997) and bias of <5%. The calculated % difference between matched adult serum and plasma samples was ∼1%.

CONCLUSIONS

Feasibility for an accurate and streamlined method suitable for measuring total testosterone in all human samples was demonstrated with a choice of sample preparation workflow to suit low or high number of samples. The method can potentially be used for plasma matrix from different blood collection tubes (Li-Heparin and K2EDTA).

Comparison of four clinically validated testosterone LC-MS/MS assays: Harmonization is an attainable goal

Introduction

Immunoassays and liquid chromatography-tandem mass spectrometry assays are commonly employed in clinical laboratories for measurement of total testosterone in serum. Results obtained from either of these methodologies compare poorly due to differences in calibration and/or inadvertent detection of interfering substances by the immunoassays. Standardization efforts are underway, but recent studies indicate that accuracy remains an issue.

Methods

This study compares the results from four independently developed and validated LC-MS/MS assays for total testosterone. The calibration for each assay was verified using National Institute of Standards and Technology Standard Reference Material 971.

Results

Initially, one of the four assays had a mean percent difference of +11.44%, compared to the All Method Mean, but following re-verification of all five non-zero calibrator concentrations with the NIST SRM 971, the mean percent difference decreased to -4.88%. Subsequently, the agreement between all four assays showed a mean bias of <5% across the range of all testosterone concentrations (0.13-38.10 nmol/L; 3.7-1098 ng/dL), including at low concentrations of <1 nmol/L (<29 ng/dL).

Conclusions

Excellent agreement between four independently developed LC-MS/MS assays demonstrates that harmonization using standard reference material is attainable. However, as we found in this study, to ensure accurate calibration it is critical to validate the concentrations of new lots of calibrators.

Assessment of the potential health risks associated with the aluminium, arsenic, cadmium and lead content in selected fruits and vegetables grown in Jamaica

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Thirteen food crops were analysed for aluminium, arsenic, cadmium and lead.

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Mean concentrations were used to calculate EDI, THQ and HI.

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TCR was calculated for arsenic for all food crops.

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The THQ and HI were <1 for all food crops; target cancer risk did not exceed 10⁻⁴.

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The food crops evaluated pose no undue risk to the consumer.

Thirteen Jamaican-grown food crops − ackee (Blighia sapida), banana (Musa acuminate), cabbage (Brassica oleracea), carrot (Daucus carota), cassava (Manihot esculenta), coco (Xanthosoma sagittifolium), dasheen (Colocasia esculenta), Irish potato (Solanum tuberosum), pumpkin (Cucurbita pepo), sweet pepper (Capsicum annuum), sweet potato (Ipomoea batatas), tomato (Solanum lycopersicum) and turnip (Brassica rapa) − were analysed for aluminium, arsenic, cadmium and lead by atomic absorption spectrophotometry and instrumental neutron activation analysis. The fresh weight mean concentrations in these food crops (4.25–93.12 mg/kg for aluminium; 0.001–0.104 mg/kg for arsenic; 0.015–0.420 mg/kg for cadmium; 0.003–0.100 mg/kg for lead) were used to calculate the estimated daily intake (EDI), target hazard quotient (THQ), hazard index (HI) and target cancer risk (TCR) for arsenic, associated with dietary exposure to these potentially toxic elements. Each food type had a THQ and HI < 1 indicating no undue non-carcinogenic risk from exposure to a single or multiple potentially toxic elements from the same food. The TCR for arsenic in these foods were all below 1 × 10⁻⁴, the upper limit used for acceptable cancer risk. There is no significant health risk to the consumer associated with the consumption of these Jamaican-grown food crops.

Development and implementation of an HPLC-ECD method for analysis of vitamin C in plasma using single column and automatic alternating dual column regeneration

Objectives

Vitamin C (l-ascorbic acid) is a water-soluble micronutrient necessary for human life. Inadequate intake can lead to the fatal disease scurvy. Measurement of vitamin C is used to assess nutritional status and to monitor supplementation. The goal of this study was to develop a chromatographic method for the quantitation of vitamin C in human plasma.

Design and methods

Samples were prepared by protein precipitation, addition of internal standard, and reduction with dithiothreitol. Separation of ascorbic acid was accomplished by isocratic elution on a reverse-phase column; concentration was determined by coulometry. The method was validated through studies of assay linearity, sensitivity, imprecision, accuracy, analytical specificity, and carryover.

Results

The new assay was developed using a single pump/single analytical column HPLC system. Results correlated well with our previously used spectrophotometric method. The analytical measurement range was 1.0–2500 µmol/L. The injection-to-injection time was 13 min. Subsequently, to increase method throughput and shorten turnaround time, a dual LC pump system with a 2-position/10-port switching valve capable of performing automatic alternating column regeneration was validated and implemented. The injection-to-injection time was reduced 2-fold to 6 min. The method was linear to 5000 µmol/L; limit of quantification was 1.9 µmol/L. Total imprecision was less than 5%.

Conclusions

We have developed a robust method suitable for routine clinical measurement of vitamin C in plasma specimens. The method incorporates a simplified sample preparation and a stable, non-endogenous internal standard to specifically quantify vitamin C. Faster throughput was achieved by employing an automatic alternating column regeneration system.

Standardization and quality management in next-generation sequencing

DNA sequencing continues to evolve quickly even after > 30 years. Many new platforms suddenly appeared and former established systems have vanished in almost the same manner. Since establishment of next-generation sequencing devices, this progress gains momentum due to the continually growing demand for higher throughput, lower costs and better quality of data. In consequence of this rapid development, standardized procedures and data formats as well as comprehensive quality management considerations are still scarce. Here, we listed and summarized current standardization efforts and quality management initiatives from companies, organizations and societies in form of published studies and ongoing projects. These comprise on the one hand quality documentation issues like technical notes, accreditation checklists and guidelines for validation of sequencing workflows. On the other hand, general standard proposals and quality metrics are developed and applied to the sequencing workflow steps with the main focus on upstream processes. Finally, certain standard developments for downstream pipeline data handling, processing and storage are discussed in brief. These standardization approaches represent a first basis for continuing work in order to prospectively implement next-generation sequencing in important areas such as clinical diagnostics, where reliable results and fast processing is crucial. Additionally, these efforts will exert a decisive influence on traceability and reproducibility of sequence data.

Evaluation of bias associated with high-multiplex, target-specific pre-amplification. Biomol Detect Quantif. 2016;6:13-21. [PMID: 27077043 PMCID: PMC4822213 DOI: 10.1016/j.bdq.2015.12.001]

We developed a novel PCR-based pre-amplification (PreAmp) technology that can increase the abundance of over 350 target genes one million-fold. To assess potential bias introduced by PreAmp we utilized ERCC RNA reference standards, a model system that quantifies measurement error in RNA analysis. We assessed three types of bias: amplification bias, dynamic range bias and fold-change bias. We show that our PreAmp workflow introduces only minimal amplification and fold-change bias under stringent conditions. We do detect dynamic range bias if a target gene is highly abundant and PreAmp occurred for 16 or more PCR cycles; however, this type of bias is easily correctable. To assess PreAmp bias in a gene expression profiling experiment, we analyzed a panel of genes that are regulated during differentiation using the NTera2 stem cell model system. We find that results generated using PreAmp are similar to results obtained using standard qPCR (without the pre-amplification step). Importantly, PreAmp maintains patterns of gene expression changes across samples; the same biological insights would be derived from a PreAmp experiment as with a standard gene expression profiling experiment. We conclude that our PreAmp technology can facilitate analysis of extremely limited samples in gene expression quantification experiments.