Accounting for differences between serum and plasma: An indirect approach to derive reference intervals for total protein, albumin, and globulin.

BACKGROUND: Observable quantitative variations exist between plasma and serum in routine protein measurements, often not reflected in standard reference intervals. In this study, we describe an indirect approach for estimating a combined reference interval (RI) (i.e., serum and plasma), for commonly ordered protein measurands: total protein, albumin, and globulin. METHODS: We applied an indirect reference interval estimation for protein measurements in serum and plasma using data from July 2018 to February 2024. The data were divided into three Epochs based on a period of plasma separator tube shortage during the COVID-19 pandemic. Bootstrap resampling was used to calculate RIs and corresponding 95% confidence intervals for each month. RESULTS: Our results demonstrate notable changes in RI limits for total protein, albumin, and globulin between Epochs, reflecting the influence of changing sample matrix. A combined RI was identified for all components and verified using plasma and serum samples from 20 healthy individuals and retrospective analysis of flagging rates on our outpatient population using new and historical RIs. CONCLUSION: The study demonstrates notable differences in the RIs for total protein, albumin, and globulin when container type changes. In addition, the results demonstrate the effectiveness of big data analytics in deriving RIs and highlights the necessity of continuous RI assessment and adjustment based on the patient population and acceptable specimen types.

Performance Evaluation of 2 FDA-Approved Fentanyl Immunoassays against LC-MS/MS Reference.

BACKGROUND: Fentanyl, a synthetic opioid, has caused many recent overdose deaths. Diagnosis of fentanyl abuse is not served by traditional opiate assays due to differences in chemical structure between synthetics and natural opioids. To our knowledge, this is the first study that uses liquid chromatography-tandem mass spectrometry (LC-MS/MS) as the reference method to evaluate and compare the ARK Fentanyl II Assay (ARK II) and the Fentanyl II Enzyme Immunoassay by Roche (FEN2). The ARK II is designed to detect fentanyl in urine samples, whereas the FEN2 is designed to detect norfentanyl, which is the major metabolite. METHODS: Two hundred patient urine samples including 100 positive and 100 negative samples according to an in-house LC-MS/MS assay were selected for the study. These samples were tested using the ARK II and the FEN2 to determine their performances relative to LC-MS/MS results. RESULTS: The FEN2 showed a positive and negative predictive value of 100% and 97% and a concordance with LC-MS/MS of 98.5% (kappa 0.97). The ARK II showed a positive and negative predictive value of 100% and 95% and a concordance with LC-MS/MS of 97.5% (kappa 0.95). Additionally, the FEN2 accurately identified 9 positive samples with a range of fentanyl concentrations from 0 to 18 ng/mL for which norfentanyl levels were less than the cutoff of 5 ng/mL, indicating potentially greater sensitivity than otherwise stated. CONCLUSIONS: The FEN2 and the ARK II were evaluated to be similar in terms of positive and negative predictive value during the analysis of 200 patient samples, as well as equally concordant with the LC-MS/MS reference, despite differences in design.

Analytical Concordance of Total Vitamin D on a Fully Automated Random-Access LC-MS/MS Platform.

BACKGROUND: The adoption of LC-MS/MS laboratory developed tests in the clinical laboratory is limited by many factors including the lack of automation. Recently, the Cascadion™ clinical analyzer was introduced as a fully automated random-access LC-MS/MS platform. Here, the analytical concordance between the platform and a Roche immunoassay analyzer was investigated for vitamin D analysis in human serum, including samples selected for high triglyceride levels. METHODS: Analytical precision was evaluated on 3 levels of QC samples (10, 30, and 90 ng/mL) within days (n = 4, 5 days) and between days (20 days). Assay comparison to the Roche was performed using reference samples from the CDC and CAP programs for accuracy. Concordance was also monitored using routine patient samples, as well as samples selected for elevated triglyceride levels (>250 mg/dL). RESULTS: Precision met manufacturer specifications (<10% CV and <15% bias), whereas the accuracy evaluations showed a linear fit (y = 0.97x - 1.1, r = 0.995) with 1:1 correlation to reference samples, independent of C-3-epi-vitamin D levels. A mean positive bias (11%) was observed for the Roche measurements in normal patient samples, whereas a mean negative bias (-8%) was observed in samples selected for elevated triglyceride levels. CONCLUSIONS: Cascadion measurements of total vitamin D compared favorably with Roche results in our laboratory, although discordance was observed in the analysis of patient serum, which could be explained in terms of known differences between the 2 assays. However, operational issues need to be addressed to effect clinical adoption.

Tall cell variant papillary thyroid carcinoma impacts disease-free survival at the 10 % cut-point on multivariate analysis.

INTRODUCTION: The diagnosis of tall cell variant papillary thyroid carcinoma (TCV-PTC) corresponds to the feature of "aggressive histology" within the framework of the American Thyroid Association (ATA) Risk of Recurrence (ROR) guidelines. Using the current World Health Organization (WHO) definition for TCV-PTC (tall cells with height at least twice the width, distribution ≥ 30 %), we examined the impact of this diagnosis on disease-free survival (DFS). METHODS: The study cohort consisted of 347 patients treated for primary papillary thyroid carcinoma (PTC). Current ATA guidelines were followed for the extent of surgery and the administration of adjuvant radioiodine therapy. Clinical surveillance included ultrasound examination and biochemical parameters according to ATA standards. The outcome was measured as time from surgery to first disease recurrence (DR) versus time from surgery until the last documented disease-free encounter (no evidence of disease, NED). Disease-free patients with fewer than 6 months of follow-up were excluded from this cohort. Structural recurrences are documented by histology or cytology whereas biochemical recurrences are documented by rising serum thyroglobulin in the absence of structural disease. All slides on all patients were examined by two pathologists with the substantial interobserver agreement (Kappa = 73 %). The primary tumors are categorically classified either as (1) TCV-PTC (definition above), (2) Papillary thyroid carcinoma with tall cell features (PTC-TCF) (≥ 10 % < 30 % tall cells), or (3) Control (< 10 % tall cells). Tumor size is categorized as either (1) ≤ 10 mm, (2) 11-29 mm, or (3) ≥ 30 mm. Degree of ETE is categorized as either intrathyroidal, microscopic ETE, histologic spread to strap muscles, or pT4 disease. RESULTS: 185 patients are classified as TCV-PTC (≥ 30 % tall cells), 62 as PTC-TCF (≥ 10 % < 30 % tall cells), and 100 as control group (< 10 % tall cells). TCV-PTC is associated with ≥ 30 mm size (p = .0246) and invasion of strap muscles and/or pT4 (p = .0325). There was no relationship between TCV-PTC and aggressive lymph node (ALN) status defined by ATA. Overall follow-up ranged from two months (one patient death) to 203 months (mean 40.8, median 33.0). DR occurred in 61 patients (mean 31.4 months, range 0 -184, 59 structural recurrences, 2 biochemical recurrences). Three models for TCV-PTC were examined: Model 1 - Tall cells ≥ 10% versus control, Model 2 - TCV-PTC versus TCF-PTC versus control, and Model 3 - TCV-PTC versus control. Kaplan Meier curves demonstrated decreased DFS with ALN status (p = .0001), ETE (p = .0295), and TCV-PTC (Model 1, p = .041). On multivariate analysis, TCV-PTC (Model 1) remained significantly predictive when adjusted for ALN (p = .0059). ETE dropped out of the model. CONCLUSION: TCV-PTC is significantly associated with larger tumors and a greater degree of ETE. The diagnosis of TCV-PTC significantly impacts DFS at the 10 % cut-point on multivariate analysis.

Updates in Anticoagulation Therapy Monitoring.

In the past six decades, heparin and warfarin were the primary anticoagulants prescribed for treatment and prophylaxis of venous thromboembolism worldwide. This has been accompanied by extensive clinical knowledge regarding dosing, monitoring, and reversal of these anticoagulants, and the resources required to do so have largely been readily available at small and large centers alike. However, with the advent of newer oral and parenteral anticoagulants such as low molecular weight heparins, factor Xa inhibitors, and direct thrombin inhibitors in recent years, new corresponding practice guidelines have also emerged. A notable shift in the need for monitoring and reversal agents has evolved as well. While this has perhaps streamlined the process for physicians and is often desirable for patients, it has also left a knowledge and resource gap in clinical scenarios for which urgent reversal and monitoring is necessary. An overview of the currently available anticoagulants with a focus on the guidelines and available tests for anticoagulant monitoring will be discussed in this article.