Preliminary evaluation of the diagnostic performance of Roche Elecsys® active vitamin B12 versus total vitamin B12 for vitamin B12 deficiency screening.

INTRODUCTION: The prevalence of vitamin B12 deficiency is high in at-risk populations with sometimes irreversible consequences. Beside total B12 (TVB12), active B12 (AVB12) is a promising first-line marker. Only Abbott AVB12 assays were largely evaluated and generally demonstrated benefit in clinical practice. More recently developed Roche AVB12 still requires some investigations. OBJECTIVES: Our study aimed to evaluate the Roche Elecsys® AVB12 immunoassay performance versus Roche Elecsys® TVB12 competition assay. DESIGN: and Methods: We included 175 patients at Rouen University Hospital who had a TVB12 value <300 pmol/L. We evaluated performance of AVB12 by comparing the results with TVB12 and MMA values in case of disagreement. RESULTS: Positive correlation was found between the AVB12 and TVB12. We found a disagreement between TVB12 and AVB12 in 18.8% of cases. Among 33 cases of disagreement, 76% had normal AVB12 but low TVB12, whereas 24% had low AVB12 and normal TVB12. Thirty-one MMA determinations were performed: 71% showed agreement between MMA and AVB12, versus 29% between MMA and TVB12. TVB12 reported a sensitivity (Se) at 66.7%, specificity (Sp) at 20%, positive predictive value (PPV) at 16.7% and negative predictive value (NPV) at 71.4% for the prediction of MMA elevation. We determined an optimized cut-off value of 45.5 pmol/L for AVB12, which reported a Se 66.7%, Sp 60%, PPV 30.7%, and NPV 88.9%. CONCLUSIONS: Our results provide preliminary evidence that Roche AVB12 may offer better discrimination than Roche TVB12 in the diagnosis of vitamin B12 deficiency. Further more detailed evaluation is warranted.

[Real-life evaluation of hypersensitive I-troponin on a point-of care analyser in an emergency unit]. / Évaluation en vie réelle de la mesure de troponine I hypersensible sur un système de biologie délocalisée pour un service d'urgences.

European Society of Cardiology (ESC) guidelines allow to perform rapid rule-in and rule-out algorithm with rapid troponin kinetics for the management of suspected Non ST-elevation acute coronary syndrome. These recommendations allow the use of point-of-care testing (POCT) systems provided that they have sufficient analytical performance. The aim of our study was to evaluate in real life the feasibility and performance of using a high sensitivity cardiac troponin I POCT system assay (hs-cTnI, Atellica® VTLi, Siemens) compared to high sensitivity cardiac troponin T values (hs-cTnT, e602®, Roche) obtained for patients admitted to emergency department. Analytical verification showed a coefficient of variation below 10% for hs-cTnI. Comparison of both troponins was moderate (r = 0.7). The study included 117 patients with a median age of 65 years, 30% had renal failure and 36% presented with chest pain. In this study, the hs-cTnT value was, more often, higher than the 99th percentile than the hs-cTnl value, even for an age-adjusted 99th percentile hs-cTnT value. The concordance of the results was moderate (Cohen's Kappa: 0.54), age remaining the most important explanatory value of discordance. Only hs-cTnT had a predictive value for hospitalization. We did not observe any interpretation discrepancies for patients who had troponin kinetics. This study confirms the feasibility of using a POCT analyzer in the emergency department, provided that it performs high sensitivity troponin. However, some data are missing to be able to use it in the framework of rapid algorithm. Finally, the implementation of POCT requires collaboration between biologists and emergency physicians in terms of organization and interpretation of values, for the overall benefit of the patient.

Lactate dehydrogenase and hemolysis index to predict vaso-occlusive crisis in sickle cell disease.

Sickle cell disease (SCD) is an inherited hemoglobinopathy disorder associated with chronic hemolysis. A major complication is vaso-occlusive crisis (VOC), associating frequent hospitalization, morbidity and mortality. The aim of this study was to investigate whether hemolysis biomarkers were able to predict VOC risk in adult patients with SCD requiring hospitalization within 1 year. This single-center prospective study included adult patients with SCD at steady state or during VOC. A total of 182 patients with SCD were included, 151 at steady state and 31 during VOC. Among the 151 patients at steady state 41 experienced VOC within 1 year (median: 3.0 months [2.0-6.5]). We observed an increase of lactate dehydrogenase (LDH) (p = 0.01) and hemolysis index (HI) (p = 0.0043) during VOC compared to steady state. Regarding patients with VOC requiring hospitalization, LDH (p = 0.0073) and HI (p = 0.04) were increased. In unadjusted logistic regression, LDH > median (> 260 U/L) (RR = 3.6 [1.29-10.88], p = 0.0098) and HI > median (> 8 UA/L) (RR = 3.13 [1.91-5.33]; p < 0.001) were associated with VOC. The association of LDH > 260 U/L and HI > 12 UA/L presented a sensitivity of 90%, and a specificity of 72.9% to predict VOC. The association of LDH and HI cut-off was able to predict VOC risk in SCD.

Biotin and high-sensitivity cardiac troponin T assay.

INTRODUCTION: The high-sensitivity cardiac troponin T assay of Roche Diagnostics is known to have interference with high concentrations of biotin as this assay uses biotin-streptavidin binding as detection method. As studies so far have not shown if different biotin concentrations could have diverse influence on various troponin concentrations and whether interference could be removed by available protocol within corresponding turnaround time we aimed to investigate it. MATERIALS AND METHODS: Plasma samples were spiked with different concentration of biotin solution. Troponin T concentrations were tested on a Roche Cobas® 8000 module 602 analyser. Final concentrations of biotin and troponin T were 50, 100, 500 and 1000 µg/L and 18, 59, 201 and 6423 ng/L, respectively. Impact of different incubation times following biotin neutralization protocol described by Piketty et al. was also tested. RESULTS: We observed a mean of negative biases of 24, 56, 97, and 98% of the troponin T expected value at biotin concentrations of 50, 100, 500, 1000 µg/L. Neutralization protocol was applied on the sample with initial concentration of TnT of 59 ng/L at a biotin concentration of 1000 µg/L. Same results across different incubation times from 60 to 0 minutes were obtained (mean value 56.8 ng/L, coefficient of variation of 1.31%). We demonstrated that neutralization process had a dilution effect of the troponin concentration (loss of 4.5% to 9.6% of initial troponin value). CONCLUSIONS: Biotin interference is not dependent of initial troponin value. Interference could be successfully neutralized within a time frame compatible with emergency but results still should be carefully interpreted due to possible dilution effect.

Dipotassium ethylenediaminetetraacetic acid is better than tripotassium salt for electrochemiluminescence insulin measurement.

Previous studies reported that stability of insulin was better on ethylenediaminetetraacetic acid (EDTA) plasma sample than serum sample. However, those studies used tripotassium EDTA (K3-EDTA) tubes, rather than dipotassium EDTA (K2-EDTA) tubes which are more commonly used in laboratories. We investigated the impact of preservative type of EDTA (K2 or K3) on the stability of C-peptide and insulin at 4°C and at room temperature room. Our study has identified that K2-EDTA achieves longer stability of insulin but does not improve the stability of C-peptide. Insulin and C-peptide are stable 24h on the same K2-EDTA sample at room temperature.