Cristina Valente

Better blood collection tubes for plasma glucose: ready for prime time?

*Corresponding author: Dominika Szoke, Laboratorio Analisi Chimico-Cliniche, Ospedale Luigi Sacco, Via GB Grassi 74, 20157 Milano, Italy, Phone: +39 02 3904 2290; Fax: +39 02 5031 9835, E-mail: szoke.dominika@hsacco.it Dominika Szoke, Cristina Valente and Mauro Panteghini: Clinical Biochemistry Laboratory, ‘Luigi Sacco’ University Hospital and Department of Biomedical and Clinical Sciences, University of Milan Medical School, Milan, Italy

Hemoglobin, bilirubin, and lipid interference on Roche Cobas 6000 assays.

We read with great interest the article by Ji and Meng regarding an experimental study on the evaluation of hemoglobin, bilirubin, and lipid interference on Roche Cobas 6000 assays [1]. The topic considered by the Authors is extremely important and useful in the clinical laboratory practice, if one considers that preanalytical errors still account for approximately 60%–70% of all errors occurring in the laboratory diagnostics [2] and the hemolysis only can be accountable for approximately half of them [3]. In this regard, the availability of the specific hemolysis, icterus and lipemia/turbidity (HIL) alert indices may significantly help to improve the prevention of laboratory test misinterpretations and subsequent possible medical errors. In our clinical laboratory, the HIL threshold values set for all analytes determined by Roche Cobas 6000 assays are those recommended by Roche in the corresponding package inserts. However, we believe that an appropriate verification study carried out with an accurately designed and well described experimental protocol could lead customers to revise their HIL alert indices currently in use. Therefore, considering the strong impact that a scientific work concerning this topic can have on routine laboratory behavior and subsequent clinical decisions, we welcomed the study of Ji and Meng [1]. Unfortunately, when we tried to compare the published data to our own situation and possibly change our daily practice according to the new information, we realized that some major limitations in the report did not permit any useful conclusion. The lack of a careful description of the protocol used in the experiments is, in our opinion, the most important limitation. Manufacturers typically follow the recommendations of the CLSI document EP07-A2 [4] or those published by Glick et al. [5]. As these well established standard protocols were not followed, authors should provide adequate and exhaustive information regarding experimental steps of the work, which are indeed very unclear in the text. Details of sampling and pooling, like the type and number of enrolled subjects, the volume of blood samples and the sample storage conditions before analysis were not described. More importantly, authors did not explain the preparation mode of samples with varying concentrations of interferents, without even specifying the maximum concentrations of hemoglobin, bilirubin and Intralipid added to the pooled plasma. Indeed, by HIL alert indices displayed in the tables it is sometimes difficult to imagine how spiking and dilutions were experimentally done. Otherwise, if these index levels were retrieved using regression analysis, an indication regarding the application of this approach would be required. Information on analytical quality performance (precision and trueness verification, carryover assessment, etc.) and of the employed experimental

Commutability of the ERM-DA470k Reference Material for two assays measuring serum albumin using immunochemical principles

The standardization of measurements is a high-priority in Laboratory Medicine; its purpose being to achieve closer comparability of results for the same analyte obtained using different commercial systems (1). The promotion of result traceability to available higher-order reference measurement procedures and reference materials is the recommended approach (2). A major prerequisite for guaranteeing comparability of results among different methods is the availability of suitable reference materials, appropriately and thoroughly defined by a set of characteristics (3, 4). Reference materials can be used for calibration of routine methods. However, when reference materials are intended for direct value assignment to manufacturer’s calibrators, they should be extensively investigated for commutability (5). The main serum proteins are among the best standardized analytes in clinical laboratories. In 1993, the Bureau Communautaire de Reference of European Commission released the certified reference material (CRM) 470 (later renamed to ERM-DA470), developed in collaboration with the IFCC, resulting in a highly significant reduction of the among-laboratory variance for most proteins (6, 7). The ERM-DA470k/IFCC is a new serum protein reference material prepared to replace ERM-DA470, and to ensure continuity of the standardization of serum protein measurements (8, 9). With regard to serum albumin, the availability of these serum protein reference materials, both including albumin in the list of certified proteins, together with immunochemical methods based on turbidimetry-nephelometry principles, recognized as reference measurement procedures by the Joint Committee on Traceability in Laboratory Medicine (JCTLM),

Impact of Implementation of the High-Sensitivity Cardiac Troponin T Assay in a University Hospital Setting

To the Editor: The performance of the high-sensitivity cardiac troponin T assay (hs-cTnT)1 has been evaluated in a multicenter study (1). Effective July 2009, we replaced the fourth-generation troponin T assay (cTnT) with the hs-cTnT assay in clinical practice. This study audits the impact of this implementation. The hs-cTnT, implemented on the cobas e 411 platform (Roche Diagnostics), fully replaced the cTnT performed on the Elecsys 2010 analyzer [cutoff, 30 pg/mL—based on actual assay performance (10% CV concentration)]. We obtained a detection limit of 5 pg/mL, a 99th percentile of 15 pg/mL, limited comparability with the cTnT at concentrations <100 pg/mL (on average, a 30-pg/mL cTnT concentration yielded a value of approximately 65 pg/mL with the hs-cTnT) and mean CVs of 9.1% for the cTnT (at 39 pg/mL) and 8.5% for the hs-cTnT (at 17 pg/mL). We retrieved hs-cTnT results for the first 3 months after implementation (July 16 to October 15, 2009) and cTnT results for the same period 1 year previously. Results were dichotomized as positive or negative …

Measurement of icteric index as approach to detect abnormal total bilirubin values

We read with great interest the article by Salinas et al 1 suggesting the use of the icteric index (II) as a front-line test for the preliminary identification of blood samples with abnormal total bilirubin (TB) concentrations. Following the authors’ suggestion, we were encouraged to experimentally confirm their findings in our own hospital setting. Particularly, in our laboratory we use platforms (Cobas c 501 and Integra 800) and reagents of the same vendor (Roche Diagnostics) used by Salinas et al, and we think that our findings could contribute further evidence to their results, even if obtained with instruments of different series. We evaluated all the measurements of TB requested to our laboratory between January and December 2011 and their corresponding II values. TB concentrations and II were measured on Cobas c 501 using serum samples (routine) and on Integra 800 using lithium-heparin plasma samples (stat). Both systems use for TB the same diazo-based colorimetric assay, and for the II determination, an assay based on calculations of absorbance measurements of diluted samples. Statistical evaluation, including linear regression analysis, calculations of sensitivity, specificity, positive (LR+) and (LR−) negative likelihood ratios, positive predictive value (PPV) and negative predictive value (NPV) was performed for both serum and plasma samples, separately, by applying the same cut-off values used by Salinas et al , that is, 1.2 mg/dl (20.5 μmol/l) for TB concentrations and 2 for II. The analysis was performed using Sigma Plot V.12.0 (Systat Software, Inc) Main results are summarised in table 1. Linear regression analysis (II vs TB) gave the following results: for serum samples measured …

Biologic variation of copper, ceruloplasmin and copper/ceruloplasmin ratio (Cu:Cp) in serum.

Diagnostic algorithms for Wilsons disease (WD) recommend the determination of serum ceruloplasmin in addition to the slit-lamp examination required to identify Kayser–Fleischer rings as clues in order to decide on or decline further testing, while measurements of total serum copper and/or ceruloplasmin-unbound (“free”) copper are of value in monitoring pharmacotherapy [1,2]. The direct measurement of “free” copper is, however, difficult and not routinely available [3]. To overcome this issue, equations have been proposed for assessing “free” copper fraction in serum; however, they can produce biologically implausible negative results in a significant number of patients [4]. The use of copper/ceruloplasmin ratio (Cu:Cp) has been proposed to overcome such problems [5]. Despite their clinical role, aspects related to biologic variation (BV) of total copper and ceruloplasmin in serum have not received enough attention, while information on “free” copper BV is totally lacking. We could retrieve only one published study carefully determining the BV of total copper using a well designed protocol [6]. Here we performed an assessment of BV components of total copper and ceruloplasmin concentrations in serum, and derived Cu:Cp, in the same cohort of subjects by an accurately designed protocol. We collected five blood specimens from each of 19 healthy volunteers (10 men and 9 women; age range, 23–48 years) on the same day, every twoweeks for twomonths. Ostensibly healthy subjects were studied to ensure that any copper and ceruloplasmin fluctuation in serum could truly reflect biology and not modifications due to pathologic (e.g., inflammatory) processes. In accordance with the Helsinki II Declaration, the study design was explained thoroughly to the subjects, and informed consent was obtained. None of subjects took any medication or consumed substantial (>10 g/day) quantities of alcohol. Women had regular menstrual cycle and did not use hormonal contraceptives. Venous blood was obtained at 0900 from subjects who had fasted for 12 h and had not smoked or exercised in thatmorning. Sampleswere collected by the same phlebotomistwith minimal stasis using vacuum collection tubes. After centrifugation, serum specimens were stored at−80 °C until analysis. When all specimens were available, they were thawed and analyzed in a single run in duplicate in random order. Copper and ceruloplasmin were determined on Roche Cobas c501 analyzer using a colorimetric and an immunoturbidimetric assay, respectively. Cu:Cp was calculated by the

Implementation of new recommendations for the diagnosis of gestational diabetes: a 5-month audit

Abstract Background: Recent international recommendations for the diagnosis of gestational diabetes (GD) were implemented in a university hospital. The aim was to audit the appropriateness of use of the new diagnostic approach. Methods: The same 5-month period, one before [2009, traditional two-step oral glucose tolerance test (OGTT) approach, S1] and one after the implementation of new criteria (2010, S2) were compared. Results: In the two periods, 256 (S1) and 245 (S2) pregnant women were examined and 298 (50 g, n=195; 100 g, n=103) and 252 (75 g) OGTTs were, respectively, executed. In S1, 54 (27.7%) 50 g OGTTs resulted positive and 36 (66.7%) of those performed the 100 g OGTT. In addition, three (1.5% of total) 50 g OGTT negative women were submitted to 100 g OGTT. Sixty-three women did 100 g OGTT only. In total, 14 (13.6%) 100 g OGTTs were positive. In S2, 38 (15.1%) 75 g OGTTs were positive. In women who did the complete protocol in the hospital, 98.3% in S1 and 77.0% in S2 performed the correct protocol (p<0.0001). Conclusions: In this hospital new recommendations for GD diagnosis are not correctly applied in 23% of cases. The main issue seems to be the lack of consideration of the new threshold for fasting glycemia (5.1 mmol/L) as a main decisional driver for performing OGTT.

Frequency of Pancreatic Hyperamylasemia in Human Immunodeficiency Virus-Positive Patients in the Highly Active Antiretroviral Therapy Era.

OBJECTIVES Increased frequency of hyperamylasemia has previously been reported in human immunodeficiency virus (HIV)-positive patients, but studies determined total amylase activity and were performed before the introduction of highly active antiretroviral therapy (HAART). We evaluated the frequency of pancreatic hyperamylasemia in a large HIV+ population mostly treated with HAART. METHODS The upper reference limit (URL) for pancreatic amylase (P-AMY) was derived from 299 healthy blood donors. A cross-sectional study was then performed on samples obtained from 1,548 consecutive patients referred to our infectious disease clinic to assess serum P-AMY and lipase concentrations. Of the patients, 94% were HIV+, and most (92%) were taking HAART (HIV+Tx+). RESULTS P-AMY URL was 51 U/L. The frequency of P-AMY increase did not significantly differ between HIV+ and HIV - populations (14.2% vs 15.2%, P = .91) or between HIV+Tx+ and HIV+Tx - (14.7% vs 8.9%, P = .11). In almost half (48.3% of HIV+ and 42.9% of HIV -) of hyperamylasemic patients, lipase was normal, indicating a non pancreatic origin of their P-AMY increase. Markedly elevated P-AMY (>3 times the URL) was found in six HIV+ patients and in one HIV - patient: two had macroamylasemia, one acute pancreatitis, three (including the HIV - patient) chronic pancreatitis, and one chronic hyperamylasemia of undefined origin. CONCLUSIONS In our study, both HIV+ and HIV+Tx+ do not show an increased frequency of P-AMY elevation. Frank pancreatic disease is rare in this clinical setting.

Measurement imprecision of common urinary biochemical analytes on the Roche Cobas 6000 system

*Corresponding author: Dominika Sz ő ke, Laboratorio Analisi Chimico-Cliniche, Azienda Ospedaliera ‘ Luigi Sacco ’ , Via GB Grassi 74, 20157 Milan, Italy, Phone: + 39 02390442290, Fax: + 39 0250319835, E-mail: szoke.dominika@hsacco.it Dominika Sz ő ke, Federica Braga, Cristina Valente and Mauro Panteghini: Clinical Biochemistry Laboratory, ‘ Luigi Sacco ’ University Hospital, and Department of Biomedical and Clinical Sciences, University of Milan Medical School, Milan, Italy

Impact of the highly sensitive cardiac troponin t (hsTnT) assay on the triage of emergency department (ED) patients

Background: A fatty acid (FA) is a carboxilic acid with a long aliphatic chain, which is either saturated or unsaturated. Recently, the role of FA and particularly omega 3 and 6 has emerged as cardiovascular risk factor in the literature. The aim of our study was to establish reference value for these FA and to compare these results with data obtained in acute myocardial infarction (AMI) patients.1 Department of Clinical Chemistry of the University of Liege, Liege, Belgium 2 Department of Cardiology, CHU Sart-Tilman, Liege, Belgium 3 Department of Motricity Sciences of the University of Liege and CHU Sart-Tilman, Liege, Belgium Introduction: Novel high-sensitive cardiac troponin T (hsTnT) and I (TnI II) assays have the potential to detect myocardial injury with a higher sensitivity. The aim of the study was to assess the level of hsTnT and TnI II in patients with atrial fibrillation (AF) as compared to control and following direct current cardioversion. Levels of NT-proBNP, myeloperoxydase (MPO) and hs-CRP were concomitantly measured.