Definition of icteric interference index for six biochemical analytes.

Introduction: Icterus, if not detected, can affect the validity of results delivered by clinical laboratories, leading to erroneous results. This study aims to define bilirubin interference for some biochemical analytes and compare it with the manufacturer's data. Material and methods: Serum pools prepared with outpatients' samples were spiked with increasing bilirubin concentration (Merck, reference14370, Darmstadt, Germany) up to 513 µmol/L in order to evaluate the bias for the following biochemical analytes: creatinine (CREA), creatine kinase (CK), cholesterol (CHOL), gamma-glutamyltransferase (GGT), high-density lipoprotein cholesterol (HDL), and total protein (TP). For each analyte, six pools of different concentrations were prepared. Measurements were made employing Cobas 8000 analyser c702-502, Roche Diagnostics (Mannheim, Germany). This study employed a study procedure defined by the Spanish Society of Laboratory Medicine. Results: Obtained bilirubin concentrations producing a negative interference were 103 µmol/L for CHOL, 205 µmol/L for TP and 410 µmol/L for CK, but only for CK values less than 100 U/L. Bilirubin concentrations lower than 513 µmol/L do not produce interference for HDL and GGT. Finally, for the studied bilirubin concentrations, there is no interference for CREA higher than 80 µmol/L. Conclusion: Icterus interferences have been defined for each analyte, observing differences compared to data provided by the manufacturer. The evidence indicates that each laboratory should evaluate icteric interferences to ensure the high quality of the delivered results, thus benefiting patient care.

Elimination of lipaemic interference by high-speed centrifugation.

Introduction: In order to deliver high quality results, detection and elimination of possible analytical interferences, such as lipaemia, is crucial. The aim of this study is to evaluate the efficacy of high-speed centrifugation in eliminating lipaemic interference and to define own lipaemic index (LI) for the studied biochemical analytes. Materials and methods: Evaluated analytes were: albumin, alkaline phosphatase, alanine-aminotransferase (ALT), aspartate-aminotransferase (AST), calcium, creatinine, gamma-glutamyltransferase (GGT), glucose, phosphates, total proteins, urea and total bilirubin. Those analytes and LIs have been analysed in duplicate in the Roche Diagnostics-c8000 analyser in samples centrifuged at 3000 rpm/10 minutes in the SL16 (Thermo Scientific, Waltham, USA) centrifuge and according to an own high-speed centrifugation protocol (12,900 rpm/15 minutes) in the MicroCL17R (Thermo Scientific, Waltham, USA) centrifuge. Lipaemia has been measured in each sample. The efficiency of high-speed centrifugation is verified by the Wilcoxon test (P < 0.05). In cases where significant differences are observed, our own LI is calculated. For ALT and AST, it is verified by McNemar test (P < 0.05). For creatinine, both Wilcoxon and McNemar test were applied. Results: There were statistically significant differences in analyte concentration before and after high-speed centrifugation for: albumin, creatinine, GGT, glucose, phosphates, urea and total bilirrubin. Own LI is calculated. McNemar test shows statistically significant diferences in the proportion of delivered results before and after high-speed centrifugation in ALT, AST and creatinine. Conclusions: This study confirms the efficacy of high-speed centrifugation protocol for all the considered analytes, excepting calcium, alkaline phosphatase and total proteins.

Impact of a Novel Strategy for Critical Values Communication for the Management of Patients Treated with Clozapine.

INTRODUCTION: Clozapine is an antipsychotic drug used to treat resistant schizophrenia and other disorders. Based on the actual Spanish legislation, patients treated with clozapine must undergo periodical haematological examinations and treatment should be reviewed when the haemogram shows either a leukocyte count of ≤ 3500/mm3 or neutrophil count < 2000/mm3. An automatic notification system has been developed to optimize patient management and it's utility was assessed following the implementation of the new system. MATERIAL AND METHODS: When clozapine (CLO) laboratory test request was made, a reflex complete blood count test was also done. An automatic e-mail was sent by the laboratory information system to the physician when a CLO was ordered and low leukocyte or neutrophil counts were detected, or when a patient with an ordered CLO test did not attend the laboratory for blood drawing. RESULTS: For patients with haemogram alterations, the time to take clinical action was significantly decreased from 23 to 7 days (p = 0.02). Moreover, the adherence to Spanish Agency of Drugs and Sanitary Devices recommendations significantly increased from 45% to 76% (p = 0.02). For not attending patients, the days out of control decreased from 29 to 12 days, although it was not statistically significant (p = 0.06). CONCLUSIONS: This strategy has allowed the compliance of legal requirements, the improvement of patient safety, and the optimisation of clinical and laboratory procedures.

Description of interference in the measurement of troponin T by a high-sensitivity method.

INTRODUCTION: Measurement of high-sensitivity troponin T (hs-TnT) has become an essential step in the diagnosis of acute myocardial infarction. This high-sensitivity method allows quantifying the concentration of troponin T in blood of healthy subjects with a lower inaccuracy compared to previous reagent generations. However, the presence of certain compounds in the sample may interfere with the result. We present a patient who had repeatedly high concentrations of hs-TnT in the serum sample that did not agreed with the signs and symptoms. In addition, ultrasensitive troponin I concentration was undetectable. MATERIALS AND METHODS: To investigate the presence of an interfering compound, different analysis were carried out. In order to discard macro complexes in the sample, the serum was precipitated with polyethylene glycol. In addition, the serum was incubated with Scantibodies Heterophilic Blocking Tube, which can block heterophilic antibodies. Finally, a size exclusion chromatography of the sample was performed by the manufacturer. WHAT HAPPENED: The interfering substance was allocated into fractions with proteins of 150kDa, corresponding to high molecular weight proteins like immunoglobulin G (IgG). This compound was responsible for the falsely elevated hs-TnT results and it affected only the high-sensitivity methods. MAIN LESSON: The detected interfering compound was probably an IgG. This type of interference must be kept in mind in front of discordant results, even if they are extremely rare. Therefore, interdisciplinary cooperation between clinicians, laboratory and manufacturer is essential.

Procedimiento para la interpretación de un cambio entre dos valores consecutivos de una magnitud biológica / Procedure for the interpretation of a change between two consecutive values of a biological quantity

Los intervalos de referencia biológicos no proporcionan información suficiente para la interpretación de un cambio entre dos valores medidos consecutivos debido a que, para la gran mayoría de las magnitudes, la variabilidad biológica intraindividual es menor que la variabilidad biológica interindividual. Teniendo en cuenta esta situación, el laboratorio podría proporcionar, conjuntamente con los intervalos de referencia, información adicional que permita estimar de manera objetiva la significación de un cambio en los valores de una magnitud biológica para un mismo individuo. En este sentido, la manera más adecuada para interpretar un cambio debe realizarse en función del concepto de incertidumbre, ya que permite considerar todas las posibles fuentes de variación a las que están sometidos los valores medidos. Este documento, basado en guías de ámbito nacional e internacional se describe un procedimiento para la interpretación de un cambio entre dos valores consecutivos de una magnitud biológica, basado en el estudio de las diversas fuentes de incertidumbre que le afectan

Biological reference intervals do not provide sufficient information for the interpretation of a change between two consecutive measured values of a biological quantity because, for the vast majority of quantities, the intra-individual biological variability is smaller than the inter-individual biological variability. Taking into account this situation, the laboratory could provide, in conjunction with the reference intervals, additional information to objectively estimate the significance of a change in the values of a biological quantity. In this sense, the most adequate way to interpret the change must be made on the basis of the uncertainty concept, since it allows taking into account all the possible sources of variation to which the measured values are subjected. This document, based on national and international guidelines, describes a procedure for the interpretation of a change between two consecutive values of a biological quantity, based on the study of the various sources of uncertainty that affect it

Analysis of laboratory critical values at a referral Spanish tertiary university hospital.

INTRODUCTION: The aim of this study was to analyse critical value data from our laboratory and compare our critical value reporting policy with others in the literature. MATERIALS AND METHODS: Analysis of critical values was performed on data obtained over a 6-month period in a tertiary university hospital. RESULTS: We identified 5723 critical values, of which approximately 80% came from STAT testing (4577), 15% from routine inpatients testing (884) and 5% from routine outpatients testing (262). The highest proportion of critical values corresponded to oxygen partial pressure (17.7%), followed by potassium ion (17.6%) concentrations. The parameters associated with the highest critical value notification percentage in emergency patients were pH, haematocrit, glucose, potassium ion and haemoglobin concentrations. In inpatients, these parameters were glucose, phosphate, haemoglobin, sodium ion and potassium ion concentrations. In outpatients, they were calcium and potassium concentrations. CONCLUSIONS: The analysis of critical values in our hospital is in accordance with that reported in the literature. Our findings demonstrate the importance of incorporating improvement actions not only in critical value notification, but especially in the registration of this activity.

Procedimiento para el estudio de interferencias exógenas en la medición de magnitudes biológicas. Documento técnico (2017) / Procedure for the study of exogenous interferences in the measurement of biological quantities. Technical document (2017)

No disponible

Nomenclatura y unidades de las propiedades biológicas. Recomendación (2016) / Nomenclature and units of biological properties. Recommendation (2016)

No disponible

Influence of 6 genetic variants on the efficacy of statins in patients with dyslipidemia.

BACKGROUND: Patients with dyslipidemia are often treated with statins to reduce lipids and hence cardiovascular risk, but treatment response is variable, partly due to genetic factors. METHODS: We studied the influence of 6 gene variants (APOE c.526C > T (APOE2), APOE c.388T > C (APOE4), SLCO1B1 c.521T > C, CYP3A4 c.-392G > A, HMGCR c.1564-106A > G, and LPA c.3947 + 467T > C) on statin efficacy assessing 2 indicators: the percent reduction in total cholesterol (TC) and non-HDL cholesterol (non-HDL), as well as the achievement of therapeutic goals. The study was performed in a group of patients (n = 100) without previous pharmacological treatment. Multiple regression models were used to calculate the percentage of explanation in response variability added by every variant to a basal model constructed with significant nongenetic control variables. RESULTS: The most influential variant was HMGCR c.1564-106A > G (rs3846662), and carriers showed a significantly lower reduction in TC and non-HDL. This variant is related to an alternative splicing involving exon 13, which is also regulated by lipid concentrations in patients without the variant. Concerning therapeutic goals, HMGCR c.1564-106A > G hindered the achievement of TC targets on patients. CONCLUSIONS: The HMGCR c.1564-106A > G variant was associated with less statin efficacy to decrease cholesterol.

Evaluation of biological fluid analysis using the sysmex XN automatic hematology analyzer.

BACKGROUND: Hematological cytometers with a biological fluid module could potentially correct the limitations of the manual chamber method. This study evaluates the agreement between the manual technique and the Sysmex XN-1000 analyzer for white blood cell (WBC) and red blood cell (RBC) counts, as well as for leukocyte differentiation in different types of fluids. This study also evaluates the advantages of incorporating the technique in routine laboratory work. METHODS: One hundred and three fluid samples examined were 45 ascite (AF), 21 synovial (SF), 33 pleural (PF), and 31 cerebrospinal (CSF) fluid samples. All cell counting was performed with a Sysmex XN-1000 and a Fuchs-Rosenthal counting chamber. May Gründwald-Giemsa stain was used for manual WBC differentiation. The manual analysis data were obtained in duplicate by the same two observers. Passing-Bablok regression and the Kappa index were used to evaluate the interchangeability and concordance. RESULTS: Good agreement was observed for WBC differentiation in all fluids and for WBC counts in SF and PF. An optimal Kappa index was obtained, which indicated agreement and clinical significance for WBC and RBC counts in CSF and for RBC counts in PF. There was disagreement for WBC and RBC analysis in AF, with significantly higher results from the Sysmex XN-1000 than from the manual method. A reduction in laboratory response time was observed when using the automatic method. CONCLUSIONS: Except for AF, the Sysmex XN-1000 results agree with those of the manual method, although to different degrees depending on the fluid type. © 2017 International Clinical Cytometry Society.