Beatriz Candás-Estébanez

HLA-B*57: 01 genotyping in the prevention of hypersensitivity to abacavir: 5 years of experience.

Introduction Most of the cost-effectiveness analyses are based on estimations to make decisions on the future implementation of a test. However, the model should be verified with real data to prove that previous estimations have been successfully fulfilled. Objective To study the economic impact of the systematic HLA-B*57:01 genotyping in preventing hypersensitivity reactions (HSRs) in the patient population of a tertiary-care hospital treated with abacavir (ABC) using retrospective data of 5 years of experience. Methods A retrospective study was carried out with two cohorts including 780 and 473 patients before and after the implementation of the systematic HLA-B*57:01 genotyping before ABC treatment. Cost-effectiveness analysis was carried out by the parameter ‘cost per HSR avoided’. The clinical utility of the test was verified by evaluating the differences in HSR incidence between both cohorts. Finally, a sensitivity analysis including all variables was carried out. Results In the population studied, systematic genotyping represents an additional cost of &OV0556;306 per HSR avoided. In the sensitivity analysis, pharmacological therapy cost is the major influencing factor found in the estimation of the ‘cost per HSR avoided’. In terms of clinical utility, the incidence ratio was 0.040 (95% confidence interval 0.0009–0.2399) and statistically significant differences were found between both groups (P=1.40×10–7). Conclusion Retrospective data from 5 years of experience have confirmed the cost-effectiveness of the systematic genotyping in candidate patients for ABC therapy, and have shown that cost-effectiveness is a dynamic parameter closely linked to allele prevalence and pharmacological therapy costs.

Lack of commutability between a quality control material and plasma samples in a troponin I measurement system.

The concept of commutability expresses the closeness of the relationship between the results of different measurement procedures for a reference or control material and those obtained for patient samples. With regard to clinical laboratories, it is frequently assumed that the imprecision in a measurement system used for commercial control materials will be similar when the system is used for human samples. However, studies suggest that this assumption may be erroneous (1 – 4) . Therefore, estimating imprecision in the measurement of human samples may be necessary for calculating the real imprecision inherent in the measurement systems. This is particularly relevant to certain cases, such as troponin measurements. This is because there is an international consensus regarding the level of imprecision in the decision limit used to diagnose myocardial injury (CV ≤ 10 % ) (5) . The CV is usually calculated using commercial control materials, and the aim of clinical laboratory professionals is to keep the level of imprecision below this level. For this reason, any lack of commutability between the control/reference material and the clinical samples means that the control material can no longer be used, as it would not accurately refl ect the real imprecision of the procedure. Therefore, to address this, we studied the interchangeability of day-to-day imprecision of measurements of the commercial control material that we usually use in our laboratory, and of the measurements of pooled plasma samples. The plasma concentrations of troponin I were measured using a Dimension RxL analyser (Siemens Healthcare Diagnostics Products, Marburg, Germany) according to the manufacturer ’ s instructions. The day-to-day imprecision in this procedure were estimated simultaneously using control materials containing cardiac markers at different concentrations (Dade ® Cardiac TL; levels 1, 2 and 3, ref B5960-1, Siemens Healthcare Diagnostics Products, Marburg, Germany), and three plasma pools containing troponin I at concentrations close to those in the controls. Each of the control materials was previously aliquoted and refrigerated at 4 ° C, and each plasma pool was divided into 20 aliquots and stored at – 20 ° C. Troponin concentrations were measured daily over a period of 20 working days (one measurement for each of the control materials and one for the plasma pool). When the 20 measurements were complete, the corresponding variances and CVs, which represent day-today imprecision in the measurements, were estimated. The CVs are shown in Table 1 . An F-test (p set at < 0.05) was then used to determine the interchangeability of day-to-day imprecision in the measurement of the control materials and plasma pools. The data (shown in Table 1) confi rm that the variances were not interchangeable. This study shows the marked lack of commutability between a very well used commercial control material and plasma pools. The most relevant fi nding was that the imprecision estimated using the control materials was higher than that obtained for the plasma samples. A previous study reported similar fi ndings (3) , although the opposite situation is more common. Since it is required that the level of imprecision for troponin measurements at the decision limit must be less than or equal to 10 % (5) , clinical laboratory professionals are always aiming to decrease the CV obtained using control materials. A lack of commutability associated with higher imprecision of control materials generates problems due to over-controlling to maintain the inter-serial imprecision level below 10 % . This results in an unnecessary waste of control materials, reagents, and human resources without any extra benefi t in terms of more accurate patient results. In conclusion, it is important to know whether there is commutability between commercially available troponin control materials and human samples, at least until the in vitro diagnostics industry can produce control materials that have imprecision interchangeable with human samples, and can provide documental evidence that this is the case. Although this study focused on troponin I, commutability is essential for all measurements made in clinical laboratories.

APOE Variants E2, E3, and E4 Can Be Miscalled By Classical PCR-RFLP When The Christchurch Variant Is Also Present.

The APOE Christchurch (APOECh) is a rare variant (c.543C>A) in codon 154. It was first described in an E2 patient with type III dyslipidemia, and thus initially called E2Ch. Its prevalence and the lipid profile of carriers remain unclear.

KIF6 gene as a pharmacogenetic marker for lipid-lowering effect in statin treatment

Introduction The therapeutic response to statins has a high interindividual variability with respect to reductions in plasma LDL-cholesterol (c-LDL) and increases in HDL cholesterol (c-HDL). Many studies suggest that there is a relationship between the rs20455 KIF6 gene variant (c.2155T> C, Trp719Arg) and a lower risk of cardiovascular disease in patients being treated with statins. Aim The aim of this study was to investigate whether or not the c.2155T> C KIF6 gene variant modulates the hypercholesteremic effects of treatment with simvastatin, atorvastatin, or rosuvastatin. Materials and methods This was a prospective, observational and multicenter study. Three hundred and forty-four patients who had not undergone prior lipid-lowering treatment were recruited. Simvastatin, atorvastatin or rosuvastatin were administered. Lipid profiles and multiple clinical and biochemical variables were assessed before and after treatment. Results The c.2155T> C variant of the KIF6 gene was shown to influence physiological responses to treatment with simvastatin and atorvastatin. Patients who were homozygous for the c.2155T> C variant (CC genotype, ArgArg) had a 7.0% smaller reduction of LDL cholesterol levels (p = 0.015) in response to hypolipidemic treatment compared to patients with the TT (TrpTrp) or CT (TrpArg) genotype. After pharmacological treatment with rosuvastatin, patients carrying the genetic variant had an increase in c-HDL that was 21.9% lower compared to patients who did not carry the variant (p = 0.008). Conclusion Being a carrier of the c.2155T> C variant of the KIF6 gene negatively impacts patient responses to simvastatin, atorvastatin or rosuvastatin in terms of lipid lowering effect. Increasing the intensity of hypolipidemic therapy may be advisable for patients who are positive for the c.2155T> C variant.

Removing Lipemia in Serum/Plasma Samples: A Multicenter Study

Background Lipemia, a significant source of analytical errors in clinical laboratory settings, should be removed prior to measuring biochemical parameters. We investigated whether lipemia in serum/plasma samples can be removed using a method that is easier and more practicable than ultracentrifugation, the current reference method. Methods Seven hospital laboratories in Spain participated in this study. We first compared the effectiveness of ultracentrifugation (108,200×g) and high-speed centrifugation (10,000×g for 15 minutes) in removing lipemia. Second, we compared high-speed centrifugation with two liquid-liquid extraction methods—LipoClear (StatSpin, Norwood, USA), and 1,1,2-trichlorotrifluoroethane (Merck, Darmstadt, Germany). We assessed 14 biochemical parameters: serum/plasma concentrations of sodium ion, potassium ion, chloride ion, glucose, total protein, albumin, creatinine, urea, alkaline phosphatase, gamma-glutamyl transferase, alanine aminotransferase, aspartate-aminotransferase, calcium, and bilirubin. We analyzed whether the differences between lipemia removal methods exceeded the limit for clinically significant interference (LCSI). Results When ultracentrifugation and high-speed centrifugation were compared, no parameter had a difference that exceeded the LCSI. When high-speed centrifugation was compared with the two liquid-liquid extraction methods, we found differences exceeding the LCSI in protein, calcium, and aspartate aminotransferase in the comparison with 1,1,2-trichlorotrifluoroethane, and in protein, albumin, and calcium in the comparison with LipoClear. Differences in other parameters did not exceed the LCSI. Conclusions High-speed centrifugation (10,000×g for 15 minutes) can be used instead of ultracentrifugation to remove lipemia in serum/plasma samples. LipoClear and 1,1,2-trichlorotrifluoroethane are unsuitable as they interfere with the measurement of certain parameters.

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

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.

Reference values assessment in a Mediterranean population for small dense low-density lipoprotein concentration isolated by an optimized precipitation method

Background High serum concentrations of small dense low-density lipoprotein cholesterol (sd-LDL-c) particles are associated with risk of cardiovascular disease (CVD). Their clinical application has been hindered as a consequence of the laborious current method used for their quantification. Objective Optimize a simple and fast precipitation method to isolate sd-LDL particles and establish a reference interval in a Mediterranean population. Materials and methods Forty-five serum samples were collected, and sd-LDL particles were isolated using a modified heparin-Mg2+ precipitation method. sd-LDL-c concentration was calculated by subtracting high-density lipoprotein cholesterol (HDL-c) from the total cholesterol measured in the supernatant. This method was compared with the reference method (ultracentrifugation). Reference values were estimated according to the Clinical and Laboratory Standards Institute and The International Federation of Clinical Chemistry and Laboratory Medicine recommendations. sd-LDL-c concentration was measured in serums from 79 subjects with no lipid metabolism abnormalities. Results The Passing–Bablok regression equation is y = 1.52 (0.72 to 1.73) + 0.07x (−0.1 to 0.13), demonstrating no significant statistical differences between the modified precipitation method and the ultracentrifugation reference method. Similarly, no differences were detected when considering only sd-LDL-c from dyslipidemic patients, since the modifications added to the precipitation method facilitated the proper sedimentation of triglycerides and other lipoproteins. The reference interval for sd-LDL-c concentration estimated in a Mediterranean population was 0.04–0.47 mmol/L. Conclusion An optimization of the heparin-Mg2+ precipitation method for sd-LDL particle isolation was performed, and reference intervals were established in a Spanish Mediterranean population. Measured values were equivalent to those obtained with the reference method, assuring its clinical application when tested in both normolipidemic and dyslipidemic subjects.

Meeting report: present state of molecular genetics in clinical laboratories. Report on the VII European Symposium on Clinical Laboratory and In Vitro Diagnostic Industry in Barcelona

Abstract The VII European Symposium of the Clinical Laboratory and In Vitro Diagnostic Industry, co-organized between the Catalan Association for Clinical Laboratory Sciences (ACCLC) and the Catalan Society of Biology, was held on May 28th–29th, 2013 in Barcelona (Catalonia, Spain) under the IFCC auspices and the IUPAC sponsorship. The subject of the present Symposium was “Molecular Genetics in the Clinical Laboratory” and began with an opening conference that was a stroll through the history of molecular genetics in the context of the clinical laboratory. The scientific program was structured in several 2-h length roundtables that dealt with the following topics: recent advances in molecular genetics for clinical microbiology, latest evidences and real applicability of pharmacogenetics in the clinical practice, quality assurance of a molecular genetics laboratory, and latest trends in prenatal genetic diagnosis. The aim of the Symposium was the discussion of the transformation that molecular genetics has generated on clinical laboratories in terms of organization, specialization, interpretation of results and fast technical and knowledge evolution. High-qualified professionals from several countries together with in-country experts formed the roundtables. Attendants participated actively in the debates, increasing the overall interest.