Exactitud y concordancia entre glucómetros: un estudio en condiciones habituales de práctica clínica / Accuracy and reliability between glucose meters: a study under normal clinical practice conditions

Introducción. Los glucómetros demuestran habitualmente una gran exactitud, y en la práctica, la glucemia capilar y la glucemia plasmática (GP) son utilizadas indistintamente. Sin embargo, numerosas variables pueden afectar la validez de estos aparatos. El objetivo de este estudio fue conocer la exactitud y la concordancia de 3 glucómetros utilizados en las consultas de un EAP. Material y métodos. De 59 participantes se obtuvieron una muestra de sangre venosa y una gota de sangre capilar, que fue analizada en 3 glucómetros: 2 FreeStyle® Optium (OP1 y OP2) y un Accu-Chek® Aviva. El valor de referencia fue la GP y fueron analizados asimismo el hematocrito y los niveles plasmáticos de urea, bilirrubina, ácido úrico y triglicéridos. Se utilizaron la regresión de Passing-Bablok para la exactitud, y el coeficiente de correlación intraclase y el método Bland-Altman para la concordancia. Se ha considerado el estándar actual (American Diabetes Association) de un error tolerado de±5%. Resultados. La diferencia de medias±desviación estándar (mg/dL) y el error sistemático fueron: 5,8±7 y 5,8% (OP1); 6,2±8 y 5,9% (OP2); 8,3±8 y 6,3% (Accu-Chek®). El par más concordante fue OP1/OP2, con un coeficiente de correlación intraclase=0,97, sesgo=−0,4mg/dL y una amplitud de los límites de acuerdo con el 95%=28,6mg/dL. Se observaron los mayores grados de exactitud y de concordancia en rangos glucémicos elevados (GP≥126mg/dL). Conclusiones. Aunque mostraron una diferencia de medias clínicamente aceptable respecto a la GP, los 3 glucómetros incumplieron el estándar actual de la American Diabetes Association. Es recomendable la realización periódica de controles de calidad de estos dispositivos (AU)

Introduction. The glucose meters usually show a high accuracy, and in clinical practice, capillary and plasma glucose (PG) are used interchangeably. However, many variables can affect the validity of these devices. The aim of this study was to determine the accuracy and reliability of 3 glucose meters that are currently used in a primary care centre. Material and methods. A sample of venous blood and a drop of capillary blood were obtained from 59 participants. The drop was analysed in 3 glucose meters: 2 FreeStyle® Optium (OP1 and OP2), and one Accu-Chek® Aviva. The PG acted as the reference value, and the haematocrit and plasma levels of urea, bilirubin, uric acid and triglycerides were also analysed. We used the Passing-Bablok regression for accuracy and the intraclass correlation coefficient and the Bland-Altman method for reliability. The current American Diabetes Association standard of a total error of±5% was applied. Results. Differences in mean±standard deviation (mg/dL) and the systematic error were 5.8±7 and 5.8% (OP1); 6.2±8 and 5.9% (OP2); 8.3±8 and 6.3% (Accu-Chek®). The OP1/OP2 pair showed the highest level of reliability, with an intraclass correlation coefficient=0.97, bias=−0.4mg/dL, and a width of the 95% limits of agreement of 28.6mg/dL. The highest levels of accuracy and reliability were observed in high glucose ranges (PG≥126mg/dL). Conclusions. Despite their clinically acceptable mean difference compared to the PG, the 3 glucose meters did not fulfill the current American Diabetes Association standard. The regular performance of quality control tests of these devices is recommended (AU)

Increased instrument intelligence--can it reduce laboratory error?

Recent literature has focused on the reduction of laboratory errors and the potential impact on patient management. This study assessed the intelligent, automated preanalytical process-control abilities in newer generation analyzers as compared with older analyzers and the impact on error reduction. Three generations of immuno-chemistry analyzers were challenged with pooled human serum samples for a 3-week period. One of the three analyzers had an intelligent process of fluidics checks, including bubble detection. Bubbles can cause erroneous results due to incomplete sample aspiration. This variable was chosen because it is the most easily controlled sample defect that can be introduced. Traditionally, lab technicians have had to visually inspect each sample for the presence of bubbles. This is time consuming and introduces the possibility of human error. Instruments with bubble detection may be able to eliminate the human factor and reduce errors associated with the presence of bubbles. Specific samples were vortexed daily to introduce a visible quantity of bubbles, then immediately placed in the daily run. Errors were defined as a reported result greater than three standard deviations below the mean and associated with incomplete sample aspiration of the analyte of the individual analyzer Three standard deviations represented the target limits of proficiency testing. The results of the assays were examined for accuracy and precision. Efficiency, measured as process throughput, was also measured to associate a cost factor and potential impact of the error detection on the overall process. The analyzer performance stratified according to their level of internal process control The older analyzers without bubble detection reported 23 erred results. The newest analyzer with bubble detection reported one specimen incorrectly. The precision and accuracy of the nonvortexed specimens were excellent and acceptable for all three analyzers. No errors were found in the nonvortexed specimens. There were no significant differences in overall process time for any of the analyzers when tests were arranged in an optimal configuration. The analyzer with advanced fluidic intelligence demostrated the greatest ability to appropriately deal with an incomplete aspiration by not processing and reporting a result for the sample. This study suggests that preanalytical process-control capabilities could reduce errors. By association, it implies that similar intelligent process controls could favorably impact the error rate and, in the case of this instrument, do it without negatively impacting process throughput. Other improvements may be realized as a result of having an intelligent error-detection process including further reduction in misreported results, fewer repeats, less operator intervention, and less reagent waste.

The new era of automated immunoassay.

Use of immunoassays and other ligand-binding assays in clinical diagnosis has increased dramatically during the last several years. Despite impressive technical advances, "mass production" of these assays in a routine laboratory still presents many difficulties. This review of ligand-binding assay technology highlights some recent developments, emphasizing challenges and possible solutions for cost-effective patient care.

Reading the future: the increased relevance of laboratory medicine in the next century.

Through intelligent process control and data management, the laboratory may become the most frequently used--and the most important--source of diagnostic information in medicine. The central laboratory of the future is destined to become an esoteric testing center, whereas routine testing--administered at the patient bedside or at home--will become more economical. Point-of-care testing will soon become the most profitable way to provide laboratory services. Novel phlebotomy techniques and noninvasive tests may allow some diagnostic testing to be done through automated robotic companions that serve homebound patients or the elderly.

The role of technology in the clinical laboratory of the future.

Advances in automation and informatics will drive the implementation of new technology as we enter the 21st century. Five technologies which will have the greatest impact on the practice of laboratory medicine during the next decade include molecular diagnostics, near patient testing, image analysis, robotics, and information management. The list of molecular pathology tests with potential clinical utility expands daily. Some, such as tests for human immune deficiency virus (HIV) and hepatitis C virus, already are available as commercial kits. Quality assessment and proficiency testing programs still are evolving. DNA tests in oncology, such as T- and B-cell gene rearrangements and t(9;22) translocation, have proven useful in detecting small numbers of tumor cells and have demonstrated clinical utility in some circumstances. Tests for monogenetic diseases, such as sickle cell disease, are useful in planning antenatal management of mothers at risk. Screening tests for the genetic predisposition for certain forms of colon and breast cancer and Alzheimer's Disease are now possible. This suggests the potential for large scale screening of populations at risk. Continued improvements in biosensor technology and miniaturization will increase the ability to test for many analytes at or near the patient. The generally increased cost per test must be reconciled with the potential to decrease the overall cost of care by improved turnaround time. Computerized image analysis will radically change, and in some cases eliminate, manual clinical microscopy in urinalysis, hematology, immunohistochemistry, and cytology. Robotics will greatly decrease personnel requirements for repetitive tasks, such as specimen transport, processing, and aliquoting. We will process many specimens from start to finish without human intervention. Image management systems will allow archiving of diagnostic gross and microscopic images along with the traditional text descriptions and diagnosis. Telepathology will link smaller centers with expert consultants in tertiary centers. Voice recognition systems will obviate the need for transcriptionists. Modern database architectures will allow the clinical laboratory to measure performance effectiveness and clinical outcomes and will place laboratorians at the forefront of outcomes research. Hand-held devices will allow physicians to conveniently order laboratory tests and retrieve results, further decreasing the functional turnaround time for laboratory testing. All of these technologies will be expensive to implement, but well-planned deployment will both decrease cost and improve the quality of medical care.

An update on chemistry analyzers.

This update of six chemistry analyzers available to the clinician discusses several points that should be considered prior to the purchase of equipment. General topics include how to best match an instrument to clinic needs and the indirect costs associated with instrument operation. Quality assurance recommendations are discussed and common terms are defined. Specific instrument features, principles of operation, performance, and costs are presented. The information provided offers potential purchasers an objective approach to the evaluation of a chemistry analyzer for the veterinary clinic.

Robotics: a way to link the "islands of automation".

This article looks at what the natural evolution of robots can do for the clinical testing industry, from performing simple functions to becoming the prime labor force of the clinical laboratory. Until now, robots have been applied to instrument processes as somewhat of an upgrade to accomplish a variety of laboratory tasks. Over the next 10 years, however, robotics development will respond to the internal and external influences expected to challenge the industry. A limited supply of human workers and the increased demands of testing volumes and cost-effectiveness will herald a new phase of robotics to link, as well as develop, technological capabilities. Since science fiction was invented, robots have teased the imagination-alternately as mindless automatons or as clones of their inventors endowed with minds of their own. The appeal in the first case was the seemingly infinite capacity for performing menial tasks too boring, complex, or dangerous for mankind. The appeal in the second was the fantasy of artificial intelligence. In both cases, the fictional concept has become reality--and, by the 21st century, should even be commonplace. Financial encouragement of robotics development might even be a mission for laboratories themselves, as they prepare for potential competition from even more complex technology.

Is automated urinalysis in your laboratory's future?

Examination of the urine, possibly the earliest diagnostic test in medicine, has only recently benefited from automation; one previous twentieth-century advance was substitution of specific reagents for earlier nonspecific chemical tests that were subject to interferences. In the mid-1970s, semiautomated urinalysis instruments were developed to read and record chemical test reactions used in manual urinalysis. Further, in 1984 the first instrument coupling automated intelligent microscopy (AIM) with a dipstick reader became available, fully automating both the biochemical screening and microscopic examination of urine specimens. This assessment describes AIM, as embodied in the Yellow IRIS instrument, and also discusses alternative strategies that laboratorians are developing to improve the cost effectiveness of conventional urinalysis.