Especificaciones de calidad en base a error total: ¿Cuál es la mejor elección? / Quality specifications based on total error: What's the best choice? / Especificações de qualidade com base em erro total: Qual é a melhor escolha?

El objetivo del trabajo fue evaluar el desempeño anual de los métodos, en términos de error total (ET), las distintas especificaciones de calidad disponibles y el modelo Seis Sigma para calificar desempeño. Se evaluaron analitos con variabilidad biológica (VB), muy baja, baja, media y alta. Se calculó el ET (ETc) y el sigma (s) mensual a dos niveles de control; el ET permitido (ETp) para cada analito se obtuvo de 8 fuentes (metas biológicas y regulatorias). Se consideró desempeño aceptable cuando ETc

The aim of this work was to evaluate the annual performance of the methods in terms of total error (TE), the different quality specifications available, and the Six Sigma model to qualify performance. Analytes with very low, low, medium and high biological variability (BV) were evaluated. TE (TEc) and sigma (s) were calculated monthly at two levels of control; allowable TE (TEa) for each analyte was obtained from 8 sources (biological and regulatory goals). Acceptable performance was considered when TEc

O objetivo do trabalho foi avaliar o desempenho anual dos métodos em termos de erro total (ET), as diferentes especificações de qualidade disponíveis e o modelo Seis Sigma para qualificar desempenho. Foram avaliados analitos com variabilidade biológica (VB) muito baixa, baixa, média e alta. Calculou-se ET (ETc) e o sigma (s) mensal a dois níveis de controle; o ET permitido (ETp) para cada analito foi obtido de 8 fontes (metas biológicas e regulatórias). Levou-se em consideração o desempenho aceitável quando ETc < ETp e s≥3. Foi observada a estabilidade analítica durante o período de avaliação. Não foram alcançadas as metas biológicas para analitos com VB muito baixa, algo semelhante aconteceu para analitos com VB baixa e média; com VB alta alcançaram todas as especificações. O desempenho s e a regra de controle de Westgard dependeram do ETp escolhido; para magnésio, com CLIA (ETp=25%) se obteve s >10 (World Class) e simples regra (13s), com VB mínima s <3 e multirregra. Conclui-se que a aceitação do desemperno do método e as regras de controle dependeram do ETp escolhido, sem disporem nesse meio de metas mínimas a alcançar. O monitoramento mensal do ETc mostrou a estabilidade analítica com variabilidade típica de cada método.

A novel 96-microwell-based high-throughput spectrophotometric assay for pharmaceutical quality control of crizotinib, a novel potent drug for the treatment of non-small cell lung cancer / Um ensaio espectrofotométrico de alto rendimento à base de novo de 96 micropoços para o controlo de qualidade farmacêutica crizotinibe, um novo potente fármaco para o tratamento de cancro do pulmão de células não-pequenas

This study describes the development and validation of a novel 96-microwell-based high throughput spectrophotometric assay for pharmaceutical quality control of crizotinib (CZT), a novel drug for the treatment of non-small cell lung cancer. We examined the reaction between CZT and 1,2-naphthoquinone-4-sulphonate, a chromogenic reagent. A red-colored product showing a maximum absorption peak (λ_max) at 490 nm was produced in an alkaline medium (pH 9). We examined stoichiometry of the reaction and postulated the reaction mechanism. To our knowledge, this is the first study to describe a color-developing reaction for the proposed assay. The reaction was performed in a 96-microwell plate, and the absorbance of the colored product was measured using an absorbance reader at 490 nm. Under optimized reaction conditions, Beer's law, which shows a correlation between absorbance and CZT concentration, was obeyed in the range of 4-50 µg/well with an appropriate correlation coefficient (0.999). The limits of detection and quantification were 1.73 and 5.23 µg/well, respectively. The assay showed high precision and accuracy. The proposed assay was applied successfully for the determination of CZT in capsules. Thus, the assay proposed in this study is practical and valuable for routine application in pharmaceutical quality control laboratories...

Este estudo descreve o desenvolvimento e a validação de um novo ensaio espectrofotométrico em larga escala em 96 micropoços para o controle farmacêutico de crizotinibe (CZT), novo fármaco para o tratamento de câncer de pulmão de células não pequenas. Examinamos a reação entre o CZT e o 4-sulfonato de 1,2-naftoquinona, um reagente cromogênico. Obteve-se, em meio alcalino (pH 9), produto vermelho, com absorção máxima (λ_max) em 490 nm. Examinamos a estequiometria da reação e propusemos mecanismo de reação. Este, segundo nosso conhecimento, é o primeiro estudo para descrever reação de desenvolvimento de cor para o ensaio proposto. A reação foi realizada em placas de 96 micropoços e mediu-se a absorbância do produto colorido utilizando-se leitor de absorbância a 490 nm. Sob condições otimizadas de reação, a lei de Beer, que mostra a correlação entre a absorbância e a concentração de CZT, foi obedecida na faixa de 4-50 µg/poço, com coeficiente de correlação apropriado (0,999). Os limites de detecção e de quantificação foram, respectivamente, 1,73 e 5,23 µg/poço. O ensaio mostrou alta precisão e exatidão. O ensaio proposto foi aplicado com sucesso para a determinação de CZT em cápsulas e é prático e válido para a aplicação de rotina em laboratórios de controle farmacêutico...

Evaluación del desempeño analítico de tres métodos de cuantificación de hemoglobina A1c / Analytical performance evaluation of three methods for hemoglobin A1c quantification / Avaliação do desempenho analítico do três métodos de quantificação de hemoglobina A1c

El laboratorio debe garantizar la exactitud de los resultados de HbA1c cumpliendo con los requisitos analíticos internacionales de calidad, cada vez más estrictos y asegurar que una variación de HbA1c de 0,5 puntos porcentuales (%-NGSP) o más entre dos controles consecutivos de un paciente diabético se deba a una variación clínica y no a una variación analítica. En este trabajo se evaluó el desempeño analítico de tres métodos comerciales para HbA1c: inmunoturbidimétrico, enzimático y cromatográfico de intercambio catiónico. Para tal fin, se procesaron por cada método distintos controles comerciales de HbA1c, con trazabilidad al método de referencia IFCC, determinándose en cada caso Coeficiente de Variación Total, Bias, Error Total, Valor de Referencia del Cambio y cambio clínico significativo de HbA1c en el punto crítico 7,0%-NGSP. En las condiciones analíticas de este trabajo, solamente el método inmunoturbidimétrico tuvo un desempeño analítico aceptable, permitiendo atribuir un cambio de 0,5%-NGSP a una variación clínica significativa del paciente. Frente a las recomendaciones internacionales sobre el uso de HbA1c en el control y diagnóstico de diabetes, es indiscutible la importancia de elegir un método que satisfaga los requerimientos analíticos mínimos de calidad para asegurar la utilidad clínica del resultado de HbA1c.

The laboratory must guarantee the accuracy of HbA1c results meeting the increasingly strict international analytical quality standards and assuring that an HbA1c variation of 0.5 percentage points (%-NGSP) or more between two consecutive controls of a diabetic patient is due to a clinical variation and not to an analytical variation. In this paper, the analytical performance of three commercial methods for HbA1c: Immunoturbidimetric, Chromatographic and Enzymatic Cation Exchange, were evaluated. For this purpose, commercial controls with assigned values traceable to the IFCC reference method for HbA1c were processed. For each methodology, total Coefficient of Variation (CV%), Bias%, Total Error (TE%), Change Reference Value and Clinically Significant Change (CSC) at the critical point of HbA1c 7.0%-NGSP were determined. Within the analytical conditions of this study, only the immunoturbidimetric method had an acceptable analytical performance, allowing attribute a change in 0.5%-NGSP to a significant clinical variation. Faced with international recommendations on the use of HbA1c on control and diagnosis of diabetes, the importance of choosing a method that meets the minimum analytical quality requirements to ensure the clinical utility of HbA1c result is undeniable.

O laboratório deve garantir a precisão dos resultados da HbA1c cumprindo com os requisitos analíticos internacionais de qualidade cada vez mais exigentes e garantir que uma variação de HbA1c de 0,5 pontos percentuais (% - NGSP) ou mais entre duas verificações consecutivas de um doente diabético seja devido a uma variação clínica e não a uma variação analítica. Neste trabalho foi avaliado o desempenho analítico de três métodos comerciais para HbA1c: imunoturbidimétrico, enzimático e cromatográfico de intercâmbio catiônico. Para esse fim, foram processados diversos controles comerciais de HbA1c por cada método, com rastreabilidade ao método de referência IFCC, determinando em cada caso Quociente de Variação Total, Bias, Erro Total, Valor de Referência da Alteração e Alteração Clinicamente Significativa de HbA1c no ponto crítico 7,0%-NGSP. Nas condições de análise deste estudo, apenas o método imunoturbidimétrico teve um desempenho analítico aceitável, permitindo atribuir uma alteração de 0,5%-NGSP a uma variação clínica significativa do paciente. Perante as recomendações internacionais sobre o uso da HbA1c no controle e diagnóstico da diabetes, é inegável a importância de escolher um método que atenda os requisitos analíticos mínimos de qualidade de análise para garantir a utilidade clínica do resultado HbA1c.

Técnica de cuantificación de la agregación eritrocitaria por análisis digital de imágenes / Erythrocyte aggregation quantification technique using digital image analysis / Técnica de quantificagáo do agregado eritrocitário por análise digital de imagens

La caracterización de agregados eritrocitarios es importante para analizar las posibles alteraciones en la microcirculación observadas en ciertas patologías vasculares como la hipertensión y la diabetes. El objetivo de este trabajo fue estandarizar una técnica que pueda ser utilizada por cualquier operador con un equipamiento similar. Para ello se prepararon distintas suspensiones de glóbulos rojos de dadores sanos en plasma autólogo, que fueron observadas con un microscopio óptico invertido. Se registraron para su análisis las imágenes de los agregados con una cámara digital. Se realizaron los recuentos de células individuales, agregados de 2 a 4 células, agregados de 5 ó más células y amas (redes de agregados de gran tamaño). Se midió el perímetro y el área, obteniéndose un parámetro de forma (ASP) de cada agregado de 5 ó más células. Los resultados obtenidos permitieron estandarizar el protocolo de trabajo concluyendo que la dilución óptima de glóbulos rojos en plasma autólogo para esta técnica es 0,5%.

Characterization of erythrocyte aggregates is important in the analysis of the possible alterations observed in the microcirculation of certain vascular pathologies such as hypertension and diabetes. The objective of this work was to standardize a technique that can be used by any operator having similar equipment. For that purpose, different suspensions of red blood cells from healthy donors were prepared in autologous plasma and then observed with an inverted light microscope. The images of the aggregates were recorded with a digital camera in order to be later analyzed. Individual cell count was carried out, as well as 2 to 4 cell- aggregates, 5 or more cell- aggregate and amas (big aggregate networks). Measurement of perimeter and area of each of the aggregates made up of 5 or more cells was performed, getting a shape parameter (ASP). Due to the results obtained, this working protocol has been standardized and it can be concluded that the optimal dilution of red blood cells in autologous plasma is 0.5% for this particular technique.

A caracterizagáo de agregados eritrocitários é importante para analisar as possíveis alteragóes na microcirculagáo observadas em certas patologias vasculares como a hipertensáo e a diabetes. O objetivo deste trabalho foi padronizar uma técnica que possa ser utilizada por qualquer operador com um equipamento similar. Para isso foram preparadas diversas suspensóes de glóbulos vermelhos de doadores saudáveis em plasma autólogo, que foram observadas com um microscópio óptico invertido. Foram registradas para a sua análise as imagens dos agregados com uma camera digital. Realizaramse as recontagens de células individuais, agregados de 2 a 4 células, agregados de 5 ou mais células e amas (redes de agregados de grande tamanho). Foi medido o perímetro e a área, obtendo um parametro de forma (ASP) de cada agregado de 5 ou mais células. Os resultados obtidos permitiram padronizar o protocolo de trabalho concluindo que a diluigáo ótima de glóbulos vermelhos em plasma autólogo para esta técnica é de 0,5%.

Impacto del Programa de Evaluación Externa de la Calidad en Química Clínica en México de 2004 a 2008 / Impact of the Program of External Quality Assessment in Clinical Chemistry in Mexico from 2004 to 2008 / Impacto do Programa de Avaliação Qualidade Externa em Química Clínica no México de 2004 a 2008

Se valoró el impacto del Programa de Evaluación Externa de la Calidad, aplicable a laboratorios clínicos en el área de Química Clínica, en México, con base en resultados obtenidos por los laboratorios durante el ciclo marzo 2008-febrero 2009 y el periodo 2004-2008, mediante un estudio analítico, longitudinal y retrospectivo de los resultados obtenidos por los laboratorios que participaron en el Programa de Evaluación Externa de la Calidad de la Facultad de Ciencias Químicas, Universidad Autónoma de San Luis Potosí. El análisis estadístico se realizó con los programas Microsoft® Office Excel y Epi Info T. El porcentaje de laboratorios clínicos con desempeño aceptable (excelente y bueno) por analito, durante el ciclo de evaluación marzo 2008-febrero 2009, fue del 75% al 82%, que aumentó cuando se utilizaron métodos automatizados y semiautomatizados. Para el periodo 2004-2008, los laboratorios en 2004 tuvieron 3,02 veces mayor riesgo de no calificar con desempeño aceptable (p<0,05) que en 2008. En conclusión, el Programa de Evaluación Externa de la Calidad de la Facultad de Ciencias Químicas, Universidad Autónoma de San Luis Potosí, ha tenido un impacto favorable en el desempeño global de los laboratorios clínicos, que permite asegurar su calidad analítica.

The impact of the External Quality Assessment Program, applicable to clinical laboratories in the area of Clinical Chemistry in Mexico, was studied, based on laboratory results during the March 2008-February 2009 cycle and the 2004-2008 period, through analytical, longitudinal, retrospective analyses of the results obtained by the laboratories that participated in the External Quality Assessment Program of the School of Chemical Sciences of Universidad Autónoma de San Luis Potosí. Statistical analysis was performed with Microsoft® Office Excel and Epi Info T programs. The percentage of clínical laboratories with acceptable performance (excellent and good) by analyte during the evaluation cycle in March 2008-February 2009 was 75% to 82%, whích íncreased when automated and semíautomated methods were used. For the 2004-2008 period, the laboratories, in 2004, had 3.02 times greatet risk of not qualifying with acceptable performance (p<0.05) than in 2008. In conclusión, the External Qualíty Assessment of the School of Chemícal Sciences of Universidad Autónoma de San Luis Potosí has had a strong impact on the overall performance of clinical laboratories, whích ensures the latter's qualíty.

Evaluación de espectrofotómetros para la elaboración de material de referencia empleado en la calibración y el control de la determinación de hemoglobina / Evaluation of spectrophotometers for the preparation of reference material used in the calibration and control of the determination of hemoglobin

Debido a la variabilidad de resultados entre laboratorios en las determinaciones de hemoglobina, se debe promover la implantación de sistemas de garantía de la calidad para generar confianza en los resultados. A fin de aportar elementos para su establecimiento, se realizó una evaluación instrumental de espectrofotómetros y se preparó un lote de controles y calibradores de hemoglobina siguiendo protocolos internacionales. Después de elaborar el material, se monitoreó homogeneidad (CV calibrador: 0,33 por ciento, control: 0,38 por ciento) y estabilidad (CV calibrador: 0,13 por ciento, control: 0,90 por ciento). La evaluación instrumental demostró la condición óptima de los espectrofotómetros (exactitud de la longitud de onda 100 por ciento, inexactitud fotométrica 0,9 por ciento y 1,2 por ciento, CV precisión fotométrica 0,25 por ciento, respuesta lineal con K2Cr2O7) lo que permitió su empleo para asignar valores al material preparado, que fue útil para el control de la determinación de hemoglobina. Esto constituye un aporte al desempeño del laboratorio y contribuye a la emisión de resultados confiables

On account of the variability of results observed between laboratories in hemoglobin determinations, the installation of quality assurance systems should be promoted to generate confidence on laboratory results. In order to contribute with elements for the establishment of these systems we realized an instrumental evaluation of photometric equipment and prepared a regular lot of hemoglobin standards and controls following international protocols. After the elaboration, we monitored the homogeneity (VC standard: 0.33 percent, control: 0.38 percent) and stability (VC standard: 0.13 percent, control: 0.90 percent). The instrumental evaluation showed the optimal condition of the photometric equipment (wave length accuracy 100 percent, photometric inaccuracy 0.9 percent y 1.2 percent, VC photometric precision 0.25 percent, lineal response with K2Cr2O7), this allowed its employment for the value assignation of the material, that was useful for the daily practice of hemoglobin determination. This constitutes a contribution to the performance of clinical laboratory and contributes with the emission of reliable results

Influencia de las variables preanalíticas en la determinación de proteína S / Influence of preanalytical variables in S protein determination

La proteína S (PS) regula el sistema de coagulación mostrando actividad de cofactor de la Proteína C activada (PCa) con la cual forma un complejo equimolecular. En presencia de iones calcio este complejo inactiva por proteólisis los factores V y VIII activados por trombina. La proteína S plasmática circula 40% libre (fracción que presenta actividad de cofactor de la PCa) y 60% unida al C4-BP (proteína ligante de la fracción C4 del complemento). El objetivo fue comparar el dosaje de PS realizado por método coagulable e inmunoturbidimétrico e investigar cómo las variables preanalíticas afectan los niveles de PS determinados. Se obtuvieron los siguientes resultados: método coagulable: CV intra ensayo: (n=20): 4%, CV interensayo (n=20, 3 días): 3,4%. Método inmunoturbidimétrico: CV intraensayo (n=20): 3,7%.CV Inter. ensayo (n=20,3 días): 4,5%. Existe buena correlación (R2=0,94) entre ambos métodos, cuando la calibración por el método coagulable se realiza en la misma corrida analítica que las muestras. Cuando se realizó el estudio de Bland y Altman los dos métodos mostraron ser comparables en todos los niveles de PS estudiados. No se observaron diferencias significativas entre las muestras determinadas frescas y conservadas a -20 y -80 °C descongeladas solo una vez.

Protein S has an essential anticoagulant function acting as activated Protein C cofactor and forming an equimolecular complex with it. In the presence of calcium this complex regulates the coagulation process inactivating thrombin activated factors V and VIII by proteolysis. In plasma there are two different forms: a) free Protein S which acts as the cofactor of activated protein C (representing about 40% of total Protein S) and b) C4-BP(C4 binding protein) bound protein S which exhibits no activity as cofactor of activated Protein C (representing about 60% of total PS). The objetive was to compare the PS dosage determination by two methods: immunoturbidimetric and clotting, and to investigate how pre-analytical variables affect the results. The following results were obtained: Clotting method: CV intra assay: (n=20): 4%, CV interassay (n=20, 3 days): 3.4%; immunoturbidimetric method CV intra assay (n=20): 3.7%: CV inter assay (n=20.3 days): 4.5%. There is a good correlation (R2 = 0.94) between both methods; when the clotting method is calibrated in batch with the samples. There is significant difference between fresh and frozen ( -20 °C and -80 °C) samples when the latter have been desfrozen only once.

The health and safety executive interlaboratory quality control scheme for isocyanates.

The inclusion of isocyanate analysis within the AQUA (Analytical Quality Assurance) interlaboratory quality assurance scheme was established in 1984. (The AQUA interlaboratory quality assurance scheme is equivalent to external quality assessment, in North America the term proficiency testing is preferred.) The participants include university, industrial, occupational consultant and government laboratories, both in the U.K. and abroad. The AQUA isocyanate scheme is linked to a specific analytical method. MDHS 25 [Health and Safety Executive, Organic isocyanates in air: laboratory method using 1-(2-methoxyphenyl) piperazine solution and high performance liquid chromatography. H.M. Stationery Office, London (1987)]. Results from the first 4 years of the scheme's operation are reviewed and individual laboratory performance indices assessed against the mean interlaboratory performance indices. Most of the laboratories in the scheme show a marked improvement with time, which in some instances has followed help and advice from the HSE. There has also been an overall reduction in intralaboratory variability over this period.

An examination of the efficiency of some quality assurance methods commonly employed in clinical trials.

The cost and efficiency of training clinical centre staff and of duplicate data entry in clinical trials is reviewed. Training is an essential component of quality assurance programmes and it is usually carried out at regular intervals in long-term clinical trials. Initial training of staff and regular retraining is important to assure standardization and it can lead to reduced trial costs. Interim training for new staff and for remedial purposes is less efficient than regularly scheduled training sessions. Regional centres for training and the use of computer aided instruction are two ways such interim training can be made more efficient and standardized. Duplicate data entry or verification can result in a substantial reduction in data entry errors depending on the nature of the data being keyed. Selective verification should especially be considered for important fields for which consistency checks cannot be performed, that are alphabetic or that are several characters in length. Quality assurance procedures should be implemented to monitor data entry accuracy in clinical trials.

New methods of examining gamma camera collimators.

New methods are proposed and described to examine the quality of gamma camera collimators in two special performance categories, namely, uniformity in regional efficiency and regional variations in channel tilt. These two performances are critical areas for SPECT imaging. Results obtained from experimental and commercial collimators illustrate the variability seen for these performance characteristics in currently available collimators.

Variación de la eficiencia de medición del cristal de pozo-espectrómetro monocanal / Variation of the efficiency of measuring of the pair cystal of water spectrometer monocanal

Ante la falta de constancia de la eficiencia de medición, en función del tiempo, de un equipo cristal de pozo-espectrómetro monocanal, se estudiaron las localizaciones de los picos fotoeléctricos de diferentes radionucleidos, utilizando como variables el tiempo, la energía de la radiación y la tensión aplicada. Los resultados indican que dichos picos van corriéndose hacia los niveles de canal más altos, al transcurrir el tiempo de funcionamiento del equipo. Estos corrimientos son más importantes cuanto mayor es la tensión aplicada y cuanto mayor es el valor de la energía de la radicación medida (AU)

Monitoring laboratory performance by statistical analysis of rescreening cervical smears.

The rescreening of cervical cytology smears, although inadequate both for checking the reliability of an individual screener and for the detection of false negatives, nonetheless represents an indispensable tool for assessing morphologic diagnostic criteria and monitoring laboratory performance. Interobserver and intraobserver concordance in a given laboratory determine the reliability of diagnostic criteria and disclose the possibility of improving diagnostic consistency. The various aspects of rescreening are discussed, and a simple statistical procedure for a quantitative comparison of screening reproducibility is described. This procedure, with calculation of phi-values and mean prevalence rates, was applied to screening and rescreening data from the Cyt-U-Universitair Cytology Laboratory from 1978 to 1983, in which the morphologic findings in each smear were recorded in detail using the QISO (Quality, Infection, Squamous epithelium and Other abnormalities) coding. The reproducibility of the reported presence of endocervical cells not only steadily improved over the years assessed, but also reached a sufficiently high level that diagnostic variability should not hamper its clinical utility. The same was true of the diagnosis of Trichomonas infection and moderate atypia of squamous cells. On the other hand, the reproducibility of the diagnosis of endometrial cells in smears did not significantly improve. However, since the intraobserver concordance on this criterion was good, it seems likely that the definitions of screeners in this area can still be brought into closer agreement. Conversely, the diagnosis of "abnormal endocervical cells" had such a high level of variability even at the intraobserver level as to question its use as a diagnostic criterion. Similar variability was seen in the distinction between atypical squamous metaplasia and mild dysplasia. Use of this statistical technique for the quality control of cytologic diagnoses frees that assessment from histopathologic control, which does not address the problem of variation within the cytologic or histologic diagnoses themselves.

Estandarización de un método analítico: aplicación a la determinación de glicosaminoaglicanos urinarios / Standardization of a analytical method: aplication to the determination of urinary glycosaminoglycans

Se presenta la estandarización de un método para la determinación cuantitativa de glicosaminoglicanos (GAGs) urinarios, empleando una combinación de los métodos descriptos por Di Ferrante y Bitter y Muir, con algunas modificaciones que debieron ser introducidas para adecuarlo a nuestras condiciones experimentales. La determinación se basa en la precipitación de los GAGs por acción de bromuro de cetiltrimetilamonio, seguida de la hidrólisis del polímero y la posterior reacción colorimétrica con carbazol de los ácidos hexurónicos liberados. Se describen, detalladamente, los estudios de estandarización: determinación de la precisión de las distintas etapas del método, linealidad y carta de control de las pendientes de las curvas de calibración, ensayos de recuperación, investigación de interferencias y variaciones en las condiciones de trabajo. Esta metodología puede servir de base para establecer protocolos de control de cualquier procedimiento analítico (AU)