Intercambiabilidad de resultados entre los diferentes laboratorios clínicos Catlab / Comparability study of analytical results between a group of clinical laboratories

Objetivo. Describir el estudio de la intercambiabilidad de los resultados de las magnitudes de bioquímica que se procesan indistintamente en los 4 laboratorios de Catlab. Material y métodos. Se establecieron requisitos de calidad de coeficiente de variación y error total (CV% y ET%). Se verificó, con materiales de control comercial, el cumplimiento del CV% en cada magnitud y para cada analizador de cada laboratorio y se estudió la intercambiabilidad con muestras recientes de suero. Se analizaron las diferencias con una aplicación en Microsoft Access® que genera gráficos de Bland-Altman modificados. Resultados. La intercomparación de las 32 magnitudes que se realizan en más de un laboratorio o analizador generó 306 gráficas de Bland-Altman: 101 (33,1%) cumplían directamente el requisito de ET% establecido a partir de la variabilidad biológica y 205 (66,9%) requirieron revisión. Se reprocesaron los datos según los requisitos mínimos de consenso de la Asociación Española de Farmacéuticos Analistas (AEFA), la Sociedad Española de Bioquímica Clínica y Enfermedad Molecular (SEQC), la Asociación Española de Biopatología Médica (AEBM) y de la Sociedad Española de Hematología y Hemoterapia (SEHH) de octubre del 2013. Aplicándolos, 170 comparaciones (56%) cumplían directamente los requisitos y 136 (44%) requerían revisión. Al valorar el número de puntos que excedían el requisito, los errores aleatorios, el intervalo de resultados en el que se detectaban discrepancias y el intervalo de decisión clínica se consideró que todos los resultados se podían aceptar y que las 32 magnitudes eran intercambiables en todos los centros y analizadores. Conclusiones. A partir del requisito de consenso de las 4 sociedades, los resultados de todas las magnitudes comparadas eran intercambiables. No obstante, cada uno de los laboratorios debe cumplir con criterios más estrictos de error total (AU)

Objective. To describe the study of the comparability of the measurements levels of biological tests processed in biochemistry in Catlab's 4 laboratories. Material and methods. Quality requirements, coefficients of variation and total error (CV% and TE %) were established. Controls were verified with the precision requirements (CV%) in each test and each individual laboratory analyser. Fresh serum samples were used for the comparability study. The differences were analysed using a Microsoft Access® application that produces modified Bland-Altman plots. Results. The comparison of 32 biological parameters that are performed in more than one laboratory and/or analyser generated 306 Bland-Altman graphs. Of these, 101 (33.1%) fell within the accepted range of values based on biological variability, and 205 (66.9%) required revision. Data were re-analysed based on consensus minimum specifications for analytical quality (consensus of the Asociación Española de Farmacéuticos Analistas (AEFA), the Sociedad Española de Bioquímica Clínica y Patología Molecular (SEQC), the Asociación Española de Biopatología Médica (AEBM) and the Sociedad Española de Hematología y Hemoterapia (SEHH), October 2013). With the new specifications, 170 comparisons (56%) fitted the requirements and 136 (44%) required additional review. Taking into account the number of points that exceeded the requirement, random errors, range of results in which discrepancies were detected, and range of clinical decision, it was shown that the 44% that required review were acceptable, and the 32 tests were comparable in all laboratories and analysers. Conclusions. The analysis of the results showed that the consensus requirements of the 4 scientific societies were met. However, each laboratory should aim to meet stricter criteria for total error (AU)

[Comparability study of analytical results between a group of clinical laboratories]. / Intercambiabilidad de resultados entre los diferentes laboratorios clínicos Catlab.

OBJECTIVE: To describe the study of the comparability of the measurements levels of biological tests processed in biochemistry in Catlab's 4 laboratories. MATERIAL AND METHODS: Quality requirements, coefficients of variation and total error (CV% and TE %) were established. Controls were verified with the precision requirements (CV%) in each test and each individual laboratory analyser. Fresh serum samples were used for the comparability study. The differences were analysed using a Microsoft Access® application that produces modified Bland-Altman plots. RESULTS: The comparison of 32 biological parameters that are performed in more than one laboratory and/or analyser generated 306 Bland-Altman graphs. Of these, 101 (33.1%) fell within the accepted range of values based on biological variability, and 205 (66.9%) required revision. Data were re-analysed based on consensus minimum specifications for analytical quality (consensus of the Asociación Española de Farmacéuticos Analistas (AEFA), the Sociedad Española de Bioquímica Clínica y Patología Molecular (SEQC), the Asociación Española de Biopatología Médica (AEBM) and the Sociedad Española de Hematología y Hemoterapia (SEHH), October 2013). With the new specifications, 170 comparisons (56%) fitted the requirements and 136 (44%) required additional review. Taking into account the number of points that exceeded the requirement, random errors, range of results in which discrepancies were detected, and range of clinical decision, it was shown that the 44% that required review were acceptable, and the 32 tests were comparable in all laboratories and analysers. CONCLUSIONS: The analysis of the results showed that the consensus requirements of the 4 scientific societies were met. However, each laboratory should aim to meet stricter criteria for total error.

[Effect of digital rectal examination on PSA]. / Efecto del tacto rectal sobre el PSA.

A prospective randomized study on 100 patients was conducted to determine the effect of the rectal digital examination on prostate specific antigen (PSA) serum concentration. The control group consisted of 50 patient, all with two PSA determinations with no urological manipulation between them. The study group had 50 patient, who underwent digital examination 24 hours before the second PSA determination. Mean difference in PSA concentration in the study group is 0.84 ng/ml, compared to 0.0048 ng/ml in the control group (p << 0.05). Only 7 patients with initial PSA within the normal range (0.0-0.4 ng/ml) had a second PSA higher than 4.0 ng/ml. Only a patient with initial PSA lower than 4.1 ng/ml, had a second PSA higher than 10.1 ng/ml. This minimal change is independent of the initial concentration and the diagnosis (benign prostate hyperplasia, prostate adenocarcinoma or chronic prostatitis). Though changes are statistically significant they are not clinically so because the 0.84 increase is irrelevant. Based on these data we believe rectal digital examination has no effect on PSA serum levels.

Reference interval for serum alpha-amylase determined with p-nitrophenyl-alpha-D-maltoheptaoside as a substrate.

The reference interval for the catalytic concentration of alpha-amylase (EC 3.2.1.1) in serum was determined in 326 blood donors. The analytic method used p-nitrophenyl-alpha-D-maltoheptaoside as substrate, which allows a continuous colorimetric measurement at 37 degrees C of the catalytic concentration of alpha-amylase in serum. The limits obtained were 0.7-3.8 mukat/l (42-228 U/l), which were in agreement with the only previous report found.