Evaluación del comportamiento en términos de error total y 6Sigma y estimación de la incertidumbre de medida de 16 magnitudes de bioquímica clínica / Evaluation of the behaviour of 16 clinical biochemistry laboratory tests in terms of total, six sigma, and measurement uncertainty

Dentro del sistema de calidad analítico de los laboratorios de análisis clínicos es usual el cálculo del error total (ET) y del Six sigma (6Sigma). La estimación de la incertidumbre de medida (U) es un parámetro que se debería incorporar como parte de la gestión de calidad, siendo esta una exigencia de la norma ISO 15189. La U aporta un intervalo de valores probables donde puede encontrarse el valor verdadero de un resultado de medida obtenido, proporcionando un valor cuantitativo del nivel de duda para cada valor. Este trabajo tiene como objetivos evaluar el comportamiento analítico de 16 métodos a través del cálculo del ET y del 6Sigma, así como estimar la U mediante un modelo de aproximación según la guía Nordtest. Se utilizaron datos del control interno (CCI) y del control externo de calidad (EQA). Se utilizaron especificaciones de calidad (ETa) basados en CLIA y variabilidad biológica para evaluar la performance de los métodos. Los 16 métodos presentaron un desempeño aceptable siendo los valores de ET obtenidos menores a los ETa propuestos y sus 6Sigma≥3 de acuerdo a lo deseado. Tres métodos presentaron valores de 6Sigma entre 3 y 4Sigma, 2 métodos presentaron valores entre 4 y 5Sigma, 5 presentaron valores entre 5 y 6Sigma; y 6 presentaron un 6Sigma mayor que 6. La U asociada a cada determinación aporta información complementaria sobre el intervalo de valores en el cual se encuentra el valor verdadero siendo parte del proceso de calidad analítica

Within the analytical quality system of the clinical analysis laboratories, it is usual to calculate Total Error (ET) and Six sigma (6Sigma). The estimation of the measurement uncertainty (U) is a parameter that should be incorporated as part of the quality management, and is a requirement of ISO 15189. The U provides a range of probable values where the true value of a measurement result can be obtained, providing a quantitative value of the level of doubt for each value. The objective of this work is to evaluate the performance of 16 analytical methods using the calculation of the ET and the 6Sigma, as well as the U, based on an approximation model of the Nordtest guide. Internal (CCI) and external quality control (EQA) data were used. Quality requirements (ETa) based on CLIA and biological variability (BV) were used to evaluate the performance of the methods. The 16 methods presented acceptable performance, with the ET values obtained being lower than the proposed ETa and the 6Sigma values≥3. Three methods have values of 6Sigma between 3 and 4, 2 methods between 4 and 5Sigma, five values between 5 and 6Sigma, and six had 6Sigmas greater than 6. The uncertainties associated with all measurements provide complementary information about the range of values in which the true value is found

Renal functional reserve evolution in children with a previous episode of hemolytic uremic syndrome.

INTRODUCTION: Glomerular filtration rate (GFR) is the most widely used indicator of kidney function in patients with renal disease, although it does not invariably reflect functional status after renal injury. The concept of renal functional reserve (RFR) as the ability of the kidney to increase GFR following a protein load was introduced in the 1980s. In this study we evaluated the RFR test in 26 children who had developed hemolytic-uremic syndrome (HUS) at least 2 years before the first evaluation, then 8 years later. At the beginning of the study they had no signs of proteinuria, hypertension or renal insufficiency. RFR was also evaluated in 15 healthy control children. METHODS: Proteinuria and creatinine in serum and urine were tested. Functional reserve index (FRI) was defined in order to evaluate RFR. Patients with FRI level >1.36 were considered as responders (R) and with FRI <1.36 as non-responders (NR). RESULTS: R and NR groups failed to show any significant differences when basal creatinine clearance (C(Cr)) was evaluated. The NR group presented a significant low initial FRI that persisted unchanged at the end of the study. These patients developed proteinuria and a renal protector treatment with protein restriction was indicated. Although the proteinuria diminished, it remained within pathological range. The lack of RFR response in the NR group was significantly related to the presence of oliguria lasting longer than 8 days during the acute phase of disease. CONCLUSIONS: Those patients with a previous history of HUS with normal basal C(Cr) should be evaluated by the RFR test to detect those at risk of developing glomerular hyperfiltration.