Internal Quality control for Urea and creatinine in cobas 6000 Analysers Using Serum Sample

Quality control is an integral part of the analytical laboratory to obtain a precise, accurate result and also to reduce errors. Many national level laboratories utilize internal and external quality control methods for this purpose. The commercially available quality materials used for assessing daily internal quality control (IQC) is expensive, and hence in this study, an attempt was made to know the usefulness of serum sample as a quality control material.

To study IQC for urea and creatinine in Cobas 6000 analyser using serum sample

The study was conducted in the Clinical Biochemistry Laboratory, Kasturba Hospital, Manipal Academy of Higher Education, Manipal. IQC for estimation of urea and creatinine was assessed using Cobas 6000-1 and compared with Cobas 6000-2 autoanalyser. Thirty anonymised fresh serum samples and quality control material from Biorad with two level were used and compared between two analysers. Bland Altman agreement statistical analysis was applied for evaluating comparability using SPSS version 15.

Quality control materials with two levels and serum samples showed good concordance for most of the urea and creatinine values, and all values were within 2SD. Mean difference for estimation of urea with serum sample was found to be 0.03 with 95% limit of agreement from-2.67 to-2.73. Mean difference for estimation of creatinine with serum sample was found to be 0.012 with 95% limit of agreement from 0.235 to-0.26.

Our study showed that the fresh serum samples could be used as an IQC when control materials are not available or available one is deteriorated. An important implication of the study findings is that using serum samples for IQC will appreciably lower the cost for validation of the accuracy of the autoanalysers.