Supraregional interlaboratory quality-control survey for an immunoradiometric renin assay.

specificities of 0.825 (confidence interval, 0.677– 0.916) and 0.965 (0.851– 0.995), respectively. We found that when RCVs from creatinine and urate combined were used to predict crises, the FP probability was reduced and there was a considerable increase in diagnostic specificity. The methodology used in this work pointed out the need to improve laboratory reports (13) as follows: • Include the RCV calculations for the combination of significant analytes for the pathology studied in the laboratory data processing system • Mark the test results showing a significant RCV with respect to the previous result • Include in the report a plot showing evolution of the analytes with a critical role in detecting changes in the pathology monitored A limitation of our RCV model to detect changes in the evolution of kidney graft recipients during monitoring is that it can only be applied to patients who have experienced a certain period of favorable clinical evolution. Regarding the usefulness of the model, we mention a few points. First, although the model can benefit only patients who have achieved an interval of clinical stability, these are precisely the ones in whom surveillance may be more relaxed (the patient has recovered from the operation and feels better; analyses are less frequent), and a specific, objective biochemical marker could be of greatest value. Second, the constituents providing an early indicator of rejection are among those analyzed in the standard protocol and at exactly the same frequency. Thus, no additional cost, effort, or discomfort to the patient is implied by the use of this approach (14). References 1. Harris EK. Some theory of reference values. Comparison of some statistical models of intraindividual variation in blood constituents. On the calculation of a " reference change " for comparing two consecutive measurements. Interpretation of serial measurements of international normalized ratio for prothrombin times in monitoring oral anticoagulant therapy. establishing biological variation in non-healthy situations: renal posttrans-plantation data. change value using specific enquiry in renal post-transplantation. Bioquimia 2000;25:85. 11. Henderson AR. Assessing test accuracy and its clinical consequences: a primer for receiver operating characteristic curve analysis. For the last 20 years, the most widely used method for assessment of the renin-angiotensin system has been the plasma renin activity assay (1). Although the assay gives useful information on the enzymatic function of the renin molecule, the intrinsic characteristics of this method limit its analytical accuracy (2). Immunoradiometric assays for renin, …