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The existence of alpha-1 antitrypsin variants with apparently unremarkable phenotypes and serum concentrations, contrasting with a clinical picture suggestive of a severe deficiency, led us to investigate whether in these cases there was a reduction or even suppression of the capacity of alpha-1 antitrypsin to inhibit elastase. To this end, in two different laboratories, we adapted and validated a method for measuring the functional activity of alpha-1 antitrypsin, based on spectrophotometric kinetic analysis of the inhibition by serum alpha-1 antitrypsin of the hydrolytic activity of porcine pancreatic elastase on a chromogenic substrate. This method has proved to be robust, reproducible and transferable and made possible to define, on the basis of an analysis of a hospital population, a functionality index with a confidence interval comprised between 0.87 and 1.2, allowing to identify subjects likely to have a functional deficiency of alpha-1 antitrypsin, whether this deficiency being of a genetic origin without any quantitative or phenotypic translation, or whether being acquired under the effect of external agents (cigarette smoke or viruses).

Research and identification of a serum cryoglobulin is a current laboratory test. This analysis is complex to accredit due to, firstly, very strict pre-analytical requirements, secondly, lack of standardization between laboratories in carrying out the different phases of sampling until results validation. The method validation of this analysis, carried out to meet requirements of the NF EN ISO 15189 standard, is a complex process divided into three sub-processes: cryoglobulin research including detection and isolation of cryoprecipitate, typing by immunofixation and quantification of cryoglobulin by immunoglobulin assays. This work made it possible, thanks to the development of a risk matrix taking into account all pre-analytical, analytical and post-analytical phases, to stress the importance of technical proficiency and management of critical equipment . With this approach, the laboratory also checked homogeneity of results validation practices.