Introducció

Antibodies are measured by means of their specific interaction with an antigen, based on the capability of mutual recognition. The nature of this binding makes the results obtained be method-dependent, which represents a pitfall for the interpretation of laboratory reports. From a metrological point of view, the existence of reference methods and reference materials are extremely important in solving this obstacle. Reference methods for autoimmune antibodies measurements have not been defined yet, forcing the international organizations devoted to standardization to assign arbitrary units to their reference material.

Standardization of autoantibodies detection by immunofluorescence is based on the identification of the reference material staining pattern, and eventually, on its titration using the same test method under the same routine conditions. The titer is expressed as a potency and provides a factor for conversion of the results obtained.

The aims of quality control schemes are, in general, to provide participants with an objective assessment of their performance within their laboratories and in relation to other laboratories, to provide information on the relative performance of the available kits and methods, and to identify factors associated with good and poor performance. External quality control must not substitute but complement the internal quality control, which, by using a positive control in each run, facilitates the detection of changes due to the antigenic substrate, the fluorescent conjugate or the developing system.

The international external quality assessment program organised by BioSystems S.A. (PREVECAL) tries to contribute to the specialist education in the interpretation of the results, and offers laboratories the possibility to complete their internal control scheme with an objective estimation of the quality of their measurement procedures. The scheme is a consequence of the BioSystems policy to actively collaborate with its customers in the achievement of results at the highest level.