[Difficulties and problems in external quality control of immunoassay].

Present status and problems in external quality control of immunoassays were described. Despite the increasing popularity of these methods, there are many difficulties in achieving good analytical performance. Consequently, immunoassay results demonstrate poor interlaboratory comparability. To exclude these difficulties, several changes should be made, for example, preparation of common reference standards, consent methods to give values to laboratory working standards, reference methods, matrix of test samples similar to actual clinical samples etc, before constructing suitable external quality control systems.