External quality assessment schemes for clinical chemistry in Germany.

The external quality assessment schemes in clinical chemistry are regulated by the guidelines of the Federal Association of Physicians for Quality Assurance in Medical Laboratories (Richtlinien der Bundesärztekammer zur Qualitätssicherung in Medizinischen Laboratorien) which are part of a legal act. The basis of the mandatory quality assessment in medical laboratories is the internal accuracy and precision control. The target values for the internal accuracy and external quality control are determined by method-independent reference methods as far as possible. But for most of the analytes method-dependent assigned values are determined by expert laboratories. The decision limits for the internal and external quality control are derived from the interindividual dispersions of the analytes of a normal population (reference intervals) and should meet the medical requirements. The advantages of method-independent target values are discussed.