Permissible measurement uncertainty in the lower part of measurement intervals

Abstract

Abstract Many laboratories observe that requirements of the Guideline of the German Medical Association RiliBÄK for the internal quality assurance are difficult to fulfill in the lower part of the measurement interval (e.g. thrombocyte count at 50·109/L). With 10 measurands, the RiliBÄK contain special limits for lower measurement quantities. But, these limits lead to artificial “jumps” and even may be too stringent in the very low region of the measurement interval. Requirements which are too stringent usually lead to repeats and unnecessary costs, and to unnecessary time delay. The DGKL working group Guide Limits proposes variable permissible limits depending on the measurand concentration applied in the control material. Then, in the 10 critical cases, higher permissible limits are obtained in the very low part of measurement intervals. The control materials used in ring trials should contain concentrations close to the lower decision limits. Then, the permissible limits provided by the RiliBÄK also appear too stringent in the lower part of the measurement intervals of many measurands.