[Achieving laboratory results you can rely on].

Many decisions within healthcare are based on results from laboratory tests. These results all have an uncertainty, which can be either neglectable or large enough to affect the clinical assessment. In external quality assessment (EQA) the laboratories make independent observations on the same control sample, with values unknown for the participants. The results can be used to determine if quality improvement is needed. We present EQA data for laboratory tests with three different measurement scales; quantitative, ordinal and nominal. Results from EQA should be used in the discussions of quality in test results and necessary analytical performance specifications should be agreed upon.