1. All you wanted to know about laboratory tests, but were afraid to ask By Dietmar Stöckl STT Consulting - 9 - The informed patient meeting the laboratory director Analytical Performance Goals

2. All you wanted to know about laboratory tests -9- 2 Today

3. All you wanted to know about laboratory tests -9- 3

4. 4 The start First general limits Belk W, Sunderman FW. A survey of the accuracy of chemical analyses in clinical laboratories. Am J Clin Pathol 1947;17:853- 61 (reprinted in: Arch Pathol Lab Med 1988;112:320-6). First goals based on biology Tonks DB. A study of the accuracy and precision of clinical chemistry determinations in 170 Canadian laboratories. Clin Chem 1963;9:217-33. % maximum total error (TE max ) = 100 * [¼ of the reference interval (RI)/mean of RI] “If the normal range for sodium is taken to be 135-145 mEq./L., then the allowable limits of error calculated by this formula are ± 1.8%”. “The maximum limits for any determination, however, were set at ± 10%, even though in some cases those calculated by the above formula exceeded this figure”.

5. All you wanted to know about laboratory tests -9- 5 The concepts The discipline agreed on the hierarchy of models for establishing analytical performance goals# Clinical concepts Questionnaires to clinicians Concepts based on biological variation Expert opinion/Regulations "State-of-the-art" #Kenny D, Fraser CG, Hyltoft Petersen P, Kallner A. Strategies to set global quality specifications in laboratory medicine, Stockholm, 24-26 April 1999. Consensus agreement. Scand J Clin Lab Invest 1999;59:585.

6. All you wanted to know about laboratory tests -9- 6 The reality Clinical concepts & questionnaires to clinicians Few data available Concepts based on biological variation Start getting used by industry; misconception: values are for the laboratory, industry should use more stringent goals Expert opinion/Regulations Highly variable "State-of-the-art“ Difficult to assess; information typically restricted to imprecision (www.westgard.com; several essays on “Sigma analysis”)

7. All you wanted to know about laboratory tests -9- 7 The reality Typically, there is no consensus between (and often within) the different concepts TEa of serum sodium measurement SourceTEa (%) Biological variation (Ricos data, “Westgard page”) 0.9 ¼ of the reference-interval2.2 American EQA (CLIA) (in % mean of RI) 2.9 German EQA5

8. All you wanted to know about laboratory tests -9- 8 Resources Educational material >www.stt-consulting.com >Education General >Analytical quality II TSH example >Analytical performance goals TSH Performance goals from biology www.westgard.com/biodatabase1.htm

9. All you wanted to know about laboratory tests -9- 9 I type... A lot to think about... more needs to be done.

10. All you wanted to know about laboratory tests -9- 10 The next visit See you next time. Performance assessment