1. All you wanted to know about laboratory tests, but were afraid to ask By Dietmar Stöckl STT Consulting - 10 - The informed patient meeting the laboratory director Assessment of Analytical Performance

2. All you wanted to know about laboratory tests -10- 2 The analytical quality triangle For "valid" measurements… Method evaluation/ comparison Improvement Assurance Control Quality creation Quality specification Planning Quality management Instrument Chemistry State-of-art Expert Biology Clinical … the analytical quality triangle!

3. All you wanted to know about laboratory tests -10- 3 Performance characteristics Precision (-profile) – Random error (RE) –Imprecision Limit of detection (LOD) Working range Trueness/traceability – Systematic error (SE) –Calibration Linearity (also may define Working range) Recovery –Interferences –Specificity –Stability (shift & drift) –Carryover Accuracy/result-traceability – Total error (TE) –Combination of precision and trueness Ruggedness (robustness) Correlation/comparison with other methods

4. All you wanted to know about laboratory tests -10- 4 Assessment of performance Requirements Standards (specifications, claims) for acceptable performance Experimental protocols to estimate performance reliably ("Error assessment") Criteria for comparing estimated performance with performance standards Note: Apply a clinical perspective to the whole task! $Carey RN, Garber CC, Koch DD. Concepts and practices in the evaluation of laboratory methods. Workshop, AACC 48th Annual Meeting, Chicago (IL), July 28, 1996.

5. All you wanted to know about laboratory tests -10- 5 Standards Analytical performance goals The best “state-of-the-art”

6. All you wanted to know about laboratory tests -10- 6 Experimental protocols CLSI protocols, for example –EP 5 Imprecision –EP 6 Linearity –EP 7 Interference –EP 9 Method comparison –EP 10 Preliminary evaluation –EP 12 Qualitative tests –EP 14 Matrix effects –EP 15 User demonstration precison & accuracy –EP 17 Limit of detection –EP 21 Total error

7. All you wanted to know about laboratory tests -10- 7 Selected experiments

8. All you wanted to know about laboratory tests -10- 8 Decision making Modern interpretation of analytical data Confidence intervals/statistical significance testing. Statistical –Statistical tests versus Nul-hypothesis (F-test, t-test, 95% confidence-intervals, …): Bias = 0; Slope = 1; Intercept = 0; etc. Analytical –Statistical tests versus estimates of stable performance (F-test, t-test, 95% confidence-intervals, etc.): Bias  calibration tolerance; etc. Clinical –Statistical tests versus clinical limits (F-test, t-test, 95% confidence-intervals, etc.): REexp  REmax; SEexp  SEmax; TEexp  TEmax In all three situations, we apply the same type of statistical tests: important is the test value

9. All you wanted to know about laboratory tests -10- 9 Decision making – Old vs modern

10. All you wanted to know about laboratory tests -10- 10 Resources Westgard products www.westgard.com EP protocols www.clsi.org Educational material www.stt-consulting.com Laboratory statistics www.medcalc.be www.cbstat.com www.analyse-it.com www.dgrhoads.com/ www.stt-consulting.com

11. All you wanted to know about laboratory tests -10- 11 I type... Assessment of analytical quality … Do it the modern way.

12. All you wanted to know about laboratory tests -10- 12 Closure of the series Thanks for your patience! You really earned your credits