Upsala J Med Sci 98: 487-491, 1993 11. Explanation of some other Concepts and Terms Used in this Report Carl-Henric de Verdier,' Torgny Groth2 and Per Hyltoft Petersen3 'Department of Clinical Chemistry, and 2Unit for Biomedical Systems Analysis, Uniuersity of Uppsala, Uppsala, Sweden and 3Departrnent of Clinical Chemistry, Odense Uniuersity Hospital, 5000 Odense, Denmark Analytical procedure An analytical procedure is made up of 1) an analytical measurement procedure consisting of the measurement procedure proper, calibration, calculation and correction procedures; 2) an analytical control procedure. This terminology was in principle introduced already in (1) and is preferred here in order to clearly distinguish between the overall procedure and its component parts. Analytical control procedures can be defined by specification of control rule(s), control limits, control material, and the number of control observations. Different types of variations Abbreviations: ST SB SA 'Bw 'Bb SpEA 'Aw SAb STBW total standard deviation (total SD) total biological SD total analytical SD biological within-subject SD biological between-subject SD pre-analytical SD analytical within-series SD analytical between-series SD total within-subject SD (including biological and analytical variation) CV, total coefficient of variation CVB total biological coefficient of variation. Etc. 21 -935253 487 SAWL SAbL s~~ 'A0 analytical within-laboratory SD, can be calculated in different ways, e.g. as i) average for an individual laboratory or ii) average for several laboratories. analytical between-laboratory SD total analytical SD (including analytical within-lab and between-lab variation) inherent stable analytical random error (estimated from sAW or sAwL dependent on problem) Definitions according to analysis of variation (ANOVA): sT2 = sB2 + SA 2 -k SpreA 2 2 - 2 2 2 2 sB - 'Bw + 'Bb SA2 = SAW + SAb 2 2 2 'TB; = 'A + 'Bw ' 'preA sAL2 = SAbL + 'AWL 2 2 ANOVA is carried out according to references (2, 3). Similar system for abbreviations of variations have been described by Dot, Mir6, and Fuentes-Arderiu ( 5 ) . Different types of bias of a measuring instrument According to Chapter 1 and VIM (4), bias (of a measuring instrument) is defined as a "systematic error of t h e indication of a measuring instrument". In accordance with ref. (8) we have used bias to describe long term stable systematic errors and ASE for short term systematic errors - not included in "averaging the error of indication over an appropriate number of repeated measurements". Abbreviations: B A analytical bias Bcorr correctable bias; that part of bias (systematic error), which is well defined and estimated. noncorrectable bias; that part of bias which can not be well estimated. BnOncOrr 488 B W L difference in bias (within a laboratory or for a given instrument) between two time points = [BA(tl) - BA(t2)]. difference in bias between two laboratories. difference in bias between two instruments. BhL 'h1 The concepts of "analytical stability" and "analytical instability" are introduced in references (8, 9) in order to describe variation in analytical performance over a longer time period expressed as distances between (k; 1) points in a two-dimensional co-ordinate system. Reference interval - reference range A (biological) reference interval is, if other characteristics are not indicated, defined as a 0.95-interfractile interval (6, 7). The statistical definition of range is "the difference between the highest and the lowest value in a distribution". Reference range is according to this definition the difference between the highest and lowest value in a distribution of reference values. Errors of a measuring instrument The total error, TE, is composed of the following terms: TE = Biascorr + Biasnoncorr + ASE * sAO t Z * ARE * SAO where ASE is a temporary increase of the systematic error, not detected/eliminated by the quality control system of the laboratory. This increase in error is expressed as multiples of sAo . Can have a positive or negative value and be of the order (0; ASEdetect). ARE is a temporary increase of the random error, not detected/eliminated by the quality control system of the laboratory. The change in random error is expressed as multiples of sAo and is in the order (0; AREdetect). z is a multiplier related to the portion of the distribution exceeding the quality requirement, often set as 2.65 to fix the maximum defect rate to 5 %. Compare ref. (8) (Chapter 5.2). 489 Quality concepts Different quality concepts are explained in Chapter 11. We are using both the defined concept "quality assurance" and the concept "quality assessment" with regard to analytical quality e.g. in the context of "internal quality assurance" and "external quality assessment and assurance". "External Quality Assessment" refers to a system of retrospectively and objectively comparing results from different laboratories by means of an external agency. The main object of EQA is to establish the degree of agreement of results, both amongst laboratories and with an absolute standard where one exists" (11). We have used the abbreviation EQAA to represent the type of active "External Quality Assessment and Assurance" program described in ref. 8. According to a document produced by ECCLS, REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. Aronsson T, de Verdier, C-H, Groth,T. Factors Influencing the Quality of Analytical Methods - A Systems Analysis with Use of Computer Simulation. Clin Chem 1974;20:738-748. Aronsson T, Bjpirnstad P, Johansson SG, Leskinen E, Raabo E, de Verdier C-H. Interlaboratory quality control with investigation of different methodological characteristics. Scand J Clin Lab Invest 1978; 3853. Aronsson T, Bjpirnstad P, Leskinen E, Uldall A, de Verdier C-H. Assessment of analytical quality in Nordic clinical chemistry laboratories using data from contemporary national programs. Scand J Clin Lab Invest 1984; 44 (Suppl 172):llS- 124. BIPM, IEC, IFCC, ISO, IUPAC, IUPAP, OIML. International Vocabulary of Basic and General Terms in Metrology, 2nd ed. ISO, 1993:l-59. Dot D, Mird J, Fuentes-Arderiu X. Biological variation of the leucocyte differential count quantities. Scand J Clin Lab Invest 1992; 52:607-611. IFCC, ICSH. Approved recommendation (1986) on theory of reference values. Part 1. The concept of reference values. J Clin Chem Clin Biochem 1987;25:337-342. IFCC, ICSH. Approved recommendation (1987) on theory of reference values. Part 6. Presentation of observed values related to reference values. J Clin Chem Clin Biochem 1987;25:657-662. Groth T, de Verdier C-H. Transferability of Clinical Laboratory Data. Upsala J Med Sciences 1993;98 (3): In Press. 490 9. 10. 11. Olafsdottir E. Aronsson T, Groth T, de Verdier C.-H. Transferability of Clinical Laboratory Data within a Health Care Region. Scand J Clin Lab Invest 1992;52:679- 687. Westgard JO. Charts of Operational Process Specifications ("OPSpecs Charts") for Assessing the Pecision, Accuracy, and Quality Control Needed to Satisfy Proficiency Testing Performance Criteria. Clin Chem 1992;38: 1226-1233. European Committee for Clinical Laboratory Standards (ECCLS) 3rd Draft, Standard for Quality Assurance Programmes. Part 1: General Principles and Terminology. ECCLS Documents 3 (9, 1983. Correspondence: Carl-Henric de Verdier, MD., professor Department of Clinical Chemistry University Hospital S-751 85 UPPSALA, Sweden Fax: t 4 6 18 552562 49 1