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. 2019 Feb 15;29(1):010701.
doi: 10.11613/BM.2019.010701. Epub 2018 Dec 15.

Standardization in laboratory medicine: Two years' experience from category 1 EQA programs in Spain

Carmen Ricós  1 , Carmen Perich  1   2 , Beatriz Boned  1   3 , Elisabet González-Lao  1   4 , Jorge Diaz-Garzón  1   5 , Montserrat Ventura  6 , Sandra Bullich  6 , Zoraida Corte  1   7 , Joana Minchinela  1   8 , Fernando Marques  1   9 , Margarita Simón  1   10 , Virtudes Alvarez  1 , José-Vicente García-Lario  1   11 , Pilar Fernández-Fernández  1 , Pilar Fernández-Calle  1   5
Affiliations

Standardization in laboratory medicine: Two years' experience from category 1 EQA programs in Spain

Carmen Ricós et al. Biochem Med (Zagreb). .

Abstract

Introduction: Standardization is the ability to obtain interchangeable results leading to same medical interpretation. External quality assessment (EQA) is the main support of the on-going harmonization initiatives. Aim of study was to evaluate results obtained from two years category 1 EQA program experience in Spain and determine the impact of applying this type of EQA program on the analytical standardization.

Materials and methods: According to the analytical method, traceability and instrument different groups were established which results were evaluated by calculating mean, coefficient of variation and percent of deviation to the reference value. Analytical performance specifications used to the results' evaluation were derived from biological variation for bias and from the inter-laboratory coefficients of variation found in a previous pilot study.

Results: Only creatinine measured by enzymatic methods gave excellent results, although few laboratories used this method. Creatine kinase and GGT gave good precision and bias in all, but one instrument studied. For the remaining analytes (ALT, ALP, AST, bilirubin, calcium, chloride, glucose, magnesium, potassium, sodium, total protein and urate) some improvement is still necessary to achieve satisfactory standardization in our setting.

Conclusions: The two years of category 1 EQA program experience in Spain have manifested a lack of standardization of 17 most frequent biochemistry tests used in our laboratories. The impact of the information obtained on the lack of standardization is to recommend abandoning methods such as ALT, AST without exogenous pyridoxal phosphate, Jaffe method for creatinine, and do not use non-commutable calibrators, such as aqueous solutions for calcium and sodium.

Keywords: bias; external quality assessment; standardization; traceability.

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Conflict of interest statement

Potential conflict of interest: None declared.

Figures

Figure 1
Figure 1
Calcium. Percentage deviation (Dev%) of peer group means from the reference value. X axis shows reference values of the six control materials. Y axis shows percent deviation of peer group mean versus the reference value. Numbers in brackets mean the number of participant laboratories. Lim Bias (m): acceptability limit for bias based on BV, minimum grade. NM-BAPTA: calcium specific amino-polycarboxylic acid.
Figure 2
Figure 2
Chloride. Percentage deviation (Dev%) of peer group means from the reference value. X axis shows reference values of the six control materials. Y axis shows percent deviation of peer group mean versus the reference value. Lim Bias (m): acceptability limit for bias based on BV, minimum grade. ISE - ion selective electrode. Numbers in brackets indicate the laboratories participating for each instrument.
Figure 3
Figure 3
Magnesium. Percentage deviation (Dev%) of peer group mean from the reference value. X axis shows reference values of the six control materials. Y axis shows percent deviation of peer group mean versus the reference value . Lim Bias (m): acceptability limit for bias based on BV, minimum grade. Xil - Xilidil blue. Numbers in brackets indicate the laboratories participating for each instrument.
Figure 4
Figure 4
Potassium. Percentage deviation (Dev%) of peer group mean from the reference value. X axis shows reference values of the six control materials. Y axis shows percent deviation of peer group mean versus the reference value. Lim Bias (m): acceptability limit for bias based on BV, minimum grade. ISE - ion selective electrode. Numbers in brackets indicate the laboratories participating for each instrument.
Figure 5
Figure 5
Sodium. Percentage deviation (Dev%) of peer group mean from the reference value. X axis shows reference values of the six control materials. Y axis shows percent deviation of peer group mean versus the reference value. Lim Bias (m): acceptability limit for bias based on BV, minimum grade. ISE - ion selective electrode. Numbers in brackets indicate the laboratories participating for each instrument.
Figure 6
Figure 6
Alkaline phosphatase. Percentage deviation (Dev%) of peer group means from the reference value. X axis shows reference values of the six control materials. Y axis shows percent deviation of peer group mean versus the reference value. Lim Bias (d): acceptability limit for bias based on BV, desirable grade. AMP - 2-amino-2-methyl-1-propanol. Numbers in brackets indicate the laboratories participating for each instrument.
Figure 7
Figure 7
Amylase. Percentage deviation (Dev%) of peer group mean from the reference value. X axis shows reference values of the six control materials. Y axis shows percent deviation of peer group mean versus the reference value. Lim Bias (d): acceptability limit for bias based on BV, desirable grade. G3 - malto trioside. G7 - malto-heptaoside. Numbers in brackets indicate the laboratories participating for each instrument.
Figure 8
Figure 8
ALT. Percentage deviation (Dev%) of peer group means from the reference value. X axis shows reference values of the six control materials. Y axis shows percent deviation of peer group mean versus the reference value. Lim Bias (d): acceptability limit for bias based on BV, desirable grade. Numbers in brackets indicate the laboratories participating for each instrument.
Figure 9
Figure 9
AST. Percentage deviation (Dev%) of peer group means from the reference value. X axis shows reference values of the six control materials. Y axis shows percent deviation of peer group mean versus the reference value. Lim Bias (d): acceptability limit for bias based on BV, desirable grade. P5P -pyridoxal-5-phosphate. Numbers in brackets indicate the laboratories participating for each instrument.
Figure 10
Figure 10
Creatine kinase. Percentage deviation (Dev%) of peer group mean from the reference value. X axis shows reference values of the six control materials. Y axis shows percent deviation of peer group mean versus the reference value. Lim Bias (d): acceptability limit for bias based on BV, desirable grade. NAC - N-acetyl-cysteine. Numbers in brackets indicate the laboratories participating for each instrument.
Figure 11
Figure 11
Gamma glutamyl transferase. Percentage deviation (Dev%) of peer group mean from the reference value. X axis shows reference values of the six control materials. Y axis shows percent deviation of peer group mean versus the reference value. Lim Bias (d): acceptability limit for bias based on BV, desirable grade. All groups use substrate: γ glutamyl-3carboxy-4nitroanilide > 4mmol/L. The exception is: Siemens Dimension, Vista that uses substrate < 4mmol/L. Numbers in brackets indicate the laboratories participating for each instrument.
Figure 12
Figure 12
Lactate dehydrogenase. Percentage deviation (Dev%) of peer group mean from the reference value. X axis shows reference values of the six control materials. Y axis shows percent deviation of peer group mean versus the reference value. Lim Bias (d): acceptability limit for bias based on BV, desirable grade. NMG - N-methyl-D-glucamine. DEA - diethanolamine. TRIS -hydroxymethyl-aminomethane. Numbers in brackets indicate the laboratories participating for each instrument.
Figure 13
Figure 13
Bilirubin. Percentage deviation (Dev%) of peer group mean from the reference value. X axis shows reference values of the six control materials. Y axis shows percent deviation of peer group mean versus the reference value. Lim Bias (d): acceptability limit for bias based on BV, desirable grade. DPD - 3,5-dicholorophenyl-diazonium- tetrafluoroborate. Numbers in brackets indicate the laboratories participating for each instrument.
Figure 14
Figure 14
Creatinine. Percentage deviation (Dev%) of peer group mean from the reference value. Methods in figure appearing according the following order: enzymatic, compensated and non-compensated. X axis shows reference values of the six control materials. Y axis shows percent deviation of peer group mean versus the reference value. Lim Bias (d): acceptability limit for bias based on BV, desirable grade. Numbers in brackets indicate the laboratories participating for each instrument.
Figure 15
Figure 15
Glucose. Percentage deviation (Dev%) of peer group mean from the reference value. X axis shows reference values of the six control materials. Y axis shows percent deviation of peer group mean versus the reference value. Lim Bias (d): acceptability limit for bias based on BV, desirable grade. GOD - glucose oxidase. HK - hexokinase. Numbers in brackets indicate the laboratories participating for each instrument.
Figure 16
Figure 16
Total protein. Percentage deviation (Dev%) of peer group mean from the reference value. X axis shows reference values of the six control materials. Y axis shows percent deviation of peer group mean versus the reference value. Lim Bias (d): acceptability limit for bias based on BV, desirable grade. B - biuret. Numbers in brackets indicate the laboratories participating for each instrument.
Figure 17
Figure 17
Urate. Percentage deviation (Dev%) of peer group mean from the reference value. X axis shows reference values of the six control materials. Y axis shows percent deviation of peer group mean versus the reference value. Lim Bias (d): acceptability limit for bias based on BV, desirable grade. POD – peroxidase. Numbers in brackets indicate the laboratories participating for each instrument.
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