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Measurements for 8 Common Analytes in Native Sera Identify Inadequate Standardization among 6 Routine Laboratory Assays
H.C.M. Stepman, U. Tiikkainen, D. Stöckl,
H.W. Vesper, S.H. Edwards, H. Laitinen, J. Pelanti,
Proficiency Testing (PT), also known as External Quality Assessment (EQA), has earned a well-deserved position as an element of laboratory quality management
PT with commutable samples and high-quality targets is essential for assessing the accuracy of diagnostic assays and the interchangeability of generated results
The “intrinsic” quality of a manufacturer’s assay may be influenced by the laboratory using it; therefore, assessment under routine conditions is essential
See Editorial by Horowitz GL. Assessing Accuracy on the Front Lines: A Pragmatic Approach for Single-Donor Proficiency Testing. Clin Chem 2014
Figure 1. Assay bias (% difference = (mean of peer group result - target value/target value)*100) and total error vs AMTM (glucose, HDL-cholesterol) or REF target values (cholesterol, creatinine). Abbott (red diamond), Beckman (blue square), Ortho (black triangle), Roche (yellow circle), Siemens (red square), and Thermo Scientific (blue diamond). The red-broken bias limits are those listed in Table 1; the blue-broken limits are optimal bias limits from biological variation (online Supplemental Table 6).
ResultsResults
For conversion of the traditional units to SI units used in the online Supplemental Figs., multiply by 0.02586 for cholesterol (mmol/L), 88.40 for creatinine (µmol/L), 0.05551 for glucose (mmol/L),and 0.02586 for HDL cholesterol (mmol/L).
Figure 2. Assay bias (% difference) and total error vs AMTM (LDL cholesterol, phosphate, triglycerides) or REF target values (uric acid). Abbott (red diamond), Beckman (blue square), Ortho (black triangle), Roche (yellow circle), Siemens (red square), and Thermo Scientific (blue diamond). The red and blue broken limits are the same as described for Fig. 1.
ResultsResults
For conversion of the traditional units to SI units used in online Supplemental Figs., multiply by 0.02586 for LDL cholesterol, 0.3229 for phosphate (mmol/L), 0.01129 for triglycerides (mmol/L), and 59.48 for uric acid (µmol/L).
Table 2. Observed AMTM bias in the participating laboratories. The blue, underlined values refer to maximum absolute laboratory biases >15% and differences between laboratories >30%. CHOL, cholesterol; CREA, creatinine; GLU, glucose; HDL, HDL cholesterol; LDL, LDL cholesterol; PHOS, phosphate; TRIGL, triglycerides; UA, uric acid; NA, not applicable. Diff 1, the difference between the most deviating laboratories, diff 2 and 3 the 2nd and 3rd most deviating laboratories. Note: “bias low and high” stand for the bias at the limits of the concentration range covered by the panel.
Final Comment in EditorialFinal Comment in Editorial
“For now, we should celebrate the insights that Stepman et al. have provided. As good as conventional PT may be, we can do better.”
“We are indebted to these authors for shedding light on a problem we may have assumed we did not have and, more important, for providing a powerful tool to help us make things better.”
Horowitz GL. Assessing Accuracy on the Front Lines: A Pragmatic Approach for Single-Donor Proficiency Testing. Clin Chem 2014.