ABSTRACT
Optima from KONE Instruments Corporation is a new selective laboratory analyzer for turbidimetric, colorimetric and ion selective electrode measurements. Overall analytical performance of Optima and reagents provided by KONE was evaluated according to ECCLS guidelines, in a multicentre study involving four different laboratories, including substrates (cholesterol, high-density lipoprotein-cholesterol, creatinine), specific proteins (transferrin, IgG), enzyme activities (gamma-glutamyltransferase, alanine aminotransferase) and electrolytes (sodium, potassium, chloride). The results obtained attest good precision of the system for all the analytes tested: the range of within-run CV is 0.5 %-4.3 %, and range of between-day CV % is 0.8 %-7.9 % (median of four laboratories). Except for total cholesterol (5 % overestimation compared to the reference method) accuracy of measurement is adequate. Creatinine and uric acid assays were subjects of interference (defined as deviation > 10 % from target value) by bilirubin and haemoglobin respectively.
Subject(s)
Blood Chemical Analysis/methods , Blood Chemical Analysis/instrumentation , Blood Proteins/analysis , Cholesterol/blood , Colorimetry/methods , Creatinine/blood , Europe , Humans , Ion-Selective Electrodes , Lipoproteins/blood , Multicenter Studies as Topic , Nephelometry and Turbidimetry/methods , Reproducibility of Results , Sensitivity and Specificity , Uric Acid/bloodABSTRACT
The results of an external quality-assessment experiment for serum creatinine measurement are described. Fifty-one laboratories performed quintuplicate analyses during three different analytical runs on six lyophilized sera and two frozen human serum pools. Isotope dilution gas chromatography-mass spectrometry (ID GC-MS) target values were assigned to all the materials. Intralaboratory within- and between-run imprecision results were very similar for all the materials tested (CV < or = 2.20% and < or = 4.70%, respectively). The overall imprecision obtained was high (CV 6.5-20.0%) because of increased interlaboratory-intermethod variability. A significant positive bias (+ 9.2-+43.7%) was found for all the materials at lower creatinine concentration. By using two human sera at different concentrations, we could calculate the constant and the proportional calibration bias displayed by each peer group. The majority of the lyophilized materials showed a behavior divergent from the frozen pools, indicating matrix-related problems. We propose a new algorithm for calculating matrix bias correction factor instrument-reagent specific for each material.
Subject(s)
Creatinine/blood , Algorithms , Calibration , Gas Chromatography-Mass Spectrometry , Humans , Italy , Observer Variation , Quality Control , Reproducibility of ResultsABSTRACT
We report the results of an external quality assessment scheme for serum total cholesterol measurement involving about 100 Italian laboratories participating in an epidemiological study of post myocardial infarction. Two frozen human serum pools with Abell-Kendall assigned values are distributed quarterly at the laboratories (up to now seven events occurred); the obtained results are evaluated and discussed. In one exercise (# 5) duplicated measurements were repeated on three different days. Eighty-five to 98% of the laboratories obtained results within the total error limits (+/- 8.9%). But, while precision (calculated on the six replicates of exercise # 5) is good (90% of the laboratories obtained CV < 3%), inaccuracy problems are evident in every event. Indeed the mean bias from the reference method value ranged from 1.54 and 3.49% in the various events.
