RESUMO
Objective To estimate the methodology for evaluating the analytical measurement range ( AMR) and the clinically reportable range ( CRR) in lab-developed system in clinical chemistry .Methods Method evaluation .Take serum CK for instance , a series of samples were prepared from both a specimen with a high concentration of the analyte of interest and a specimen with a low concentration for the following assays.Average slope method , linear dilution recovery method and the method recommended by Clinical and Laboratory Standards Institute ( CLSI ) EP6-A were used to established AMR in the lab-developed clinical chemistry system.Based on the maximum valid dilution of the specimen and the results of AMR , CRR were determined.One-half of the total error allowance ( TEa) of Chinese health standard was set up as allowance error (7.5%).Results X-Y scatter plot was made by assigning sample numbers to the horizontal axis and actual measured values to the vertical axis , which determined the upper limit of AMR was approximate 1 651 U/L.The results analyzed by average slope method indicated that the linear correlation between expected values and actual measured values was determined , the correlation (r), the intercept (a) and the slope (b) met the linear standard, and AMR was 5-1 699 U/L.The results analyzed by EP6-A indicated that the best fitting curve was obtained by using cubic polynomial method , and the linearity deviation of the minimum concentration was -77.1%, which exceeded one-half of TEa.Followed by the deletion of the maximum concentration , the resumed experiment was done .The results showed that the nonlinear coefficient c of quadratic polynomial and the nonlinear coefficient c and d of cubic polynomial have no significant difference to 0, and AMR was 7.5-1 458.0 U/L.By linear dilution recovery method , the linear correlation between expected values and actual measured values was determined , the correlation ( r) , the intercept ( a) and the slope ( b) met the linear standard , the recovery rates was between 100.0%and 104.8%, and AMR is 5 -1 699 U/L.The CRR was determined to be 5 -33 880 U/L, which met the standard of TEa . Conclusions Average slope method, linear dilution recovery method and EP 6-A method were all used to established AMR in lab-developed clinical chemistry system .Without complicated statistical analysis , linear dilution recovery method was suitable for clinical use .The linearity deviation of the minimum concentration analyzed by EP6-A did not meet the standard of the quality objective system , suggesting defects in the statistical analysis of the results .CRR was feasibly determined by using linear dilution recovery method align with AMR.
RESUMO
Objective To investigate the precision, trueness, and accuracy of self-developed detection system in clinical chemistry.Methods This was a methodological evaluation.Take serum creatine kinase( CK) for instance, 6 serum sampleswith different leves ( on the upper or lower limit of the reference range or close to the medicine decide levels ( MDLs) , were collected for within-run precision( repeatability) and within-laboratory precision ( intermediate precision ) experiments.5 proficiency testing ( PT ) samples, 5 samples assigned value by reference method, and 40 fresh-frozen serums were measured and compared with reference method for trueness verification.Drawing method evaluation decision chart, calculating total errors and sigma level evaluation experiment based on the CV, bias, and allowed total errors(TEa)were used to evaluate the accuracy performance.The precision, trueness, and accuracy were compared with the quality indicators.Results The within-run precision and within-laboratory precision were less than the highest requirement of Chinese industrial standard.The mean bias was -8.96%, didn′t reachthe required standard (5.5%).After taking corrective actions, all samples but one ( -5.8%) met the required standard. Compared with the reference method, the mean bias on the MDLs was less than TEa.The performance points of the method evaluation decision chart indicated excellence performance.The total errors on MDLs were 14.2%, 10.4% and 7.6%, less than 15%.The sigma levels on MDLs were 5.9, 7.5 and 15, also achieved excellent level. Conclusions The precision, trueness, and accuracy performance of CK measured by self-developed detection system achieved excellent level of the Chinese industry standard, and the same results were found from different evaluation methods.