Agrawal Y.,New York Medical College |
Cid M.,New York Medical College |
Westgard S.,Westgard QC Inc. |
Parker T.,New York Medical College |
And 4 more authors.
Therapeutic Drug Monitoring | Year: 2014
BACKGROUND:: A global tacrolimus proficiency study recently showed clinically significant variability between laboratories, the inability of a common calibrator to harmonize methods, and differences in patient classification depending on the test method. The authors evaluated (1) the effect of a change in methodology on patient classification based on tacrolimus blood concentration and (2) the ability of 2 methods to position the concentration in a given specimen within the correct range. METHODS:: A total of 839 consecutive samples were analyzed at The Rogosin Institute and New York Presbyterian Hospital for routine tacrolimus monitoring over 30 days. Concordance analysis between the methods was performed covering dosage target ranges of 8-10, 6-8, 4-6 ng/mL currently used at our center. Six Sigma Metrics were applied to statistically evaluate the discordance rate. RESULTS:: Deming regression comparing liquid chromatography-tandem mass spectrometry and immunoassay yielded y = 0.927x - 0.24; 95% confidence interval, 0.903-0.951; R = 0.875; n = 839. There were 310 pairs (37%) discordant by 1, 21 (2.5%) discordant by 2, and 4 (0.5%) discordant by 3 therapeutic ranges. Surprisingly, 40% of patient samples were discordant when therapeutic ranges were 2 ng/mL wide. This discordant rate is equivalent to 1.7 Sigma and falls far below the minimum acceptable threshold of 3 Sigma. CONCLUSIONS:: Both methods are capable of measuring tacrolimus in the clinically relevant range between 1 and 10 ng/mL, yet 40% of the samples were discordant with an unacceptable Sigma level. Standardization of tacrolimus assays will mitigate this issue. © 2014 by Lippincott Williams & Wilkins. Source
Westgard J.O.,University of Wisconsin - Madison |
Westgard J.O.,Westgard QC Inc.
Clinics in Laboratory Medicine | Year: 2013
The right quality control (QC) should ensure the detection of important errors. Statistical QC (SQC) should be included in all QC plans. The Clinical and Laboratory Standards Institute (CLSI) C24A3 provides guidance for the application of SQC in medical laboratories. It describes a QC planning process and provides an SQC selection tool that relates the sigma-metric of a testing process to the medically important systematic error and the rejection characteristics of different SQC procedures. Once the right SQC has been selected, the laboratory must implement SQC right. CLSI C24A3 also provides guidance for establishing run length and control limits. © 2013 Elsevier Inc. Source
Utilizing global data to estimate analytical performance on the Sigma scale. A global comparative analysis of methods, instruments, and manufacturers through external quality assurance and proficiency testing programs
Westgard S.A.,Westgard QC Inc.
Clinical Biochemistry | Year: 2016
Objective: To assess the analytical performance of instruments and methods through external quality assessment and proficiency testing data on the Sigma scale. Design and methods: A representative report from five different EQA/PT programs around the world (2 US, 1 Canadian, 1 UK, and 1 Australasian) was accessed. The instrument group standard deviations were used as surrogate estimates of instrument imprecision. Performance specifications from the US CLIA proficiency testing criteria were used to establish a common quality goal. Then Sigma-metrics were calculated to grade the analytical performance. Results: Different methods have different Sigma-metrics for each analyte reviewed. Summary Sigma-metrics estimate the percentage of the chemistry analytes that are expected to perform above Five Sigma, which is where optimized QC design can be implemented. The range of performance varies from 37% to 88%, exhibiting significant differentiation between instruments and manufacturers. Median Sigmas for the different manufacturers in three analytes (albumin, glucose, sodium) showed significant differentiation. Conclusions: Chemistry tests are not commodities. Quality varies significantly from manufacturer to manufacturer, instrument to instrument, and method to method. The Sigma-assessments from multiple EQA/PT programs provide more insight into the performance of methods and instruments than any single program by itself. It is possible to produce a ranking of performance by manufacturer, instrument and individual method. Laboratories seeking optimal instrumentation would do well to consult this data as part of their decision-making process. To confirm that these assessments are stable and reliable, a longer term study should be conducted that examines more results over a longer time period. © 2016 The Canadian Society of Clinical Chemists. Source
Westgard QC Inc. | Date: 2015-05-05
Digital materials, namely, computer software for testing purposes, namely, for testing the performance and integrity of scientific measurement procedures and laboratory measurement devices, audio files, and publications in the nature of brochures, worksheets, and articles, all the aforementioned goods being in the field of scientific and laboratory quality control procedures, and all being either downloadable or available on CDs or digital storage media. Books, posters, and printed instructional, educational, and teaching materials in the field of scientific and laboratory quality control procedures. Educational services, namely, conducting seminars and conferences in the field of scientific and laboratory quality control procedures and distribution of training material in connection therewith; providing on-line training courses in the field of scientific and laboratory quality control procedures. Consulting services in the field of scientific and laboratory quality control procedures; providing a website featuring information in the field of scientific and laboratory quality control procedures.
Bio Rad Laboratories Inc. and Westgard QC Inc. | Date: 2003-04-22
statistical process control software for quality control of analytical test methods in clinical laboratories.