Multimode Sigma metric analysis of a DxC 700

Taking a new study on the DxC 700, we assess what goals can be achieved by one of the leading chemistry platforms.

Sigma metric analysis of a DxC 700 - benchmarking with multiple goals

January 2020
Sten Westgard, MS

Continuing in our series of analyzing major diagnostic instrumentation using the latest sets of performance specifications
(EFLM/EuBIVAS 2020, Ricos 2014, CLIA 2019, and CLIA 1992), we came across a new paper on the Beckman Coutler DxC 700.

Evaluation of the Beckman Coulter DxC 700 AU chemistry platform, Bush VJ, Smola C, Schmitt P, Practical Laboratory Medicince 18 (2020); early online publication.

See the other analyses in this series:

The raw data of imprecision and bias

We're displaying a select set of the imprecision and bias measured in the study. The published study mentioned the comparison of methods study and the details were not Some assays we excluded because most of the TEa resources did not set TEa performance specifications (for example, hs-CRP, or CSF and Urine analytes). "Precision studies were performed for two levels of quality control for intra-run precision, two levels for most inter-run precision assays with three levels for lipids, bilirubins, and proteins. Quality Control materials (QC) were obtained from Bio-Rad....Intra-run precision was evaluated using 20 replicates of each level of qC for each analyte." This study nearly completed the study at the level of specification of CLSI EP05. "Correlation studies were performed according to CLSI EP09... except samples were analyzed in singlet instead of duplicate. Fresh or frozen/ thawed patient specimens were used for evaluation of the method correlation....Deming regression analysis was performed to calculate the slope, intercept, correlation coefficient (R)...." These biases were determined between the instrument that the laboratory had been previously using (Siemens Dimension Vista for most analytes) and the DxC 700.

Note, however, in the study, the biases used to calculate analytical Sigma-metrics were not the biases calculated from the the Deming regression and comparison study. Instead, those biases were determined from proficiency testing. Those biases were significantly lower.

DXC 700 performance data
TEST	% Bias	CV
Albumin	12.1	3.0
Albumin	0.0	1.9
Alk Phos	26.6	5.5
Alk Phos	13.1	2.1
ALT	30.4	2.2
ALT	20.0	1.7
Amylase	53.3	2.1
Amylase	14.5	1.0
AST	20.2	1.5
AST	24.9	2.6
Bilirubin, Direct	16.9	3.8
Bilirubin, Direct	16.6	2.5
Bilirubin, Total	0.8	1.4
Bilirubin, Total	0.3	1.8
C3	11.3	2.4
C3	8.2	1.3
C3	7.1	1.0
C4	10.2	3.6
C4	25.4	2.1
C4	30.0	1.7
Calcium	4.3	0.9
Calcium	1.1	0.7
Chloride	0.7	0.6
Chloride	0.1	0.6
Cholesterol	1.7	1.1
Cholesterol	3.5	1.0
CO2	6.5	8.6
CO2	1.4	7.2
Creatinine Kinase (CK)	2.6	2.3
Creatinine Kinase (CK)	12.5	1.2
Creatinine	15.0	4.1
Creatinine	2.9	1.7
Ferritin	43.6	9.8
Ferritin	11.0	2.3
Ferritin	6.8	1.4
GGT	22.6	2.2
GGT	26.9	0.7
Glucose	2.6	1.8
Glucose	7.8	0.8
HDL	5.9	5.1
HDL	3.5	3.0
IgA	2.8	2.5
IgA	3.5	2.4
IgA	5.6	1.6
IgG	1.9	1.4
IgG	4.1	1.3
IgG	5.0	2.1
IgM	5.8	3.5
IgM	5.9	2.1
IgM	5.9	1.2
Iron	6.4	5.5
Iron	8.7	1.8
Lactate	16.6	3.5
Lactate	9.1	2.3
LDL	0.7	2.9
LDL	1.9	3.3
LDH	17.7	3.0
LDH	13.0	2.1
Lipase	113.6	6.1
Lipase	81.8	3.9
Magnesium	17.6	3.8
Magnesium	7.0	1.8
Phosphorous	7.5	2.5
Phosphorous	5.9	1.2
Potassium	0.9	0.9
Potassium	0.8	0.9
Protein, Total	1.9	1.4
Protein, Total	4.1	1.4
Sodium	1.5	0.4
Sodium	0.1	0.6
Triglycerides	3.8	2.1
Triglycerides	1.3	0.9
Triglycerides	2.0	1.8
Urea Nitrogen	0.8	1.6
Urea Nitrogen	1.7	1.7
Uric Acid	11.7	1.6
Uric Acid	6.4	1.6

Now, the next thing to do is take a look at the latest EFLM performance specifications, as derived from the EuBIVAS biological variation database, which is being updated frequently, so we have 2020 TEa goals for this analysis; Ricos 2014 performance specifications; proposed CLIA 2019 goals; and finally the current 1992 CLIA goals.

Please note that the number of assays will vary from table to table, since not all assays are covered by the latest EuBIVAS database, nor by the CLIA goals. That makes the comparison slightly uneven - but it's a comparison of slightly different sizes of apples, not entirely different fruits.

Sigma-metrics according to EuBIVAS-derived desirable performance specifications (as of January 2020)

If you're looking for the toughest set of specifications, this is it. More than half of the assay performance is below 3 Sigma, while just under a quarter of performance is at 6 Sigma. That's the most worst and the least best in our comparison.

2020 dxc 700 sigma metrics eubivas 2020 medx chart

DXC 700 performance data according to EuBIVAS 2020 goals
TEST	TEa Source	TEa	% Bias	CV	Sigma
Albumin	EuBIVAS	3.6	12.1	3.0	*negative*
Albumin	3.6%	3.6	0.0	1.9	*1.9*
Alk Phos	EuBIVAS	10.6	26.6	5.5	*negative*
Alk Phos	10.60%	10.6	13.1	2.1	*negative*
ALT	EuBIVAS	16.1	30.4	2.2	*negative*
ALT	16.1%	16.1	20.0	1.7	*negative*
Amylase	EuBIVAS	13.1	53.3	2.1	*negative*
Amylase	13.1%	13.1	14.5	1.0	*negative*
AST	EuBIVAS	13.7	20.2	1.5	*negative*
AST	13.7%	13.7	24.9	2.6	*negative*
Bilirubin, Direct	EuBIVAS	44.50	16.9	3.8	*7.3*
Bilirubin, Direct	44.50%	44.50	16.6	2.5	*11.2*
Bilirubin, Total	EuBIVAS	25.70	0.8	1.4	*17.8*
Bilirubin, Total	25.70	25.70	0.3	1.8	*14.1*
C3	EuBIVAS	7.8	11.3	2.4	*negative*
C3	7.8	7.8	8.2	1.3	*negative*
C3	7.80%	7.8	7.1	1.0	*0.7*
Calcium	EuBIVAS	2.30	4.3	0.9	*negative*
Calcium	2.30%	2.30	1.1	0.7	*1.7*
Chloride	EuBIVAS	1.2	0.7	0.6	*0.9*
Chloride	1.2%	1.2	0.1	0.6	*1.8*
Cholesterol	EuBIVAS	8.80	1.7	1.1	>6
Cholesterol	8.80%	8.80	3.5	1.0	*5.3*
Creatinine Kinase (CK)	EuBIVAS	21.60	2.6	2.3	>6
Creatinine Kinase (CK)	21.60%	21.60	12.5	1.2	>6
Creatinine	EuBIVAS	7.20	15.0	4.1	*negative*
Creatinine	7.2%	7.20	2.9	1.7	*2.5*
GGT	EuBIVAS	17.70	22.6	2.2	*negative*
GGT	17.7%	17.70	26.9	0.7	*negative*
Glucose	EuBIVAS	5.80	2.6	1.8	*1.8*
Glucose	5.8%	5.80	7.8	0.8	*negative*
HDL	EuBIVAS	12.20	5.9	5.1	*1.2*
HDL	12.20%	12.20	3.5	3.0	*2.9*
IgG	EuBIVAS	7.30	1.9	1.4	*3.9*
IgG	7.3%	7.30	4.1	1.3	*2.4*
IgG	7.3%	7.30	5.0	2.1	*1.1*
IgM	EuBIVAS	17.10	5.8	3.5	*3.2*
IgM	17.10	17.10	5.9	2.1	*5.3*
IgM	17.10	17.10	5.9	1.2	>6
LDL	EuBIVAS	13.80	0.7	2.9	*4.5*
LDL	14%	13.80	1.9	3.3	*3.6*
LDH	EuBIVAS	7.70	17.7	3.0	*negative*
LDH	8%	7.70	13.0	2.1	*negative*
Lipase	EuBIVAS	14.20	113.6	6.1	*negative*
Lipase	14.20	14.20	81.8	3.9	*negative*
Potassium	EuBIVAS	4.8	0.9	0.9	*4.4*
Potassium	4.8	4.8	0.8	0.9	*4.5*
Protein, Total	EuBIVAS	3.50	1.9	1.4	*1.1*
Protein, Total	3.5%	3.50	4.1	1.4	*negative*
Sodium	EuBIVAS	0.7	1.5	0.4	*negative*
Sodium	0.7	0.7	0.1	0.6	*1.0*
Transferrin	EuBIVAS	6.40	0.2	1.5	*4.1*
Transferrin	6.40	6.40	2.4	0.9	*4.5*
Transferrin	6.40	6.40	3.3	0.8	*3.9*
Triglycerides	EuBIVAS	26.50	3.8	2.1	>6
Triglycerides	26.5	26.50	1.3	0.9	>6
Triglycerides	26.5	26.50	2.0	1.8	>6
Urea Nitrogen	EuBIVAS	17.80	0.8	1.6	>6
Urea Nitrogen	18%	17.80	1.7	1.7	>6

Negative Sigma, just to be clear, is when the bias is larger than the TEa. So the method is significantly different than the target. In this case, that means the methods on the Dimension Vista and the Beckman Coulter DxC, even when the methodology is similar, are very different.

Next, we can look at the "original" version of the biological variation database. The last version of the database was last updated in 2014 by Ricos et al, so we refer to these performance specifications as "Ricos 2014 goals."

Sigma-metrics according to Ricos 2014 desirable performance specifications

The original Ricos goals (desirable performance specifications) are still quite hard on the DxC 700, with a majority of assays below 3 Sigma, and less than a quarter of assay performance at 6 Sigma. Considerably far from desirable.

2020 dxc 700 evaluated by Ricos 2014 goals medx

DXC 700 performance data according to Ricos 2014 goals
TEST	TEa Source	TEa	% Bias	CV	Sigma
Albumin	Ricos 2014	4.1	12.1	3.0	*negative*
Albumin	4.1%	4.1	0.0	1.9	*2.2*
Alk Phos	Ricos 2014	12.04	26.6	5.5	*negative*
Alk Phos	12.04%	12.04	13.1	2.1	*negative*
ALT	Ricos 2014	27.5	30.4	2.2	*negative*
ALT	27.5%	27.5	20.0	1.7	*4.4*
Amylase	Ricos 2014	14.6	53.3	2.1	*negative*
Amylase	14.6%	14.6	14.5	1.0	*0.1*
AST	Ricos 2014	16.7	20.2	1.5	*negative*
AST	16.7%	16.7	24.9	2.6	*negative*
Bilirubin, Direct	Ricos 2014	44.50	16.9	3.8	>6
Bilirubin, Direct	44.50%	44.50	16.6	2.5	>6
Bilirubin, Total	Ricos 2014	26.94	0.8	1.4	>6
Bilirubin, Total	26.94	26.94	0.3	1.8	>6
C3	Ricos	8.4	11.3	2.4	*negative*
C3	8.4	8.4	8.2	1.3	*0.2*
C3	8.40%	8.4	7.1	1.0	*1.3*
C4	Ricos	16	10.2	3.6	*1.6*
C4	16.00%	16	25.4	2.1	*negative*
C4	16	16.00	30.0	1.7	*negative*
Calcium	Ricos 2014	2.55	4.3	0.9	*negative*
Calcium	2.55%	2.55	1.1	0.7	*2.1*
Chloride	Ricos 2014	4.6	0.7	0.6	>6
Chloride	4.6%	4.6	0.1	0.6	>6
Cholesterol	Ricos 2014	9.01	1.7	1.1	>6
Cholesterol	9.01%	9.01	3.5	1.0	*5.6*
CO2	Ricos 2014	4.86	6.5	8.6	*negative*
CO2	4.86%	4.86	1.4	7.2	*0.5*
Creatinine Kinase (CK)	Ricos 2014	30.30	2.6	2.3	>6
Creatinine Kinase (CK)	30.30%	30.30	12.5	1.2	>6
Creatinine	Ricos 2014	8.90	15.0	4.1	*negative*
Creatinine	8.9%	8.90	2.9	1.7	*3.5*
Ferritin	Ricos 2014	16.9	43.6	9.8	*-2.7*
Ferritin	16.9	16.9	11.0	2.3	*2.6*
Ferritin	16.9	16.9	6.8	1.4	>6
GGT	Ricos 2014	22.10	22.6	2.2	*negative*
GGT	22.1%	22.10	26.9	0.7	*negative*
Glucose	Ricos 2014	6.96	2.6	1.8	*2.4*
Glucose	7.0%	6.96	7.8	0.8	*negative*
HDL	Ricos	11.63	5.9	5.1	*1.1*
HDL	11.63%	11.63	3.5	3.0	*2.7*
IgA	Ricos	13.50	2.8	2.5	*4.3*
IgA	13.50%	13.50	3.5	2.4	*4.2*
IgA	13.50%	13.50	5.6	1.6	*5.0*
IgG	Ricos 2014	8.00	1.9	1.4	*4.4*
IgG	8%	8.00	4.1	1.3	*3.0*
IgG	8%	8.00	5.0	2.1	*1.4*
IgM	Ricos 2014	16.80	5.8	3.5	*3.1*
IgM	16.80	16.80	5.9	2.1	*5.2*
IgM	16.80	16.80	5.9	1.2	>6
Iron	Ricos 2014	30.70	6.4	5.5	*4.4*
Iron	31%	30.70	8.7	1.8	>6
Lactate	Ricos 2014	30.40	16.6	3.5	*3.9*
Lactate	30%	30.40	9.1	2.3	>6
LDL	Ricos 2014	11.90	0.7	2.9	*3.9*
LDL	12%	11.90	1.9	3.3	*3.0*
LDH	Ricos 2014	11.40	17.7	3.0	*negative*
LDH	11%	11.40	13.0	2.1	*negative*
Lipase	Ricos 2014	37.88	113.6	6.1	*negative*
Lipase	37.88	37.88	81.8	3.9	*negative*
Magnesium	Ricos 2014	4.80	17.6	3.8	*negative*
Magnesium	5%	4.80	7.0	1.8	*negative*
Phosphorous	Ricos 2014	10.11	7.5	2.5	*1.0*
Phosphorous	10%	10.11	5.9	1.2	*3.5*
Potassium	Ricos 2014	5.61	0.9	0.9	*5.3*
Potassium	5.61	5.61	0.8	0.9	*5.4*
Protein, Total	Ricos 2014	3.63	1.9	1.4	*1.2*
Protein, Total	4%	3.63	4.1	1.4	*negative*
Sodium	Ricos 2014	0.73	1.5	0.4	*negative*
Sodium	0.73	0.73	0.1	0.6	*1.0*
Triglycerides	Ricos 2014	25.99	3.8	2.1	>6
Triglycerides	25.99	25.99	1.3	0.9	>6
Triglycerides	26%	25.99	2.0	1.8	>6
Urea Nitrogen	Ricos 2014	15.55	0.8	1.6	>6
Urea Nitrogen	16%	15.55	1.7	1.7	>6
Uric Acid	Ricos 2014	11.97	11.7	1.6	*0.2*
Uric Acid	12%	11.97	6.4	1.6	*3.5*

Next we can look at performance specifications which are set by regulatory authorities, not biological variation.

Sigma-metrics according to Proposed CLIA goals of 2019 performance specifications

The 2019 proposals for updated CLIA goals exapnded the number of analytes covered and tightened goals over the original CLIA specifications. almost a third of the assay performance reaches 6 Sigma. Just over a third of the performance is still considered minimally acceptable or unacceptable.

2020 dxc 700 performance according to CLIA 2019 proposed goals

DXC 700 performance according to CLIA proposed 2019 goals
TEST	TEa Source	TEa	% Bias	CV	Sigma
Albumin	CLIA 2019	8	12.1	3.0	*negative*
Albumin	8%	8	0.0	1.9	*4.2*
Alk Phos	CLIA 2019	20	26.6	5.5	*negative*
Alk Phos	20%	20	13.1	2.1	*3.3*
ALT	CLIA 2019	15	30.4	2.2	*negative*
ALT	15%	15	20.0	1.7	*negative*
Amylase	CLIA 2019	10.00	53.3	2.1	*negative*
Amylase	10%	10.00	14.5	1.0	*negative*
AST	CLIA 2019	15	20.2	1.5	*negative*
AST	15%	15	24.9	2.6	*negative*
Bilirubin, Total	CLIA 2019	20.00	0.8	1.4	>6
Bilirubin, Total	20	20.00	0.3	1.8	>6
C3	CLIA 2019	15	11.3	2.4	*1.5*
C3	15.00%	15	8.2	1.3	*5.3*
C3	15.00%	15	7.1	1.0	>6
C4	CLIA 2019	20.00	10.2	3.6	*2.7*
C4	5 or 20%	20.00	25.4	2.1	*negative*
C4	16.00%	20.00	30.0	1.7	*negative*
Calcium	CLIA	15.625	4.3	0.9	>6
Calcium	1 mg/dL	7.692308	1.1	0.7	>6
Chloride	CLIA 2019	5	0.7	0.6	>6
Chloride	5%	5	0.1	0.6	>6
Cholesterol	CLIA	10	1.7	1.1	>6
Cholesterol	10%	10	3.5	1.0	>6
CO2	CLIA 2019	20	6.5	8.6	*1.6*
CO2	20%	20	1.4	7.2	*2.6*
Creatinine Kinase (CK)	CLIA 2019	20	2.6	2.3	>6
Creatinine Kinase (CK)	20%	20	12.5	1.2	>6
Creatinine	CLIA 2019 10% or	31.78	15.0	4.1	*4.1*
Creatinine	0.3 mg/dL	31.78	2.9	1.7	>6
Ferritin	CLIA 2019	20	43.6	9.8	*negative*
Ferritin	20	20	11.0	2.3	*3.9*
Ferritin	20	20	6.8	1.4	>6
GGT	CLIA 2019	22.32	22.6	2.2	*negative*
GGT	5 or 15%	15.00	26.9	0.7	*negative*
Glucose	CLIA 2019	8.00	2.6	1.8	*3.0*
Glucose	8%	8.00	7.8	0.8	*0.2*
HDL	CLIA 2019	20.00	5.9	5.1	*2.8*
HDL	20%	20.00	3.5	3.0	*5.5*
IgA	CLIA 2019	15.00	2.8	2.5	*4.9*
IgA	15.00%	15.00	3.5	2.4	*4.8*
IgA	15.00%	15.00	5.6	1.6	*5.9*
IgG	CLIA 2019	20.00	1.9	1.4	>6
IgG	20%	20.00	4.1	1.3	>6
IgG	20%	20.00	5.0	2.1	>6
IgM	CLIA 2019	20.00	5.8	3.5	*4.1*
IgM	20%	20.00	5.9	2.1	>6
IgM	20%	20.00	5.9	1.2	>6
Iron	CLIA 2019	15.00	6.4	5.5	*1.6*
Iron	15%	15.00	8.7	1.8	*3.5*
LDL	CLIA 2019	20.00	0.7	2.9	>6
LDL	20%	20.00	1.9	3.3	*5.5*
LDH	CLIA 2019	15.00	17.7	3.0	*negative*
LDH	15%	15.00	13.0	2.1	*1.0*
Magnesium	CLIA 2019	15.00	17.6	3.8	*negative*
Magnesium	15%	15.00	7.0	1.8	*4.4*
Phosphorous	CLIA 2019	16.67	7.5	2.5	*3.7*
Phosphorous	0.3 or 10%	10.00	5.9	1.2	*3.4*
Potassium	CLIA	12	0.9	0.9	>6
Potassium	0.3 mEq/L	4.054054	0.8	0.9	*3.7*
Protein, Total	CLIA 2019	8.00	1.9	1.4	*4.3*
Protein, Total	8%	8.00	4.1	1.4	*2.8*
Sodium	CLIA 2019	3.542958	1.5	0.4	*5.2*
Sodium	4 mEq/L	2.574003	0.1	0.6	*4.1*
Triglycerides	CLIA 2019	15.00	3.8	2.1	*5.3*
Triglycerides	15	15.00	1.3	0.9	>6
Triglycerides	15%	15.00	2.0	1.8	>6
Urea Nitrogen	CLIA 2019 9% or	13.33	0.8	1.6	>6
Urea Nitrogen	2.0 mg/dL	9.00	1.7	1.7	*4.3*
Uric Acid	CLIA 2019	10.00	11.7	1.6	*negative*
Uric Acid	10%	10.00	6.4	1.6	*2.3*

Sigma-metrics according to current CLIA performance specifications (established 1992)

Finally, the oldest set of performance specifications grades more than half of assay performance at 6 Sigma. This also benchmarks less than 25% of the assays as minimally acceptable or unacceptable.

2020 dxc 700 performance according to CLIA 1992 goals

DXC 700 performance data CLIA original 1992 goals
TEST	TEa Source	TEa	% Bias	CV	Sigma
Albumin	CLIA	10	12.1	3.0	*negative*
Albumin	10%	10	0.0	1.9	*5.3*
Alk Phos	CLIA	30	26.6	5.5	*0.6*
Alk Phos	30%	30	13.1	2.1	>6
ALT	CLIA	20	30.4	2.2	*negative*
ALT	20%	20	20.0	1.7	*0.0*
Amylase	CLIA	30.00	53.3	2.1	*negative*
Amylase	30%	30.00	14.5	1.0	>6
AST	CLIA	20	20.2	1.5	*negative*
AST	20%	20	24.9	2.6	*negative*
Bilirubin, Total	CLIA 20% or	20.00	0.8	1.4	>6
Bilirubin, Total	0.4 mg/dL	20.00	0.3	1.8	>6
Calcium	CLIA	15.625	4.3	0.9	>6
Calcium	1 mg/dL	7.692308	1.1	0.7	>6
Chloride	CLIA	5	0.7	0.6	>6
Chloride	5%	5	0.1	0.6	>6
Cholesterol	CLIA	10	1.7	1.1	>6
Cholesterol	10%	10	3.5	1.0	>6
Creatinine Kinase (CK)	CLIA	30	2.6	2.3	>6
Creatinine Kinase (CK)	30%	30	12.5	1.2	>6
Creatinine	CLIA 15% or	37.50	15.0	4.1	*5.5*
Creatinine	0.3 mg/dL	15.00	2.9	1.7	>6
Glucose	CLIA 10% or	10.00	2.6	1.8	*4.1*
Glucose	6 mg/dL	10.00	7.8	0.8	*2.7*
HDL	CLIA	30.00	5.9	5.1	*4.7*
HDL	30%	30.00	3.5	3.0	>6
Iron	CLIA	20.00	6.4	5.5	*2.5*
Iron	20%	20.00	8.7	1.8	>6
LDL	CLIA	20.00	0.7	2.9	>6
LDL	20%	20.00	1.9	3.3	*5.5*
LDH	CAP	20.00	17.7	3.0	*0.8*
LDH	20%	20.00	13.0	2.1	*3.4*
Potassium	CLIA	20	0.9	0.9	>6
Potassium	0.5 mEq/L	6.756757	0.8	0.9	>6
Protein, Total	CLIA	10.00	1.9	1.4	*5.8*
Protein, Total	10%	10.00	4.1	1.4	*4.2*
Sodium	CLIA	3.542958	1.5	0.4	*5.2*
Sodium	4 mEq/L	2.574003	0.1	0.6	*4.1*
Triglycerides	CLIA	25.00	3.8	2.1	>6
Triglycerides	CLIA	25.00	1.3	0.9	>6
Triglycerides	25%	25.00	2.0	1.8	>6
Urea Nitrogen	CLIA 9% or	13.33	0.8	1.6	>6
Urea Nitrogen	2.0 mg/dL	9.00	1.7	1.7	*4.3*

Conclusion

The data here reinforces what we saw in other analyses in this series: the latest desirable performance specifications derived from EuBIVAS are not practical or achievable in their current form with today's instrumentation. Furthermore, even one of the most advanced chemistry platforms, by any of the approaches used here, has around 1/4 to more than half of the performance considered as minimally acceptable or unacceptable. Clearly, even the advanced instruments still have room for improvement. Finally, there is a clear vote against choosing just one set of goals. While CLIA's goals are often considered too wide, even those goals are not uniformly achieved by the DxC 700. A mixed used of goals, as recommended by the 2015 EFLM Milan Consensus, is the approach that maximizes the successful assessment of instrument performance.

The other factor is the difference between the Dimension Vista and the DxC 700. Much of the poor Sigma metric performance can be attributed to large analytical biases (or differences) between these two instruments. Considering these are major instruments and are in an area (biochemistry) where standardization is supposed to be strong and many labs often assume that quality is a commodity. There are significant discrepancies between the instruments. It's not possible to know which instrument is "right" and which is "wrong" but this does underscore the need for labs to always assure quality, not assume quality.

Tools, Technologies and Training for Healthcare Laboratories

Sigma Metric Analysis