Harmonisation of controls

NORIP

Nordic Reference Interval Project

Harmonisation effect on control values, Pål Rustad (rustadp@furst.no), 12/8-2003

Question:

What effect have correction with a commutable material (CAL) run ten times in a series on different control materials (X, P, HIGH, LOW) run three times each in the same series?

Answer:

For all the series used for calculating reference intervals, the coefficient of variation (CV) have been calculated for the series mean of each control before (CVb) and after (CVa) correction with CAL. The harmonisation effect have been calculated as (CVb² -CVa²)/CVb² in percent and can be interpreted as the percent of total variation that can be eliminated by correcting the results with a commutable material in each series. Negative values indicate that the coefficient of variation is increased after correction! These values are indicated by yellow background.

The enzymes have been included in the table even if the results are NOT corrected when calculating reference intervals.

The calculations have been made for all series and also split into Vitros and not Vitros series. The reason for the this splitting is that the control LOW gives different results than wet chemistry because of the dilution effect on Vitros instruments. As the Vitros instruments generally has good precision and the operation of the instruments should be fairly standardized between laboratories, it is reasonable to believe that the correction effect should not be as evident as for the different wet chemistry methods. More detailed data here.

The number of values used for calculation are shown in coulumn 2-4.

Some comments: The harmonisation effect is obvious for most components and controls, also for the HIGH and LOW control. The effect is generally about the same for Vitros instruments, 12 of the components have a smaller effect of correction than wet chemistry methods and 9 have better effect.

By looking at the detailed data for HIGH control for HDL-cholesterol on Vitros, the CV is increased for the 3 series from 0.7% to 3.9% by correction. For LD the CV for LOW control for the the 3 laboratories (Roche Modular) increase from 7.4% to 8.8% by correction.

	Number of means			X			P			HIGH			LOW
Component	All	Vitros	Rest	All	Vitros	Rest	All	Vitros	Rest	All	Vitros	Rest	All	Vitros	Rest
Albumin	111	20	91	88 %	65 %	92 %	68 %	82 %	67 %	82 %	77 %	82 %	33 %	28 %	75 %
ALP	23	20	3	100 %	99 %	18 %	100 %	99 %	83 %	99 %	97 %	14 %	97 %	96 %	96 %
Alt	90	22	68	59 %	87 %	49 %	74 %	79 %	49 %	27 %	87 %	62 %	73 %	70 %	59 %
Amylase	25	0	25	100 %		100 %	100 %		100 %	100 %		100 %	100 %		100 %
AST	84	19	65	86 %	74 %	84 %	82 %	79 %	79 %	74 %	29 %	78 %	65 %	77 %	60 %
Bilirubin	109	22	87	71 %	95 %	63 %	59 %	93 %	44 %	67 %	90 %	70 %	48 %	59 %	48 %
Ca	107	21	86	68 %	82 %	65 %	63 %	86 %	57 %	33 %	66 %	30 %	75 %	82 %	73 %
Cholesterol	110	19	91	77 %	53 %	81 %	67 %	83 %	67 %	74 %	65 %	79 %	44 %	71 %	62 %
CK	85	19	66	90 %	89 %	89 %	79 %	68 %	82 %	9 %	75 %	84 %	58 %	63 %	53 %
Creatinin	109	21	88	74 %	75 %	73 %	87 %	76 %	87 %	69 %	26 %	82 %	79 %	86 %	81 %
Fe	93	14	79	80 %	71 %	81 %	68 %	83 %	65 %	37 %	69 %	62 %	33 %	64 %	62 %
Ferritin	8	0	8	96 %		96 %	96 %		96 %	98 %		98 %	96 %		96 %
Glucose	94	18	76	83 %	86 %	83 %	66 %	92 %	63 %	69 %	80 %	69 %	63 %	77 %	74 %
GT	53	18	35	92 %	92 %	93 %	73 %	83 %	73 %	73 %	91 %	90 %	39 %	77 %	56 %
HDL	105	3	102	85 %	23 %	91 %	83 %	66 %	87 %	77 %	-2910 %	89 %	71 %	63 %	73 %
K	108	21	87	66 %	41 %	70 %	45 %	69 %	42 %	20 %	53 %	17 %	47 %	65 %	47 %
LD	3	0	3	60 %		60 %	74 %		74 %	6 %		6 %	-43 %		-43 %
Mg	84	19	65	79 %	82 %	79 %	85 %	87 %	85 %	48 %	-8 %	76 %	36 %	12 %	43 %
Na	108	21	87	54 %	45 %	57 %	37 %	75 %	28 %	29 %	63 %	26 %	35 %	57 %	47 %
P inorg	102	20	82	85 %	74 %	87 %	79 %	89 %	78 %	73 %	24 %	75 %	77 %	80 %	79 %
P-Amylase	21	0	21	100 %		100 %	100 %		100 %	100 %		100 %	100 %		100 %
Protein	80	14	66	88 %	70 %	89 %	77 %	81 %	76 %	74 %	12 %	77 %	72 %	69 %	72 %
T4	7	1	6	74 %		74 %	55 %		54 %	15 %		10 %	44 %		43 %
TIBC	28	1	27	93 %		93 %	56 %		56 %	91 %		91 %	70 %		76 %
Trigly	102	18	84	77 %	86 %	72 %	72 %	21 %	79 %	77 %	49 %	79 %	75 %	80 %	78 %
TSH	10	1	9	59 %		64 %	15 %		31 %	-44 %		-16 %	88 %		90 %
Urea	101	20	81	80 %	54 %	83 %	82 %	89 %	79 %	83 %	78 %	82 %	60 %	73 %	76 %
Uric acid	105	22	83	98 %	83 %	98 %	96 %	88 %	97 %	96 %	89 %	97 %	94 %	88 %	96 %