Performance Characteristics of the UniCel DxI 800 Immunoassay for the Maternal Serum Quadruple Test, Including Median Values for Each Week of Gestation, in Korean Women

Jeong Hoon Lee; Yongjung Park; Borum Suh; Seon-Mi Song; Oh Hun Kwon; Jeong-Ho Kim

doi:10.3343/kjlm.2010.30.2.126

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Lee, Park, Suh, Song, Kwon, and Kim: Performance Characteristics of the UniCel DxI 800 Immunoassay for the Maternal Serum Quadruple Test, Including Median Values for Each Week of Gestation, in Korean Women

Original Article

Korean J Leg Med 2010;30(2):126-132.

Published online: 14 January 2010

DOI: https://doi.org/10.3343/kjlm.2010.30.2.126

Performance Characteristics of the UniCel DxI 800 Immunoassay for the Maternal Serum Quadruple Test, Including Median Values for Each Week of Gestation, in Korean Women

Jeong Hoon Lee, M.D.¹, Yongjung Park, M.D.¹, Borum Suh, M.D.¹, Seon-Mi Song, M.D.², Oh Hun Kwon, M.D.¹, Jeong-Ho Kim, M.D.¹

¹Department of Laboratory Medicine, Yonsei University College of Medicine, Seoul, Korea

²Division of Immunology, Department of Laboratory Medicine, Seoul Medical Science Institute, Seoul Clinical Laboratories, Seoul, Korea

Corresponding author: Jeong-Ho Kim, M.D. Department of Laboratory Medicine, Gangnam Severance Hospital, Yonsei University College of Medicine, 712 Eonju-ro, Gangnam-gu, Seoul 135-720, Korea Tel: +82-2-2019-3532 Fax: +82-2-2019-4822 E-mail: jeongho@yuhs.ac

Revised 15 September 200924 February 2010 Accepted 22 March 2010

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Background:

Maternal serum prenatal quadruple screening includes testing for alpha-fetoprotein (AFP), human chorionic gonadotrophin (hCG), unconjugated estriol (uE3), and dimeric inhibin A (DIA). We evaluated quadruple screening using an automated platform and looked for any ethnic differences in the median values of each marker.

Methods:

We measured the concentrations of each quadruple test analyte using the UniCel DxI 800 system (Beckman Coulter, USA) in 788 Korean mid-trimester maternal serum samples and calculated their median values using Benetech software (Benetech, Canada). We also compared the results with those obtained using the Immulite 2000 assay (Siemens Healthcare Diagnostics, USA) or ELISA (DSL, USA) in 442 samples.

Results:

We obtained mid-trimester median values for each marker. The following are the comparative results for each test using the Immulite 2000 assay or ELISA (x) and the UniCel DxI 800 immunoassay (y): AFP, y=1.10x+0.01, r=0.925; uE3, y=0.28x+0.24, r=0.885; hCG, y=1.22x-3047.8, r=0.944; and DIA, y=0.86x+15.31, r=0.833. Assay results for each of the four markers showed good correlations. However, significant biases necessitated new median calculations of prenatal risk estimates in all four tests.

Conclusions:

We established gestational age-specific second-trimester median values for four markers in Korean samples using the UniCel DxI 800 immunoassay system. Despite significant bias, there were good correlations between the results obtained using the UniCel DxI 800 immunoassay and those obtained using the Immulite 2000 assay.

Keywords: Prenatal screening, Down syndrome, Immunoassay, Quadruple test

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Fig. 1.

Comparison study of each of the four tests of the quadruple marker by DxI vs Immulite or DSL ELISA. (A) AFP, (B) uE3, (C) hCG, (D) DIA.

Abbreviations: DXI, UniCel DxI 800 (Beckman Coulter, Fullerton, CA, USA); Immulite, Immulite 2000 (Siemens Healthcare Diagnostics, Deerfield, IL, USA); DSL ELISA (DSL, Webster, TX, USA); AFP, alpha-fetoprotein; uE3, unconjugated estriol; hCG, human chorionic gonadotrophin; DIA, dimeric inhibin A (DIA).

Fig. 2.

Bland-Altman plots for each of the four markers in the quadruple test using Unicel DxI 800 vs Immulite 2000 or DSL ELISA. (A) AFP, (B) uE3, (C) hCG, (D) DIA.

Abbreviations: See Fig. 1.

Table 1.

Precision of the Beckman Coulter DxI for the quadruple assay

Sample	Level	Mean	CV (%)
Sample	Level	Mean	Within-run	Total
AFP (ng/mL)	Low	9.94	3.36	4.45
	Middle	30.14	4.25	4.14
	High	76.21	3.84	3.84
uE3 (ng/mL)	Low	0.46	5.85	5.77
	Middle	1.45	3.02	2.79
	High	4.61	4.05	4.50
Beta-hCG (IU/mL)	Low	7,955	2.30	2.12
	Middle	24,300	5.39	5.07
	High	51,426	3.73	4.81
DIA (pg/mL)	Low	150.4	3.91	3.88
	Middle	390.4	5.23	5.83
	High	802.9	5.27	5.36

Abbreviations: AFP, alpha-fetoprotein; uE3, unconjugated estriol; hCG, human chorionic gonadotrophin; DIA, dimeric inhibin A.

Table 2.

Median values of each of the four quadruple markers determined using the Beckman Coulter DxI

Gestational week∗	N. of samples	AFP (ng/mL)		uE3 (ng/mL)		hCG (IU/mL)		DIA (pg/mL)
Gestational week∗	N. of samples	Obs	Reg^†	Obs	Reg	Obs	Reg	Obs	Reg
15th	130	40.9	39.7	0.8	0.9	46.2	46.7	222.4	222.3
16th	219	44.1	45.4	1.1	1.1	37.4	36.3	188.0	190.0
17th	160	53.4	52.0	1.4	1.4	28.7	30.2	185.3	178.1
18th	165	58.8	59.6	1.7	1.7	25.9	26.6	176.8	183.0
19th	97	67.0	68.2	2.0	2.1	26.6	24.6	209.2	206.3
20th	17	89.1	78.1	2.8	2.7	21.1	23.4	258.9	254.9
Total	788

^∗ Completed gestational week as determined by ultrasound;

^† Regression equations used were derived using Benetech software as follows: Median AFP=10^{(005874×wk+069234)}; Median uE3=10^{(009983×wk-161100)}; Median hCG=21.66705+54.07473×e^{-0.53946×(wk-14)}; and Median DIA=10 ^{(002002×wk2-0.70594×wk+847311)}.

Abbreviations: AFP, alpha-fetoprotein; uE3, unconjugated estriol; hCG, human chorionic gonadotrophin; DIA, dimeric inhibin A; Obs, observed median values; Reg, regressed median values.

Table 3.

Comparison of the median values (pg/mL) of dimeric inhibin A

Gestational week∗	Lambert-Messerlian et al.^† [9]			Rawlins et al.^† [11]		Present study
Gestational week∗	N	Observed	Regressed	N	Observed	N	Observed	Regressed^‡	Maternal weight-corrected values^§
15th	82	157.3	147.0	2,422	166	130	222.4	222.3	225.9
16th	126	126.0	138.6	3,897	149	219	188.0	190.0	195.4
17th	106	134.3	135.0	2,851	150	160	185.3	178.1	187.2
18th	103	142.1	136.5	1,079	151	165	176.8	183.0	178.8
19th	90	147.4	143.0	526	161	97	209.2	206.3	206.2
20th	58	144.4	155.4	279	174	17	258.9	254.9	277.7
Total	565			11,054		788

^∗ Completed gestational week as determined by ultrasound;

^† Beckman Coulter Access;

^‡ Log-linear regression; ^§Median MoM=10 to the power (slope∗ weight+intercept), slope=-0.00175, intercept=0.22616.

Table 4.

Comparison of dimeric inhibin A (DIA) between automated assay and ELISA

Study	N	Slope	Intercept	r	Mean % difference	Mean ratio of the two assays
Lambert-Messerlian et al.∗ [9]	565	1.00	-0.776	0.960	NE	0.768
Rawlins et al.∗ [11]	119	0.88	-3.67	0.980	-14.6%	NE
Present study	447	0.86	14.88	0.834	-8.0%	0.949

^∗ Beckman Coulter Access.

Abbreviations: NE, not evaluated.

Table 5.

Regressed median values of alpha-fetoprotein (AFP) compared with those of samples from other countries

Gestational week∗	AFP (IU/mL)
	Vranken et al. [13]					Present study
	Belgium	Canada	Germany	UK	USA	Korea^†	Weight-corrected^‡
14th	22.1	-	21.8	23.6	-	-	-
15th	25.8	27.5	25.3	27.0	25.7	32.8	31.9
16th	30.2	31.1	29.2	30.8	29.7	37.5	38.2
17th	35.3	35.1	32.5	35.2	34.4	43.0	43.8
18th	41.2	39.7	37.5	40.2	39.7	49.2	49.8
19th	48.2	44.9	46.3	46.0	46.0	56.3	55.8
20th	-	50.6	-	52.5	53.2	64.5	78.0

^∗ Completed gestational week as determined by ultrasound;

^† Median values of this study were converted to IU/mL from ng/mL by multiplying by 0.826 for the comparison;

^‡ Median values corrected for maternal weight using log-linear regression, Median MoM=10 to the power (slope∗weight+intercept), slope=-0.00236, intercept=0.29407.

Table 6.

Regressed median values of uE3 compared with those of samples from other countries

Gestational week∗	uE3 (nmol/L)
	Vranken et al. [13]				Present study^†
	Belgium	Canada	Germany	UK	Korea	Weight-corrected^‡
14th	2.15	-	2.22	2.26	-	-
15th	2.80	2.53	3.02	2.84	3.12	2.93
16th	3.66	3.19	3.92	3.58	3.82	3.81
17th	4.77	3.99	5.00	4.51	4.86	4.87
18th	6.22	4.96	6.21	5.67	5.90	5.92
19th	8.11	6.21	7.95	7.14	7.29	6.99
20th	-	7.77	-	8.99	9.37	10.00

^∗ Completed gestational week determined by ultrasound;

^† Median values of this study were converted to nmol/L from ng/mL by multiplying by 3.47 for the comparison;

^‡ Median values corrected for maternal weight using log-linear regression, Median MoM=10 to the power (slope∗weight+intercept), slope=-0.00061, intercept=0.09007.

Table 7.

Regressed median values of human chorionic gonadotrophin (hCG) compared with those of samples from other countries

Gestational week∗	hCG (IU/mL)
	Vranken et al. [13]				Present study
	Belgium	Canada	Germany	UK	Korea	Weight-corrected^†
14th	37.3	-	34.9	40.0	-	-
15th	30.2	42.4	26.5	33.2	46.7	43.9
16th	24.5	34.1	21.4	27.6	36.3	35.6
17th	19.9	28.3	18.9	22.9	30.2	26.6
18th	16.1	24.1	17.3	19.1	26.6	23.4
19th	13.0	21.2	14.8	15.9	24.6	23.2
20th	-	19.1	-	13.2	23.4	19.6

^∗ Completed gestational week determined by ultrasound;

^† Median values corrected for maternal weight using log-linear regression, Median MoM=10 to the power (slope∗weight+intercept), slope=-0.00258, intercept=0.29094.

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