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Choi, Lee, Park, Yoon, Kim, and Park: Clinical Usefulness of ImmuneCheck™ IgG for Rapid Semiquantitation of Total IgG
Original Article

Lab Med Online 2018;8(4):140-147.

Published online: 19 October 2018

DOI: https://doi.org/10.3343/lmo.2018.8.4.140

Clinical Usefulness of ImmuneCheck™ IgG for Rapid Semiquantitation of Total IgG

Jinyoung Choi, M.D.1, Sang Chul Lee, M.D.1, 2, Kyung Hee Park, Ph.D.1, 2, Heylyeong Yoon, Ph.D.3, Hyon Suk Kim, Ph.D.4, Jung-Won Park, Ph.D.1, 2

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

2Institute of Allergy, Yonsei University College of Medicine, Seoul, Korea

3Department of Laboratory Medicine, Hanshin Medipia, Seoul, Korea

4Department of Laboratory Medicine, Yonsei University College of Medicine, Seoul, Korea

Corresponding author: Jung-Won Park Department of Internal Medicine, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea Tel: +82-2-2228-1961, Fax: +82-2-2227-7932, E-mail: PARKJW@yuhs.ac

Received 16 September 2017       Revised 8 February 2018       Accepted 14 March 2018

Copyright © 2018 The Korean Society for Laboratory Medicine

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Background:

Conventional IgG assays require costly equipment and skilled experts. Semiquantitative measurement of total IgG using point-of-care testing devices may be the solution for these limitations. This study evaluated the reproducibility of the ImmuneCheck™ IgG assay (Proteom-eTech Inc., Korea) and the correlation of its results with conventional laboratory IgG results in the serum and whole blood.

Methods:

Both the serum and whole blood samples from 120 patients were used. To evaluate the intra-test reproducibility and inter-test correlation, intraclass correlation coefficient (ICC) analysis was used.

Results:

The concentration of serum total IgG measured by cobas® 6000 (Roche Diagnostics, Switzland) ranged from 690.4 to 2,756.4 mg/dL. The intra-test reproducibility of ImmuneCheck™ IgG was high (Serum ICC=0.724, P<0.001; Whole blood ICC=0.843, P<0.001). The inter-test correlation between the ImmuneCheck™ IgG and cobas® 6000 results was very good (Serum ICC=0.805, P<0.001; Whole blood ICC=0.842, P<0.001). Because there were no samples with a total IgG level lower than 600 mg/dL, the pre-existing serum samples were diluted and then the linearity tests were conducted. The intra-test reproducibility for the diluted serum samples was almost perfect (ICC=0.995, P<0.001), and the inter-test correlation between the ImmuneCheck™ IgG and cobas® 6000 results was also strong (ICC=0.992, P<0.001).

Conclusions:

The ImmuneCheck™ IgG assay is reproducible and highly correlated with the conventional IgG assay for the serum and whole blood. It could be applied for the rapid detection of total IgG.

Keywords: Total IgG POCT, Rapid semiquantitation, Total IgG assay

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Fig. 1.
Experimental process of ImmuneCheck™ IgG.
lmo-8-140f1.tif
Fig. 2.
Flowchart of ImmuneCheck™ IgG analysis. Fig. 2. Flowchart of ImmuneCheck™ IgG analysis.
lmo-8-140f2.tif
Fig. 3.
Scatter plots of whole blood total IgG titers (A) and serum total IgG titers (B) obtained with ImmuneCheck™ IgG.
lmo-8-140f3.tif
Fig. 4.
Scatter plot of diluted serum total IgG titers obtained with Im-muneCheck™ IgG.
lmo-8-140f4.tif
Table 1.
Comparison of baseline characteristics between the male and female patients included in this study
Item Males (n=44) Females (n=76) P value
Mean age, year (SD) 41.7 (17.7) 52.6 (19.4) 0.003
No. of patients with atopy∗ (%) 30 (68.2) 59 (77.6) 0.258
Mean of hematocrit, % (SD) 44.9 (3.6) 39.9 (3.3) <0.001
Mean of serum total IgG by Roche cobas® 6000, mg/dL (SD) 1,162.4 (172.8) 1,196.7 (298.2) 0.426

∗ Atopy refers to the genetic tendency to develop allergic diseases, such as allergic rhinitis, asthma, and atopic dermatitis. Abbreviation: SD, standard deviation.

Table 2.
Comparison of the serum total IgG results obtained with Roche cobas® 6000 and ImmuneCheck™ IgG
ImmuneCheck™ IgG results, mg/dL Mean of total IgG results by Roche cobas® 6000, mg/dL (SD
0, 0.12, 0.24, 0.49, 1, 2, 3.9, 7.8, 16, 31, 63, 125, 250, 375, 500 ND
750 778.7 (66.1)
1,000 1,008.1 (139.3)
1,500 1,231.8 (161.7)
2,000 1,645.5 (411.6)
4,000 ND

Abbreviations: ND, no data; SD, standard deviation.

Table 3.
ICC analysis of the test results for serum, whole blood, and diluted serum
Specimen ICC 95% CI P value
Serum 0.724 0.626–0.800 <0.001
 Intra-test reproducibility      
 Inter-test correlation 0.805 0.721–0.864 <0.001
Whole blood 0.843 0.787–0.886 <0.001
 Intra-test reproducibility      
 Inter-test correlation 0.842 0.772–0.890 <0.001
Diluted serum 0.995 0.989–0.998 <0.001
 Intra-test reproducibility      
 Inter-test correlation 0.992 0.975–0.997 <0.001

Abbreviations: CI, confidence interval; ICC, intraclass correlation coefficient.

Table 4.
Inter-test ICC results for serum and whole blood according to age, gender, and hematocrit
Specimen     ICC 95% CI P value
Serum Age (year) <30 0.743 0.407–0.889 0.001
    30–49 0.776 0.577–0.882 <0.001
    50–69 0.833 0.665–0.917 <0.001
    ≥70 0.861 0.666–0.942 <0.001
  Sex Male 0.600 0.267–0.782 0.002
    Female 0.856 0.773–0.909 <0.001
Whole blood Age (year) <30 0.695 0.294–0.868 0.003
    30–49 0.871 0.753–0.932 <0.001
    50–69 0.857 0.711–0.929 <0.001
    ≥70 0.775 0.458–0.907 0.001
  Sex Male 0.687 0.422–0.830 <0.001
    Female 0.884 0.816–0.927 <0.001
  Hct (%) 1st quarter; Hct≤38.98 0.909 0.805–0.957 <0.001
    2nd quarter; 38.98<Hct≤42.00 0.790 0.570–0.898 <0.001
    3rd quarter; 42.00<Hct≤44.20 0.801 0.576–0.906 <0.001
    4th quarter; Hct>44.20 0.687 0.324–0.855 0.002

Abbreviations: CI, confidence interval; ICC, intraclass correlation coefficient; Hct, hematocrit; 1st quarter, range of minimum to first quartile; 2nd quarter, range of first quartile to median; 3rd quarter, range of median to third quartile; 4th quarter, range of third quartile to maximum.

Table 5.
Comparison between the conventional laboratory test (Roche cobas® 6000) and ImmuneCheck™ IgG assay
Item Roche cobas® 6000 ImmuneCheck™ IgG
Minimum sample volume Primary tubes: 700 μL 2–5 μL
  Sample cup: 100 μL  
  Micro cup (FTB): 50 μL  
Recommended specimen Serum Serum, whole blood
Required time 2–3 hours 20 minutes
Physical dimensions Width: 188–498 cm Width: 7 cm
  Height: 130 cm Length: 2 cm
  Depth: 98 cm Height: 0.5 cm
Detection range 0–5,000 mg/dL 0–4,000 mg/dL
Analysis Quantitative Semiquantitative
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