SHORT REPORT

An evaluation of the performance of the Point of Care Test iCHROMA™ AFP method: Precision and accuracy

John Bolodeoku1*, Olu Coker1, Suman Bains1, Chidi Anyaeche2 and Tae Kyum Kim3

1JB Consulting (MDP) Limited, Cherwell Innovation Centre, Oxfordshire, UK; 2Pathaway Services Limited, Headlands House, Berkhamsted, UK; 3Boditech Med Inc., Chuncheon-si, Gangwon-do 24398, Korea

Abstract

The estimation of serum alpha-fetoprotein (AFP) is useful in the diagnosis and monitoring of primary hepatocellular carcinoma, hepatoblastoma, non-seminomatous testicular germ cell tumours and other germ cell tumours. The iCHROMA™ AFP is a lateral flow chromatography, fluorescence immunoassay (FIA) for the quantitative determination of AFP in serum or plasma. In this study, the Boditech iCHROMA™ AFP assay had a very good precision of 9.8%. It showed a very good correlation with the following 12 methods: Abbott Architect (r2 = 0.9705), BioMerieux VIDAS (r2 = 0.9717), Roche Cobas 6000/8000 (r2 = 0.9738), Siemens Centaur XP/XPT/Classic (r2 = 0.9654), Siemens/DPC/Immulite 2000/2500 (r2 = 0.9673), Siemens/DPC/Immulite 1000 (r2 = 0.9670), Beckman Dxl 600/800 (r2 = 0.9676), Roche Elecsys (r2 = 0.9683), Roche Cobas 4000/e411 (r2 = 0.9688), Roche Modular E170 (r2 = 0.9692), SNIBE Maglumi (r2 = 0.9457) and Ortho Vitros 3600/5600/ECi (r2 = 0.9714). In summary, the iCHROMA™ AFP, a rapid point of care test method, has a within-run precision value of less than 10% and excellent correlations with traditional laboratory methods. There is a consistent overestimation with the iCHROMA™ method, which must be taken into consideration when setting a reference range.

Keywords: iCHROMA, AFP, RIQAS, comparison, accuracy

 

Alpha-fetoprotein (AFP) is a carcinoembryonic glycoprotein present in abundance in foetal blood, with <15 ng/mL in normal adults. Its measurement can significantly increase the specificity at lower levels (i.e. between 10 and 500 ng/mL). These are available but have, to date, been too complex to be widely applied in clinical practice. Serum AFP estimation is useful in the diagnosis and monitoring of primary hepatocellular carcinoma, hepatoblastoma, non-seminomatous testicular germ cell tumours and other germ cell tumours. Estimation of AFP levels in maternal serum and amniotic fluid have been a useful tool in the pre-natal diagnosis of many foetal disorders, such as Down’s syndrome, spina bifida, anencephaly and other neural tube defects [1–6]. There are a very few points of care test (POCT) methods for measuring AFP that have data in their literature. One of such methods shows the performance of a rapid quantitative method with a gold immunochromatographic strip, which showed a good correlation (r2 = 0.961) with a chemiluminescent immunoassay analyser [7]. We have extensively evaluated the comparative performance of the qualitative point of care device Boditech iCHROMA™ for estimating prostate specific antigen (PSA) [8–10], vitamin D [11], human chorionic gonadotrophin (HCG) [12], luteinizing hormone (LH) [12], follicle stimulating hormone (FSH) [12], C-reactive protein (CRP) [13], microalbumin [13] and TSH [14], and found a very good correlation with other traditional laboratory methods. In this study, we set out to evaluate the precision and accuracy performance of the Boditech iCHROMA™ AFP method, a rapid POCT method that uses a very small amount of blood and can be performed on whole blood, with an analysis time of 15 min, and compared its performance with the traditional laboratory AFP methods enrolled in the Randox International Quality Assessment Scheme (RIQAS).

Materials and methods

The Boditech iCHROMA™ uses a sandwich immuno-detection principle, such that the fluorescence-labelled detector antibody binds to the target protein in the sample. The sample is then applied onto a test strip and the fluorescence labelled antigen-antibody complex is captured by a second antibody embedded in the solid phase. The signal intensity of fluorescence of the captured complex is directly proportional to the amount of AFP present and thus allows for the calculation of sample AFP concentration and the result is displayed on the reader as nanograms per millilitre (ng/mL). A fluorescence-labelled control protein is included in the reaction and the intensity of the control line is measured as a quality check.

AFP concentration method

The assay was performed following the manufacturer’s instructions:

  1. Transfer 30 μL (whole blood), or 15 μL (serum, plasma, control) using a pipette to the detection buffer tube.
  2. Close the lid of the detection buffer tube.
  3. Shake the tube up and down 10 times or more.
  4. Transfer 75 μL of the mixture onto the sample well of the test device.
  5. Wait 15 min.
  6. Insert test cartridge into the Test Cartridge holder in the Boditech iCHROMA™ reader.
  7. Press ‘Select’
  8. Read the result on the display screen.

Part 1

Precision tests the ability of the tests to be repeated on the same device; there are two types of precision tests, within- and between-run tests. In this study, the within-run precision was estimated using the universal control provided by the manufacturer. The control was made up with water and run 25 times on the iCHROMA™ using the AFP method described previously using 15 μL. The mean, standard deviation (SD) and coefficient of variation percent (CV%) were then estimated from the data. The coefficient of variation (CV) is defined as the ratio of the standard deviation to the mean. It is used to express the precision and repeatability of an assay.

Part 2

The accuracy study was carried out with external quality control material (EQA) samples 1–12 of cycles 40 purchased from the RIQAS. These samples (1–12) were constituted and run-in duplicate on the Boditech iCHROMA™ using the method described. The results were compared with the mean results of the following laboratory methods that were registered with the RIQAS database: Abbott Architect, BioMerieux VIDAS, Roche Cobas 6000/8000, Siemens Centaur XP/XPT/Classic, Siemens/DPC/Immulite 2000/2500, Siemens/DPC/Immulite 1000, Beckman Dxl 600/800, Roche Elecsys, Roche Cobas 4000/e411, Roche Modular E170, SNIBE Maglumi and Ortho Vitros 3600/5600/ECi. The results were plotted in a spreadsheet using an XY plot. The iCHROMA AFP method was plotted on the Y axis and the other laboratory methods on the X axis. A linear regression line was inserted through the data points, and the slope and Y intercept were calculated. The best-fit line will be defined by the equation: Y =m + b, where m is the slope and b is the intercept. The degree of association was measured by a correlation coefficient (R2) on a scale that varies from +1 through 0 to –1.

Results

Part 1

Precision

Twenty-four (96%) of the 25 tests had values that fell within the range of the universal control (lower limit 16.25 ng/mL, an average 21.67 ng/mL, an upper limit 27.09 ng/mL), except for the fourth test with a value of 34.73 ng/mL, see Fig. 1. The Boditech iCHROMA™ AFP intra-assay results ranged from 22.25 to 34.73 ng/mL, with a mean value of 24.5 ng/mL, a SD of ±2.4 ng/mL and a coefficient of variation percent (CV%) of 9.8%.

Fig 1
Fig. 1. Twenty-five AFP estimations run on the same day as the universal control.

Part 2

The mean values of the duplicate iCHROMA™ AFP results of the RIQAS samples, 1–12, were 21.10, 350, 88.27, 172.11, 193.39, 46.18, 277.93, 200.36, 95.67, 63.34, 155.09 and 15.83 ng/mL, respectively.

Accuracy

The iCHROMA™ AFP mean estimates for the RIQAS samples 1–12 were consistently overestimated (positive bias) compared with the mean estimates of the 12 other traditional laboratory AFP methods (see Table 1). The average percentage difference between the iCHROMA™ AFP and the methods was Abbott Architect (48%), BioMerieux VIDAS (52%), Roche Cobas 6000/8000 (38%), Siemens Centaur XP/XPT/Classic (39%), Siemens/DPC/Immulite 2000/2500 (46%), Siemens/DPC/Immulite 1000 (45%), Beckman Dxl 600/800 (45%), Roche Elecsys (38%), Roche Cobas 4000/e411 (39%), Roche Modular E170 (40%), SNIBE Maglumi (44%) and Ortho Vitros 3600/5600/ECi (43%), respectively.


Table 1. AFP estimations of the methods in the RIQAS Samples 1–12.
Method Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Sample 7 Sample 8 Sample 9 Sample 10 Sample 11 Sample 12
Abbott Architect 9.096484 169.793 47.22094 108.2988 90.37115 28.30127 170.3701 107.8964 47.51272 28.3656 91.20265 9.096123
bioMerieux, Vidas/Mini Vidas 8.6294 161.4363 40.4248 96.00143 82.68017 25.894 159.34 110.814 44.75229 27.238 87.00929 8.534
Roche Cobas 6000/8000 10.62209 194.5909 52.99876 122.3518 106.4544 32.95655 196.0695 123.7311 52.87621 32.564 105.4668 10.61144
Siemens Centaur XP/XPT/Classic 10.54653 198.0714 54.98807 124.2966 101.4718 31.64804 195.898 120.7891 54.77936 31.78392 102.4904 10.44253
Siemens/DPC Immulite 2000/2500 9.353571 177.7557 48.34188 110.5056 96.30545 28.7102 186.5882 111.1667 48.3979 29.11788 96.46091 9.6005
Siemens/DPC Immulite 1000 9.83238 175.2 48.62 104.22 91.28 29.26 177.8 105.8429 49.67143 30.2125 91.9875 9.502857
Beckman DxI 600 /800 9.66406 177.6159 48.7631 114.0399 92.59606 27.82608 176.0888 111.2946 47.54214 29.02904 92.9531 9.512804
Roche Elecsys 10.75335 193.3664 50.33068 127.0314 103.9865 33.62196 194.4745 124.1741 54.35563 31.88223 104.2455 10.54152
Roche Cobas 4000/e411 10.38268 199.6713 54.31559 122.7732 104.2007 31.86843 198.4786 121.1884 53.17305 32.54559 104.9461 10.25012
Roche Modular E170 10.34424 191.835 52.54106 123.051 104.3345 32.80996 197.1814 121.9721 53.54494 32.50451 106.391 10.48977
SNIBE Maglumi analysers 10.284 163.1595 50.566 119.8475 92.5605 26.74575 169.673 99.8305 39.1285 23.275 81.221 9.3005
Ortho Vitros 3600/5600/ECi 10.33775 176.9886 49.10138 110.76 93.512 28.99356 178.1725 114.8744 49.36608 29.10056 94.759 9.783636
Boditech iCHROMA™ 21.10 350.00 88.27 172.11 193.39 46.18 277.93 200.36 95.67 63.34 155.09 15.83

Correlations

The coefficient of correlation measures the strength of a possible linear relationship between the other methods. The plots in Fig. 2A–L show the results of the various method estimation comparisons with the 12 quality control samples analysed using the iCHROMA™ AFP method. The coefficient of correlations ranged between + 0.9457 and + 0.9738.

Fig 2
Fig. 2. a) Abbott Architect, b) bioMerieux, Vidas/Mini Vidas, c) Roche Cobas 6000/8000, d) Siemens Centaur XP/XPT/Classic, e) Roche Elecsys, f) Siemens/DPC Immulite 2000/2500, g) Siemens/DPC Immulite 1000, h) Beckman Dxl 600/800, i) Ortho Vitros 3600/5600/ECi, j) Roche Cobas 4000/e411, k) Roche Modular E170, l) SNIBE Maglumi analysers. Showing iCHROMA™ AFP comparison (correlation) with other AFP methods

Discussion

Most AFP measuring immunoassays have a high sensitivity and specificity but could be time consuming, expensive and complex. The value of a POCT to measure AFP is, therefore, invaluable. A simple and rapid point-of-care system that uses Eu (III) chelate microparticles with lateral flow immunoassay (LFIA) had been described to determine AFP in serum with an assay time of 15 min and excellent correlation (r = 0.9860) [15]. In this study, another POCT using LFIA, the iCHROMA™ AFP method showed a very good within-run precision of 9.8%, showing that the repeatability of the test performance is good with 95% of the estimated values falling within two standard deviations of the mean (19.7–29.3 ng/mL). There was a consistent overestimation with the iCHROMA™ AFP method compared with the other laboratory methods. The laboratory method’s percent bias to the the iCHROMA™ AFP method ranged from 38% in Roche Cobas 6000/8000 and Roche Elecsys to 53% in BioMerieux Vidas. The difference (positive bias) observed between the values of the iCHROMA™ AFP method and the other traditional laboratory methods was consistent and could be due to calibration or the set point on the iCHROMA™ AFP method.

Despite the overestimations of the iCHROMA™ AFP method, there was a very good correlation with the methods ranging from r2 = 0.9457 with SNIBE Maglumi to r2 = 0.9738 with Roche Cobas 6000/8000 (Fig. 2). This confirms that the iCHROMA™ AFP method’s results compare very well with those of the other traditional laboratory methods of measuring AFP, and the constant positive bias observed is probably as a result of a calibration or set point of the iCHROMA™ AFP method, thus suggesting that the reference range of the iCHROMA™ AFP method should be set up taking into consideration a proportional error of 38–52.

In summary, the iCHROMA™ AFP has excellent correlations with traditional laboratory methods, and the assay has a within-run precision value of <10%. These data here show that the iCHROMA™ is a very practical solution for laboratories that require to assay for AFP at the point of care.

Authors’ contributions

JB concept, study development and initiator, OC and SB sample analysis evaluation and statistics, CA and TKK material and method support.

 

Citation: Journal of Global Medicine 2021, 1: 7 - http://dx.doi.org/10.51496/jogm.v1.7

Copyright: © 2021 J Bolodeoku et al. This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), allowing third parties to copy and redistribute the material in any medium or format and to remix, transform, and build upon the material for any purpose, even commercially, provided the original work is properly cited and states its license.

Competing interests and funding: JB is a consultant advisor to Boditech Med Inc. Tae Kyum Kim is an employee of Boditech Med Inc. Boditech Med Inc. is the manufacturer of the iCHROMA.

*John Bolodeoku, JB Consulting MDP Limited 1 Bell Street Maidenhead, SL6 1BU, UK Email: john.bolodeoku@jbconsultingmdp.com

Received: 14 December 2020; Revised: 22 November 2021; Accepted: 23 November 2021; Published: 28 December 2021

 

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