Abstract
Background: The Hepatitis B surface antigen (HBsAg) commercially-available screening test suggests a confirmatory testing in all cases that are reactive, but this will take a long time to reporting of results and increase the total test cost.
Objectives: To investigate the correlation between cutoff index (COI) values of initial HBsAg screening test and their corresponding confirmatory neutralization results in order to identify a COI value for distinguishing samples that truly need confirmatory neutralization testing.
Methods: A retrospective study of 72,496 HBsAg screening test results using the Elecsys HBsAg II kit of patients at King Chulalongkorn Memorial Hospital, the Thai Red cross Society, Thailand from October 2019 to March 2022 were conducted. Elecsys HBsAg II neutralization tests were performed on samples with COI values ranging from 0.9 to 30.0. The correlation between the cutoff index (COI) value (0.9-30.0) and the percentage of neutralization confirmatory testing (the HBsAg confirmed negative and positive groups) was plotted. The receiver operating characteristic (ROC) was also assessed.
Results: Out of 72,496 test results, 337 samples with COI ≤30.0 underwent confirmatory testing, with 313 samples confirming positive. ROC analysis revealed that the area under the curve (AUC) was 0.9429 (P4.00 and 13.00 had a 3.9% false positive rate. On the other hand, a COI value of 13.0 had 100.0% specificity.
Conclusion: In diagnostics, a COI value of ≥4.0 may be more practical in areas with limited resources for confirmatory testing. This can reduce the number of samples required for additional confirmatory testing. However, if the reasons for increase the specificity outweighs the cost of confirmatory testing, a COI value of 13.0 is more appropriate. Each diagnostic laboratory may choose the COI value that suit their settings for practical diagnostic application in areas with limited resources for confirmatory tests.
DOI
10.56808/2673-060X.5457
Recommended Citation
Wongchampa, Piya; Chaiwongkot, Arkom; and Reantragoon, Rangsima
(2024)
"Determination of initial hepatitis B surface antigen (HBsAg) cutoff index (COI) threshold for reporting HBsAg reactivity,"
Chulalongkorn Medical Journal: Vol. 68:
Iss.
2, Article 3.
DOI: https://doi.org/10.56808/2673-060X.5457
Available at:
https://digital.car.chula.ac.th/clmjournal/vol68/iss2/3
5397 Determination of initial HBsAg COI cut-off threshold edited 8 March 24