The grey area of HBsAg enzyme-linked immunosorbent assay (ELISA) in blood screening laboratory / 中国输血杂志

ABSTRACT

【Objective】 To evaluate the necessity and rationality of setting 0.8 CO of the gray area of hepatitis B surface antigen(ELISA) reagent in our laboratory. 【Methods】 1) 792 samples of serum plates from the Clinical Laboratory Centre, Ministry of Health (NCCL) were tested by two HBsAg ELISA reagents. The true positive rate, and confirmed positive rate of gray area samples revealed by 2 reagents were calculated. ROC curve was drawn to determine the best CO value of 2 reagents. The changes in sensitivity and specificity under different CO values were compared. 2) Based on previous data, the HBV-DNA-yield rate among HBsAg gray area samples was analyzed, and the relationship between the distribution of ELISA results of solo HBV-DNA positive samples and gray area was analyzed. 【Results】 Of the 792 samples that form NCCL, 587 were positive, 197 negative and 8 indeterminate. The true positive detection rates of reagents A and B were 82.45% and 71.89%. The confirmed positive rate of gray area samples given by 2 reagents were 94.74%(18/19)and 93.10%(27/29). The best CO values of reagents A and B are 0.49 and 0.27, which are both lower than the 0.8. The specificity corresponding to the best CO values of the two reagents decreased slightly, but the sensitivity increased greatly. From January 2015 to January 2019, 183 551 samples were tested. Of the 13 cases of HBsAg gray area samples, 7 were revealed by reagent A and 1 was positive for NAT; 6 were revealed byreagent B and all negative for NAT. Out of 134 cases of solo HBV-DNA positive samples, 96.27% (129/134) samples had S/CO values below 0.4, overlapped with negative samples, and were far from 0.8. 【Conclusion】 It is necessary to set gray area for these two HBsAg ELISA reagents. The gray area value setting to 0.8 CO corresponds to poor reagent sensitivity. The best cutoff value would be selected according to the ROC curve 0.49 CO in Reagent A and 0.27 CO in Reagent B. Gray area has no obvious effect on screening of single-virus NAT-yield sample.