Positive rate analysis on HIV-1 antibody confirmation in AIDS screening population

ObjectiveTo compare and analyze the positive samples of human immunodeficiency virus (HIV) antibody screening and immunoblotting tests (WB), and to explore the conformity of the results of screening test and WB confirmation.

MethodsAccording to the requirements of National AIDS Testing Technical Specification (2015 edition) of China Center for Disease Control and Prevention, 289 HIV screening test positive samples in Baoshan District of Shanghai from December 2017 to December 2018 were confirmed by WB method, and the results of screening and confirmation were compared and analyzed.Of them, 286 were ELISA positive, 276 immunoosmosis/chromatography positive and 70 samples of chemiluminescence positive.Both ELISA and immunoosmosis/chromatography tests were negative.The negative samples of ELISA and immunoosmosis/chromatography were detected by immunoblotting (WB).

ResultsOf 289 HIV screening test positive samples, 245 (84.78%) were HIV-1 positive, 34 (11.76%) uncertain and 10 (3.46%) negative.The coincidence rates of ELISA, IMC and WB were 85.66% (245/286) and 88.77% (245/276), respectively.There was no significant difference between them (χ²=1.211, P=0.271).The average S/c.o values of positive, uncertain and negative HIV-1 antibodies in WB confirmation test were (24.66±1.37), (20.15±8.06) and (7.96±8.40), respectively.There were significant differences among the three groups (F=137.96, P=0.000).Among 289 screening test positive samples, the S/c.o values of 9 samples were between 1 and 6, and the positive coincidence rate was 11.11%.The S/c.o values of 3 samples were between 7 and 10, and the positive coincidence rate of 2 samples was 66.67%.The S/c.o values of the other 277 samples were all over 10.Of 242 samples were confirmed positive, and the rate of positive coincidence was 87.36%.In HIV-1 positive samples, the probability of simultaneous occurrence of gp160, gp120, gp41, p66 and p24 bands was 95%.Of 70 HIV screening responded positive by chemiluminescent method.In ELISA and immunoosmosis/chromatography negative samples, 51.43% (36/70) were negative by WB; 38.57% (27/70) were one band; 10% (7/70) were two bands.

ConclusionHIV screening should be used of highly sensitive and specific reagent, namely antigen and antibody detection at the same time, which can reduce the early missed screening of infection and improve the coincidence with the confirmation results.Because of the influence of samples or certain diseases, false positivity may exist in screening tests, which must be based on the results of antibody confirmation or nucleic acid supplementation tests.HIV antibody confirmation tests, because of the late occurrence of IgG antibodies detected, have the risk of missed screening for early infected persons.It is suggested that there should be a counter-reaction to the initial screening.Those with low S/c.o values (between 1 and 6), negative or uncertain antibody confirmation tests, responding to chemiluminescent HIV screening, negative samples from ELISA and immunoosmosis/chromatography tests, should be followed up by nucleic acid supplementation test or by combination check with epidemiological data.