Establishment Of Pooled HIV RNA RT-PCR And Estimating HIV Incidence In IDU Population

Context Acute human immunodeficiency virus infection is a transient symptomatic illness associated with high titer HIV replication (103-108copies/ml) and absent HIV Ab, and cannot be diagnosed by routine antibody tests, also rarely diagnosed in clinical practice. All the antigen test, NAT, HIV isolation/ culture that apply to diagnose acute HIV infection have limitation on sensitivity and cost. Recent years, US and European countries established method of Pooled HIV RNA RT-PCR to screen acute HIV infection samples in blood bank, in order to decrease the residual risk of HIV transmission by blood donation (mostly by viremic but antibody-negative donors), VCT testing and also to estimate HIV incidence. There are rare researches on this field in our country. Surveillance of HIV infection is according to HIV infection prevalence. Pooled HIV RNA RT-PCR has very important significance in taking measure to prevent HIV spread, enhancing function of immunity system, and delaying times progressing to AIDS. Objectives to establish the method of Pooled HIV RNA RT-PCR and assess the feasibility of screening in high-volume laboratories for acute HIV infection in IDU population, using specimen pooling and HIV RNA RT-PCR tests. And estimate HIV incidence in IDU population. HIV uniform Ag/Ab kits test the same specimens and are compared with the method of Pooled HIV RNA RT-PCR in the fact of diagnoses acute HIV infection.Materials and methods A total of 2745 specimens respectively from Sichuan' 1020, Xinjiang'458 and Guizhou' 1267 are screened using EIA HIV Ab tests, 144 HIV Ab sero-positive specimens and 166 haemolytic/low volume specimens are excluded following assays. 2425 HIV Ab sero-negative specimens are enrolled in the 3-stage 50 :1,10 : 1.1 : 1 pooling method and grouped forty-eight master pools of 50 specimens and 242 seconds pools of 10 specimens.HIV RNA RT-PCR applies to test pools (master and second pools using ultra-sensitive RT-PCR, individual specimen using standard RT-PCR). Positive pools are re-analyzed in smaller pools or/and single specimen. Positive specimens are repeatedly tested HIV RNA RT-PCR, HIV Ab EIA, WB confirmatory, HIV Ag/Ab EIA, , P24 tests and followed up if condition is allowable. Vironostika HIV Uni-Form II Ag/Ab kits screen these 2425 specimens again. Based on RNA/Ag/Ab-positive individual specimens and formula: {11- (M / N) 1/C} / u, calculate HIV infection incidence in province.Results Pooled HIV RNA RT-PCR screen out one positive specimen, the HIV load of this specimen is 6.74* 104 copies/ml and can be repeated. The results of HIV Ab EIA, WB tests, HIV Ag/Ab EIA, are all negative, according to diagnostic standard of acute HIV infections, this positive specimen is considered acute HIV infection. This specimen came from serum bank of Sichuan CDC in 2003, based on this positive specimen , the point estimate of HIV incidence is 1.69% per year (95% CI 0.86%-2.79%) in Sichuan province in 2003. Vironostika HIV Uni-Form II Ag/Ab kits un-screen out this RNA positive specimen and other Ag positive acute HIV infection specimens, but screen five false positive specimens. Based on five false positive specimens, rate of false positive of Vironostika HIV Uni-Form II Ag/Ab kits is 0.2887% (95%CI 0.115%-0.594%), Specificity is 99.71%. Conclusion These findings suggest that method of pooled HIV RNA RT-PCR has been established in China. The 3-stage 50 '. 1,10 '?1,1 .' 1 pooling scheme is feasible and reliable for manually specimen pooling and nucleic acid testing. This method is more effective on estimation of current HIV incidence in cross-sectional investigation. Compared with individual specimen NAT, this method is more sensitive and cost saving in diagnosing acute HIV infection as screening method, also further shorten the window period to 7-11 days, decrease the residual risk ofHIV sero-negative blood, being practical for use in developing countries. HIV infection incidence is 1.69% per year (95% CI 0.86%-2.79%) Sichuan province in 2003, larger specimen sizes are required for more accurate e...