Collaborative study for the calibration of an Italian HIV RNA reference preparation against the International Standard

The implementation of nucleic acid amplification techniques (NAT) for detection of blood- borne viruses in the routine screening system of Transfusion Centres required the acquisition of specific skills and levels of organisation. In this respect, it is advisable to include, as run controls, reference preparations at known concentrations calibrated against their respective International Standards. Some laboratories already use commercial assays that can detect both HCV RNA and HIV RNA. A reference preparation for HIV RNA is not yet available, as is the case with HCV RNA (ISS 0102). Hence the Laboratory of Immunology of the Istituto Superiore di Sanità was prompted to develop such a preparation (HIV-1 RNA ISS 0103). A national collaborative study for the calibration of this preparation in IU/mL has been organised in collaboration with the Research and Development Division of the Italian Society of Transfusion Medicine and Immunohaematology. The candidate preparation was obtained from an HIV-1 RNA-positive plasma sample appropriately diluted in negative plasma. Twelve Transfusion Centres scattered throughout Italy participated in this collaborative study. Two qualitative commercial assays were used, the COBAS Ampliscreen HIV-1 Test, version 1.5 (Roche) and the Procleix HIV-1 TMA Assay (Chiron). Each participant was sent four calibration panels made of half-log dilutions of the International Standard and the ISS 0103 preparation. Results were elaborated by Probit analysis. The mean titres calculated for the ISS 0103 preparation, using these two NAT methods, were quite similar: 3.74 log 10 IU/mL for the COBAS Ampliscreen and 3.88 log10 IU/mL for the Procleix TMA Assay. In conclusion, based on these results, a titre of 6,500 IU/mL was assigned to the HIV-1 RNA ISS 0103 preparation.