**3.3.2 HIV testing**

The oral fluid samples were sent for the analysis by each national reference laboratory to the Teaching Hospital-University of Verona, Immunology Unit, Verona, Italy. EIA testing GENSCREEN HIV 1/2 version 2, BIO-RAD on oral fluid sample was performed according to the manufacturer's instructions. All positive samples were confirmed with a Western Blot test. In terms of quality control, for each oral fluid sample, a total IgG antibodies ELISA test was performed in order to assess the sample suitability for testing. Samples below 3.5 titre (cut-off) were excluded from the study as invalid (see Fig. 1: Survey testing algorithm). A validation

(1) Rapid Immunocromatograpy Determine HIV 1/2 ( Unipath Ltd, Bedford UK) CE marked for serum were used

(2) HIV 1/2 BLOT 2.2 ( MP Biomedical, China) CE marked for serum

Fig. 1. HIV testing algorithm on oral fluid samples

study of Bio-Rad OF testing comparing serological testing involving 37 HIV positive patients and 35 controls per country was carried out according to Commission decision of 7 May 2002 on common technical specifications for in vitro medical devices. EIA on oral fluid samples from 259 of the 263 HIV positive subjects were positive, giving a sensitivity of 98.5% (CI 96.2- 99.6). All 233 controls were found negative for HIV in oral fluid and no false positives were detected (100% specificity; CI 98.4-100). The positive and negative predictive values of the OF test according to HIV prevalence are presented in Table 1.


Table 1. PPV and NPV according to prevalence
