Relationship of incremental specimen volumes and enhanced detection of human immunodeficiency virus type 1 RNA with nucleic acid amplification technology

The relationship between specimen input volume and the frequency of reporte d human immunodeficiency virus type 1 (HIV-1) RNA copy numbers by nucleic a cid amplification technology (the NASBA HIV-1 RNA QT system) was investigat ed. Results obtained with both clinical specimens and dilution panels indic ated that both the absolute number of reported results and the reported HIV -1 RNA copy number were directly proportional to the specimen input volumes evaluated (0.1, 0.5, and 1.0 mi), Conversion of the reported HIV-I RNA cop y numbers to a constant 1.0-ml volume indicated that the numerical relation ship among the specimen input volumes and the HIV-1 RNA copy numbers was mu ltiplicative. The HIV-I RNA copy numbers reported for the 0.5-ml input volu me were approximately 5-fold increased over those reported for the 0.1-ml i nput volume, and those reported for the 1.0 ml input volume were 10-fold in creased over those reported for the 0.1-ml input volume. For the specimen i nput volumes investigated, a common linear range of 264 to 5,400,000 HIV-I RNA copies was observed. The use of increased specimen input volumes did no t result in a loss of assay specificity, as the results reported for specim ens from 50 seronegative blood donors were negative at all three specimen i nput volumes. In conclusion, an increase in the input volume of specimens a nalyzed by nucleic acid amplification technology can be useful for the enha nced detection of HIV-1 RNA.