[1] Univ Amsterdam, Acad Med Ctr, Dept Human Retrovirol, NL-1105 AZ Amsterdam, Netherlands
[2] Univ Amsterdam, Acad Med Ctr, Dept Clin Chem, NL-1105 AZ Amsterdam, Netherlands
[3] Chiron Corp, Amsterdam, Netherlands
[4] Municipal Hlth Ctr, Dept Publ Hlth & Environm, Amsterdam, Netherlands