AIDS RESEARCH AND HUMAN RETROVIRUSES Volume 24, Number 1, 2008 © Mary Ann Liebert, Inc. DOI: 10.1089/aid.2007.0116 Sequence Note Prevalence of Primary Antiretroviral Resistance: Trends in Korea JI HWAN BANG, KYOUNG HO SONG, SUNG-HAN KIM, JAE HYUN CHO, WAN BEOM PARK, SANG WON PARK, HONG BIN KIM, NAM JOONG KIM, MYOUNG-DON OH, and KANG WON CHOE ABSTRACT Primary drug resistance is an emerging problem in HIV infections. We have investigated the current preva- lence of primary resistance in Korea and compared it with previous data. Drug-naive HIV patients attend- ing the outpatient clinic of Seoul National University Hospital between April and August 2006 were enrolled. A medical interview and a genotypic resistance test were performed for each patient. The International AIDS Society-USA Panel consensus statement issued in 2006 was used to define resistance mutations. Eighty-one drug-naive HIV patients were enrolled. Two (2.5%) were infected with primary drug-resistant virus: M41L and K103N, respectively. In our previous study, conducted between 1998 and 2002, three (6%) of 50 subjects harbored resistant viruses. Thus the frequency of primary resistance was lower in the present sample than in the earlier one, though the difference is not statistically significant (p  0.37). In view of our findings, rou- tine antiretroviral resistance tests for drug-naive HIV patients are not obligatory in Korea. 83 I N KOREA, zidovudine alone or a combination of two nucle- oside analog reverse transcriptase inhibitors (NRTIs) was prescribed to HIV patients until the introduction of highly ac- tive antiretroviral therapy (HAART) in the late 1990s. As a con- sequence, incomplete viral suppression and the induction of an- tiretroviral resistance were common among the patients who had been treated before the introduction of HAART. We have reported the prevalence of primary drug resistance in 50 drug- naive patients who attended Seoul National University Hospi- tal (SNUH) between 1998 and 2002. 1 In that study, the preva- lence of primary resistance was 8.0%: but it would be 6.0% on the basis of the current consensus developed in 2006. 2 Currently HAART is widely employed in Korea and the prevalence of antiretroviral drug resistance in drug-naive pa- tients may have changed. We have investigated the current prevalence of antiretroviral resistance in drug-naive Korean pa- tients. Drug-naive HIV patients who visited the outpatient clinic of SNUH between April and August 2006 were enrolled. Medical interviews and reviews of medical records were car- ried out to obtain clinical information, and peripheral blood was taken to assess the genotypic resistance of the HIV of each patient. The ViroSeq HIV-1 Genotyping System v2.5 (Celera Diag- nostics, Alameda, CA), which was designed to analyze the pol gene of HIV-1, was used to sequence plasma HIVs. The IAS- USA Drug Resistance Mutations Group consensus issued in 2006 was employed to decide whether the sequences contained resistance mutations. 2 Only major mutations were included for protease inhibitors (PIs). The REGA HIV subtyping tool v2.0 (http://dbpartners.stanford.edu/RegaSubtyping/) was used to identify virus subtypes. We compared the current prevalence of primary antiretrovi- ral resistance with our previous data. 1 In the previous study, 50 preserved HIV-infected patient plasmas were used to test for resistance and clinical data were acquired retrospectively. Eighty-one patients were enrolled during the present study period. All were male and infected by sexual intercourse. Table 1 presents the clinical features of the subjects. All the patients were infected with HIV-1 subtype B, except two who were in- fected with HIV-1 subtype CRF01_AE and subtype C, respec- tively. Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.