anaemia at the time of seroconversion was a predictor of rapid HIV disease progression. The objective of this study was to describe the prevalence and characteristics of anaemia during the first 12 months following infection in a southern African population. We report on early haematologic changes in a cohort of 57 South African women with acute HIV-1 subtype C infection, twenty-three of whom had haematologic profiles available prior to infection. Materials and Methods Study Population The Centre for the AIDS Programme of Research in South Africa (CAPRISA) Acute Infection Study is a prospective observational cohort study of reproductive age women that will provide information about the clinical, immunological, and virological natural history of HIV-1 subtype C infection. HIV-uninfected women at high risk of infection were recruited into an HIV-negative cohort where they received extensive risk reduction counseling including condom provision and underwent monthly HIV testing. Women from the cohort with evidence of new HIV-1 infection on monthly testing were enrolled into the acute HIV infection phase of the study. In addition, seroconverters were also identified from other studies on the basis of a positive HIV antibody test within 3 months of a negative test. Participants with acute infection were followed weekly for 3 weeks, fortnightly until 3 months, monthly until 1 year post-enrollment and every 3 months thereafter. Any participant with a CD4+ cell count less than 350 cells/mm3 at more than one study visit was referred to an antiretroviral treatment program; none of the women in this study took antiretrovirals at any time. Ethics approval for this study was obtained from the Nelson Mandela School of Medicine in Durban, the University of Cape Town, and the University of Witwatersrand in Johannesburg, South Africa. Written informed consent was obtained from all participants. Clinical Data and Laboratory Methods Participants in the HIV-negative cohort underwent a baseline evaluation that included a physical examination and blood collection for a full haematological profile. Two HIV-1 rapid antibody tests (Determine: Abbott Laboratories, Tokyo, Japan and Capillus; Trinity Biotech, Jamestown, NY, USA) were performed on a monthly basis and pooled PCR testing (Amplicor v1.5: Roche Diagnostics, Rotkreuz, Switzerland) for HIV-1 RNA was performed on all antibody negative samples. All samples identified to be HIV- infected through the pooling assay were confirmed using a quantitative RNA PCR (Amplicor v1.5) and an HIV enzyme Anaemia in Acute HIV Infection immunoassay (EIA) test (BEP 2000; Dade Behring, Marburg, Germany) on the same and subsequent samples from the participant. Acute infection was diagnosed following a positive HIV RNA PCR in the absence of HIV-1 antibodies (i.e. pre-seroconversion) or detection of HIV-1 antibodies within 3 months of a previously negative antibody test. Time of infection was defined as 14 days prior to a positive RNA PCR assay in the absence of HIV-1 antibodies or as the mid-point between the last HIV seronegative test and the first HIV seropositive test. Haemoglobin was measured using an Abbott Celldyne 3700 machine (Abbott Laboratories, Abbott Park, IL, USA) and anaemia was defined as a haemoglobin value of less than 12g/ dL in keeping with the WHO definition[11]. Viral loads were measured using the Amplicor v1.5 machine. All analyses were conducted using the SAS statistical package version 9.1 (SAS Institute, Cary, NC, U.S.A.). A paired t-test was used to determine differences between groups at different time points. Results Between October 2004 and October 2006, 57 women with acute HIV-1 infection were identified; 28 from the HIV-negative cohort and 29 from other seroincidence studies. The mean age of the women in the acutely HIV-infected cohort was 27.3 years (standard deviation [SD] 8.70) and their mean body mass index was 28.5 kg/m2 (SD 7.15). The women with acute infection were identified at a median of 14.5 days post-infection (range 10-81) and were enrolled into the Acute Infection cohort at a median of 41 days post-infection (range 15–104). For the 28 women from the HIV-negative cohort, the mean pre-infection haemoglobin level was 12.7 g/dL (SD 1.40) and eleven (39.3%) of them were anaemic; these results are summarized in Table 1. From pre-infection to the first post- infection study visit, the mean decline in haemoglobin was 0.46 g/ dL (SD 1.09). The mean decline in haemoglobin between identification of acute infection and 3 months post-infection was 0.55 g/dL (SD 1.05) and between identification of acute infection and 6 months post-infection was 0.93 g/dL (SD 1.16). For the 26 participants with data available at 12 months, there was a mean increase of 0.10 g/dl (SD 0.97) between the 6 and 12 months post- infection measurements. The prevalence of anaemia, as defined by a haemoglobin level less than 12 g/dL, increased steadily throughout the first 6 months following acute infection, reaching 61.1% at 6 months, and remained close to 51.4% at 12 months post-infection (Figure 1). 3 months (n = 57) 11.81 (1.51) 52.6% (30) 83.68 (6.41) 28.27 (2.68) 16.03 (1.78) 48 800 (269– 1 390 000) 6 months (n = 36) 11.39 (1.57) 61.1% (1722) 80.86 (7.23) 26.72 (2.89) 16.31 (2.04) 9 months (n = 33) 11.39 (1.62) 60.6% (20) 79.83 (8.38) 26.22 (3.02) 17.16 (2.28) 12 months (n = 35) 11.41 (1.41) 51.4% (18) 81.72 (7.94) 26.81 (3.02) 17.18 (2.47) 45 300 (,400– 673 000) 49 400 (,400– 494 000) 33 600 (,400– 1 750 000) Table 1. Haematologic parameters and median viral load prior to infection and by post-infection month. Pre-seroconversion (n = 28) Post-seroconversion* (n = 55) Mean (SD) haemoglobin (g/dl) % (#) with Anaemia (Hb,12g/dl) Mean (SD) MCV (fl) Mean (SD) MCH (pg) Mean (SD) RDW (%) Median (range) viral load (copies/mL) 12.68 (1.40) 25.0% (7) 85.60 (6.64) 29.13 (2.75) 15.03 (1.34) 12.36 (1.35) 43.6% (24) 83.97 (6.20) 28.32 (2.55) 16.40 (2.00) 75600 (547– 5 510 000) Normal values are as follows: Hb 12.0–16.5 g/dl, MCV 76–99 fl, MCH 26–34 pg, RDW 11–16%. (*Note: The post-seroconversion visit refers to the first visit after identification of acute infection and was at a median of 41.5 days post-infection (range 15–104). Also, since acute infections were identified at different time points, not all participants have data at each month post-infection.) doi:10.1371/journal.pone.0001626.t001 PLoS ONE | www.plosone.org 2 February 2008 | Volume 3 | Issue 2 | e1626