HIV-1限制性抗原亲和力检测方法的影响因素及应用

艾滋病病毒(HIV)目前依然是公共健康需要解决的重大问题之一。新发感染率的估算目前有队列研究,数学模型和实验室检测三种方式。利用实验室技术限制性抗原亲和力方法(LAg-Avidity EIA)检测横断面样本,从而估算HIV-1新发感染率越来越受到重视。研究表明,目前使用的新发感染实验室检测方法中该方法的影响因素较少,因而有较好的现场应用价值。文章通对限制性抗原亲和力方法的原理、影响因素和应用进行综述,为HIV-1新发感染率的估算、HIV-1高危人群的及时预防和采取干预措施提供一些有价值参考。     

南京市2013年MSM的HIV新发感染情况分析

目的了解南京市男男性行为人群(MSM)艾滋病病毒(HIV)的感染状况,估算HIV在该人群中的新发感染率。方法通过滚雪球方法在南京市招募到656例MSM,进行问卷调查和HIV血清学检测;检出的HIV阳性样本,再应用BED HIV IgG捕获酶免疫法(BED-CEIA)检出其中的新发感染样本,进而估算该人群的HIV新发感染率。结果 656名调查对象平均年龄(31.12±10.80)岁(16~78岁);未婚占67.8%;本省占68.3%;在本地居住时间2年以上占79.4%;大专及以上占57.3%。认同自己为同性恋者占62.5%,认同自己为双性恋者占31.7%。寻找性伴场所最多的为网络/论坛,占52.1%。其次为酒吧/会所,占16.0%。93.3%的调查对象掌握艾滋病预防控制知识;58.5%的调查对象在近6个月内与同性发生过无保护性肛交性行为。656份样本检测出HIV阳性64份,HIV感染率为9.76%。进行BED检测的59份HIV阳性样本中,20份被判定为新发感染,感染者中新发感染比例为33.90%;校正公式计算的HIV新发感染率为6.39%[95%可信区间(CI):3.03%~9.76%]。HIV阳性病例中,判定为新发感染的病例CD+4T淋巴细胞计数均值高于判定为长期感染病例,均值差异有统计学意义。结论南京市MSM的HIV感染率处于较高水平,新发感染情况不容乐观,必须加大综合干预力度,促进该人群改变行为。     

哈尔滨市2013-2015年男男性行为者HIV-1新发感染情况分析北大核心CSCD

目的了解哈尔滨市男男性行为者（MSM）艾滋病病毒（HIV）感染情况,估算及分析该人群中的HIV-1新发感染率及其影响因素。方法 2013-2015年开展四轮横断面调查,对2 531名MSM进行行为学调查及生物学检测。对HIV-1阳性的样本,进行BED HIV-1IgG捕获酶免疫法（BED-CEIA）检测,以此估算该人群的HIV-1新发感染率。结果 2013-2015年,四轮调查中HIV感染率分别为9.6%、16.8%、14.7%及17.3%。2013年、2014年HIV-1年平均新发感染率为4.6%[95%可信区间（CI）：2.5%~6.8%],2014年9-11月、2015年4-6月新发感染率分别为9.2%（95%CI：4.8%~13.6%）,6.2%（95%CI：2.4%~9.9%）。HIV-1新发感染的影响因素分析显示,性角色为被插入方[比值比（OR）=5.105,95%CI：2.626~9.925]和既作为插入方与又作为被插入方（OR=2.454,95%CI：1.306~4.613）的危险性显著高于插入方;现患梅毒者感染HIV-1的危险性（OR=4.006,95%CI：2.320~6.915）高于未患梅毒者;最近一年进行过HIV检测（OR=0.532,95%CI：0.327~0.868）是HIV-1新发感染的保护性因素。结论哈尔滨市MSM中,HIV感染率及新发感染率均较高,HIV感染的危险因素广泛存在,但在MSM中开展艾滋病知识的宣传教育、咨询及检测,对于遏制艾滋病的发展是有积极意义的。     

凉山州2011-2015年哨点监测孕产妇HIV-1感染率及新发感染率结果分析北大核心

目的在凉山州孕产妇人群中开展1型艾滋病病毒（HIV-1）新发感染检测,并估算该人群的HIV-1感染率和新发感染率,了解凉山州2011-2015年孕产妇人群HIV-1感染状况及防控策略探讨。方法用BED捕获酶免疫技术检测2011-2015年3个孕产妇哨点采集的HIV确证阳性样本,计算HIV-1在该人群中的感染率,并估算新发感染率,采用χ^2检验进行统计分析。结果 2011-2015年共对5486例血样进行HIV-1抗体筛查,确证阳性243例,HIV-1感染率4.43%;新发感染24例,新发感染率1.13%[95%可信区间（CI）：0.68~1.59]。χ^2趋势检验得到各年度新发感染率差异无统计学意义（χ^2=2.235,P=0.135）。结论 2011-2015年,凉山州孕产妇HIV-1感染率及新发感染率均处于较高水平,需进一步加强孕产妇人群的行为干预和监测工作。     

应用不同方法估计2010-2013年中山市MSM的HIV新发感染率

目的探索用不同方法评估中山市男男性行为人群(MSM)的艾滋病病毒(HIV)新发感染率的有效性,评估中山市MSM艾滋病疫情流行形势。方法综合利用中山市人口学、哨点监测,自愿咨询检测(VCT)门诊、CD+4T淋巴细胞(简称CD4细胞)计数检测和BED捕获酶免疫试验(BED-CEIA)数据,分别采用Spectrum/EPP模型、BED-CEIA、首次CD4细胞计数和队列研究,估计2010-2013年MSM的HIV新发感染率。结果 Spectrum/EPP模型估计:中山市MSM 2010年新发感染率为1.85%,2011、2012和2013年维持在1.91%;BED-CEIA估算:2010-2013年新发感染率分别为9.14%、5.19%、10.86%和7.90%。首次CD4细胞计数估算:2010-2013年新发感染率分别为1.88%、1.99%、3.06%和2.01%。2010-2013年,VCT门诊125名MSM的开放队列,合计观察150人年,4例HIV抗体阳转,发病密度2.67/100人年。结论 Spectrum/EPP模型、首次CD4细胞计数和队列研究估计得到的2010-2013中山市MSM新发感染率相近;BED-CEIA估计得到的结果高于其他三种方法,存在高估的可能。     

运用限制性抗原亲和力酶联免疫法估计云南省德宏州婚检与孕产妇人群HIV新近感染率

目的了解云南省德宏傣族景颇族自治州(简称德宏州)2009—2017年婚检与孕产妇人群艾滋病病毒(HIV)新发感染情况。方法婚检人群血浆样本210 486份和孕产妇血浆样本220 703份进行HIV检测,婚检和孕产妇人群HIV检测阳性分别为1 409例和1 475例。对德宏州2009—2017年血浆样本符合新发感染检测条件的388例婚检人群和336例孕产妇人群HIV阳性样本进行限制性抗原亲和力酶联免疫法检测以确定HIV新近感染,估计婚检人群和孕产妇HIV新近感染率。结果 2009—2017年婚检人群各年度HIV新近感染率分别为0.01%、0.04%、0.02%、0.05%、0.05%、0.08%、0.01%、0.03%和0.01%,总体相对稳定,差异无统计学意义(χ~2=13.805,P0.05)。2009—2017年各年度孕产妇人群HIV新近感染率分别为0.02%、0.11%、0.07%、0.04%、0.04%、0.08%、0.02%、0.04%和0.04%,总体相对稳定,差异有统计学意义(χ~2=15.608,P0.05)。结论德宏州2009—2017年婚检与孕产妇人群HIV新近感染率均保持较稳定的水平。     

2014-2018年山东省MSM哨点HIV-1新发感染研究

目的分析山东省2014-2018年MSM哨点HIV-1新发感染率,全面了解新发感染情况。方法按照全国艾滋病哨点监测实施方案要求,用实验室方法对2014-2018年采集的MSM哨点人群血液样本进行HIV抗体检测和HIV-1新发感染检测,计算HIV抗体阳性率和HIV-1新发感染率等指标。结果 2014-2018年山东省8个MSM哨点共监测15 820人,HIV抗体阳性656人,总阳性率为4.15%。2014-2018年HIV抗体阳性率分别为4.41%(135/3 060)、4.55%(146/3 210)、4.57%(151/3 307)、3.91%(124/3 169)和3.25%(100/3 074);HIV-1新发感染率分别为4.16%、3.25%、3.44%、2.77%和3.06%。2014-2018年山东省8个MSM哨点中,HIV抗体阳性率和HIV-1新发感染率排前三位的是烟台、济南和淄博市,抗体阳性率分别是8.84%(179/2 024)、6.92%(148/2 140)和6.33%(119/1 879);HIV-1新发感染率分别为7.42%、6.29%和6.66%,远高于全省总体水平,其他哨点HIV抗体阳性率均低于全省总体水平。结论山东省MSM的HIV感染情况相对严重,不同哨点之间差别明显,应继续加强宣传干预等措施。     

探索应用常规工作数据估计MSM人群HIV新发感染率

目的探索应用常规工作数据建立简便、实用的数学模型,估计男男性行为人群（MSM）艾滋病病毒（HIV）新发感染率。方法假设某小年龄组MSM人群的HIV新发感染率与整体MSM人群相同,以15~49岁年龄组的MSM人群规模、HIV/AIDS病例现存人数、HIV感染率、小年龄组当年新发现HIV感染者人数（CD4淋巴细胞〉200/μL）,横断面调查小年龄组样本在15~49岁年龄组样本中的构成等作为参数建立模型,并进行适用性评估。结果模型估计2006-2012年哈尔滨市MSM人群的HIV新发感染率分别为0.3%、0.8%、0.4%、0.9%、1.3%、1.7%、3.1%,呈线性上升趋势（P=0.000）,相应年度的新发感染率支持年度间的HIV感染率变化。新报告HIV/AIDS病例数量及经同性性传播构成的变化、15~20岁感染者数量及特点的变化、梅毒感染率、无保护肛交比例、≥2个性伴比例水平,另外两种HIV新发感染率估计法的估计结果等均支持此判断。结论研究设计的HIV新发感染率估计模型,应用常规工作数据,估计值有参考价值,值得有需求地区探索使用。     

南阳市MSM人群HIV新发感染情况研究

目的了解南阳市男男性行为(MSM)人群艾滋病病毒(HIV)新发感染情况及影响因素。方法采用动态队列研究的方法,于2010-2011年间建立MSM队列,对入组时HIV抗体阴性者每半年随访1次,收集HIV检测结果及其行为学信息。采用Cox比例风险模型进行HIV新发感染的单因素和多因素分析。结果南阳市429例MSM队列成员中,有20例新发HIV感染,2010-2011年总的HIV新发感染率(发病密度)为3.41/100人年。两年间4次随访的HIV新发感染率有所上升,依次为2.06/100人年、0.71/100人年、3.44/100人年和6.29/100人年。Cox回归多因素分析表明,少数民族[相对危险度(RR):4.91,95%可信区间(CI):1.04～23.17,P=0.04]、月收入≥2 000元(RR:7.99,95%CI:2.01～31.77,P<0.01)、性取向为同性(RR:3.16,95%CI:1.09～9.14,P=0.03)、近半年与男性发生肛交性行为从未使用安全套(RR:4.96,95%CI:1.10～22.42,P=0.04),是当地MSM人群HIV新发感染的影响因素。结论南阳市MSM人群HIV新发感染呈上升趋势,今后应考虑加强以关注同志场所和安全套使用为主的干预措施。     

乌苏市美沙酮药物维持治疗者4种传染病的检出率和新发感染率分析

目的掌握新疆乌苏市维持治疗人员HIV、HCV和梅毒的感染现状,为在该人群中提供相应的预防控制措施提供科学依据。方法对292名入组人员进行问卷调查,并采集血样进行HIV、HCV和梅毒的检测。结果 2010—2013年在首次入组的292人中累计检出艾滋病、丙型肝炎、梅毒、肺结核病4种传染病患者156例,总检出率53.42%;艾滋病、丙型肝炎、梅毒、肺结核病4种传染病检出率分别为7.19%、41.44%、3.76%、1.03%;未感染上述4种传染病165人、占56.51%;感染1种传染病100人、占34.25%,感染2种传染病23人、占7.88%,感染3种传染病4人、占1.36%,无同时感染4种传染病者;HIV新发感染率为0.46/100人年,丙型肝炎新发感染率0.44/100人年,梅毒新发感染率为1.09/100人年;肺结核病无新发感染;4种传染病累计新发感染率1.99/100人年。结论吸毒人员中HIV及HCV的感染情况较为严重,应普及美沙酮维持治疗,提高美沙酮维持治疗的依从性和覆盖面,控制HIV、HCV感染及相应的疾病在吸毒者中的流行。     

Comparison of methods to detect recent HIV type 1 infection in cross-sectionally collected specimens from a cohort of female sex workers in the Dominican Republic

Interest in estimating HIV-1 incidence using specimens obtained as part of cross-sectional surveys has led to the development of new methods to detect recent HIV-1 infection through the testing of a single anti-HIV-positive specimen. These assays are based on quantitative and qualitative differences in anti-HIV-1 antibodies between recent and long-standing infections. An ongoing vaccine preparedness study enrolled female sex workers in the Dominican Republic. Specimens from women found to be HIV positive at baseline were tested for recent HIV-1 infection using the detuned assay, avidity index, and BED-CEIA assay. An unweighted kappa statistic in pairwise comparisons was used to estimate the correlation of recent HIV-1 infection detection by the three methods. Nineteen (3.9%) of 482 women were positive for HIV-1 infection. The incidence of HIV infection was 1.4% [95% confidence interval (CI): 0.2, 5.3], 0.9%(95% CI: 0.1, 4.4), and 1.0%(95% CI: 0.1, 4.4) using detuned assay, avidity index, and BED-CEIA techniques, respectively. The overall agreement between both detuned assay and avidity index and detuned assay and BED-CEIA was 94%(kappa = 0.8, 95% CI; 0.3, 1.0). The correlation was highest between BED-CEIA and avidity index methods (100%; kappa = 1.0). All three methods performed similarly in detecting recent HIV-1 infection in this region dominated by clade B HIV-1 infection. Although incidence estimates were slightly higher using the detuned assay method, they were not significantly different. These assays may be of value in both clinical research and practice. The utility of individual assays for recent infection detection will depend upon operating characteristics, HIV-1 subtype limitations, and selection of appropriate assay cutoff values.     

Correlation of prospective and cross-sectional measures of HIV type 1 incidence in a higher-risk cohort in Ho Chi Minh City, Vietnam

The primary aim of this study was to estimate HIV incidence within a high-risk population in Ho Chi Minh City (HCMC), Vietnam using both cross-sectional and prospective methodologies. A secondary aim was to develop a local correction factor for the BED and avidity index incidence assays. The research study design consisted of three phases: (1) cross-sectional, (2) prospective, and (3) BED false recent (BED FR). A total of 1619 high-risk, sexually active individuals were enrolled in the cross-sectional phase and 355 of the opiate-negative, HIV-negative women were subsequently enrolled in the prospective phase. Four-hundred and three men and women with known HIV infection duration of greater than 12 months were enrolled in the BED FR phase. The HIV prevalence for all participants in the cross-sectional phase was 15.8%. HIV incidence in the cross-sectional group was estimated using the BED IgG capture assay and AxSYM avidity index assay for recent HIV infection and incidence within the prospective cohort was determined by observations of HIV seroconversion. HIV incidence in opiate-negative women was estimated using the BED assay to be 0.8% unadjusted and 0.5% after applying the locally derived BED false recent rate of 1.7%; no seroconversions were observed in the prospective cohort. We also screened the cross-sectional samples for evidence of acute infection using nucleic acid testing, 4th generation HIV EIA, and SMARTube coupled with Genscreen and Determine diagnostic tests; no confirmed acute infections were identified by any method. HIV incidence within this opiate-negative study population was low and incidence estimates from the two methods compared favorably with each other. Incidence estimates and false recent rates using the AxSYM assay were higher: AI FRR of 2.7% and adjusted incidence of 1.7% per year (95% CI, 0.6, 2.8). By comparison, both HIV prevalence and incidence estimates for the opiate-positive group were higher.     

Comparison among the BED capture enzyme immunoassay test and AxSYM avidity index assay for determining recent HIV infection and incidence in two Voluntary Counselling and Testing Centres in Northeast Brazil

The aims of this study were to compare the automated AxSYM avidity assay index with the BED capture enzyme immunoassay test and to calculate the HIV-1 incidence using the BED capture enzyme immunoassay and AxSYM avidity assay index algorithms within a population seeking the Voluntary Counselling and Testing Centres in two municipalities in the Metropolitan Region of Recife, Northeast of Brazil. An analysis was conducted in 365 samples that tested positive for HIV infection from frozen serum collected during the period 2006–2009. There was a similar proportion of males and females; most patients were heterosexual (86%) with a median age of 29 years. Of the 365 samples, 102 (28%) and 66 (18.1%) were identified as recent infections by BED capture enzyme immunoassay and AxSYM avidity assay index, respectively. The HIV-1 total incidence in the BED capture enzyme immunoassay and AxSYM avidity assay index algorithms were: 0.79 (95% CI: 0.60–0.98) and 0.34 (95% CI: −0.04 to 0.72), respectively. Incidence was higher among men. There was good agreement between the tests, with a kappa of 0.654 and a specificity of 95.8%. AxSYM avidity assay index may be helpful in improving the quality of the estimates of recent HIV infection and incidence, particularly when used in a combined algorithm with BED capture enzyme immunoassay.     

Development and characterization of a bead-based, multiplex assay for estimation of recent HIV type 1 infection

Estimation of HIV-1 incidence is an important public health tool for understanding the status of the epidemic, identifying high-risk populations, and assessing various intervention strategies. Several laboratory-based methods have been developed for distinguishing recent from long-term HIV-1 infection; however, each exhibits some degree of misclassification, particularly among AIDS patients and those taking antiretroviral therapy (ART). To improve upon the limitations associated with measuring responses to a single analyte, we have developed a bead-based, multiplex assay for determination of HIV recent infection based on total antibody binding and antibody avidity to multiple analytes. An HIV-specific, multiplex panel was created by coupling the recombinant HIV-1 proteins p66, gp120, gp160, and gp41 to Bio-Plex COOH microspheres. Longitudinal plasma specimens from recent seroconverters were tested for reactivity to the coupled microspheres using the Bio-Plex 200 System. For each analyte, HIV-specific antibody binding and avidity increased for 1-2 years post-seroconversion, leading to a significant difference in reactivity between recent and long-term specimens. While the potential for misclassification of individuals diagnosed with AIDS or receiving ART appears to be minimal with avidity measures, the impact on total antibody binding was variable, depending on the individual analyte. This bead-based, HIV-specific multiplex assay measures several distinct immune responses in a single assay plate, allowing for sampling of multiple analytes in the determination of recent infection, which could aid in the development of improved statistical methods or algorithms that will more accurately estimate HIV incidence.     

Stabilization of HIV incidence in women of reproductive age in southern Mozambique

Introduction

The collection of incidence data on HIV infection is necessary to evaluate the status and dynamics of the epidemic and the effectiveness of intervention strategies. However, this is usually difficult in low‐income countries.

Methods

Five yearly point HIV prevalence estimations (in 1999, 2003, 2004, 2005 and 2008) were obtained for women between 15 and 45 years of age participating in three studies carried out for other purposes at the Antenatal Clinic (ANC) in Manhiça, Mozambique. HIV incidence was estimated between prevalence points using a previously validated methodology. Two methods were used, one based on mortality rates for three HIV epidemic scenarios, and the other based on survival information after infection. The pattern over time was captured by fitting a log‐regression model.

Results

The prevalence of HIV infection ranged from 12% in 1999 to 49% in 2008. The HIV incidence increased from approximately 3.5 cases per 100 person‐years in 2001 to 14 per 100 person‐years in 2004, with stabilization thereafter to levels of around 12 cases per 100 person‐years. The incidence estimates were comparable for the two methods used.

Conclusion

These findings indicate an increase in the prevalence and incidence of HIV infection among women of reproductive age over the 9 years of the analysis, with a plateau in the incidence of infection since 2005. However, the very high figures for both prevalence and incidence highlight the importance of the continuation of the prevention and treatment programmes that already exist, and suggest that implementation of preventive measures is needed in this area.     

Strengthening HIV surveillance: measurements to track the epidemic in real time

Surveillance for HIV as a public health initiative requires timely, detailed and robust data to systematically understand burden of infection, transmission patterns, direct prevention efforts, guide funding, identify new infections and predict future trends in the epidemic. The methods for HIV surveillance have evolved to reliably track the epidemic and identify new infections in real time.

Initially HIV surveillance relied primarily on the reporting of AIDS cases followed by measuring antibodies to HIV to determine prevalence in key populations. With the roll-out of antiretroviral therapy (ART) resulting in better survival and the corresponding increase in HIV prevalence, the landscape of surveillance shifted further to track HIV prevalence and incidence within the context of programmes. Recent developments in laboratory assays that potentially measure and differentiate recent versus established HIV infection offer a cost-effective method for the rapid estimation of HIV incidence. These tests continue to be validated and are increasingly useful in informing the status of the epidemic in real time.

Surveillance of heterogeneity of infections contributing to sub-epidemics requires methods to identify affected populations, density, key geographical locations and phylogenetically linked or clustered infections. Such methods could provide a nuanced understanding of the epidemic and prioritise prevention efforts to those most vulnerable. This paper brings together recent developments and challenges facing HIV surveillance, together with the application of newer assays and methods to fast-track the HIV prevention and treatment response.     

Vertical transmission of human immunodeficiency virus is correlated with the absence of high-affinity/avidity maternal antibodies to the gp120 principal neutralizing domain.

Many, but not all, infants born to mothers infected with the human immunodeficiency virus (HIV) are infected in utero. We have now shown that mothers who have high-affinity/avidity antibodies directed toward the principal neutralizing domain (PND) of gp120 are less likely to transmit HIV to their children. An ELISA that preferentially measures the level of the biologically functioning, high-affinity/avidity antibodies against PND is described. In a retrospective study of 15 maternal/neonatal serum samples, the assay correctly identified the 4 uninfected and the 11 HIV-infected infants. Other clinical and laboratory parameters such as p24 antigen, phytohemagglutinin mitogenic index, and absolute surface antigen T4+ cell counts did not accurately predict HIV fetal transmission. In addition to introducing a promising diagnostic tool, this study provides the in vivo evidence that protective antibodies may prevent infection by HIV.     

HIV早期感染检测及其使用策略

在艾滋病病毒(HIV)早期感染阶段,感染者体内会出现高病毒血症和高抗原血症,具有较强的传染性,但不能通过抗体检测做出诊断。早期感染的检测对HIV传播阻断非常重要。文章对HIV早期感染检测技术及相应技术,在急性HIV感染诊断、血液筛查及发病率估算中的使用情况及策略做一综述。新技术的发展和改进是HIV早期感染检测策略发展的关键。     

HIV感染并发心血管疾病发病机制研究进展

随着高效抗反转录病毒治疗（HAART）的应用,心血管疾病（CVD）已经成为人类免疫缺陷病毒（HIV）感染者死亡的一个重要原因。据报道,HIV感染人群的CVD发病率至少是普通人群的3倍。因此,HIV感染并发CVD的发病机制成为艾滋病（AIDS）研究最关注的领域之一。现对HIV感染者独特的CVD危险因素及宿主、HIV和抗反转录病毒药物等三个方面致病机制研究的最新进展做一简要综述。     

Temporal trends in the incidence of HIV infection in antenatal clinic attendees in Addis Ababa, Ethiopia, 1995-2003

BACKGROUND: The HIV incidence data are relevant in depicting the current dynamics and trend of the epidemic. Using a new laboratory method for HIV-1 incidence, we aimed at estimating a 10-year trend in HIV-1 incidence in Addis Ababa, Ethiopia. METHODS: We determined the temporal trends in HIV incidence based on a total of 7744 serum specimens from pregnant women who attended antenatal clinics in Addis Ababa between 1995 and 2003. HIV incidence was determined by IgG-capture HIV-1 BED incidence enzyme immunoassay following a validation using a well-characterized panel of serial serum specimens from subtype C-infected seroconverters. FINDINGS: Of the 1350 HIV+ specimens tested as part of the annual sentinel survey between 1995 and 2003, a total of 1332 (98.7%) were tested by BED HIV-1 incidence assay. The incidence rate of HIV-1 infection declined significantly from 7.7% (95% CI, 3.9-11.5%) in 1995 to 2.0% (95% CI, 0.7-3.3%) in 2003. Although there was a trend, amongst the age group of 15-29 years, in age-specific decline in incidence, it was not statistically significant. No change in HIV incidence rate was observed for the group aged above 30 years. INTERPRETATION: A corresponding decline in the incidence of HIV infection was observed with the decline in the prevalence of HIV infection between 1995 and 2003 in Addis Ababa City. Whether the declines were because of changes in sexual behaviours or other reasons needs to be explored. The BED HIV-1 incidence assay provides a valuable tool in obtaining information on recent HIV-1 infection.