Projecting the demographic impact of AIDS and the number of people in need of treatment: updates to the Spectrum projection package

BACKGROUND

In the Joint United Nations Programme on HIV/AIDS (UNAIDS) approach to HIV and AIDS estimates, estimates of adult prevalence produced by the Estimation and Projection Package (EPP) or the Workbook are transferred to Spectrum to estimate the consequences of the HIV/AIDS epidemic, including the number of people living with HIV by age and sex, new infections, AIDS deaths, AIDS orphans, treatment needs, and the impact of treatment on survival.

METHODS

The UNAIDS Reference Group on Estimates, Models and Projections recommends updates to the methodology and assumptions based on the latest research findings and international policy and programme guidelines. The latest update to Spectrum has been used in the 2005 round of global estimates.

RESULTS

Several new features have been added to Spectrum in the past two years. New patterns of the age distribution of prevalence over time are based on the latest survey data. A more detailed treatment of mother to child transmission of HIV is now based on information about current breastfeeding practices, treatment options offered to prevent mother to child transmission (PMTCT), infant feeding options, and the percentage or number of pregnant women accessing PMTCT services. A new section on child survival includes the effects of cotrimoxazole and ART on child survival. Projections can now be calibrated with national survey data. A new set of outputs is provided for all adults over the age of 15 in addition to the traditional 15-49 age group. New outputs are now available to show plausibility bounds and regional estimates for key indicators.

CONCLUSIONS

The latest update to the Spectrum program is intended to incorporate the latest research findings and provide new outputs needed by national and international planners.

Improving analysis of the size and dynamics of AIDS epidemics

Supplement editors Peter D Ghys and Neff Walker and the Chair of the UNAIDS Reference Group on Estimates, Modelling and Projections, Geoff P Garnett, introduce 13 papers describing the data, methods, and tools used to produce the 2005 UNAIDS/WHO HIV and AIDS estimates

Improved plausibility bounds about the 2005 HIV and AIDS estimates

BACKGROUND

Since 1998 the Joint United Nations Programme on HIV/AIDS and the World Health Organization has provided estimates on the magnitude of the HIV epidemic for individual countries. Starting with the 2003 estimates, plausibility bounds about the estimates were also reported. The bounds are intended to serve as a guide as to what reasonable or plausible ranges are for the uncertainty in HIV incidence, prevalence, and mortality.

METHODS

Plausibility bounds were developed for three situations: for countries with generalised epidemics, for countries with low level or concentrated epidemics (LLC), and for regions. The techniques used build on those developed for the previous reporting round. However the current bounds are based on the available surveillance and survey data from each individual country rather than on data from a few prototypical countries.

RESULTS

The uncertainty around the HIV estimates depends on the quality of the surveillance system in the country. Countries with population based HIV seroprevalence surveys have the tightest plausibility bounds (average relative range about the adult HIV prevalence (ARR) of -18% to +19%.) Generalised epidemic countries without a survey have the next tightest ranges (average ARR of -46% to +59%). Those LLC countries which have conducted multiple surveys over time for HIV among the populations most at risk have the bounds similar to those in generalised epidemic countries (ARR -40% to +67%). As the number and quality of the studies in LLC countries goes down, the plausibility bounds increase (ARR of -38% to +102% for countries with medium quality data and ARR of -53% to +183% for countries with poor quality data). The plausibility bounds for regions directly reflect the bounds for the countries in those regions.

CONCLUSIONS

Although scientific, the plausibility bounds do not represent and should not be interpreted as formal statistical confidence intervals. However in order to make the bounds as meaningful as possible the authors have tried to apply reasonable statistical approaches and assumptions to their derivation. An understanding of the uncertainty in the HIV estimates may help policy makers take better informed decisions to address the epidemic in their respective countries.

Declines in HIV prevalence can be associated with changing sexual behaviour in Uganda, urban Kenya, Zimbabwe, and urban Haiti

OBJECTIVE

To determine whether observed changes in HIV prevalence in countries with generalised HIV epidemics are associated with changes in sexual risk behaviour.

METHODS

A mathematical model was developed to explore the relation between prevalence recorded at antenatal clinics (ANCs) and the pattern of incidence of infection throughout the population. To create a null model a range of assumptions about sexual behaviour, natural history of infection, and sampling biases in ANC populations were explored to determine which factors maximised declines in prevalence in the absence of behaviour change. Modelled prevalence, where possible based on locally collected behavioural data, was compared with the observed prevalence data in urban Haiti, urban Kenya, urban Cote d'Ivoire, Malawi, Zimbabwe, Rwanda, Uganda, and urban Ethiopia.

RESULTS

Recent downturns in prevalence observed in urban Kenya, Zimbabwe, and urban Haiti, like Uganda before them, could only be replicated in the model through reductions in risk associated with changes in behaviour. In contrast, prevalence trends in urban Cote d'Ivoire, Malawi, urban Ethiopia, and Rwanda show no signs of changed sexual behaviour.

CONCLUSIONS

Changes in patterns of HIV prevalence in urban Kenya, Zimbabwe, and urban Haiti are quite recent and caution is required because of doubts over the accuracy and representativeness of these estimates. Nonetheless, the observed changes are consistent with behaviour change and not the natural course of the HIV epidemic.

Blood pressure cuffs: friend or foe?

A study to assess the level of bacterial contamination of blood pressure cuffs in use on hospital wards was performed. Viable organisms were recovered from all the 24 cuffs sampled at a density of between 1000 and >25 000 colony-forming units/100 cm2. Potential pathogens were isolated from 14 cuffs (58%). Eleven cuffs grew a single pathogen and three cuffs grew a mixture, yielding a total of 18 isolates. Meticillin-susceptible Staphylococcus aureus was isolated from eight (33%) cuffs, meticillin-resistant S. aureus was isolated from two (8%) cuffs and Clostridium difficile was isolated from eight (33%) cuffs. This study serves as a reminder that hands are not the only fomite to go from patient to patient on hospital wards, and that measures should be taken to reduce the risks posed by blood pressure cuffs.

Bovine tuberculosis infection in wild mammals in the South-West region of England: a survey of prevalence and a semi-quantitative assessment of the relative risks to cattle

In the United Kingdom, badgers are implicated in the transmission of Mycobacterium bovis to cattle, but little information is available on the potential role of other wild mammals. This paper presents the results of the largest systematic UK survey of M. bovis infection in other wild mammals. Mammal carcasses (4715) from throughout the South-West region of England were subjected to a systematic post mortem examination, microbiological culture of tissues and spoligotyping of isolates. Infection was confirmed in fox, stoat, polecat, common shrew, yellow-necked mouse, wood mouse, field vole, grey squirrel, roe deer, red deer, fallow deer and muntjac. Prevalence in deer may have been underestimated because the majority were incomplete carcasses, which reduced the likelihood of detecting infection. Infected cases were found in Wiltshire, Somerset, Devon and Cornwall, Gloucestershire and Herefordshire. Lesions were found in a high proportion of spoligotype-positive fallow, red and roe deer, and a single fox, stoat and muntjac. M. bovis spoligotypes occurred in a similar frequency of occurrence to that in cattle and badgers. Data on prevalence, pathology, abundance and ecology of wild mammals was integrated in a semi-quantitative risk assessment of the likelihood of transmission to cattle relative to badgers. Although most species presented a relatively low risk, higher values and uncertainty associated with muntjac, roe, red and in particular fallow deer, suggest they require further investigation. The results suggest that deer should be considered as potential, although probably localised, sources of infection for cattle.

Quality of life and acne in Scottish adolescent schoolchildren: use of the Children's Dermatology Life Quality Indexc (CDLQI) and the Cardiff Acne Disability Indexc (CADI)

BACKGROUND

Acne vulgaris is known to adversely affect all aspects of quality of life. However, although acne is thought to occur in the majority of adolescents, there are few data currently available on the impact of acne in this age group.

OBJECTIVES

Measurement of the impairment of health-related quality of life (HRQoL) in teenage Scottish schoolchildren in a comparative study using two HRQoL questionnaires. A secondary objective was to collect data on the use and perceived efficacy of medical and over-the-counter (OTC) preparations.

STUDY DESIGN

An anonymous cross-sectional survey of 200 adolescent (15-18 years) Dundee schoolchildren was conducted by means of two self-reported questionnaires: the Children's Dermatology Life Quality Index (CDLQI) and the Cardiff Acne Disability Index (CADI). Data on demographics and therapeutic modalities and their perceived efficacy were also collected.

ANALYSIS

Statistical analysis was performed using the package Stata 7.0.

RESULTS

Self-reported acne was present in 83% of teenagers (147/178), with similar sex distribution (54% male, 46% female). The overall mean CDLQI score (max. 30) was low 1.7 {6% impairment} (CI -1 to 0), range 0-19. Nine pupils scored between 5 and 9 {17-30% impairment} suggesting moderate HRQoL impairment and three scored > 10 {> 33% impairment} indicating severe impairment. The overall mean CADI score (max. 15) of 1.9 {13% impairment}, CI 0 to 1 (range 0-15) was also low, but 12 pupils scored between 5 and 9 {33-60% impairment}, one scoring 10 + {> 67% impairment} and one scoring the maximum, 15 {100% impairment}. There was no significant difference in mean scores between the sexes in either questionnaire (P = 0.5). There was good correlation between the results from the two questionnaires (Spearman's rho = 0.62). Three-quarters (75%) had used OTC products, of which only a third (33%) felt they helped 'a lot'. Fifteen per cent were receiving prescribed treatment from their doctors of which 66% found it helpful.

CONCLUSIONS

Self-reported acne occurred in 83% (147/178) of the Scottish teenagers involved in this study, which confirms previous reports of a high prevalence of acne in teenagers. Cross-validation of the CLDQI and CADI demonstrated good correlation and both scales were easy to administer and identified 11% (16/147) of teenagers who perceive their lives to be significantly affected by their acne (8% moderately to severely, 3% severely). It is important to identify and treat such teenagers early to reduce the future socio-economic burden of their acne.

Distribution of productive antigen-processing activity for MHC class II presentation in macrophages

We demonstrated that an epitope from the recombinant protective antigen (rPA) of Bacillus anthracis was presented by mature major histocompatibility complex class II (MHC-II) molecules, whereas an epitope from the recombinant virulent (rV) antigen of Yersinia pestis was presented by newly synthesized MHC-II. We addressed which endosomal compartments were involved in the antigen processing of each epitope. Bone-marrow-derived macrophages were subjected to subcellular fractionation; fractions were analysed for the expression of endosomal markers and used as a source of enzyme activity for the processing of rPA and rV antigens. The rPA epitope was productively processed by dense lysosomal fractions and light membrane fractions expressing early endosomal markers Rab5 and early endosomal antigen-1 as well as markers of antigen-presenting compartments (MHC-II, DM, DO and Ii chain). In contrast, the rV epitope was productively processed only by dense fractions with lysosomal activity. No productive antigen-processing activity was associated with fractions of intermediate density expressing Rab7 and Rab9, characteristic of late endosomes. The data suggest that endosomal compartments expressing Rab5 guanosine triphosphatase can productively process protein antigens for presentation by mature MHC class II molecules.

Identifying potential risk haplotypes for schizophrenia at the DTNBP1 locus in Han Chinese and Scottish populations

The dystrobrevin-binding protein 1 (DTNBP1) gene on chromosome 6p has emerged as a potential susceptibility gene for schizophrenia. Although a number of attempts to replicate the original association finding have been successful, they have not identified any obvious pathogenic variants or a single at risk haplotype common to all populations studied. In the present study we attempted further replication in an independent sample of 638 nuclear families from the Han Chinese population of Sichuan Province, SW China. We also examined 580 Scottish schizophrenic cases and 620 controls. We genotyped 10 single-nucleotide polymorphisms (SNPs) in DTNBP1 that were used in the original report of association, plus rs2619538 (SNP 'A') in the putative promoter region, which has also been associated with schizophrenia. In the Chinese trios we found that two SNPs (P1635 and P1765) were significantly overtransmitted, but with alleles opposite to those reported in the original studies. SNPs P1757 and P1765 formed a common haplotype, which also showed significant overtransmission. In the Scottish cases and controls, no individual markers were significantly associated with schizophrenia. A single haplotype, which included rs2619538 and P1583, and one rare haplotype, composed of P1320 and P1757, were significantly associated with schizophrenia, but no previously reported haplotypes were associated. Based on the data from the Chinese population, our results provide statistical support for DTNBP1 as a susceptibility gene for schizophrenia, albeit with haplotypes different from those of the original study. However, our lack of replication in the Scottish samples also indicates that caution is warranted when evaluating the robustness of the evidence for DTNBP1 as genetic risk factor for schizophrenia.

Association analysis of the RGS4 gene in Han Chinese and Scottish populations with schizophrenia

We investigated the RGS4 as a susceptibility gene for schizophrenia in Chinese Han (184 trios and 138 sibling pairs, a total of 322 families) and Scottish (580 cases and 620 controls) populations using both a family trio and case-control design. Both the samples had statistical power greater than 70% to detect a heterozygote genotype relative risk of >1.2 for frequent RGS4-risk alleles. We genotyped four single nucleotide polymorphisms (SNPs) which have previously been associated with schizophrenia as either individually or part of haplotypes. Allele frequencies and linkage disequilibrium between the SNPs was similar in the two populations. In the Chinese sample, no individual SNPs or any of their haplotypes were associated with schizophrenia. In the Scottish population, one SNP (SNP7) was significantly over-represented in the cases compared with the controls (0.44 vs. 0.38; A allele; chi(2) 7.08, P = 0.011 after correction for correlation between markers by permutation testing). One two-marker haplotype, composed of alleles T and A of SNP4 and SNP7, respectively, showed individual significance after correction by permutation testing (chi(2) 6.8; P = 0.04). None of the full four-marker haplotypes showed association, including the G-G-G-G haplotype previously associated with schizophrenia in more than one sample and the A-T-A-A haplotype. Thus, our data do not directly replicate previous associations of RGS4, but association with SNP 7 in the Scottish population provides some support for a role in schizophrenia susceptibility. We cannot conclusively exclude RGS4, as associated haplotypes are likely to be surrogates for unknown causative alleles, whose relationship with overlying haplotypes may differ between the population groups. Differences in the association seen across the two populations could result from methodological factors such as diagnostic differences but most likely result from ethnic differences in haplotype structures within RGS4.

BDNF gene is a risk factor for schizophrenia in a Scottish population

Schizophrenia is a severe psychiatric disease with a strong genetic component. Brain-derived neurotrophic factor (BDNF) has been implicated in the pathogenesis of schizophrenia and bipolar (BP) disorders. The present study has examined two polymorphisms in linkage disequilibrium in the BDNF gene, which have been variously reported as associated with schizophrenia and BP. In our study, 321 probands with a primary diagnosis of schizophrenia or schizoaffective disorder, and 263 with a diagnosis of bipolar affective disorder, were examined together with 350 controls drawn from the same geographical region of Scotland. The val66met single-nucleotide polymorphism (SNP) showed significant (P = 0.005) association for valine (allele G) with schizophrenia but not bipolar disorder. Haplotype analysis of val/met SNP and a dinucleotide repeat polymorphism in the putative promoter region revealed highly significant (P < 1 x 10(-8)) under-representation of the methionine or met-1 haplotype in the schizophrenic but not the BP population. We conclude that, although the val66met polymorphism has been reported to alter gene function, the risk may depend upon the haplotypic background on which the val/met variant is carried.

A global analysis of trends in the quality of HIV sero-surveillance

OBJECTIVE

To examine the quality of HIV sero-surveillance systems in countries by 2002, as well as trends between 1995 and 2002.

METHODS

The quality of countries' surveillance systems was scored for five years: 1995, 1997, 1999, 2001, and 2002. Sero-surveillance data were compiled from the US Census Bureau's HIV/AIDS Surveillance Database, the EuroHIV database, and from countries' national HIV surveillance reports that were available to WHO/UNAIDS. The quality of systems was scored according to the level of the countries' epidemic.

RESULTS

There has been a large variation in the quality of HIV surveillance systems across the 132 countries by type of the epidemic and over time from 1995 to 2002. Over the 1995-2002 period the number of countries with a fully implemented system decreased from 57 (43%) in 1995 to 48 (36%) in 2002. The proportion of countries with a fully implemented system was 58%, 34%, and 10% in countries with a generalised, concentrated, and low level epidemic, respectively. In the 53 countries with generalised epidemics the number of countries with a fully implemented system increased from 24 (45%) in 2001 to 31 (58%) in 2002.

CONCLUSION

Many countries still have poor functioning HIV surveillance systems and require urgent strengthening. Countries should monitor and evaluate their own HIV surveillance systems and examine whether the systems are appropriate and adequate.

The UNAIDS Estimation and Projection Package: a software package to estimate and project national HIV epidemics

This paper describes the Estimation and Projection Package (EPP) for estimating and projecting HIV prevalence levels in countries with generalised epidemics. The paper gives an overall summary of the software and interface. It describes the process of defining and modelling a national epidemic in terms of locally relevant sub-epidemics and the four epidemiological parameters used to fit a curve to produce the prevalence trends in the epidemic. It also provides an example of using the EPP in a country with a generalised epidemic. The paper discusses the strengths and weaknesses of the software and its envisaged future developments.

The workbook approach to making estimates and projecting future scenarios of HIV/AIDS in countries with low level and concentrated epidemics

This paper describes an approach to making estimates and short term projections of future scenarios of HIV/AIDS in countries with low level and concentrated epidemics. This approach focuses on identifying populations which through their behaviour are at higher risk of infection with HIV or who are exposed through the risk behaviour of their sexual partners. Estimates of the size and HIV prevalence of these populations allow the total number of HIV infected people in a country or region to be estimated. Subsequently, assumptions about the possible level and timing of saturation of HIV prevalence among each population can be used to explore future scenarios of HIV prevalence. The basic structure of the software used to make estimates and projections is described. This software includes a set of consistency and audit checks to help exclude unrealistic projections. The paper also discusses the strengths and weakness to this approach to making estimates and projections of HIV/AIDS in countries with low level and concentrated epidemics.

Uncertainty in estimates of HIV/AIDS: the estimation and application of plausibility bounds

OBJECTIVES

To establish the accuracy of the country specific estimates of HIV prevalence, incidence, and AIDS mortality published every 2 years by UNAIDS and WHO.

METHODS

We review sources of error in the data used to generate national HIV/AIDS and where possible estimate their statistical properties. We use numerical and approximate analytic methods to estimate the combined impact of these errors on HIV/AIDS estimates. Heuristic rules are then derived to produce plausible bounds about these estimates for countries with different types of epidemic and different qualities of surveillance system.

RESULTS

Although 95% confidence intervals (CIs) can be estimated for some sources of error, the sizes of other sources of error must be based on expert judgment. We therefore produce plausible bounds about HIV/AIDS estimates rather than statistical CIs. The magnitude of these bounds depends on the stage of the epidemic and the quality and coverage of the sentinel HIV surveillance system. The bounds for adult estimates are narrower than those for children, and those for prevalence are narrower than those for new infections.

CONCLUSIONS

This paper presents a first attempt at a rigorous description of the errors associated with estimation of global statistics of an infectious disease. The proposed methods work well in countries with generalised epidemics (>1% adult HIV prevalence) where the quality of surveillance is good. Although methods have also been derived for countries with low level or concentrated epidemics, more data on the biases in the estimation process are required.

Factors influencing concordance with compression stockings after venous leg ulcer healing

OBJECTIVE

To investigate the factors influencing patient concordance with compression stockings after venous leg ulcer healing.

METHOD

In 2001 patients discharged from a specialist leg ulcer service in New Zealand were approached to participate in a structured interview about their use of compression stockings in the first six months following venous leg ulcer healing. Univariate analyses were performed to identify significant associations between factors and stocking use. Multiple logistic regression was employed to model the factors associated with frequency of stocking use.

RESULTS

A total of 163 patients were identified, of whom 129 (79%) agreed to participate. Sixty-seven (52%) reported wearing stockings every day for the first six months after their ulcers had healed, 21 (16%) stated that they had worn the most days, seven (5%) had worn them occasionally and 29 (22%) had not worn them at all after their ulcer had healed. Five (4%) did not provide data. Two factors distinguished those who wore stockings from those who did not 75% of the time: the belief that wearing stockings was worthwhile and the belief that stockings were uncomfortable to wear. Commonly cited factors, such as age, sex, difficulty in applying stockings and cosmetic appearance were not significantly related to stocking use. Cost did not seem to influence the decision to purchase compression stockings.

CONCLUSION

Many factors previously thought to influence concordance appear to have little impact on compression-stocking use in people whose venous leg ulcers had healed.

Association of neuregulin 1 with schizophrenia confirmed in a Scottish population

Recently, we identified neuregulin 1 (NRG1) as a susceptibility gene for schizophrenia in the Icelandic population, by a combined linkage and association approach. Here, we report the first study evaluating the relevance of NRG1 to schizophrenia in a population outside Iceland. Markers representing a core at-risk haplotype found in Icelanders at the 5' end of the NRG1 gene were genotyped in 609 unrelated Scottish patients and 618 unrelated Scottish control individuals. This haplotype consisted of five SNP markers and two microsatellites, which all appear to be in strong linkage disequilibrium. For the Scottish patients and control subjects, haplotype frequencies were estimated by maximum likelihood, using the expectation-maximization algorithm. The frequency of the seven-marker haplotype among the Scottish patients was significantly greater than that among the control subjects (10.2% vs. 5.9%, P=.00031). The estimated risk ratio was 1.8, which is in keeping with our report of unrelated Icelandic patients (2.1). Three of the seven markers in the haplotype gave single-point P values ranging from .000064 to .0021 for the allele contributing to the at-risk haplotype. This direct replication of haplotype association in a second population further implicates NRG1 as a factor that contributes to the etiology of schizophrenia.