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Biomedical subjects

A E Ades

Publications and source records attributed to A E Ades.

At least 37 records · Page 2Linked to original sources
PubMed1999

Effect of the worldwide epidemic on HIV prevalence in the United Kingdom: record linkage in anonymous neonatal seroprevalence surveys.

OBJECTIVE: To assess the impact of the worldwide HIV/AIDS epidemic on the prevalence of HIV in women in the United Kingdom (UK), particularly in the large immigrant and ethnic minority communities. METHOD: Unlinked anonymous neonatal seroprevalence survey with electronic record linkage of data from child health computers (maternal age and ethnic status) and birth registration (parent's country of birth). RESULTS: Of a total 137456 samples collected in 1997-1998, 188 (0.14%) were anti-HIV-1 seropositive. Seroprevalence was highest in women born in East Africa (2.3%) and Central Africa (1.9%). 76.4% of seropositive newborns were delivered to mothers born in sub-Saharan Africa; a further 6.0% had fathers from sub-Saharan Africa. However, there was little evidence of HIV in women born in Southern Asia [prevalence 0.0081%; 95% confidence interval (CI) 0-0.04], and none within UK-born Asian communities. Prevalence among the UK-born Black African community was low (0.14%; 95% CI 0-0.6). Among infants with both parents known to be born in the UK, seroprevalence was 0.023% (95% CI 0.01-0.04) in London, and zero (95% CI 0-0.007) in non-Metropolitan areas. Irrespective of mother's region of birth, seroprevalence was 4.2 times higher (95% CI 3.0-5.8) in newborns whose father's details were not recorded at birth registration, a marker for single unsupported mothers. CONCLUSION: The risk of HIV among pregnant women from sub-Saharan Africa has been recognized. However, in southern England, HIV is very rare in women from Southern Asia and in UK-born women in ethnic minority communities, in spite of cultural and travel ties to high-prevalence countries. Data linkage in anonymous surveys assists in monitoring the impact of the worldwide epidemic on prevalence and incidence locally.

Adult↗
PubMed1999

Vertical transmission rates for HIV in the British Isles: estimates based on surveillance data.

OBJECTIVE: To estimate and interpret time trends in vertical transmission rates for HIV using data from national obstetric and paediatric surveillance registers. DESIGN: Prospective study of HIV infected women reported through obstetric surveillance. HIV infection status of the child and onset of AIDS were reported through paediatric surveillance. Rates of vertical transmission and progression to AIDS rate were estimated by methods that take account of incomplete follow up of children with indeterminate infection status and delay in AIDS reporting. SETTING: British Isles. SUBJECTS: Pregnant women infected with HIV whose infection was diagnosed before delivery, and their babies. MAIN OUTCOME MEASURES: Mother to child transmission of infection and progression to AIDS in children. RESULTS: By January 1999, 800 children born to diagnosed HIV infected women who had not breast fed had been reported. Vertical transmission rates rose to 19.6% (95% confidence interval 8. 0% to 32.5%) in 1993 before falling to 2.2% (0% to 7.8%) in 1998. Between 1995 and 1998 use of antiretroviral treatment increased significantly each year, reaching 97% of live births in 1998. The rate of elective caesarean section remained constant, at around 40%, up to 1997 but increased to 62% in 1998. Caesarean section and antiretroviral treatment together were estimated to reduce risk of transmission from 31.6% (13.6% to 52.2%) to 4.2% (0.8% to 8.5%). The proportion of infected children developing AIDS in the first 6 months fell from 17.7% (6.8% to 30.8%) before 1994 to 7.2% (0% to 15. 7%) after, coinciding with increased use of prophylaxis against Pneumocystis carinii pneumonia. CONCLUSIONS: In the British Isles both HIV related morbidity and vertical transmission are being reduced through increased use of interventions.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Cost effectiveness analysis of antenatal HIV screening in United Kingdom.

OBJECTIVE: To assess the cost effectiveness of universal antenatal HIV screening compared with selective screening in the United Kingdom. DESIGN: Incremental cost effectiveness analysis relating additional costs of screening to life years gained. Maternal and paediatric costs and life years were combined. SETTING: United Kingdom. MAIN OUTCOME MEASURES: Number of districts for which universal screening would be cost effective compared with selective screening under various conditions. RESULTS: On base case assumptions, a new diagnosis of a pregnant woman with HIV results in a gain of 6.392 life years and additional expenditure of 14 833 pounds. If decision makers are prepared to pay up to 10 000 pounds an additional life year, this would imply a net benefit of 49 090 pounds (range 12 300 pounds- 59 000 pounds), which would be available to detect each additional infected woman in an antenatal screening programme. In London, universal antenatal screening would be cost effective compared with a selective screening under any reasonable assumptions about screening costs. Outside London, universal screening with uptake above 90% would be cost effective with a 0.60 pounds HIV antibody test cost and up to 3.5 minutes for pretest discussion. Cost effectiveness of universal testing is lower if selective testing can achieve high uptake among those at higher risk. A universal strategy with only 50% uptake may not be less cost effective in low prevalence districts and may cost more and be less effective than a well run selective strategy. CONCLUSIONS: Universal screening with pretest discussion should be adopted throughout the United Kingdom as part of routine antenatal care as long as test costs can be kept low and uptake high.

Anti-HIV Agents↗
PubMed1999

Costs and benefits to the mother of antenatal HIV testing: estimates from simulation modelling.

OBJECTIVE: To assess the health service costs and benefits for the woman of an earlier HIV diagnosis as a result of antenatal HIV testing. DESIGN: A model of maternal disease progression was developed based on the rate of decline in CD4 cell counts and applied to two matched simulated cohorts of women with identical initial CD4 cell levels and decline rates but whose HIV diagnosis occurred at different times as a result of antenatal HIV testing. UK data on CD4 cell count at HIV diagnosis and annual health service costs of care excluding antiretroviral therapy (ART) incurred at defined states of CD4 cell count were taken from published UK data. Costs of triple ART were added and effectiveness modelled by retarding the rate of CD4 cell count decline. Discounting costs at 6% and life-years at 2% per year, the additional costs per life-year gained by screening were calculated. Uncertainty was explored using sensitivity analysis. RESULTS: Costs per life-year gained by antenatal diagnosis of women were pound sterling 51258 ($76887) assuming untested women were diagnosed a median of 20.4 months later than tested women, ART was initiated at a CD4 cell count of 350x10(6) cells/l and ART efficacy retarded decline in CD4 cell counts by 40% for life. Sensitivity analyses showed results were most sensitive to the assumed efficacy of lifetime ART and time assumed to HIV diagnosis for women not tested in pregnancy. CONCLUSION: This model provides a way of estimating the additional costs and benefits of future care for the woman resulting from an earlier HIV diagnosis through antenatal testing. These should be included with the paediatric costs averted and life-years gained from interventions to reduce mother-to-child transmission in order to evaluate the cost-effectiveness of antenatal screening in different populations and settings.

CD4 Lymphocyte Count↗
PubMed1999

Selective versus universal antenatal HIV testing: epidemiological and implementational factors in policy choice.

OBJECTIVE: To develop an epidemiological basis for economic analyses of selective and universal antenatal screening strategies, and to apply it to the UK. METHODS: The prevalence of higher-risk women and the prevalence of undiagnosed infection within groups of high-risk and low-risk women was estimated from surveillance and survey data. The numbers of women tested and the numbers of infected women who would be identified by universal and selective strategies were then calculated under a range of assumptions about the identification of higher-risk women and acceptance of testing. RESULTS: In higher-risk women estimated prevalence of undiagnosed infection was between 0.06% and 2.8%, comparing well with independent estimates. In low-risk women, estimates ranged from 0.014% in London to 0.002% in the rest of the UK. If uptake among the high-risk women was the same in selective and universal strategies, universal testing would entail testing between 7100 (London) and 50000 (rest of England) additional women to detect an additional case. However, if selective screening identified only 60% of those at high risk and achieved only 60% acceptance compared with a universal programme, then universal screening would require only 1150 additional women to identify one additional case in London, compared to 6470 in Scotland and 13140 in the rest of the UK. CONCLUSIONS: Overall prevalence does not form an adequate basis for determining screening strategy. Instead, universal screening can be justified either because the prevalence of HIV in the low-risk group is sufficiently high, or because it achieves sufficiently higher uptake relative to selective screening among those at higher risk.

Female↗
PubMed1999

Non-participation bias in unlinked anonymous HIV-prevalence surveys in England and Wales.

The objective was to assess the potential bias in unlinked anonymous HIV-seroprevalence surveys from objections to specimens being included. Objection rates in seroprevalence surveys were examined. Statistically large clusters of objections were considered to be the result of health care worker behaviour, and were disregarded. Underlying objection rates were estimated from remaining data and compared to seroprevalence. Overall objection rates approached or exceeded seroprevalence in many participating centres. However, underlying objection rates declined with time while prevalences were generally unchanging. Also, underlying rates correlated poorly with observed seroprevalences. Findings were therefore consistent with processes producing the clusters of objections and underlying objection rates independently of serostatus of individuals. Although national seroprevalence estimates produced by the surveys are reasonably free from objection bias, regional seroprevalence estimates outside London remain vulnerable to bias as a result of some centres returning data whose quality cannot be guaranteed.

Bias↗
PubMed1999

Lifetime treatment costs of beta-thalassaemia major.

Beta-thalassaemia major is a serious genetic disorder, which results in a considerable increase in both acute and chronic morbidity, and mortality. Although beta-thalassaemia major is a rare disease affecting approximately 600 people in the UK, treatment is intensive and predictions of the costs incurred may aid health care planning. In this report, the cost to the health service of providing treatment services for beta-thalassaemia major patients, over the course of a lifetime, is calculated in order to assist resource allocation decisions. A cost model was developed, incorporating data from disparate sources. The undiscounted lifetime cost of treating a beta-thalassaemia major patient was estimated to be pound 803,002, although when the costs were discounted at a rate of 6%, the lifetime cost was reduced to pound 219,068. Within sensitivity analyses, the discounted cost ranged from approximately pound 188,000 to pound 226,000. This report may act as a guide to those involved in the planning of health care provision with regard to the resources required to treat beta-thalassaemia major patients. Such information may also be incorporated into the decision-making process for the provision of antenatal screening programmes for beta-thalassaemia major.

Adolescent↗
PubMed1998

Mother-to-child transmission of HIV: implications of variation in maternal infectivity.

OBJECTIVES: To examine the implications of variation in maternal infectivity on the timing of mother-to-child HIV transmission through breastfeeding. DESIGN AND METHODS: A mathematical model of mother-to-child HIV transmission was developed that incorporates two main features: (i) the fetus/child potentially experiences a series of exposures (in utero, intrapartum, and via breastmilk) to HIV; and (ii) variation in maternal infectivity. The model was estimated from different sources of epidemiological data: a retrospective cohort study of children born to HIV-1-infected women in Sao Paulo State, Brazil, the International Registry of HIV-Exposed Twins, and the AIDS Clinical Trials Group 076 trial, which assessed the effectiveness of zidovudine in preventing mother-to-child HIV transmission. RESULTS: Variation in maternal infectivity results in higher average risk of breastfeeding-related transmission in the early stages of breastfeeding than in the late stages, even in the absence of a direct relationship between transmission risk and the age of the child. However, the available data were unable to resolve the quantitative importance of this mechanism. CONCLUSIONS: Our model has helped identify a previously unrecognized determinant of the timing of breastfeeding-related HIV transmission, which may have adverse implications for the effectiveness of certain interventions to reduce mother-to-child HIV transmission such as maternal antiretroviral therapy in breastfeeding populations and the early cessation of breastfeeding.

Breast Feeding↗
PubMed1998

Incorporating correlations between measurements into the estimation of age-related reference ranges.

An LMS-based maximum likelihood method of fitting age-related reference ranges is extended to incorporate non-independent measurements by including the matrix of the correlations between standard normalized repeat measurements into the likelihood. The likelihood is maximized via iterative re-estimation of the correlation structure and the reference range parameters until convergence is achieved. The correlation structure is explicitly modelled and the extent to which the estimated centiles depend on the adequacy with which the correlation structure is modelled is investigated. The method is illustrated using CD4 counts of uninfected children born to HIV-1 infected women. This data set consists of 5063 CD4 counts taken from 745 children at irregular ages between birth and 10 years of age. The data exhibited a strong correlation structure with correlations decreasing with increasing time between measurements and being lower for younger measurement ages. However, incorporation of the correlation had little effect on the choice of model for the median or on the fitted centiles or their precision.

Adolescent↗
PubMed1998

Modelling the costs of paediatric HIV infection and AIDS: comparison of infected children born to screened and unscreened mothers.

OBJECTIVE: To estimate the cost of managing children with HIV/AIDS in the UK from a health service perspective. DESIGN AND METHODS: Epidemiological, resource use and unit cost data were combined within a decision analytic model. A Markov model was developed to predict the prognoses of HIV-infected children under different assumptions about natural history, treatment efficacy and the timing of antiretroviral therapy. Resource use estimates for various stages of HIV/AIDS were based on published data relating to the UK health service and clinical judgement; unit cost data were taken from a London centre. RESULTS: The base-case results suggest that the cost of caring for an HIV-infected child is higher if the mother's infection was known about at or before the child's birth (antenatal screened cohort): lifetime costs ranged from 46 427 pound sterling to 119 502 pound sterling per child in the screened cohort and from 38 691 pound sterling to 86 014 pound sterling in the unscreened cohort. However, the screened cohort benefited from longer life expectancy (base-case, 11.66 versus 10.09 years) and AIDS-free life expectancy (base-case, 7.13 years versus 6.22 years). Results are sensitive to assumptions about natural history and treatment efficacy: for example, if antiretroviral therapy was initiated at birth, and assuming optimistic natural history parameters, discounted costs could increase to 215 077 pound sterling and the additional lifetime cost of a child born to a screened mother could be 72 491 pound sterling. CONCLUSIONS: Results reflect the marked uncertainty regarding the cost of, and prognosis for, children with HIV/AIDS in the new era of more potent antiretroviral combination therapies. These results are part of an assessment of the relative cost-effectiveness of alternative antenatal HIV testing strategies.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Prevention of mother-to-child transmission of HIV-1 infection: alternative strategies and their cost-effectiveness.

OBJECTIVE: To estimate the cost-effectiveness of alternative interventions to reduce the risk of mother-to-child transmission of HIV. DESIGN: A model capturing the sequential nature of mother-to-child transmission in utero, at delivery and postnatally was used to determine how the effects of bottle-feeding, elective Cesarean section (CS) and zidovudine (ZDV) would combine to prevent mother-to-child HIV transmission. Parameter estimates were derived from the literature, UK health service costs applied, and incremental cost effectiveness ratios (ICER) estimated for alternative risk reduction strategies. Results can be transposed to other cost assumptions or currencies. RESULTS: In a woman who breast-feeds her baby, has a vaginal or emergency CS delivery and takes no ZDV, the estimated transmission risk is 31.6% (range, 23.7-38.1%), at a cost of 400 UK pound per woman; this falls to a risk of 3.7% (range, 1.7-6.9%) when bottle-feeding, ZDV therapy and elective CS are all implemented at a cost of 1968 UK pound per woman. From a public health perspective the ICER of ZDV and elective CS each depend on the acceptance rates of the other. In women counselled against breast-feeding, ZDV with 100% acceptance of elective CS has an ICER of 11 342 UK pound (95% confidence interval (CI), 7084-21 515 UK pound]. However, the ICER of CS ranges from 9248 UK pound (95% CI, 5072-46 913 pound sterling) at zero ZDV acceptance to 27 895 UK pound (95% CI, 10 018-154 462 pound sterling) at 100% ZDV acceptance. CONCLUSIONS: Considering the estimated cost of caring for an infected child, ZDV appears to be cost-effective under any of the circumstances examined. However, elective CS may not be cost-effective in populations where the uptake of ZDV is high, and a more precise estimate of its efficacy is required.

Anti-HIV Agents↗
PubMed1998

Epidemiology and detection of HIV-1 among pregnant women in the United Kingdom: results from national surveillance 1988-96.

OBJECTIVE: To describe the epidemiology of HIV-1 infection in pregnant women in the United Kingdom. DESIGN: Serial unlinked serosurveillance for HIV-1 in neonatal specimens and surveillance through registers of diagnosed maternal and paediatric infections from reporting by obstetricians, paediatricians, and microbiologists. SETTING: United Kingdom, 1988-96. SUBJECTS: Pregnant women proceeding to live births and their children. MAIN OUTCOME MEASURES: Time trends in prevalence of HIV-1 seropositivity in newborn infants (as a proxy for infection in mothers); the proportions of mothers with diagnosed HIV-1 infections, and their characteristics. RESULTS: HIV-1 prevalence among mothers in London rose sixfold between 1988 and 1996 (0.19% of women tested; 1 in 520 in 1996). Apart from in Edinburgh and Dundee, levels remained low in Scotland (0.025%; 1 in 3970) and elsewhere in the United Kingdom (0.016%; 1 in 1930). Over a third of births to infected mothers in 1996 occurred outside London. In London the reported infections were predominantly among black African women, whereas in Scotland most were associated with drug injecting. The contribution of reported infection among African women increased over time as that of drug injecting declined. In Scotland 51% of mothers' infections were diagnosed before the birth. In England, despite a national policy initiative in 1992 to increase the antenatal detection rate of HIV, no improvement in detection was observed, and in 1996 only 15% of previously unrecognised HIV infections were diagnosed during pregnancy. CONCLUSIONS: HIV-1 infection affects mothers throughout the United Kingdom but is most common in London. Levels of diagnosis in pregnant women have not improved. Surveillance data can monitor effectively the impact of initiatives to reduce preventable HIV-1 infections in children.

Female↗
PubMed1998

Factors affecting uptake of antenatal HIV testing in London: results of a multicentre study.

OBJECTIVES: To measure the uptake of antenatal HIV testing and determine its relation to risk of HIV and to screening practices. DESIGN: Multicentre prospective questionnaire study. SUBJECTS: Pregnant women attending six maternity units. SETTING: Inner London, 1995-6. MAIN OUTCOME MEASURES: Uptake of testing by risk factors for HIV, ethnicity, and factors about the antenatal interview. RESULTS: All units had a "universal offer" policy for HIV testing. In five units forms were completed for 18,791 (88%) of 21,247 pregnant women. The sixth unit, where the response rate was too low to assess uptake, was excluded from the analysis. Uptake ranged from 3.4% to 51.2% (overall 22.9%), in parallel with detection of previously undiagnosed infection in pregnant women (4.9-60%). Controlling for unit, uptake was higher among the 7% who disclosed risk factors. Among those at low risk, uptake varied by ethnic group (South Asian women 9%; Latin American and Mediterranean women 33%). The relation between uptake and HIV risk category varied greatly across units. Despite increased HIV seroprevalence in black African women, uptake was similar in this group to that among women at low risk (24%). Uptake increased 2.1-fold if HIV transmission was discussed. Midwives reported spending 7 (2-15) minutes discussing HIV issues. CONCLUSIONS: Uptake of HIV testing was unacceptably low in all units, with maternity unit the strongest predictor. New approaches to antenatal HIV testing are urgently required and uptake should be audited routinely.

Africa↗
PubMed1998

A review of hepatitis C virus (HCV) vertical transmission: risks of transmission to infants born to mothers with and without HCV viraemia or human immunodeficiency virus infection.

BACKGROUND: Hepatitis C virus (HCV) vertical transmission studies have reported conflicting findings, possibly due to differences in HCV transmission risk factors among maternal populations, or to methodological differences. METHODS: Systematic review of worldwide published and unpublished HCV vertical transmission studies. Standardized diagnostic criteria were applied to minimize methodological differences, and transmission rates recalculated according to maternal HCV viraemic and human immunodeficiency virus (HIV) infection status. RESULTS: In all, 976 eligible infants from 28 studies were followed up sufficiently for recalculation of transmission rates. Overall transmission rates were less than 10% in 8/12 studies of HIV negative mothers, compared with 2/7 studies comprising at least 50% HIV-coinfected mothers. Rates from 409 viraemic mothers in 15 studies ranged from 0% to 41%, being less than 10% from HIV negative mothers in 6/13 studies and from HIV positive mothers in 1/6 studies. Nine studies measured maternal viraemia levels, with only 2/30 transmitting mothers having < 10(6) copies/ml of HCV RNA. Eight transmissions were identified overall from non-viraemic mothers. Significant transmission rate variation remained after accounting for maternal viraemia and HIV coinfection, possibly due to differences in other vertical transmission risk factors, in frequencies of postnatal transmission, or residual differences in study methodologies. CONCLUSIONS: Overall, HCV transmission is largely restricted to infants born to HCV viraemic mothers, and low risks among most HIV negative mothers may be due to lower HCV viraemia levels. International agreement on standardized diagnostic criteria for HCV vertical transmission would facilitate pooling of individual findings, to allow more precise transmission estimates and further investigation of risk factors.

Adult↗
PubMed1998

Performance of antenatal HIV screening strategies in the United Kingdom.

BACKGROUND: In 1996 only 13.5% of previously undiagnosed HIV infected women were detected in pregnancy. In this study, all 265 maternity units in the United Kingdom were surveyed to determine the relation between screening strategy, uptake of testing, and detection rate. METHODS: Data on HIV screening strategy and uptake of testing were collected in 1997 by postal questionnaire. The proportion of women with previously undiagnosed HIV infection identified during pregnancy (detection rate) was calculated using data from national obstetric HIV surveillance and unlinked anonymous seroprevalence studies. RESULTS: 239 (90%) units responded; 25 of these (10%) had a universal offer strategy, 89 (37%) a selective offer, and 125 (52%) tested only women who requested it. All selective units offered testing to injecting drug users, but only 26% to women who had lived abroad in high prevalence areas. Uptake was over 10% in only eight units, all with a universal strategy, and in 76% of selective units it was below 0.1%. The detection rate was 14.7% in universal units, 7.8% in selective units, and 7.7% in on request units. In universal units, detection increased by 6.3% (95% confidence interval 3.7% to 8.8%) for every 10% increase in uptake of testing. There was evidence of both selective presentation for testing and avoidance of testing among infected women. CONCLUSIONS: All current antenatal HIV testing strategies fail to identify most infected women. Universal offer strategies achieve a very low uptake and a poor detection rate. Units with selective strategies tend to test only a minority of women at high risk and do not target all the main high risk groups.

Female↗
PubMed1998

Obstacles to timely neonatal screening in North Thames.

OBJECTIVE: To assess the timeliness of neonatal (Guthrie card) screening in North Thames, and to identify the most effective ways of improving it. DESIGN: Analysis of information routinely collected in the course of neonatal screening; reanalysis of published data on blood phenylalanine concentration in phenylketonuria (PKU) over the first two weeks; simulation studies on the impact of different interventions. SUBJECTS: 100,690 infants born over one year and screened at Great Ormond Street Hospital NHS Trust. OUTCOME MEASURE: Interval between birth and reading PKU screen results. RESULTS: Although 75% of samples (district range 55-91%) were collected by day 7, only 81% had arrived in the laboratory seven days later (range 57-96%). The average interval between birth and reading results was 14.5 days, with only 9.7% read by day 10. Samples could be collected from day 4 without significant impact on false negative rates for PKU. If samples were collected from day 4 and posted promptly (second class), the average interval between birth and reading results could be reduced to 9.3 days. If first class mail were used and the laboratory operated on Saturdays, and used assays that could be read the same day rather than bacterial inhibition assays, the average would be 7.8 days, with 96% read by day 10. CONCLUSION: Timeliness of neonatal screening shows unacceptable variation between districts, and delays in dispatch of specimens to the laboratory. Same day, first class posting should be introduced, and samples could be collected between days 4 and 8.

Blood Specimen Collection↗
PubMed1997

Use of polymerase chain reaction and antibody tests in the diagnosis of vertically transmitted hepatitis C virus infection.

Data on patterns of polymerase chain reaction (PCR) and antibody test results in infants born to hepatitis C virus (HCV)-infected mothers were systematically reviewed to aid development of optimum testing schedules and diagnostic criteria for vertically exposed infants and to facilitate early identification of infected infants. Survival and cross-sectional analyses were used to estimate the timing of initial PCR positivity and subsequent PCR negativity in infected infants, and maternal antibody loss in uninfected infants was estimated as a weighted average of individual study findings. Of 74 eligible infants with strong evidence of HCV infection, an estimated 89% (90% confidence interval, 80-95%) were first PCR positive by 3 months of age, and less than 10% had subsequent PCR negativity attributable to intermittent viraemia or resolved infection in the first 18 months of life. The negative predictive value of PCR at 3 months of age was greater than 98% at an assumed rate of 5% vertical transmission, but as low as 88% at 25% transmission. The inclusion of 22 infants, each with a single PCR-positive result, increased the estimated frequency of resolved infections but made little difference to other estimates. A minority of PCR-positive infants had periods of antibody negativity by second- or third-generation assays, and among 297 uninfected infants, maternal antibody was not detected beyond 18 months. Thus, the majority of infected infants may be persistently PCR positive from 3 months of age, and the negative predictive value of PCR at 3 months is generally high. However, poor repeatability of PCR, inadequate infant follow-up, and inclusion of postnatally infected infants limits interpretation of the pooled data. Further studies using standardised PCR methodologies are needed.

Cross-Sectional Studies↗