P–282 A time lapse analysis of 36,671 embryos to compare the incidence of early stage abnormal cleavage events in ICSI and IVF derived embryos

Study question

Is this incidence of early stage abnormal cleavage events different between embryos created following ICSI compared with IVF?

Summary answer

Embryos derived from ICSI are more likely to exhibit abnormal cleavage compared with those from IVF. This difference is most marked in women ≥35 years.

What is known already

Time lapse imaging (TLI) has been instrumental in allowing detailed annotation of early embryo development to provide an objective aid for embryo selection in ART cycles. Amongst several abnormal cleavage events reported, rapid cleavage and multichotomous mitosis/direct cleavage, during the first days after fertilisation have been demonstrated to be associated with lower blastulation rates, reduced implantation potential, increased aneuploidy and poor pregnancy outcomes. With ICSI being utilised commonly, and being the insemination method of choice in some clinics, the incidence of abnormal cleavage was investigated in association with insemination method, ICSI or IVF.

Study design, size, duration

The incidence of abnormal cleavage events was evaluated in a large multicentre retrospective analysis of 36,671 embryos from 6689 patients treated in 8 IVF clinics enabled with time lapse imaging, between 2011 - 2019. This constituted 10931 IVF embryos and 25740 ICSI embryos.

Participants/materials, setting, methods

Following ICSI or after IVF fertilisation check, embryos were time-lapse imaged every 10 minutes and annotated using the EmbryoScope. Second cell cycle durations were calculated as follows: time to reach 3-cell (t3) from 2-cell (t2) (t3-t2 = cc2). These were analysed using a welch t-test as three groups of abnormal cleavage: direct cleavage/trichotomous mitosis (DC) - where cc2=0 hours(h), rapid cleavage within 2h (R2) - where 0<cc2<2h and rapid cleavage between 2–5h (R5) where 2h<cc2<5h.

Main results and the role of chance

The incidence of DC, R2 and R5 in the whole cohort of embryos was 5%, 8% and 9% respectively. In the subpopulation of IVF embryos the incidence of DC, R2 and R5 was 4%, 8% and 9% respectively. In the subpopulation of ICSI embryos the incidence of DC, R2 and R5 was 6%, 8% and 9% respectively. The incidence of DC was significantly higher in ICSI embryos compared with IVF (p < 0.001) whilst R2 and R5 were the same. ICSI derived embryos had a mean (± SE) cc2 value of 9.39 ± 0.03h, compared with 9.56 ± 0.05h for IVF embryos (p < 0.0038). Examination of data split by maternal age demonstrated that ICSI oocytes from women of advanced maternal age (≥35) also had significantly more embryos exhibiting rapid cleavages R2 and R5 than IVF oocytes (p < 0.007). There were no significant differences however, in rates of abnormal cleavages between ICSI and IVF in embryos from women aged <30 (p = 0.06).

Male-factor diagnoses showed no significant differences in abnormal cleavage values between ICSI or IVF in all three abnormal cleavage categories.

Limitations, reasons for caution

This analysis could not control for all potential confounders therefore it is possible that the increased abnormal cleavages observed in this investigation are a result of another, or combination of factors. Despite quality assurance programs being in place across all clinics, there is a risk of annotation bias.

Wider implications of the findings: There is a higher incidence of early abnormal cleavage in embryos derived from ICSI, particularly in those from women of increased age and this research may help elucidate the reasons for this and add to the debate regarding the appropriateness of the increasing use of ICSI.

Trial registration number

Not applicable

Protein Phosphatase 5 Contributes to the Overexpression of Epigenetically Regulated T-Lymphocyte Genes in Patients with Lupus

OBJECTIVE

Lupus develops when genetically predisposed people encounter certain drugs or environmental agents causing oxidative stress such as infections and sun exposure, and then typically follows a chronic relapsing course with flares triggered by the exogenous stressors. Current evidence indicates that these environmental agents can trigger lupus flares by inhibiting the replication of DNA methylation patterns during mitosis in CD4⁺ T cells, altering the expression of genes suppressed by this mechanism that convert normal "helper" cells into auto reactive cells which promote lupus flares. How environmental stressors inhibit T cell DNA methylation though is incompletely understood. Protein phosphatase 5 (PP5) is a stress induced inhibitor of T cell ERK and JNK signaling in "senescent" CD4⁺CD28^- T cells, also characterized by DNA demethylation and altered expression of genes that promote atherosclerosis. We tested if PP5 is increased in CD4⁺CD28⁺ T cells by oxidative stress, if PP5 transfection causes overexpression of methylation sensitive genes in T cells, and if PP5 is overexpressed in lupus T cells.

RESULTS

PP5 was found to be overexpressed in CD4⁺CD28⁺ T cells treated with H₂O₂ and ONOO- and in T cells from lupus patients.

CONCLUSION

The results indicate that PP5 increases expression of methylation sensitive T cell genes, and may contribute to the aberrant gene expression in CD4⁺CD28⁺ T cells that characterize lupus flares as well as the aberrant gene expression in CD4⁺CD28^- T cells that promote atherosclerosis.

Maternal plasma and breastmilk viral loads are associated with HIV-1-specific cellular immune responses among HIV-1-exposed, uninfected infants in Kenya

Infants exposed to maternal HIV-1 provide an opportunity to assess correlates of HIV-1-specific interferon (IFN)-γ responses and may be informative in the development of HIV-1 vaccines. HIV-1-infected women with CD4 counts 200-500 cells/mm(3) were randomized to short-course zidovudine/nevirapine (ZDV/NVP) or highly active anti-retroviral therapy (HAART) between 2003 and 2005. Maternal plasma and breastmilk HIV-1 RNA and DNA were quantified during the first 6-12 months postpartum. HIV-1 gag peptide-stimulated enzyme-linked immunospot (ELISPOT) assays were conducted in HIV-1-exposed, uninfected infants (EU), and correlates were determined using regression and generalized estimating equations. Among 47 EU infants, 21 (45%) had ≥1 positive ELISPOT result during follow-up. Infants had a median response magnitude of 177 HIV-1-specific spot-forming units (SFU)/106 peripheral blood mononuclear cells (PBMC) [interquartile range (IQR)=117-287] directed against 2 (IQR = 1-3) gag peptide pools. The prevalence and magnitude of responses did not differ by maternal anti-retroviral (ARV) randomization arm. Maternal plasma HIV-1 RNA levels during pregnancy (P=0.009) and breastmilk HIV-1 DNA levels at 1 month (P=0.02) were associated with a higher magnitude of infant HIV-1-specific ELISPOT responses at 1 month postpartum. During follow-up, concurrent breastmilk HIV-1 RNA and DNA (cell-free virus and cell-associated virus, respectively) each were associated positively with magnitude of infant HIV-1-specific responses (P=0.01). Our data demonstrate the importance of antigenic exposure on the induction of infant HIV-1-specific cellular immune responses in the absence of infection.

Evaluating a federated medical search engine: tailoring the methodology and reporting the evaluation outcomes

BACKGROUND

Federated medical search engines are health information systems that provide a single access point to different types of information. Their efficiency as clinical decision support tools has been demonstrated through numerous evaluations. Despite their rigor, very few of these studies report holistic evaluations of medical search engines and even fewer base their evaluations on existing evaluation frameworks.

OBJECTIVES

To evaluate a federated medical search engine, MedSocket, for its potential net benefits in an established clinical setting.

METHODS

This study applied the Human, Organization, and Technology (HOT-fit) evaluation framework in order to evaluate MedSocket. The hierarchical structure of the HOT-factors allowed for identification of a combination of efficiency metrics. Human fit was evaluated through user satisfaction and patterns of system use; technology fit was evaluated through the measurements of time-on-task and the accuracy of the found answers; and organization fit was evaluated from the perspective of system fit to the existing organizational structure.

RESULTS

Evaluations produced mixed results and suggested several opportunities for system improvement. On average, participants were satisfied with MedSocket searches and confident in the accuracy of retrieved answers. However, MedSocket did not meet participants' expectations in terms of download speed, access to information, and relevance of the search results. These mixed results made it necessary to conclude that in the case of MedSocket, technology fit had a significant influence on the human and organization fit. Hence, improving technological capabilities of the system is critical before its net benefits can become noticeable.

CONCLUSIONS

The HOT-fit evaluation framework was instrumental in tailoring the methodology for conducting a comprehensive evaluation of the search engine. Such multidimensional evaluation of the search engine resulted in recommendations for system improvement.

Clinical and pathologic differences in interstitial lung disease based on antisynthetase antibody type

BACKGROUND

Interstitial lung disease (ILD) is a common extramuscular manifestation of the idiopathic inflammatory myopathies (IIMs), dermatomyositis (DM) and polymyositis (PM). Patients with antisynthetase antibodies (ASA) demonstrate some or all of the features of the antisynthetase syndrome including IIM and ILD. It has been hypothesized that the clinical expression of antisynthetase syndrome varies between specific ASAs.

OBJECTIVE

We sought to determine whether the myositis-associated ILD (MA-ILD) phenotype differs based on the presence of ASAs and by ASA subtype.

METHODS

A cross-sectional and longitudinal analysis of consecutive patients enrolled at the Johns Hopkins Myositis Center with ILD in the setting of clinically diagnosed autoimmune myositis was conducted.

RESULTS

Seventy-seven subjects were included; 36 were ASA negative, 28 were anti-Jo1 positive, and 13 were non-Jo1 ASA positive (5 anti-PL-12, 4 anti-PL-7, 2 anti-EJ, and 2 anti-OJ). Non-Jo1 ASA positive participants were more likely to be African-American than Caucasian as compared to both the anti-Jo1 positive (p = 0.01) and ASA negative groups (p < 0.01). ASA negative participants had better mean forced vital capacity percent predicted (FVC%) and total computed tomography scores over time compared to those with anti-Jo1 after controlling for potential confounders.

CONCLUSIONS

ASA status was significantly different by race. Those with anti-Jo1 antibodies had worse lung function and CT scores over time compared to those without detectable antisynthetase antibodies. Further prospective study in a larger cohort is needed to determine whether these apparent antibody-specific differences in demographics and manifestations of disease translate into meaningful disparities in clinical outcomes.

Relative efficiencies of the 7 rheumatoid arthritis Core Data Set measures to distinguish active from control treatments in 9 comparisons from clinical trials of 5 agents

The 7 Core Data Set measures to assess rheumatoid arthritis (RA) were analysed for their relative efficiencies to distinguish active from control treatments in 9 comparisons of 5 agents, methotrexate, leflunomide, infliximab, adalimumab, and abatacept, in 8 clinical trials. Among the 7 measures, levels of relative efficiencies were in a similar range, highest for the physician global estimate, followed by, in order, patient global estimate, physical function on a health assessment questionnaire (HAQ), pain, swollen joint count (SJC), an acute phase reactant laboratory test - erythrocyte sedimentation (ESR) or C-reactive protein (CRP), and tender joint count (TJC). Comparisons of only 3 measures, SJC and ESR/CRP (regarded as optimal indicators of inflammation) and HAQ function (regarded as most likely to be affected by joint damage and therefore least reversible) indicated relative efficiencies for HAQ function at least as great as for SJC or ESR/CRP, although 8 of the nine comparisons involved patients with disease duration > 6.9 years. The findings indicate a strong rationale for a Core Data Set of 7 measures, as no single measure was clearly superior in relative efficiency in all clinical trials. At the same time, 'objective' laboratory ESR/CRP, TJC and SJC were not superior to 'subjective' global estimates of the physician or patient or patient self-report measures of physical function or pain, to differentiate active from control treatments. The findings challenge a traditional view that laboratory and clinical examination findings are more robust than patient self-report scores and physician global estimates to assess and monitor RA patients.

Associations between child temperament, maternal feeding practices and child body mass index during the preschool years: a systematic review of the literature

It is a research priority to identify modifiable risk factors to improve the effectiveness of childhood obesity prevention strategies. Research, however, has largely overlooked the role of child temperament and personality implicated in obesogenic risk factors such as maternal feeding and body mass index (BMI) of preschoolers. A systematic review of relevant literature was conducted to investigate the associations between child temperament, child personality, maternal feeding and BMI and/or weight gain in infants and preschoolers; 18 papers were included in the review. The findings revealed an association between the temperament traits of poor self-regulation, distress to limitations, low and high soothability, low negative affectivity and higher BMI in infants and preschool-aged children. Temperament traits difficult, distress to limitations, surgency/extraversion and emotionality were significantly associated with weight gain rates in infants. The results also suggested that child temperament was associated with maternal feeding behaviours that have been shown to influence childhood overweight and obesity, such as using restrictive feeding practices with children perceived as having poor self-regulation and feeding potentially obesogenic food and drinks to infants who are more externalizing. Interestingly, no studies to date have evaluated the association between child personality and BMI/weight gain in infants and preschoolers. There is a clear need for further research into the association of child temperament and obesogenic risk factors in preschool-aged children.

Childhood cruelty to animals in China: the relationship with psychological adjustment and family functioning

BACKGROUND

The current study broadened the general scope of research conducted on childhood cruelty to animals by examining the association between psychological adjustment, family functioning and animal cruelty in an Eastern context, China.

METHOD

The mothers and fathers of 729 children attending primary school in Chengdu, China participated in this study. Each parent completed the Strengths and Difficulties Questionnaire, the Chinese Family Assessment Instrument, and the Children's Attitudes and Behaviours towards Animals questionnaire.

RESULTS

Findings from an actor partner interdependence model demonstrated that parents' ratings of family functioning and of their child's externalizing coping style predicted only modest amounts of variance in animal cruelty. In particular, parents' ratings of their child's externalizing coping style most consistently predicted animal cruelty. Family functioning, fathers' ratings in particular, played a minor role, more so for boys compared with girls.

CONCLUSION

This study provided the first insight into childhood animal cruelty in China, and suggests that further research may enhance our understanding of these phenomena.

Physics-Based Haptic Simulation of Bone Machining

We present a physics-based training simulator for bone machining. Based on experimental studies, the energy required to remove a unit volume of bone is a constant for every particular bone material. We use this physical principle to obtain the forces required to remove bone material with a milling tool rotating at high speed. The rotating blades of the tool are modeled as a set of small cutting elements. The force of interaction between a cutting element and bone is calculated from the energy required to remove a bone chip with an estimated thickness and known material stiffness. The total force acting on the cutter at a particular instant is obtained by integrating the differential forces over all cutting elements engaged. A voxel representation is used to represent the virtual bone and removed chips for calculating forces of machining. We use voxels that carry bone material properties to represent the volumetric haptic body and to apply underlying physical changes during machining. Experimental results of machining samples of a real bone confirm the force model. A real-time haptic implementation of the method in a dental training simulator is described.

Prevalence and risk factors for sexually transmitted infections in a high-risk occupational group: the case of fishermen along Lake Victoria in Kisumu, Kenya

The aim of this study was to assess prevalence and risk factors for sexually transmitted infections (STIs) among fishermen along Lake Victoria, Kenya. This cross-sectional study surveyed 250 fishermen from beaches in Kisumu District using proportional-to-size sampling based on the number of registered boats per beach. Participants provided demographic and sexual behaviour information, blood for HIV-1 herpes simplex virus type 2 (HSV-2) and syphilis serological tests urine for transcription-mediated amplification assays for Neisseria gonorrhoeae and Chlamydia trachomatis and penile and scrotal swabs for human papillomavirus (HPV) DNA assay. Consistent condom use with the three most recent sexual partners was reported by 30%; 38% reported concurrent sexual partnerships and 65% reported ever having transactional sex. HIV seroprevalence was 26%, HSV-2 seroprevalence by Western blot assay was 58% and 9.5% were rapid plasma reagin and Treponema pallidum particle agglutination assay positive. Genital HPV DNA of any type was detected in 57.2% with 74% of these having two or more HPV types. C. trachomatis and N. gonorrhoeae were detected in 3.2% and 1.2% respectively. Risk factors for syphilis seropositivity included working on multiple beaches during the past year (adjusted odds ratio [AOR] 3.81; 95% confidence interval [CI] 1.29–11.28). HPV infection was associated with owning a radio which is a marker for higher socioeconomic status (AOR 6.33; 95% CI 2.94–7.14) and reporting transactional sex with the most recent sexual partner (AOR 3.03; 95% CI 1.23–7.69). In conclusion, 90% of fishermen had evidence of one or more STIs. This exceptionally high-risk occupational group represents a high priority for preventive interventions.

Effects of nitrogen limitation on the growth and composition of unicellular algae in continuous culture

Since fat accumulation takes place in many algae as a response to exhaustion of the nitrogen supply, it has been suggested that this may provide a means of enhancing the potential food value of algae. To test this possibility, chemostatic continuous cultures of Chlorella sorokiniana and Oocystis polymorpha were subjected to successive reductions in influent nitrogen. As cellular nitrogen content decreased from about 10 to 4%, oxygen evolution, carbon dioxide uptake, chlorophyll content, and tissue production were drastically reduced, but total lipid content was essentially unchanged. Caloric values and C, H, and N analyses suggested a moderate increase in carbohydrate content, but gas chromatographic analyses revealed no significant qualitative or quantitative changes in the fatty acid fraction. In batch-cultured cells, nitrogen could be reduced to 3% of dry weight, causing a concomitant increase in total fatty acids and pronounced changes in the composition of the fatty acid fraction. These results suggest that cellular nitrogen must fall to approximately 3% of dry weight before appreciable increases in lipid synthesis can occur. Cell nitrogen is then apparently completely bound in essential cell constituents, and carbon subsequently fixed is converted into lipid products. The findings indicate that nitrogen limitation may be useful in increasing the food quality of batch-cultured cells, but the technique has little value for continuous culture systems per se.

Methylation of the OP-1 promoter: potential role in the age-related decline in OP-1 expression in cartilage

OBJECTIVE

An age-related decline in chondrocyte production of osteogenic protein-1 (OP-1) (Bone Morphogenetic Protein-7) may contribute to cartilage loss in osteoarthritis. This study was designed to determine if increased methylation of the OP-1 promoter might serve as a mechanism for the age-related decline in OP-1 expression.

METHODS

Human articular chondrocytes were isolated from cartilage obtained after death from tissue donors (ages 19-86 years) without a known history of arthritis. DNA was obtained from isolated chondrocytes in primary culture and analyzed for OP-1 promoter methylation by polymerase chain reaction (PCR) after bisulfite treatment. Cultured cells were treated with the DNA methyltransferase inhibitor 5-azacytidine and OP-1 production was measured in the media by enzyme-linked immunosorbent assay (ELISA). RNA was isolated to measure expression of insulin-like growth factor-1 (IGF-1), the IGF-1 receptor (IGF-1R), aggrecan, and OP-1 by real-time PCR.

RESULTS

Methylation of the OP-1 promoter was detected in chondrocytes isolated from tissue obtained from older adults and there was a positive correlation between age and OP-1 methylation status (n=22, R(2)=0.277, P=0.014). Inhibition of methylation in cultured cells with 5-azacytidine increased chondrocyte production of OP-1 protein and increased the expression of the IGF-1, the IGF-1R, aggrecan, and OP-1 genes but not GAPDH.

CONCLUSION

Age-related methylation of the OP-1 promoter may contribute to a decrease in OP-1 production in cartilage and a decrease in expression of OP-1 responsive genes such as IGF-1, the IGF-1R, and aggrecan.

PCR amplification of microsatellites from single cells of Karenia brevis preserved in Lugol's iodine solution

A simple and effective protocol is described for multiplex polymerase chain reaction (PCR) amplification of single cells of Karenia brevis. The protocol requires minimum processing, avoids additions that might dilute target DNA template, and can be used on cells preserved in Lugol's iodine preservative. Destaining of Lugol's-preserved cells with sodium thiosulfate allowed successful amplification of single-copy, nuclear-encoded microsatellites in single cells of K. brevis that have been preserved for up to 6 years.

Introducing a post-registration interprofessional learning programme for healthcare teams

INTRODUCTION

Few studies have evaluated interprofessional learning (IPL) and teamworking in active clinical teams. The aim of this study was to evaluate an IPL programme offered to established clinical teams by assessing team climate before, during and after the intervention.

METHODS

A previously validated questionnaire, that explored team members' views of team climate, was administered before the IPL programme, at four months following facilitated meetings, and again at eight months. Responses were analysed using one-sample and independent samples t-tests.

RESULTS

Nine teams, made up of 79 individuals, agreed to join the IPL programme. After four months, during which time the teams were supported by an educational facilitator, the overall team climate increased by 8.0% of the maximum possible score of the questionnaire (95% confidence interval = 7.4% to 8.6%). This difference was highly statistically significant (p-value <0.001) and similar increases in scores were seen in each section of the questionnaire. This significant change was sustained after a further four months when the programme continued without the support of an educational facilitator.

CONCLUSION

An IPL programme, such as the one described in this paper, can improve team climate and raise awareness of professional roles within established clinical teams.

Identification of two novel allelic variants of ESX1L in the human placenta: lack of an association with intrauterine growth restriction

Intrauterine growth restriction (IUGR) is a leading cause of neonatal morbidity and mortality. Although epidemiological studies implicate an important role for genetic factors in determining birth weight, few candidate genes for IUGR have been identified. ESX1L, the orthologue of Esx1, is an X chromosome-linked human homeobox gene expressed in the placenta and testis. The present study was undertaken to determine if aberrations in the ESX1L gene were associated with idiopathic IUGR because targeted deletion of Esx1 in the mouse leads to abnormal placental development and consequent IUGR. Genotyping analysis of ESX1L gene was performed on placental samples from 22 normal term and 12 IUGR term fetuses. Two allelic variants were identified, and they contain an insertion and a deletion, respectively, of the same 27 nucleotides in the highly repetitive region of exon-4 that encodes the previously identified 12 contiguous repeats of a unique 9-amino acid motif, PPMAP(V/L)PPG. Thus, the insertion and deletion variants were predicted to code for an aberrant ESX1L protein containing 13 and 11 contiguous repeats, respectively. However, both variants were detectable and evenly distributed in normal as well as IUGR placentae, indicating that these two variants of ESX1L do not contribute to genetic susceptibility to idiopathic IUGR. Furthermore, no single nucleotide polymorphisms were identified, and there was no difference in the level of ESX1L mRNA between control and IUGR placentae. Taken together, these findings provide the first evidence that two allelic variants of ESX1L exist in the human placenta but they are not associated with idiopathic IUGR.

Implementing home care in Canada: four critical elements

While MacAdam proposes a "national approach to home care#8221; the obstacles to this are well known and substantial. They are the likely cost and the limitations of the federal government s role in healthcare. Building on MacAdam's assessment, this paper outlines four problems embedded in the various home-care service delivery models in Canada: the lack of factual client outcome information to support decision-making, the limited client choice of provider, the perverse incentive of fee for service and the bias against the for-profit provider. The paper proposes that the assessment, classification and measurement of outcomes for every recipient of home-care services be standardized using a proven assessment instrument, such as OASIS-B or MDS-HC, by healthcare professionals certified in its use. The resulting information would be captured in a regional database and available for analysis and research. CIHI would be contracted to manage a national database and to fund the training and certification of assessors. The paper proposes a new service delivery and funding model, utilizing standard client outcome information, different roles for regional health authorities and service providers, and a prospective payment mechanism replacing fee for service. A national home care program may be an elusive dream, but that shouldn't stop experimentation, evaluation and improvement.

Autoreactive murine Th1 and Th2 cells kill syngeneic macrophages and induce autoantibodies

D10 cells, a cloned Th2 line, become autoreactive following treatment with DNA methylation inhibitors like 5-azacytidine (5-azaC), and induce anti-DNA antibodies if injected into unirradiated syngenic mice. The mechanism by which the autoreactive cells break tolerance is unknown. To further define effector functions required, we asked if 5-azaC-treated Th1 cells could also induce autoimmunity. AE7 cells, a cloned Th1 line, were treated with 5-azaC and shown to become autoreactive and induce anti-DNA antibodies in vivo. Comparison of effector mechanisms demonstrated that the two cell lines secreted a distinct repertoire of cytokines, and that only killing of syngeneic Mø was common to both AE7 and D10 cells. This suggests that Mø killing may be an early step in the induction of anti-DNA antibodies, providing antigenic nucleosomes and decreasing clearance of apoptotic material. Secretion of cytokines promoting B cell differentiation may play a role, but no one cytokine is required.

Estimating the efficacy of interventions to prevent mother-to-child transmission of HIV in breast-feeding populations: development of a consensus methodology

Postnatal transmission of HIV through breast milk complicates both the design of effective interventions to prevent mother-to-child transmission of HIV (PMTCT) and their evaluation. Estimated long-term efficacy in five African trials (four with peri-partum antiretrovirals and one with artificial feeding) varied from 25 to 50 per cent. This variation may be due, at least in part, to differences in analytical methodology. To facilitate direct comparison between trials, a methodological consensus approach to the analysis and presentation of the results of PMTCT trials was developed. The initial methodology used and results presented from African trials with available long-term efficacy data were reviewed during a workshop in Bordeaux, France, in September 2000. A consensus approach for evaluating efficacy applicable across PMTCT studies was developed. There are four typical situations defined by duration of follow-up (short versus long), and the available demographic (vital status) and biological data (single versus repeat HIV testing). Efficacy can be assessed from the risk of infection directly or from HIV-free survival by combining infection and death as a single endpoint. Studies should report results in a standardized format including infection, weaning, mortality and loss to follow-up. New statistical methods that account for the unknown date when a child would first test positive for HIV, for weaning as a competing risk for HIV infection, and for increased risk of death among HIV-infected children should be used in analysing data from PMTCT studies with repeat HIV testing. All estimates should be reported with confidence intervals. This standardized methodology that allows direct comparison between studies is now being applied to four randomized clinical trials.