Bridging preference-based instrumental variable studies and cluster-randomized encouragement experiments: Study design, noncompliance, and average cluster effect ratio

Instrumental variable (IV) methods are widely used in medical research to draw causal conclusions when the treatment and outcome are confounded by unmeasured confounding variables. One important feature of such studies is that the IV is often applied at the cluster level, for example, hospitals' or physicians' preference for a certain treatment where each hospital or physician naturally defines a cluster. This paper proposes to embed such observational IV data into a cluster-randomized encouragement experiment using nonbipartite matching. Potential outcomes and causal assumptions underpinning the design are formalized and examined. Testing procedures for two commonly used estimands, Fisher's sharp null hypothesis and the pooled effect ratio (PER), are extended to the current setting. We then introduce a novel cluster-heterogeneous proportional treatment effect model and the relevant estimand: the average cluster effect ratio. This new estimand is advantageous over the structural parameter in a constant proportional treatment effect model in that it allows treatment heterogeneity, and is advantageous over the PER estimand in that it does not suffer from Simpson's paradox. We develop an asymptotically valid randomization-based testing procedure for this new estimand based on solving a mixed-integer quadratically constrained optimization problem. The proposed design and inferential methods are applied to a study of the effect of using transesophageal echocardiography during coronary artery bypass graft surgery on patients' 30-day mortality rate. R package ivdesign implements the proposed method.

Hemoglobin Levels Among Male Agricultural Workers: Analyses From the Demographic and Health Surveys to Investigate a Marker for Chronic Kidney Disease of Uncertain Etiology

OBJECTIVE

Estimate agricultural work's effect on hemoglobin (Hgb) level in men. A negative effect may indicate presence of chronic kidney disease of uncertain etiology.

METHODS

We use Demographic and Health Surveys data from seven African and Asian countries and use matching to control for seven confounders.

RESULTS

On average, Hgb levels were 0.09 g/dL lower among agricultural workers compared with matched controls. Significant effects were observed in Ethiopia, India, Lesotho, and Senegal, with effects from 0.07 to 0.30 g/dL lower Hgb level among agricultural workers. The findings were robust to multiple control groups and a modest amount of unmeasured confounding.

CONCLUSIONS

Men engaged in agricultural work in four of the seven countries studied have modestly lower Hgb levels. Our data support integrating kidney function assessments within Demographic and Health Surveys and other population-based surveys.

Testing Biased Randomization Assumptions and Quantifying Imperfect Matching and Residual Confounding in Matched Observational Studies

One central goal of design of observational studies is to embed non-experimental data into an approximate randomized controlled trial using statistical matching. Despite empirical researchers' best intention and effort to create high-quality matched samples, residual imbalance due to observed covariates not being well matched often persists. Although statistical tests have been developed to test the randomization assumption and its implications, few provide a means to quantify the level of residual confounding due to observed covariates not being well matched in matched samples. In this article, we develop two generic classes of exact statistical tests for a biased randomization assumption. One important by-product of our testing framework is a quantity called residual sensitivity value (RSV), which provides a means to quantify the level of residual confounding due to imperfect matching of observed covariates in a matched sample. We advocate taking into account RSV in the downstream primary analysis. The proposed methodology is illustrated by re-examining a famous observational study concerning the effect of right heart catheterization (RHC) in the initial care of critically ill patients. Code implementing the method can be found in the supplementary materials.

Relationship between changing malaria burden and low birth weight in sub-Saharan Africa: A difference-in-differences study via a pair-of-pairs approach

Background

According to the World Health Organization (WHO), in 2018, an estimated 228 million malaria cases occurred worldwide with most cases occurring in sub-Saharan Africa. Scale-up of vector control tools coupled with increased access to diagnosis and effective treatment has resulted in a large decline in malaria prevalence in some areas, but other areas have seen little change. Although interventional studies demonstrate that preventing malaria during pregnancy can reduce the rate of low birth weight (i.e. child's birth weight <2500 g), it remains unknown whether natural changes in parasite transmission and malaria burden can improve birth outcomes.

Methods

We conducted an observational study of the effect of changing malaria burden on low birth weight using data from 18,112 births in 19 countries in sub-Saharan African countries during the years 2000-2015. Specifically, we conducted a difference-in-differences study via a pair-of-pairs matching approach using the fact that some sub-Saharan areas experienced sharp drops in malaria prevalence and some experienced little change.

Results

A malaria prevalence decline from a high rate (Plasmodium falciparum parasite rate in children aged 2-up-to-10 (i.e. PfPR2-10) > 0.4) to a low rate (PfPR2-10 < 0.2) is estimated to reduce the rate of low birth weight by 1.48 percentage points (95% confidence interval: 3.70 percentage points reduction, 0.74 percentage points increase), which is a 17% reduction in the low birth weight rate compared to the average (8.6%) in our study population with observed birth weight records (1.48/8.6 ≈ 17%). When focusing on first pregnancies, a decline in malaria prevalence from high to low is estimated to have a greater impact on the low birth weight rate than for all births: 3.73 percentage points (95% confidence interval: 9.11 percentage points reduction, 1.64 percentage points increase).

Conclusions

Although the confidence intervals cannot rule out the possibility of no effect at the 95% confidence level, the concurrence between our primary analysis, secondary analyses, and sensitivity analyses, and the magnitude of the effect size, contribute to the weight of the evidence suggesting that declining malaria burden can potentially substantially reduce the low birth weight rate at the community level in sub-Saharan Africa, particularly among firstborns. The novel statistical methodology developed in this article-a pair-of-pairs approach to a difference-in-differences study-could be useful for many settings in which different units are observed at different times.

Funding

Ryan A. Simmons is supported by National Center for Advancing Translational Sciences (UL1TR002553). The funder had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Perioperative intravenous contrast administration and the incidence of acute kidney injury after major gastrointestinal surgery: prospective, multicentre cohort study

BACKGROUND

This study aimed to determine the impact of preoperative exposure to intravenous contrast for CT and the risk of developing postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery.

METHODS

This prospective, multicentre cohort study included adults undergoing gastrointestinal resection, stoma reversal or liver resection. Both elective and emergency procedures were included. Preoperative exposure to intravenous contrast was defined as exposure to contrast administered for the purposes of CT up to 7 days before surgery. The primary endpoint was the rate of AKI within 7 days. Propensity score-matched models were adjusted for patient, disease and operative variables. In a sensitivity analysis, a propensity score-matched model explored the association between preoperative exposure to contrast and AKI in the first 48 h after surgery.

RESULTS

A total of 5378 patients were included across 173 centres. Overall, 1249 patients (23·2 per cent) received intravenous contrast. The overall rate of AKI within 7 days of surgery was 13·4 per cent (718 of 5378). In the propensity score-matched model, preoperative exposure to contrast was not associated with AKI within 7 days (odds ratio (OR) 0·95, 95 per cent c.i. 0·73 to 1·21; P = 0·669). The sensitivity analysis showed no association between preoperative contrast administration and AKI within 48 h after operation (OR 1·09, 0·84 to 1·41; P = 0·498).

CONCLUSION

There was no association between preoperative intravenous contrast administered for CT up to 7 days before surgery and postoperative AKI. Risk of contrast-induced nephropathy should not be used as a reason to avoid contrast-enhanced CT.

Analytical and field evaluation of the Biocentric Generic HCV assay on open polyvalent PCR platforms in France and Cambodia

BACKGROUND

Implementation of affordable methods for HCV viremia is a key priority for identifying individuals who need treatment among persons screened positive for HCV antibodies. Different HCV PCR assays for use on open polyvalent PCR platforms are currently commercially available but studies evaluating the performances of these nucleic acid tests are needed.

OBJECTIVES

In the present study, we evaluated the analytical and clinical performances of a recently developed HCV RNA PCR assay for detection and quantification of HCV viremia.

STUDY DESIGN

In this study the Biocentric Generic HCV PCR was compared to the Roche Cobas AmpliPrep/Cobas TaqMan HCV RNA assay. Analytical and clinical performances was evaluated on reference materials and HCV plasma samples collected in 141 patients attending at the Montpellier University Hospital in France. Field evaluation was performed on samples collected in 185 patients attending at Medical Laboratory, Institut Pasteur in Cambodia.

RESULTS

The lower limit of detection ranged from 50 HCV RNA IU/ml to 300 HCV RNA IU/ml using four different Diasorin and Qiagen automated or manual extraction methods. The specificity (CI) and sensitivity of the assay were 100% (92.5-100), and 98.7% (92.3-99.9), respectively, in France, and 100% (95.5-100), and 100% (94.4-100%), respectively, in Cambodia. Bland-Altman analysis shown good agreement between the two assays including for genotypes 6 HCV, which represent the majority of HCV isolates in Cambodia.

CONCLUSIONS

The Biocentric Generic HCV assay has shown overall satisfactory analytical performances and a close agreement to the Cobas HCV assay on clinical specimens collected in France and Cambodia. There is an urgent need to further evaluate commercial assays dedicated to HCV detection and quantification using open polyvalent PCR platforms in different settings.

153 Fertilisation of Cattle Oocytes is Linked to Novel Waves of a Ca2+ Fluorophore in Cumulus Cells

During fertilization, multiple intracellular calcium (Ca2+) oscillations are initiated after sperm binding to the oocyte vitelline membrane. This Ca2+ signalling has been extensively studied in denuded mouse and Xenopus oocytes but minimally studied in larger mammals. Cows in particular are unusual, as the few studies on oocyte activation have observed fewer Ca2+ oscillations during fertilisation compared with mice. Furthermore, cattle intracytoplasmic sperm injection (ICSI) is inefficient, despite parthenogenetic activation occurring readily. We hypothesise that cumulus cells are important for cattle oocyte activation at fertilisation. Here, we assessed the behaviour of Ca2+oscillations in fertilising intact cattle cumulus–oocyte complexes (COC). Abattoir-derived cattle COC were matured and fertilised in vitro using Bovine Vitro Media Suite (IVF Vet Solutions). The COC were stained 3.5 h after insemination with the Ca2+ fluorescent probe Fluo4AM (5 μM, Molecular Probes Inc., Eugene, OR, USA) for 30 min, washed, and imaged every 5 min for 6 h in a Fluoview FV10i incubating time-lapse confocal microscope (Olympus) before being returned to culture. Embryo development was assessed at Day 8 to confirm fertilisation. Fluo4AM fluorescence intensity was assessed using FIJI ImageJ. Mean relative intensity over time was graphed for specific regions of interest and the area under graphs was calculated to quantify differences for comparison using a Mann-Whitney Test (mean ± SEM). Experiment 1 (4 reps of 10 COC) compared confirmed fertilised v. uninseminated; experiment 2 (2 reps of 10 COC) compared inseminated COC ± 10 μM BAPTA-AM (Ca2+ chelator, Sigma-Aldrich, St. Louis, MO, USA). There were distinct coordinated waves of differing Fluo4AM intensity in both the oocyte and the cumulus cells surrounding the confirmed fertilised oocytes. This contrasted to the random uncoordinated flashes of Fluo4AM fluorescence in the cumulus cells of the uninseminated oocytes. The fluorescence pattern in +BAPTA-AM COC matched the random flashes observed in the uninseminated group of experiment 1. The fluorescence in the media surrounding the COC immediately following the Fluo4AM waves spiked and then plateaued at a higher level of fluorescence. This was quantified by assessing the area under the graph for 1 h of the plateau following the fluorescence spike. There were no differences between confirmed fertilised (346.4 ± 41.62) and uninseminated groups (239.8 ± 32.08; P > 0.05), but this was affected by differences in cumulus dispersal due to the presence or absence of sperm. Experiment 2 used BAPTA-AM to block oocyte activation with sperm present in both groups and showed a significant difference between the fluorescence increase in the media of the 2 groups (–BAPTA-AM: 311.2 ± 31.57, +BAPTA-AM: 201.4 ± 26.59; P < 0.03). Although the physiological significance has yet to be determined, we have observed a novel Ca2+ wave in the cumulus cells that could be linked to oocyte activation in cattle. There was a significant increase in Fluo4AM fluorescence in the media surrounding the COC, which may indicate cumulus cells are releasing Ca2+ at the time of oocyte activation.

Can phoretic particles swim in two dimensions?

Artificial phoretic particles swim using self-generated gradients in chemical species (self-diffusiophoresis) or charges and currents (self-electrophoresis). These particles can be used to study the physics of collective motion in active matter and might have promising applications in bioengineering. In the case of self-diffusiophoresis, the classical physical model relies on a steady solution of the diffusion equation, from which chemical gradients, phoretic flows, and ultimately the swimming velocity may be derived. Motivated by disk-shaped particles in thin films and under confinement, we examine the extension to two dimensions. Because the two-dimensional diffusion equation lacks a steady state with the correct boundary conditions, Laplace transforms must be used to study the long-time behavior of the problem and determine the swimming velocity. For fixed chemical fluxes on the particle surface, we find that the swimming velocity ultimately always decays logarithmically in time. In the case of finite Péclet numbers, we solve the full advection-diffusion equation numerically and show that this decay can be avoided by the particle moving to regions of unconsumed reactant. Finite advection thus regularizes the two-dimensional phoretic problem.

Crowned spiropyran fluoroionophores with a carboxyl moiety for the selective detection of lithium ions

The absorbance and fluorescence spectra of carboxylated spiropyrans containing methyl-1-aza-12-crown-4, methyl-1-aza-15-crown-5, methyl-1-aza-18-crown-6 moieties are compared in the presence of alkali metal ions.

Formation of Organic Molecular Nanocrystals under Rigid Confinement with Analysis by Solid State NMR

Crystallization in rigid confinement is a promising method to obtain organic molecular nanocrystals. However, the crystallization behavior and the related characterization methods are not well studied. Here we present a systematic study of the nucleation of organic molecular nanocrystals in rigid pores. Four different compounds were studied, ibuprofen, fenofibrate, griseofulvin, and indomethacin, which range from simple to complex molecules. Solid-state Nuclear Magnetic Resonance (NMR) was employed to analyse the structure of these compounds inside pores which are difficult to characterize by other analytical methods. We successfully demonstrated the production of nano-crystalline ibuprofen, fenofibrate and griseofulvin in porous silica particles with ~ 40 nm pores. These nanocrystals showed significant enhancement in dissolution rates. These results help advance the fundamental understanding of nucleation under rigid confinement and may lead to potential applications in developing new formulations in the pharmaceutical industry.

156. IDENTIFICATION OF SCAFFOLDING PROTEINS AS PC6 SUBSTRATES IN THE HUMAN ENDOMETRIAL EPITHELIAL CELLS FOR EMBRYO IMPLANTATION

Successful embryo implantation is an important step in establishing pregnancy, which requires a healthy embryo and a receptive endometrium. Establishment of endometrial receptivity involves morphological and physiological changes initially in the endometrial epithelium, however the underlying molecular mechanisms are not fully understood. We have previously demonstrated that proprotein convertase 5/6 (PC6), a member of the proprotein convertase (PC) family, is up-regulated in the endometrium specifically at implantation in association with epithelial differentiation in the human and monkey. PCs convert a range of precursor proteins of important functions into their bioactive forms, they are thus regarded as critical ‘master switch’ molecules. The aim of this study was to identify target proteins of PC6 in the endometrial epithelial cells important for implantation. We used a HEC1A cell line in which PC6 was stably knocked down by siRNA approach (HEC1A-PC6). HEC1A cells that were similarly transfected with a scrambled siRNA sequence (HEC1A-control) were used as the control. Previous study confirmed that HEC1A-PC6 cells had much reduced capacity to adhere to blastocyst. A proteomic comparison between HEC1A-PC6 treated with or without human recombinant PC6 identified ezrin as a potential PC6 substrate. Ezrin is a cytoplasmic protein which is known to bind to ezrin-radixin-moesin-binding phosphoprotein 50 (EBP50) thereby translocating to the plasma membrane.This complex has been associated with cytoskeletal re-organisation and changes in cell polarity. Co-immunoprecipitation of ezrin and EBP50 showed that knockdown of PC6 allowed the binding of ezrin to the C-terminus of EBP50 in HEC1A-PC6, whereas PC6 cleavage of EBP50 in HEC1A-control prevented the binding. This was also confirmed by immunofluorescence showing that ezrin and EBP50 were co-localized to the plasma membrane in HEC1A-PC6. This study thus identified that PC6 regulates scaffolding proteins such as EBP50 and ezrin in the endometrium for embryo implantation.

A description of influenza-like illness (ILI) sentinel surveillance in Cambodia, 2006-2008

Influenza-Like Illness (ILI) sentinel surveillance was initiated by the Communicable Disease Control Department (CDC), Ministry of Health, Cambodia and its partners to evaluate the epidemiology of influenza and identify the circulating strains. The surveillance started in late 2006 in four sentinel sites. The objectives of this study were 1) to document the incidence of LI and confirmed influenza cases reported in the national surveillance system from 2006 to 2008, just after the system and the definition were revised, 2) to identify the strains of influenza virus, 3) to compare the major demographic and clinical characteristics between ILI patients having positive and negative tests for influenza virus. An ILI case was defined as having a fever of at least 38 degrees C (axillary), cough or sore throat. A total of 155,866 ILI cases were reported to the CDC from 4 sentinel sites in Cambodia from August 2006 to December 2008. Specimens were collected in 1.8%. Of these, 9.6% tested positive for influenza. Influenza was observed to occur mainly from August to December, with a clear seasonal peak in October, as shown in the data from 2008. A new case definition beginning in August 2008 resulted in a decrease in weekly RI reported cases (from an average of 1,474 cases to 54 cases) and the proportion of positive tests for influenza increased (5.3% vs 29.3%). Influenza and ILI are seasonal in Cambodia. A higher body temperature was used to define ILI, which improved the influenza positivity rates.

166. EMBRYO IMPLANTATION IS ASSOCIATED WITH SPECIFIC EXPRESSION OF PROPROTEIN CONVERTASE 6 IN THE RABBIT UTERUS

Proprotein convertase 5/6 (PC6) is a member of the proprotein convertase family that endoproteolytically cleave latent precursor proteins into their biologically active state. We have previously demonstrated that endometrial PC6 is critical for embryo implantation in mice and primates, including human. PC6 regulates the endometrial physiology specifically at implantation in association with epithelial differentiation during the establishment of endometrial receptivity (in human and monkey) and stromal cell decidualization (in the mouse, human and monkey). PC6 was further confirmed to be a unique PC member that is tightly regulated in the endometrium in relation to implantation. Our further studies (unpublished) suggest that PC6 regulates adhesion molecules in the endometrial epithelium for implantation in women. It is known that between the mouse and human, the endometrial stroma-mediated responses are similar whereas the epithelial cells behave differently. Because PC6 regulates primarily the stromal component (decidualization) in the mouse, in vivo mouse models are critical to investigate the roles of PC6 in decidualization. To address the function of PC6 in endometrial epithelium, non-mouse models relevant to human implantation are required. The rabbit is regarded as an excellent model to study the molecular events of embryo adhesion and attachment. The current study aimed to determine the expression pattern and localisation of PC6 in the rabbit uterus during early pregnancy. Quantitative RT-PCR analysis showed that PC6 mRNA expression was dynamically up-regulated in the rabbit uterus immediately prior to implantation. Western blotting and immunohistochemical analyses demonstrated that PC6 protein was predominantly localised to the basal glands throughout pregnancy, and up-regulated specifically in the epithelium at the embryo attachment site. These findings suggest that PC6 may play an essential role in rabbit implantation, and that the rabbit is a useful animal model to investigate the function of PC6 during embryo attachment.

529. PROPROTEIN CONVERTASE 6 PLAYS A CRITICAL ROLE IN MODULATING THE HUMAN ENDOMETRIAL EPITHELIUM FOR RECEPTIVITY AND IMPLANTATION

Successful embryo implantation is an important step in establishing pregnancy, requiring a healthy embryo and a receptive endometrium. Establishment of endometrial receptivity involves morphological and physiological changes initially in the endometrial epithelium, but the underlying molecular mechanisms are not fully understood. We have previously demonstrated that proprotein convertase 5/6 (PC6), a member of the proprotein convertase (PC) family, is up-regulated in the endometrium specifically at implantation in association with epithelial differentiation, in the human and monkey. PCs convert a range of precursor proteins of important functions into their bioactive forms; they are thus regarded as critical “master switch” molecules. The present study aimed to determine whether PC6 is a critical regulator in the endometrial epithelium for receptivity and implantation. We examined whether endometrial epithelial PC6 dys-regulation is associated with implantation failure in women and whether knockdown of PC6 by siRNA in human endometrial epithelial cells affects embryo adhesion in a cell culture model. Endometrial PC6 expression was assessed by immunohistochemistry in the mid-secretory phase of the menstrual cycle (receptive phase) in two unique clinical cohorts comprising women of known fertility and infertility (with no obvious gynecological disorders, and with fertile males). Endometrial epithelial PC6 levels were significantly lower in infertile vs fertile women in both cohorts. To further establish that PC6 is important for receptivity, a cell model relevant to human implantation was used involving co-culture of uterine epithelial cells with mouse embryos. The epithelial cells were stably transfected with PC6 siRNA and PC6 knock down was confirmed at the levels of mRNA, protein, and activity by real-time RT-PCR, Western blotting and activity assay respectively. Embryos readily adhered to normal epithelial cells, but the adhesion was significantly reduced in the PC6 knockdown epithelial cells. We are currently using proteomics technology to identify the pathways affected by PC6 knockdown. These results strongly suggest that PC6 plays a critical role in modulating the human endometrial epithelium for receptivity and implantation.

175. THE ROLE OF PROPROTEIN CONVERTASE 6 DURING DECIDUALIZATION: REGULATION OF BONE MORPHOGENETIC PROTEIN 2 ACTIVATION

Proprotein convertase 5/6 (PC6), a member of the proprotein convertase (PC) family, is a critical endometrial factor for implantation. PC6 is up-regulated in the endometrium specifically at implantation in association with epithelial differentiation (in human and monkey) and stromal cell decidualization (in the mouse, human and monkey). PC6 is the only PC member that was significantly up-regulated during decidualization. Knockdown of PC6 inhibits decidualization. PCs function by converting a range of important precursor proteins into their bioactive forms. One group of such proteins is the transforming growth factor beta (TGF-beta) superfamily proteins. They are first synthesized as larger biologically inactive precursors, and then are processed by PCs into their active forms. Bone morphogenetic protein 2 (BMP2) is a TGF-beta superfamily member and demonstrated to be essential for decidualization. We hypothesized that BMP2 is one of the proteins that PC6 activates during decidualization. Freshly isolated stromal cells from human endometrium were decidualized in culture with and without inhibition of PC6 activity. The full-length (precursor, non-active) and processed (activated) forms of BMP2 were determined in cellular lysates and media. The precursor form of BMP2 was reduced whereas the active form was increased during decidualization. Inhibition of PC6 activity inhibited decidualization, and this inhibition was accompanied by a total inhibition of the production of active BMP2. To further confirm the role of PC6 in activating BMP2 in decidualization, active BMP2 was added into cells and the decidualization arrest caused by PC6 inhibition was partially rescued. This study demonstrated that PC6 regulates decidualization by activating molecules such as BMP2 that are essential for decidualization.

Etiology of acute lower respiratory tract infection in children at Srinagarind Hospital, Khon Kaen, Thailand

We investigated the etiology of acute lower respiratory infection (ALRI) in children under 5 admitted to Srinagarind Hospital. The causative bacteria and viruses were determined by hemoculture and viral isolation from blood and nasopharyngeal aspirate samples. Antigens of respiratory syncytial virus (RSV) and Chlamydia trachomatis were detected using EIA. The 74 children less than 5 years of age with ALRI enrolled in our study were diagnosed with pneumonia (75.7%), croup (16.2%), and bronchiolitis (8.1%), respectively. Examination of blood or nasopharyngeal aspirate revealed viral or bacterial infections in 26 and 22 cases, respectively, whereas 5 of the children aged under 1 year (10%) were diagnosed with pneumonia caused by Chlamydia trachomatis. RSV was the most common virus detected (24.3%) and was associated with pneumonia and bronchiolitis, while the parainfluenza virus was the primary cause of croup. In cases of pneumonia, bacterial infections were identified in almost all of the cases: and Streptococcus pneumoniae and Haemophilus influenzae were the most commonly isolated (at 8.9% each). Mixed infections were detected in 8 cases (10.8%). The incidence of RSV infection peaked during the especially warm and cool seasons, whereas the bacterial infections were primarily associated with the relatively cool season. Our study indicates that a combined pneumococcal and Hib vaccine and a RSV vaccine would reduce the high rate of pneumonia in children under 5 years of age in Northeast Thailand.

Survey of the prevalence of asthma, allergic rhinitis and eczema in schoolchildren from Khon Kaen, Northeast Thailand. an ISAAC study. International Study of Asthma and Allergies in Childhood

This survey of schoolchildren from Khon Kaen, Northeast Thailand used the standardized ISAAC questionnaires to estimate the prevalence of asthma and other allergic diseases and to compare the results with two previous studies. A total of 6,068 questionnaires were analyzed (2,658, 45.6% males from the 6 to 7 years old group and 3,410, 49.5% male from the 13 to 14 years old group). The three predominant cumulative and 12-month conditions discerned from the written questionnaires among the 6 to 7 vs 13 to 14 years old were: wheezing, at 18.6% and 10.2% vs 20.5% and 11.0%; rhinitis at 38.4% and 33.5% vs 59.4% and 42.5%; and eczema at 18.0% and 15.2% vs 9.9% and 7.4%, respectively. The observed prevalences in our study were similar to those found in Bangkok and slightly higher than those in Chiang Mai, except for 'exercise wheezing' in older children which was two times higher in our study than in the two previous studies. Our study showed seasonal variation of the 'nose' symptoms. The peak prevalence was in the relatively cool and dry season (between November and January), which was the same pattern as Chiang Mai but different from Bangkok (which had a perennial pattern and less climatic variation). Our results concurred with the two previous Thai ISAAC studies. There is a high prevalence of asthma and other allergic diseases among Thai children and there has been a four-fold increase in symptoms since the last decade. If the trend persists asthma and allergic disease may become a pressing health concern of the country.

Behavioural and serological human immunodeficiency virus risk factors among female commercial sex workers in Cambodia

BACKGROUND

The spread of human immunodeficiency virus (HIV) in Cambodia is mainly caused by sexual transmission and the high-risk group in this country are female commercial sex workers (CSW). There are two types of CSW, direct CSW (DCSW) and indirect CSW (IDCSW), who are different from each other in sexual activities. This study was conducted in order to describe the risk factors on HIV for each type of CSW, and to establish effective preventive strategies against the HIV epidemic among CSW.

METHODS

The participants, 143 DCSW and 94 IDCSW, were interviewed using a questionnaire to determine their demographic characteristics and behaviour. Blood samples were taken for serological tests on HIV, Chlamydia trachomatis and syphilis. The association between their behavioural pattern and their serological results was analysed.

RESULTS

The questionnaire study showed that IDCSW had a riskier behavioural pattern than DCSW. The HIV seroprevalence rates of the DCSW and the IDCSW were 52.4% and 22.3%, respectively. Univariate logistic analyses showed a significant association between HIV antibody (HIV-Ab) and current age, age at commencement of commercial sex work, duration of commercial sex work, and the seropositivity of Chlamydia trachomatis-IgG antibody (CT-IgG-Ab) among the DCSW. The analyses also showed a significant relationship between HIV-Ab and CT-IgG-Ab among the IDCSW.

CONCLUSIONS

Improving condom use rate is very important in order to prevent an HIV epidemic among the two types of CSW. This study also suggests it is important to prevent sexually transmitted disease (STD) such as Chlamydia trachomatis infection. The STD control programme could be efficient for HIV prevention, especially among DCSW.

Cross-sectional study on risk factors of HIV among female commercial sex workers in Cambodia

To describe epidemiological features on HIV prevalence among female commercial sex workers (CSWs), a cross-sectional study on sexual behaviour and serological prevalence was carried out in Cambodia. The CSWs were interviewed on their demographic characters and behaviour and their blood samples were taken for testing on sexually transmitted diseases, including HIV, Chlamydia trachomatis, syphilis, and hepatitis B. Associations between risk factors and HIV seropositivity were analysed. High seroprevalence of HIV and Chlamydia trachomatis IgG antibody (CT-IgG-Ab) was shown among the CSWs (54 and 81.7%, respectively). Univariate logistic regression analyses showed an association between HIV seropositivity and age, duration of prostitution, the number of clients per day and CT-IgG-Ab. Especially, high-titre chlamydial seropositivity showed a strong significant association with HIV prevalence. In multiple logistic regression analyses, CT-IgG-Ab with higher titre was significantly independently related to HIV infection. These suggest that existence of Chlamydia trachomatis is highly related to HIV prevalence.