A tool to assess knowledge, attitude and behavior of Indonesian health care workers regarding infection control.

AIM: to investigate knowledge, attitude and behaviour toward infection control in two teaching hospitals on the island of Java by means of a questionnaire and to evaluate the use of the questionnaire as a tool. METHODS: we investigated knowledge, attitude and behaviour toward infection control in two teaching hospitals on the island of Java by means of a questionnaire to identify problem areas, barriers and facilitators. The target was to include at least 50% of all health care workers (physicians, nurses, assistant nurses and infection control nurses) in each hospital, department and profession. Differences between demographic variables and scores for individual questions and groups of questions were compared using the chi-square statistic and analysis of variance and Spearman's rho was used to test for correlations between knowledge, attitude, self-reported behaviour and perceived obstacles. RESULTS: more than half of the health care workers of the participating departments completed the questionnaire. Of the 1036 respondents (44% nurses, 37% physicians and 19% assistant nurses), 34% were vaccinated against hepatitis B, 77% had experienced needle stick accidents and 93% had been instructed about infection control. The mean of the correct answers to the knowledge questions was 44%; of the answers to the attitude questions 67% were in agreement with the correct attitude; obstacles to compliance with infection control guidelines were perceived in 30% of the questions and the mean self-reported compliance was 63%. Safe handling of sharps, hand hygiene and the use of personal protective equipment were identified as the most important aspects for interventions. Significant positive correlations were found between knowledge, attitude, self-reported behaviour and perceived obstacles. CONCLUSION: the questionnaire in conjunction with site visits and interviews was a valuable strategy to identify trouble spots in the hospitals and to determine barriers to facilitators of change that should be taken into account when planning interventions. Successful interventions should cover hospital management, the infection control team, as well as the health care workers on the wards.

In search of hidden Q-fever outbreaks: linking syndromic hospital clusters to infected goat farms.

Large Q-fever outbreaks were reported in The Netherlands from May 2007 to 2009, with dairy-goat farms as the putative source. Since Q-fever outbreaks at such farms were first reported in 2005, we explored whether there was evidence of human outbreaks before May 2007. Space-time scan statistics were used to look for clusters of lower-respiratory infections (LRIs), hepatitis, and/or endocarditis in hospitalizations, 2005-2007. We assessed whether these were plausibly caused by Q fever, using patients' age, discharge diagnoses, indications for other causes, and overlap with reported Q fever in goats/humans. For seven detected LRI clusters and one hepatitis cluster, we considered Q fever a plausible cause. One of these clusters reflected the recognized May 2007 outbreak. Real-time syndromic surveillance would have detected four of the other clusters in 2007, one in 2006 and two in 2005, which might have resulted in detection of Q-fever outbreaks up to 2 years earlier.

Evaluation of syndromic surveillance in the Netherlands: its added value and recommendations for implementation.

In the last decade, syndromic surveillance has increasingly been used worldwide for detecting increases or outbreaks of infectious diseases that might be missed by surveillance based on laboratory diagnoses and notifications by clinicians alone. There is, however, an ongoing debate about the feasibility of syndromic surveillance and its potential added value. Here we present our perspective on syndromic surveillance, based on the results of a retrospective analysis of syndromic data from six Dutch healthcare registries, covering 1999­2009 or part of this period. These registries had been designed for other purposes, but were evaluated for their potential use in signalling infectious disease dynamics and outbreaks. Our results show that syndromic surveillance clearly has added value in revealing the blind spots of traditional surveillance, in particular by detecting unusual, local outbreaks independently of diagnoses of specific pathogens, and by monitoring disease burden and virulence shifts of common pathogens. Therefore we recommend the use of syndromic surveillance for these applications.

Antibodies to opacity proteins (Opa) correlate with a reduced risk of gonococcal salpingitis.

Acute salpingitis complicating cervical gonococcal infection is a significant cause of infertility. Relatively little data are available concerning the pathophysiologic mechanisms of this disease. A cohort of 243 prostitutes residing in Nairobi were followed between March 1985 and April 1988. Gonococcal cultures were performed at each visit, and acute salpingitis was diagnosed clinically. Serum at enrollment was tested by immunoblot for antibody to gonococcal outer membrane proteins. 8.6% (146/1689) of gonococcal infections were complicated by salpingitis. Increased risk of salpingitis was associated with younger age, shorter duration of prostitution, HIV infection, number of gonococcal infections, and episodes of nongonococcal salpingitis. Rmp antibody increased the risk of salpingitis. Antibody to Opa decreased the risk of salpingitis. By logistic regression analysis, antibody to Opa was independently associated with decreased risk of gonococcal salpingitis (adjusted odds ratio [OR], 0.35; 95% confidence interval [95%CI], 0.17-0.76); HIV infection (adjusted OR, 3.5; 95% CI, 0.96-12.8) and episodes of nongonococcal salpingitis (adjusted OR, 3.4; 95% CI, 1.8-6.4) were independently associated with an increased risk of salpingitis. Antibody to Opa appears to protect against ascending gonococcal infection, perhaps by interfering with Opa mediated adherence and endocytosis. The demonstration of natural immunity that protects against upper genital tract infection in women suggests that a vaccine to prevent gonococcal salpingitis is possible.

Plasma N terminal pro-brain natriuretic peptide levels and its determinants in a multi-ethnic population.

This study documents the determinants and plasma levels of N-terminal pro-brain natriuretic peptide (NT-proBNP) among hypertensive and normotensive subjects in a multi-ethnic population in the United Arab Emirates (UAE). We obtained demographic, anthropometric and clinical data, together with fasting NT-proBNP and biochemical indices from 128 hypertensive patients and 138 normotensive subjects matched for age, gender and ethnicity. Plasma NT-proBNP levels were significantly (P<0.001), and several-fold higher among hypertensives (median 5.92, inter quartile range (IQR): 1.79-18.48 pmol/l) than normotensives (median 1.78, IQR: 0.59-4.32 pmol/l) in the total study population, and the same was true for the ethnic groups separately. Similarly, plasma levels of glucose, blood urea nitrogen (BUN) and creatinine, but not insulin, were significantly (P<0.05) higher among hypertensives than normotensives. For all subjects combined, log NT-proBNP correlated positively and significantly with age (P<0.01), log glucose (P<0.05), systolic blood pressure (SBP, P<0.001), log BUN (P<0.001) and log creatinine (P<0.001). Multivariate regression analysis showed that NT-proBNP levels were independently and positively correlated with SBP, age, gender, log BUN, Emirati and South East Asian ethnic groups and inversely associated with current exercise. In conclusion, we found circulating levels of NT-proBNP to be significantly increased in hypertensive versus normotensive subjects in the UAE and independently related to SBP, age, gender, indices of renal function and possibly exercise. Our results further suggest a possible modulating effect of ethnicity on NT-proBNP levels.

Preventing nosocomial infections: improving compliance with standard precautions in an Indonesian teaching hospital.

Standard precautions can prevent transmission of micro-organisms. This study investigated hand hygiene, handling of needles and use of personal protective equipment in an Indonesian teaching hospital, and performed a multi-faceted intervention study to improve compliance. An intervention was performed in an internal medicine ward and a paediatric ward, consisting of development of a protocol for standard precautions, installation of washstands, educational activities and performance feedback. Before, during and after the intervention, observers monitored compliance with hand hygiene, safe handling of needles and use of gloves, gowns and masks. A gynaecology ward served as the control. Unobtrusive observations were performed to check for an influence of the observers on the overt observations. In total, 7,160 activities were observed. Compliance with hand hygiene increased from 46% to 77% in the internal medicine ward and from 22% to 62% in the paediatric ward. Before the intervention, no safe recapping of needles was recorded in either ward. After the intervention, 20% of needles were recapped safely. Inappropriate gown use decreased in the internal medicine ward. There were no significant changes in use of gloves and masks. There may have been an effect of the overt observations in the paediatric ward, but there was no effect in the internal medicine ward. There were no significant changes in the control ward, except for a decrease in the use of gloves. In conclusion, compliance with hand hygiene procedures improved significantly due to an intervention project focused on education and improved facilities. Compliance with safe handling of needles improved slightly due to introduction of the one-handed method for safe recapping of used needles.

Surveillance of healthcare-associated infections in Indonesian hospitals.

A cross-sectional surveillance of healthcare-associated infections (HAIs) and exposure to risk factors was undertaken in two Indonesian teaching hospitals (Hospitals A and B). Patients from internal medicine, surgery, obstetrics and gynaecology, paediatrics, a class department and intensive care were included. Patient demographics, antibiotic use, culture results, presence of HAI [phlebitis, surgical site infection (SSI), urinary tract infection (UTI) and septicaemia] and risk factors were recorded. To check for interobserver variation, a validation study was performed in Hospital B. In Hospitals A and B, 1,334 and 888 patients were included, respectively. Exposure to invasive devices and surgery was 59%. In Hospital A, 2.8% of all patients had phlebitis, 1.7% had SSI, 0.9% had UTI and 0.8% had septicaemia. In Hospital B, 3.8% had phlebitis, 1.8% had SSI, 1.1% had UTI and 0.8% had septicaemia. In the validation study, the prevalence as recorded by the first team was 2.6% phlebitis, 1.8% SSI, 0.9% UTI and no septicaemia, and that recorded by the second team was 2.2% phlebitis, 2.6% SSI, 3.5% UTI and 0.9% septicaemia. This study is the first to report on HAI in Indonesia. Prevalence rates are comparable to those in other countries. The reliability of the surveillance was insufficient as a considerable difference in prevalence rates was found in the validation study. The surveillance method used is a feasible tool for hospitals in countries with limited healthcare resources to estimate their level of HAI and make improvements in infection control. Efficiency can be improved by restricting the surveillance to include only those patients with invasive procedures. This can help to detect 90% of all infections while screening only 60% of patients.

Inter- and intra-individual variation in applied force when listening at a surface, and resulting variation in earprints.

We aimed to explore the level of inter- and intra-individual variation in applied force when listening at a surface, and assess the resulting variation in earprints. We further intended to identify possible sources of this variation. Forty subjects each listened twenty-four times at a surface while applied force was recorded. In between efforts the level and frequency of the target sound, and the level of ambient noise were varied. Each listening effort was characterized by two values: the mean of a series of force recordings ('functional force') and the highest force reading of the effort ('peak value'). A mixed model analysis of variance revealed that repetition during multiple efforts of listening and the level of the target sound significantly affected both values for applied force. The frequency of the target sound affected the peak value, but we assume this was due to confounding effects. The level of ambient noise did not affect applied force. To explore the correlation between values for applied force of various efforts by single ear, the intra-class correlation coefficient was calculated. For functional force it was 0.80; for the peak value it was 0.79. To study intra-individual variation in earprints, five prints from each ear were lifted and studied. Variation in prints is discussed.

Can viral load, semi-quantitatively evaluated, of human papillomavirus predict cytological or histological outcome in women with atypical squamous or glandular cells of undetermined significance cytology?

OBJECTIVE: 1) To assess the regression to normal cytology in women with cervical smears diagnosed as atypical squamous or glandular cells of undetermined significance (ASCUS/AGUS) and absence or clearance of human papillomavirus (HPV) infection; 2) To evaluate the association between viral load, semi-quantitatively evaluated, and cytological or histological outcome. MATERIAL AND METHODS: In this cohort study HPV test and biopsy was taken in 148 women with ASCUS/AGUS cytology. After 12-18 months a HPV test and cervical smear were repeated in 121 women. RESULTS: Absence or clearance of HPV showed significantly more regression to normal cytology than persistent or newly acquired infected women, odds ratio 27 (95% confidence interval; 7-103). The viral load of the HPV test at enrollment was not correlated with the follow-up cytological outcome (Spearman correlation coefficient 0.2, p = 0.2). A marked association between viral load and histological outcome at enrollment was shown (Spearman correlation coefficient 0.43, p < 0.0001). CONCLUSION: Absence or clearance of HPV can predict regression to normal cytology. Viral load at enrollment cannot predict cytological regression. There was a marked association between viral load and the underlying CIN at enrollment. However, there was large overlapping of viral loads among the grades of CIN. Therefore, viral load is not a useful parameter to predict high-grade lesions in women with ASCUS/AGUS cytology.

Study of the relationship between a person's stature and the height of an ear imprint from the floor.

Occasionally ear prints are found at crime scenes. The height of the ear imprint may provide the police with information regarding the stature of the perpetrator and may therefore help to narrow down the number of suspects. The research provides calculations for the determination of stature from the height of the tragus imprint found at crime scenes. It takes into account various variables such as age, stature and gender.

The importance of core groups in the epidemiology and control of HIV-1 infection.

PIP: In Africa, HIV transmission occurs mainly through heterosexual intercourse. High-frequency transmitter core groups are key to the epidemiology of HIV-1 and STD on the continent. The rapid growth of the HIV-1 epidemic in Africa appears to have resulted, in part, from social and economic factors which result in individuals' frequent engagement in sexual intercourse with members of HIV-infected core groups. Understanding the importance of core groups in HIV-1 transmission is therefore key to developing more effective programs for the control of HIV-1. Sections explore the core groups concept and the sexual transmission of infection, social and economic forces creating core groups in Africa, the interaction of STD and HIV-1 in core groups, the effect of STD on HIV-1 disease progression in core groups in accelerating the HIV-1 epidemic, the role of core group interventions in control programs, balancing disease control with the potential for victimization, and research needs.^ieng

Controlling HIV in Africa: effectiveness and cost of an intervention in a high-frequency STD transmitter core group.

Since 1985, a population of over 1,000 predominantly HIV-positive female prostitutes residing in a low-income area of Nairobi, has been enrolled in a sexually transmitted disease (STD)/HIV control programme. The major elements of the programme include the diagnosis and treatment of conventional STD, and the promotion of condom use to prevent the transmission of HIV and other sexually transmitted infections. Using estimates of numbers of HIV-seropositive prostitutes, numbers of sexual contacts, susceptibility of clients to HIV, HIV transmission efficiency, rates of condom use and the basic reproductive rate of HIV infection in Kenya, we estimate that the programme is responsible for preventing between 6,000 and 10,000 new cases of HIV infection per year among clients and contacts of clients. The total annual operating cost of the programme is approximately US$77,000 or between US$8.00 and US$12.00 for each case of HIV infection prevented. Programmes to reduce the transmission of HIV and other sexually transmitted infections which are targeted at high-frequency STD transmitters, such as prostitutes, can be effective and relatively inexpensive to undertake. More such programmes should be developed and evaluated in different settings.

Transition dynamics of HIV disease in a cohort of African prostitutes: a Markov model approach.

The progression of HIV-related disease from infection to death is represented as a staged Markov model. Transitions between stages are considered reversible. The model is fitted to data from a cohort of African prostitutes by means of maximum likelihood. It appears that the progression to symptomatic disease (Centers for Disease Control stage IV) in this population is considerably more rapid than that reported from studies in Western countries.

PIP: Identifying the incubation period of HIV infection is important for individual prognoses, for developing and testing intervention strategies, for determining the reproductive rate of the disease, and for prevalence of the disease. Mathematical modeling of HIV infection in Africa is necessitated because the disease is more widespread and the immune system is constantly active due to the exposure to diseases such as malaria and tuberculosis. The Markov model for this analysis was selected because parametric estimation is not based on the time a stage is entered, but on the duration between observations and the stages at the time of observation. The HIV infected female prostitutes in the Pumwani area of Nairobi, Kenya (a population primarily of Tanzanian origin) have been identified as a study population since 1985, and seen every 6 months in clinic, or as needed. Data are constricted by the movement out of the area in the end stage of disease, which is only partially solved by tracking with community health workers. The stages identified in incubation estimation are stage 1: seropositive but symptom free (CDC stage II); stage 2: generalized lymphadenopathy (CDC stage III); stage 3: symptomatic disease (CDC stage IV); and stage 4: death. Data reflect the movement back and forth between stage 1 and 2, between 2 and 3, so the model is not a pure Longini model but rather a timed homogeneous staged model with reversible stages called transition parameters computed in a numerical differentiation. The Fortran computer program for the analyses is available from the authors. The results suggest a quick transition between seroconversion and lymphadenopathy (2.4 months) and unlikely reversal, with the mean waiting time until passage to stage 3 is approximately 2.6 years and conversions are common. Since opportunistic infections are treatable, this makes sense. Assuming a correct model, the estimation of the transition time of 20 months of h34 value of .01 and .05, the mean passage time from stage 1, 2, 3 to 4 (death) is 9.1, 8.9, and 6.2 years 12.9, 12.7, and 10.1 years respectively. The implications are that 1) when infectiousness is hypothesized to be not uniform, peak infectivity occurs earlier in Africa than in the West at least among prostitutes, or 2) if infectivity is constant throughout the incubation period, then HIV transmission must be higher in Africa to explain the high rate of infection.

Risk factors for postnatal mother-child transmission of HIV-1.

OBJECTIVE: To identify factors affecting HIV-1 breastfeeding transmission. DESIGN: Longitudinal observational cohort study. METHODS: HIV-1 seropositive pregnant women and seronegative controls were enrolled at a maternity hospital in Nairobi. Women and their children were followed from birth, and data on HIV-1 transmission, breastfeeding, clinical illness, and growth were collected. Specimens for HIV-1 serology and/or polymerase chain reaction were obtained at birth, 2, 6, and 14 weeks, 6, 9, 12, and 18 months, and every 6 months thereafter. Children were classified as HIV-1 uninfected, perinatally, or postnatally infected. Potentially breastfeeding transmission related risk factors were compared between postnatally infected and uninfected children. RESULTS: Among children born to seropositive or seroconverting mothers, 317 were uninfected, 51 infected perinatally and 42 infected postnatally. Identified risk factors for postnatal transmission were maternal nipple lesions (OR = 2.3, CI 95% 1.1-5.0), mastitis (OR = 2.7, CI 95% 1.1-6.7), maternal CD4 cell count < 400 mm3 (OR = 4.4, CI 95% 1.9-9.9), maternal seroconversion while breastfeeding (OR = 6.0, CI 95% 1.8-19.8), infant oral thrush at < 6 months of age (OR = 2.8, CI 95% 1.3-6.2) and breastfeeding longer than 15 months (OR = 2.4, CI 95% 1.2-5.1). All factors, except maternal seroconversion due to its rarity, were independently associated with an increased postnatal transmission risk by multivariate logistic regression analysis. CONCLUSION: In addition perinatal antiretroviral therapies, public health strategies should address: (i) prevention of maternal nipple lesions, mastitis and infant thrush; (ii) reduction of breastfeeding duration by all HIV-1-infected mothers; (iii) absolute avoidance of breastfeeding by those at high risk, and (iv) prevention of HIV-1 transmission to breastfeeding mothers.

Vitamin A and risk of HIV-1 seroconversion among Kenyan men with genital ulcers.

BACKGROUND: Vitamin A is involved in normal immune function and the maintenance of mucosal integrity through complex effects on cellular differentiation. OBJECTIVE: We sought to determine whether serum vitamin A levels were associated with altered susceptibility to primary infection with HIV-1 in men with high-risk sexual behaviour and genital ulcers who presented for treatment at an STD clinic in Nairobi, Kenya. METHODS: HIV-1 seronegative men were prospectively followed. Vitamin A levels at study entry were compared among 38 men who HIV-1 seroconverted versus 94 controls who remained HIV seronegative. RESULTS: Vitamin A deficiency (retinol less than 20 microg/dl) was very common and was present in 50% of HIV-1 seroconverters versus 76% of persistent seronegatives. Seroconversion was independently associated with a retinol level greater than 20 microg/dl (HR 2.43, 95% CI 1.25-4.70, P = 0.009), and a genital ulcer aetiology caused by Haemophilus ducreyi (HR 3.49, 95% CI 1.03-11.67, P = 0.04). Circumcision was independently associated with protection (HR 0.46, 95% CI 0.23-0.93, P = 0.03). CONCLUSION: Vitamin A deficiency was not associated with an increased risk of HIV-1 infection among men with concurrent STD. A decreased risk of HIV-1 seroconversion was independently associated with lower retinol levels. The effects of vitamin A on macrophage and lymphoid cell differentiation may paradoxically increase mucosal susceptibility to HIV-1 in some vulnerable individuals, such as men with genital ulcers. Lack of circumcision and chancroid are confirmed as important co-factors for heterosexual HIV-1 transmission. The role of vitamin A in heterosexual HIV-1 transmission requires further study.

Modeling familial clustered breast cancer using published data.

The purpose of this research was to model the familial clustering of breast cancer and to provide an accurate risk estimate for individuals from the general population, based on their family history of breast and ovarian cancer. We constructed a genetic model as an extension of a model by Claus et al. (E. B. Claus et al., Am. J. Hum. Genet., 48: 232-242, 1991), with three breast cancer genes, BRCA1, BRCA2, and a hypothetical BRCAu, in two variants, one in which BRCAu was dominant and one in which BRCAu was recessive. The model parameters were estimated using published estimates of population incidence and relative risks. Risk estimation was performed for a set of 196 counselees and for a set of simulated counselees with both the dominant BRCAu and the recessive BRCAu model, and compared relating to medical management. Estimates of the model parameters were found. Relative risks among family members were comparable between the model of Claus et al. (E. B. Claus et al., Am. J. Hum. Genet., 48: 232-242, 1991) and our model. The dominant and the recessive model provided approximately similar lifetime risks for breast cancer. Our model is suitable for breast cancer risk estimation in a health care setting.

Undertreatment of hypertension in a population-based study in The Netherlands.

OBJECTIVE: To estimate the level of undertreatment of hypertension in a population-based study by taking into account the co-existence of additional cardiovascular risk factors in untreated hypertensives, uncontrolled blood pressure among pharmacologically treated hypertensives and within-person variability in blood pressure and total cholesterol. DESIGN: Cross-sectional. SETTING: Two population-based surveys on cardiovascular disease risk factors conducted during 1987-1995 in The Netherlands. PARTICIPANTS: 56 026 men and women aged 20-59 years. MAIN OUTCOME MEASURES: Prevalence of hypertension, of treatment and of undertreatment of hypertension. Undertreated hypertensives were those who were treated pharmacologically, but whose blood pressure was still elevated and those who inappropriately received no medication for the treatment of hypertension. RESULTS: During the past decade in The Netherlands, 30% of the hypertensive women and 47% of the hypertensive men aged 20-59 years were undertreated for hypertension. In both men and women treated pharmacologically, 42 and 29%, respectively, still had elevated blood pressure levels. Of those hypertensive men and women not treated pharmacologically, 53 and 34%, respectively, should have been treated when additional cardiovascular risk factors were taken into account Among those diagnosed but untreated for hypertension, 58 and 31% of the men and women, respectively, should have been treated pharmacologically. CONCLUSION: A considerable proportion of hypertensives were undertreated for hypertension. To decrease the undertreatment of hypertension, it is necessary to obtain better control of blood pressure in patients already being treated, increase the detection of hypertension and improve adherence to the current guidelines.

Human leucocyte antigen supertypes and immune susceptibility to HIV-1, implications for vaccine design.

T cell responses against HIV-1 have been identified in a number of exposed uninfected populations. We hypothesized that the ability to mount an effective T cell response is partly determined by the human leucocyte antigens (HLA) phenotype of the individual. We examined whether certain HLA supertypes were associated with differential HIV-1 susceptibility in sexually exposed adults and in the setting of mother to child HIV-1 transmission. By multivariate analysis, decreased HIV-1 infection risk was strongly associated with possession of a cluster of closely related class I HLA alleles (A2/6802 supertype) in sexually exposed adults (Hazard ratio=0.42, 95% confidence intervals (CI): 0.22-0.81, P=0.009) and perinatally exposed infants (Odds ratio=0.12, 95% CI: 0.03-0.54, P=0.006). The alleles in this HLA supertype are known in some cases, to present the same peptide epitopes (termed 'supertopes'), for T cell recognition. The identification of HIV-1 supertopes, which are associated with protection from HIV-1 infection, has important implications for the application of epitope-based HIV-l vaccines in a variety of racial groups.

Anti-HLA alloantibody is found in children but does not correlate with a lack of HIV type 1 transmission from infected mothers.

Searching for mechanisms of natural resistance to HIV infection with which to guide HIV vaccine design, we have examined antibody responses to HLA class I antigens in children of HIV-1-infected mothers. Anti-HLA antibodies are known to block HIV infectivity in vitro and can be protective against SIV challenge in macaques immunized with purified class I HLA. It was hypothesized that alloantibody to maternal HLA in children might contribute to the prevention of mother-to-child transmission of HIV-1. In fact, a surprisingly high proportion of the children examined, 22%, were found to have antibody against class I alloantigens. This alloantibody, however, did not correlate with the HIV status of the children and was found in a similar proportion of children of HIV-negative mothers. The HLA specificity of the antibody was not correlated with noninherited maternal HLA alleles and occurred with a higher frequency in older children. This result suggests environmental factors, rather than exposure to maternal cells, are involved in the formation of the alloantibody. The finding that anti-allo-class I HLA antibodies are not associated with a decreased risk of mother-to-child transmission indicates that this humoral immune response is unlikely to be the natural mechanism that accounts for the lack of transmission observed in many births. This result, however, does not preclude the further investigation of cellular alloimmune responses, or the use of alloimmunization as an artificial HIV immunization strategy.

Estimating the prevalence of hypertension corrected for the effect of within-person variability in blood pressure.

The objective of our study was to assess the applicability of using estimates of within-person variance (WPV) from reproducibility studies for a correction of blood pressure values in another study to improve the accuracy of the prevalence estimation of hypertension. Data were collected from two cross-sectional population-based studies on cardiovascular disease risk factors conducted from 1987 to 1995 among 55,026 subjects aged 20-59 years. Correction factors were calculated from a reproducibility study among 924 subjects who were examined in 1989 and 1990. All other studies with repeated measurements of blood pressure were searched in MEDLINE from 1966 onward. Six studies satisfied the inclusion criteria. The prevalence of hypertension, uncorrected and corrected with factors from other studies, were compared with the prevalence of hypertension corrected with the factor from our study. The uncorrected prevalence of hypertension was 17.3% [95%CI:17.0-17.7]. The prevalence of hypertension after correction for WPV with the factor from our study was 13.5% [95%CI:13.2-13.8]. Correction for WPV with factors from the appropriate studies (depending on factors such as number of measurements taken per visit, and time interval between visits) resulted in prevalences ranging from 13.9% to 14.7%. The bias that occurs when no correction for WPV is performed is much larger (29% overestimation) than the bias that occurs when correction factors are derived from other studies (3.1-8.4% overestimation). When repeated measurements of blood pressure are not available in a population study for a sample of that same study, it is advisable to use data from another study to correct for WPV.