Clustering of lifestyle risk behaviours among residents of forty deprived neighbourhoods in London: lessons for targeting public health interventions.

BACKGROUND: Clustering of lifestyle risk behaviours is very important in predicting premature mortality. Understanding the extent to which risk behaviours are clustered in deprived communities is vital to most effectively target public health interventions. METHODS: We examined co-occurrence and associations between risk behaviours (smoking, alcohol consumption, poor diet, low physical activity and high sedentary time) reported by adults living in deprived London neighbourhoods. Associations between sociodemographic characteristics and clustered risk behaviours were examined. Latent class analysis was used to identify underlying clustering of behaviours. RESULTS: Over 90% of respondents reported at least one risk behaviour. Reporting specific risk behaviours predicted reporting of further risk behaviours. Latent class analyses revealed four underlying classes. Membership of a maximal risk behaviour class was more likely for young, white males who were unable to work. CONCLUSIONS: Compared with recent national level analysis, there was a weaker relationship between education and clustering of behaviours and a very high prevalence of clustering of risk behaviours in those unable to work. Young, white men who report difficulty managing on income were at high risk of reporting multiple risk behaviours. These groups may be an important target for interventions to reduce premature mortality caused by multiple risk behaviours.

Economic growth and decline in mortality in developing countries: an analysis of the World Bank development datasets.

OBJECTIVES: The 1999 World Bank report claimed that growth in gross domestic product (GDP) between 1960 and 1990 only accounted for 15% of concomitant growth in life expectancy in developing countries. These findings were used repeatedly by the World Health Organization (WHO) to support a policy shift away from promoting social and economic development, towards vertical technology-driven programmes. This paper updates the 1999 World Bank report using the World Bank's 2005 dataset, providing a new assessment of the relative contribution of economic growth. STUDY DESIGN: Time-series analysis. METHODS: Cross-sectional time-series regression analysis using a random effect model of associations between GDP, education and technical progress and improved health outcomes. The proportion of improvement in health indicators between 1970 and 2000 associated with changes in GDP, education and technical progress was estimated. RESULTS: In 1970, a 1% difference in GDP between countries was associated with 6% difference in female (LEBF) and 5% male (LEBM) life expectancy at birth. By 2000, these values had increased to 14% and 12%, explaining most of the observed health gain. Excluding Europe and Central Asia, the proportion of the increase in LEBF and LEBM attributable to increased GDP was 31% and 33% in the present analysis, vs. 17% and 14%, respectively, estimated by the World Bank. In the poorest countries, higher GDPs were required in 2000 than in 1970 to achieve the same health outcomes. CONCLUSIONS: In the poorest countries, socio-economic change is likely to be a more important source of health improvement than technical progress. Technical progress, operating by increasing the size of the effect of a unit of GDP on health, is likely to benefit richer countries more than poorer countries, thereby increasing global health inequalities.

Think of your art-eries: arts participation, behavioural cardiovascular risk factors and mental well-being in deprived communities in London.

OBJECTIVES: To investigate the association of participation in arts and cultural activities with health behaviours and mental well-being in low-income populations in London. STUDY DESIGN: Cross-sectional, community-based observational study. METHODS: Data were taken from the cross-sectional baseline survey of the Well London cluster randomized trial, conducted during 2008 in 40 of the most deprived census lower super output areas in London (selected using the English Indices of Multiple Deprivation). Multiple imputation was used to account for missing data in the Well London survey. Descriptive statistics and regression analyses were used to examine the association between participation in arts and cultural activities and physical activity (meeting target of five sessions of at least 30 min of moderate-intensity physical activity per week), healthy eating (meeting target of at least five portions of fruit or vegetables per day) and mental well-being (Hope Scale score; feeling anxious or depressed). RESULTS: This study found that levels of arts and cultural engagement in low-income groups in London are >75%, but this is well below the national average for England. Individuals who were more socially disadvantaged (unemployed, living in rented social housing, low educational attainment, low disposable income) were less likely to participate in arts or cultural activities. Arts participation was strongly associated with healthy eating, physical activity and positive mental well-being, with no evidence of confounding by socio-economic or sociodemographic factors. Neither positive mental well-being nor social capital appeared to mediate the relationship between arts participation and health behaviours. CONCLUSION: This study suggests that arts and cultural activities are independently associated with health behaviours and mental well-being. Further qualitative and prospective intervention studies are needed to elucidate the nature of the relationship between health behaviours, mental well-being and arts participation. If arts activities are to be recommended for health improvement, social inequalities in access to arts and cultural activities must be addressed in order to prevent further reinforcement of health inequalities.

LRRK2 expression in idiopathic and G2019S positive Parkinson's disease subjects: a morphological and quantitative study.

AIMS: Mutations in the gene encoding leucine-rich repeat kinase-2 (LRRK2) have been established as a common genetic cause of Parkinson's disease (PD). The distribution of LRRK2 mRNA and protein in the human brain has previously been described, although it has not been reported in PD cases with the common LRRK2 G2019S mutation. METHODS: To further elucidate the role of LRRK2 in PD, we determined the localization of LRRK2 mRNA and protein in post-mortem brain tissue from control, idiopathic PD (IPD) and G2019S positive PD cases. RESULTS: Widespread neuronal expression of LRRK2 mRNA and protein was recorded and no difference was observed in the morphological localization of LRRK2 mRNA or protein between control, IPD and G2019S positive PD cases. Using quantitative real-time polymerase chain reaction, we demonstrated that there is no regional variation in LRRK2 mRNA in normal human brain, but we have identified differential expression of LRRK2 mRNA with significant reductions recorded in limbic and neocortical regions of IPD cases compared with controls. Semi-quantitative analysis of LRRK2 immunohistochemical staining demonstrated regional variation in staining intensity, with weak LRRK2 immunoreactivity consistently recorded in the striatum and substantia nigra. No clear differences were identified in LRRK2 immunoreactivity between control, IPD and G2019S positive PD cases. LRRK2 protein was identified in a small proportion of Lewy bodies. CONCLUSIONS: Our data suggest that widespread dysregulation of LRRK2 mRNA expression may contribute to the pathogenesis of IPD.

The impact of ART scale upon health workers: evidence from two South African districts.

This study explores the effects of antiretroviral treatment (ART) programmes on health-care human resources in South Africa. The study included two parts, a questionnaire-based survey of 269 health workers published earlier and a qualitative study of 21 purposively selected health practitioners involved in ART scale up. Contrary to what has been presented in literature, our survey showed that health workers in ART programmes experienced higher levels of morale, lower stress, lower sickness absenteeism and higher levels of job satisfaction. This paper uses qualitative data to provide insights into the working environment of ART workers and examines some possible explanations for our survey findings. The key factors that contribute to the different perception of working environment by ART workers identified in this study include bringing hope to patients, delaying deaths, acquiring training and the ability to better manage and monitor the disease.

Association of Mycoplasma genitalium with acute non-gonococcal urethritis in Russian men: a comparison with gonococcal and chlamydial urethritis.

Urethral specimens from 172 men who attended sexually transmitted disease clinics in the Moscow Oblast were examined for Neisseria gonorrhoeae, Chlamydia trachomatis and Mycoplasma genitalium by nucleic acid amplification tests. N. gonorrhoeae was detected in the urethra of 41 (24%) of the 172 men and C. trachomatis in 57 (33%). The latter occurred in 15 (36%) of the 41 men who were infected by N. gonorrhoeae and in 42 (32%) of 131 uninfected by gonococci. Of the 42 men uninfected by gonococci but chlamydia infected, 39 (93%) had symptoms and/or signs of urethritis. M. genitalium was detected in 45 (26%) of the 172 men, in nine (22%) of the 41 men infected with N. gonorrhoeae and in 12 (21%) infected with C. trachomatis. M. genitalium was detected alone in 25 (28%) of the 89 men uninfected by either gonococci or C. trachomatis. Of these 25 men, 24 (96%) had urethral symptoms and signs of inflammation, a proportion significantly more than experienced by the 64 men uninfected by any of the microorganisms. Of the 31 men who apparently had no symptoms or signs of urethritis, only three (10%) were infected by M. genitalium. The data provide evidence for the pathogenicity and frequent occurrence of M. genitalium in men in Moscow and presumably elsewhere in Russia.

A trial of the validity of genital smears and cultures with gonococcal vaccine provocation in diagnosing genital gonorrhoea in women.

In Russia the diagnosis of gonorrhoea in women relied on microscopy, justified by the hypothesis that sensitivity increases using 'provocation' techniques. The aim was to test the value of Gonovaccine as provocation in women who would have received it normally. Cervical specimens from 204 women were tested by culture and a ligase chain reaction (LCR) assay before the women were randomized to receive provocation or not. Further cervical specimens were obtained 24, 48 and 72 hours later for microscopy, culture and LCR tests. In both provocation and non-provocation arms, 24 women were positive for gonorrhoea by the LCR assay. Test-by-test, sensitivity of microscopy was 30% in the provocation arm and 13% in the control arm (P = 0.0407, Fisher's exact test). Patient-by-patient, sensitivity of microscopy was 50% in the provocation arm, but only 25% in the control arm (P = 0.0675, Fisher's exact test). The cost per case was greater ($214) using provocation with microscopy than culture and microscopy at the first visit ($150). Thus, although Gonovaccine provocation doubled the sensitivity of microscopy in detecting gonococci, the internationally recommended protocol of microscopy and culture at first visit should be adopted as routine practice in Russia. The findings raise questions about the pathogenesis and natural history of gonorrhoea.

Performance of direct fluorescent antibody tests for routine diagnosis of Chlamydia trachomatis in Russian sexually transmitted disease clinics.

SUMMARY: Testing for Chlamydia trachomatis in Russia is usually done by microscopic examination of genital smears stained with fluorescent antibody provided in locally produced kits. The aim was to assess the sensitivity and specificity of such direct fluorescent antibody (DFA) tests compared with a nucleic acid amplification test (NAAT) (ligase chain reaction) to detect C. trachomatis in 171 cervical smears and 201 urethral smears from men. The patients were at high risk of chlamydial infection and had been recruited at three sexually transmitted disease clinics in Moscow. Among women, DFA test sensitivity was 6% (95% CI 0-14) and the specificity was 92% (95% CI 88-97). Among men, the sensitivity was 9% (95% CI 2-16) and the specificity was 90% (95% CI 83-94). Poor DFA test performance was probably due to poor antibody quality and such tests are not adequate for routine examination of populations with either low or high chlamydial prevalence. As there may remain a place for DFA testing where few patients are seen, the Russian Ministry of Health should enforce registration of diagnostic tests, and Russian manufacturers should seek ways of improving DFA test performance. However, the mainstay of testing should depend on NAATs.

Chlamydia trachomatis in cervical and vaginal swabs and urine specimens from women undergoing termination of pregnancy.

The study was devised to assess the prevalence of Chlamydia trachomatis in endocervical and vaginal swabs and first pass urine specimens from women presenting for termination of pregnancy (TOP) and to evaluate the performance of the tests used, namely the ligase chain reaction (LCR) and the direct fluorescence antibody (DFA) test. Eight hundred and sixty three (91%) of 948 women invited to participate agreed to do so; a complete set of results for all test-site combinations was achieved for 793 (92%). The overall prevalence of C. trachomatis was 8.54% (95% confidence interval [CI]: 7.6-10.5%) with a significant negative association with age. The sensitivity (95% CI) of the LCR test for cervical, vaginal and urine specimens was 97% (93-99%); 94% (88-99%) and 83% (75-92%), respectively. The sensitivity (95% CI) of the DFA test for cervical, vaginal and urine specimens was 93% (87-99%); 92% (86-99%) and 78% (68-88%), respectively. Concordance between the LCR and DFA test results was very high for specimens from the same site. The results indicate that nucleic acid amplification tests are appropriate for screening women seeking TOP and, indeed, other women in early pregnancy. The sensitivity of the LCR test for urine specimens was less, but the high levels of concordance observed between the LCR and DFA test results for urine specimens indicates that this was due to a lower organism load rather than inhibition of the LCR.

HIV prevalence and risk behaviour among female injecting drug users in London, 1990 to 1996.

OBJECTIVE: To describe trends in HIV prevalence among female injecting drug users (IDU) in London between 1990 and 1996. DESIGN: HIV prevalence and risk behaviour were measured yearly between 1990 and 1993, and in 1996, in point prevalence HIV surveys of IDU recruited from both drug-treatment and community-based settings within Greater London. Sample sizes were 173 in 1990, 111 in 1991, 128 in 1992, 146 in 1993 and 200 in 1996. METHODS: Each survey used structured questionnaires and common sampling and interview strategies. Oral fluid specimens were collected for testing for antibodies to HIV (anti-HIV). Multiple logistic regression was used to assess the trend in HIV prevalence. RESULTS: The percentage of female IDU testing positive for antibodies to HIV showed a marked decline over the study period, from 15.0% in 1990 to 1.0% in 1996 (P < 0.001). This trend was independent of all other variables examined. Each year, higher HIV prevalences were found among IDU recruited from community settings compared with treatment agencies. CONCLUSIONS: These results concur with those of IDU recruited from treatment sites, although the yearly estimates in this study are higher. London benefits from low prevalence of HIV infection among IDU, coupled with behaviour change facilitated by early intervention. Continued surveillance of injectors recruited from both community and treatment settings is necessary in order properly to assess HIV prevalence among IDU.

Genital herpes infection: a review.

Genital herpes infection is life-long and may result in painful and recurrent genital lesions, systemic complications, serious psychosocial morbidity, and rare but serious outcomes in neonates born to infected women, including permanent neurological handicap and death. Herpes simplex virus (HSV)-2 is the principal cause, with an increasing proportion of first-episode disease caused by HSV-1. Genital HSV transmission is usually due to asymptomatic viral shedding by people who are unaware that they are infected and clinical screening fails to detect most infections. Type-specific serological assays can distinguish the two viral subtypes, but these are expensive and currently restricted to a few research settings. Most infections are asymptomatic, or cause a mild illness which does not lead to health service attendance; but the limited evidence suggests a rise in disease incidence, perhaps related to a fall in HSV-1 age-specific prevalences. The prevalences of HSV genital infections increase with age and numbers of sexual partners, with higher rates in specific ethnic and low socioeconomic groups. However, infection is not restricted to high-risk populations. Antiviral agents, such as acyclovir, can reduce disease severity, prevent recurrences and shorten periods of viral shedding, but currently there are no effective population control measures. This may change with the advent of HSV vaccines, if their safety and long-term efficacy are confirmed. Possible applications for vaccines may include the suppression of disease and recurrences in patients with genital infections (immunotherapy), the prevention of viral transmission to their seronegative partners, and immunoprevention through vaccinating the latter. Economic evaluations of existing and potential control strategies, age-specific population HSV-1 and 2 seroprevalence studies for targeting future interventions, and cohort studies to elucidate the natural history of HSV-2 infections are needed.

Immunological events in regressing genital warts.

Little is known of the in vivo role of the immune system in controlling human papillomavirus infection in the genital tract. The authors have studied 125 closely monitored patients with genital warts. Of these 125 patients, wart regression was seen in 28 patients. This study provides evidence that clearance of human papillomavirus from the genital tract is characterized by an active cell-mediated immune response. Regressing warts (n = 14) contained significantly more T lymphocytes (P < .05, Wilcoxon rank sum test) and macrophages (P < .01) than did nonregressing controls (n = 14). CD4-positive lymphocytes predominated in regression, both within the wart stroma and the surface epithelium, where there was a significant change in the ratio of CD4+ to CD8+ cells (P < .01). Lymphocytes in regression also showed greater expression of activation markers, and the majority were of the "antigen-experienced" phenotype. There was no difference in Langerhans cell numbers, although there was significant induction of the immune accessory molecules HLA-DR and ICAM1 (P < .05) on keratinocytes, and E-selectin and VCAM1 (P < .05) on endothelial cells in regressing warts. The changes in regression are consistent with a delayed-type hypersensitivity reaction to foreign antigen, and the ability to induce and mount such a response may be a critical determinant of effective natural immunity to the genital HPVs. Specific targeting of delayed-type hypersensitivity responsiveness may increase the efficacy of strategies for immuno-intervention against HPV infection in the genital tract.

HIV infection associated with drug injecting in the newly independent states, eastern Europe: the social and economic context of epidemics.

AIMS: We review recent trends in HIV associated with injecting drug use (IDU) in the Newly Independent States (NIS) in eastern Europe, including Belarus, Moldova, Russia, Ukraine, and Kazakhstan in central Asia. We aim to draw attention to the social and economic "risk environments" in which rapid HIV spread among IDUs has occurred. METHODS: Findings draw on centrally registered HIV surveillance data, published research studies and assessment reports funded by international development agencies. FINDINGS: Since 1995, there is evidence of rapid HIV spread in Belarus, Kazakhstan, Moldova, Russia and Ukraine, with estimates suggesting between 50% and 90% of new HIV infections among IDUs. At the same time, there have been rapid increases in the incidence of syphilis and declines in health and welfare status, including outbreaks of diphtheria, tuberculosis and cholera. Findings emphasize the potential influence of the social and economic context in creating the "risk environments" conducive to HIV and epidemic spread. Key factors include: rapid diffusions in IDU; population migration and mixing; economic transition and decline; increasing unemployment and impoverishment; the growth of informal economies; modes of drug production, distribution and consumption; declines in public health revenue and infrastructure; and political, ideological and cultural transition. CONCLUSIONS: An understanding of the social and economic contexts mediating HIV spread is a prerequiste to identifying the environmental "pre-conditions" of epidemic outbreaks, and thus also, for predicting and preventing HIV transmission. The "risk environment" may influence the efficacy of individual and community-level HIV prevention and highlights the concomitant urgency for interventions targeting social and environmental change.

Epidemiology and causation: a realist view.

In this paper the controversy over how to decide whether associations between factors and diseases are causal is placed within a description of the public health and scientific relevance of epidemiology. It is argued that the rise in popularity of the Popperian view of science, together with a perception of the aims of epidemiology as being to identify appropriate public health interventions, have focussed this debate on unresolved questions of inferential logic, leaving largely unanalysed the notions of causation and of disease at the ontological level. A realist ontology of causation of disease and pathogenesis is constructed within the framework of "scientific materialism", and is shown to provide a coherent basis from which to decide causes and to deal with problems of confounding and interaction in epidemiological research. It is argued that a realist analysis identifies a richer role for epidemiology as an integral part of an ontologically unified medical science. It is this unified medical science as a whole rather than epidemiological observation or experiment which decides causes and, in turn, provides a key element to the foundations of rational public health decision making.

Estimating the sexual mixing patterns in the general population from those in people acquiring gonorrhoea infection: theoretical foundation and empirical findings.

STUDY OBJECTIVES: To describe mathematically the relationship between patterns of sexual mixing in the general population and those of people with gonorrhoea infection, and hence to estimate the sexual mixing matrix for the general population. DESIGN: Integration of data describing sexual behaviour in the general population, with data describing sexual behaviour and mixing among individuals infected with gonorrhoea. Use of these data in a simple mathematical model of the transmission dynamics of gonorrhoea infection. SETTING: The general population of London and a genitourinary medicine (GUM) clinic in west London. PARTICIPANT: These comprised 1520 men and women living in London who were randomly selected for the national survey of sexual attitudes and lifestyles and 2414 heterosexual men and women who presented to the GUM clinic with gonorrhoea. MAIN RESULTS: The relationship between sexual mixing among people with gonorrhoea and sexual mixing in the general population is derived mathematically. An empirical estimate of the sexual mixing matrix for the general population is presented. The results provide tentative evidence that individuals with high rates of acquisition of sexual partners preferentially select other individuals with high rates as partners (assortative mixing). CONCLUSIONS: Reliable estimates of sexual mixing have been shown to be important for understanding the evolution of the epidemics of HIV infection and other sexually transmitted diseases. The possibility of estimating patterns of sexual mixing in the general population from information routinely collected in gonorrhoea contact tracing programmes is demonstrated. Furthermore, the approach we describe could, in principle, be used to estimate the same patterns of mixing, using contact tracing data for other sexually transmitted diseases, thus providing a way of validating our results.

The economic costs of caring for people with HIV infection and AIDS in England and Wales.

The objectives of this study were firstly to estimate total lifetime care costs for an individual with HIV/AIDS, and secondly to estimate the total costs of caring people with HIV infection and AIDS in England and Wales between 1992 and 1997 inclusive. Questionnaires and monthly diaries were used to collate data on healthcare utilisation from patients with HIV infection over a 6-month period. These data were then used to estimate the annual total direct costs of care (stratified by disease stage), total lifetime costs of care, and present and future total national care costs for England and Wales. Costing data were obtained from providers of services throughout Greater London. In total, 235 patients with HIV infection were recruited from 2 clinics in Greater London. All costs were calculated in 1992-93 pounds sterling (pound; 1 pound = $US1.58, December 1995). Annual care costs were estimated at 4515 pounds ($US7134) for a person with asymptomatic HIV disease, 8836 pounds ($US13,961) for a person with symptomatic non-AIDS and 15 268 pounds ($US24,123) for a person with AIDS. Lifetime care costs were estimated at 84,522 pounds ($US133,545) per patient. The total costs of care for England and Wales were forecast to increase from 116,627,400 pounds ($US184,271,300) in 1992 to 162,638,100 pounds ($US256,968,200) in 1997. In conclusion, our study further emphasises the continued shift in hospital services from the inpatient sector to the outpatient sector. The importance of community care and informal care, in terms of the associated direct economic costs, is also highlighted. This emphasises the need for close collaboration between different agencies and strategic coordination of services. Finally, the study forecasts an increase in care costs in England and Wales during the 1990s.

Using STD occurrence to monitor AIDS prevention.

Monitoring the effects of AIDS prevention programmes is increasingly important but methodologically difficult. The use of surveillance derived measures of the occurrence of sexually transmitted diseases as indicators of high risk sexual behaviour, or of HIV incidence, has been widely recognized as a possible approach. This paper first examines the theoretical and empirical basis for this strategy, and highlights, using examples, some of the pitfalls in the interpretation of trends in sexually transmitted disease occurrence. Problems arising in the interpretation of the types of STD surveillance data currently available in countries in Western Europe are discussed. Ways in which STD surveillance systems might be developed so as to enhance their value in monitoring AIDS prevention are proposed. The paper goes on to identify areas of clinical and epidemiological research which might improve our ability to interpret such enhanced STD surveillance data.

Demograghic and socio-economic determinants of community and hospital services costs for people with HIV/AIDS in London.

We examined the influence of demographic, social and economic background of people with HIV/AIDS in London on total community and hospital services costs. This was a retrospective study of community and hospital service use, needs and costs based on structured questionnaires administered by trained interviewers and costing information obtained from the service purchasers and providers, based on two Genito-urinary Medicine clinics in London: the Jefferiss Wing at St. Mary's Hospital and Patric Clements at the Central Middlesex Hospital, London, England. The subjects were 225 HIV infected patients (105 asymptomatic, 59 symptomatic non-AIDS and 61 AIDS). We found that over and above well established determinants of health care costs for HIV infected people such as disease stage and transmission category, social and economic factors such as employment and support of a living-in partner significantly reduced community services costs. Private health insurance had a similar effect, though only a small proportion of HIV people had such cover. The cost of community services for HIV infected non-European Union nationals, mainly of African origin, was one quarter that for the European Union nationals. Community services costs were highest for heterosexually infected women and lowest for heterosexually infected men after adjusting for other factors. Hospital services costs were significantly higher for HIV infected people lacking educational qualifications and employment. We conclude that access to community care for HIV infected non-EU nationals appears to be very poor as the cost of their community services was one quarter that for the EU nationals after adjusting for the effects of transmission category, disease stage, living with a partner, employment and having a private health insurance. Additional incentives for informal care for HIV infected people could be a cost-effective way to improve their community health service provisions.

Qualitative and quantitative aspects of the ligase chain reaction assay for Chlamydia trachomatis in genital tract samples and urines.

The performance of the ligase chain reaction (LCR) assay for Chlamydia trachomatis was evaluated in a genitourinary medicine (GUM) clinic population. Its sensitivity was 100%, 91% and 95%, respectively, for cervical, vaginal and urine samples from 417 women, when compared with direct fluorescent antibody (DFA) staining of cervical samples, and 100% and 91%, respectively, for urethral and urine samples from 317 men, when compared with DFA staining of urethral smears. An enzyme immunoassay (EIA) was only 65% sensitive for cervical samples. Urethral swabs from a number of treated men remained LCR-positive when antigen was no longer detectable by DFA staining. An association between quantitative data from the LCR assay (i.e. the optical density of samples, measured in relation to internal controls and calibrators) and the antigen load of the samples, measured by DFA staining, indicated a lack of significant inhibition in the LCR assay in this study. This was probably due to freezing of the samples before testing. Diluting 20 LCR-positive urines with a range of antigen loads resulted in loss of positivity in 3, and a reduction in the signal in 13. The implications of the antigen load on the performance of detection assays for chlamydia-positive patients are discussed.

Quantification of Chlamydia trachomatis in cervical and urine specimens from women attending a genitourinary medicine clinic: implications for screening strategies.

Population screening and intervention programmes can reduce the prevalence and incidence of infection with Chlamydia trachomatis, especially if sensitive molecular diagnostic tests are used. However, diagnostic tests that perform well on genitourinary medicine (GUM) clinic populations may be less useful for screening, particularly if the majority of infected subjects are asymptomatic and their samples contain fewer organisms. We have compared the extent of low organism load in cervical and urine samples from symptomatic and asymptomatic chlamydia-positive women, by using a direct fluorescent antibody staining method and counting the chlamydial elementary bodies (EBs). We have investigated the ability of an enzyme immunoassay (EIA; MicroTrak) and a DNA amplification (ligase chain reaction; LCR) assay to detect low numbers of organisms in cervical samples and the ability of the LCR assay to detect low numbers of organisms in urine. A low organism load (< 10 EBs) was seen by direct fluorescent antibody (DFA) staining in about 30% of cervical samples and in about 75% of urines from chlamydia-positive women; the proportions in symptomatic women were not significantly different from those in asymptomatic women. The EIA identified only 16% of cervical samples that contained < 10 EBs by DFA staining; the LCR identified 100% of cervical samples and 93% of urine samples that contained < 10 EBs by DFA staining. The findings suggest that the ability of chlamydial diagnostic tests to identify positive women should be similar among patients attending a GUM clinic and those taking part in a population screening programme, and that sensitive molecular assays such as the LCR should identify subjects with a low organism load in both groups.