Accuracy and economic evaluation of screening tests for undiagnosed COPD among hypertensive individuals in Brazil.

In Brazil, prevalence of diagnosed COPD among adults aged 40 years and over is 16% although over 70% of cases remain undiagnosed. Hypertension is common and well-recorded in primary care, and frequently co-exists with COPD because of common causes such as tobacco smoking, therefore we conducted a cross-sectional screening test accuracy study in nine Basic Health Units in Brazil, among hypertensive patients aged ≥40 years to identify the optimum screening test/combinations to detect undiagnosed COPD. We compared six index tests (four screening questionnaires, microspirometer and peak flow) against the reference test defined as those below the lower limit of normal (LLN-GLI) on quality diagnostic spirometry, with confirmed COPD at clinical review. Of 1162 participants, 6.8% (n = 79) had clinically confirmed COPD. Peak flow had a higher specificity but lower sensitivity than microspirometry (sensitivity 44.3% [95% CI 33.1, 55.9], specificity 95.5% [95% CI 94.1, 96.6]). SBQ performed well compared to the other questionnaires (sensitivity 75.9% [95% CI 65.0, 84.9], specificity 59.2% [95% CI 56.2, 62.1]). A strategy requiring both SBQ and peak flow to be positive yielded sensitivity of 39.2% (95% CI 28.4, 50.9) and specificity of 97.0% (95% CI 95.7, 97.9). The use of simple screening tests was feasible within the Brazilian primary care setting. The combination of SBQ and peak flow appeared most efficient, when considering performance of the test, cost and ease of use (costing £1690 (5554 R$) with 26.7 cases detected per 1,000 patients). However, the choice of screening tests depends on the clinical setting and availability of resources.ISRCTN registration number: 11377960.

Enhancement of antibacterial activity through phyto-fabrication of silver nanoparticles with Ficus thonningii aqueous extracts.

The World Health Organisation reports higher levels of bacterial resistance to cephalosporins and carbapenems of above 54%. The sufficient redox capabilities of Ficus thonningii phytochemicals for Ag+  reduction to Ag0 and ultimately aggregation to nucleation are exploited for the first time in attempting to enhance the antibacterial activity. Solution colour change to brown due to surface plasmon resonance phenomenon confirmed nanoparticle fabrication with a UV/Vis absorption peak at 426 nm. Fourier Transform Infrared spectra revealed functional groups (C=C at 1620-1680 cm-1 ; C=H at 1400-1600 cm-1 aromatics) for encapsulation, stabilisation, and reduction of the silver ion. The Dynamic Light Scattering technique verified F. thonningii encapsulated silver nanoparticles particle size of 57.84 nm with a negative zeta potential (-19.8 mV) as proof of stability. The surface, shape and topographical features were shown by Scanning Electron Microscopy as spherical orientations. An enhanced antimicrobial efficacy was displayed by the nanoparticles (inhibition zones of 26.1, 24.1 and 15.2 mm from 11.5, 10.6 and 6.5 mm) for Staphylococcus aureus, Streptococcus pyrogenes and Escherichia coli, respectively, compared to Flucloxacillin standard that was in the ranges of 21.5, 23.5 and 25.7 mm. The enhanced potency provides a basis for diversified approaches of generating novel drugs for treating bacterial infections.

Dimethyl fumarate decreases short-term but not long-term inflammation in a focal EAE model of neuroinflammation.

BACKGROUND: Dimethyl fumarate (DMF) is an oral immunomodulatory drug used in the treatment of autoimmune diseases. Here, we sought to study whether the effect of DMF can be detected using positron emission tomography (PET) targeting the 18-kDa translocator protein (TSPO) in the focal delayed-type hypersensitivity rat model of multiple sclerosis (fDTH-EAE). The rats were treated orally twice daily from lesion activation (day 0) with either vehicle (tap water with 0.08% Methocel, 200 µL; control group n = 4 (3 after week four)) or 15 mg/kg DMF (n = 4) in 0.08% aqueous Methocel (200 µL) for 8 weeks. The animals were imaged by PET using the TSPO tracer [18F]GE-180 in weeks 0, 1, 2, 4, 8, and 18 following lesion activation, and the non-displaceable binding potential (BPND) was calculated. Immunohistochemical staining for Iba1, CD4, and CD8 was performed in week 18, and in separate cohorts of animals, following 2 or 4 weeks of treatment. RESULTS: Using the fDTH-EAE model, DMF reduced the [18F]GE-180 BPND in the DMF-treated animals compared to control animals after 1 week of treatment (two-tailed unpaired t test, p = 0.031), but not in weeks 2, 4, 8, or 18 when imaged in vivo by PET. Immunostaining for Iba1 showed that DMF had no effect on the perilesional volume or the core lesion volume after 2 or 4 weeks of treatment, or at 18 weeks. However, the optical density (OD) measurements of CD4+ staining showed reduced OD in the lesions of the treated rats. CONCLUSIONS: DMF reduced the microglial activation in the fDTH-EAE model after 1 week of treatment, as detected by PET imaging of the TSPO ligand [18F]GE-180. However, over an extended time course, reduced microglial activation was not observed using [18F]GE-180 or by immunohistochemistry for Iba1+ microglia/macrophages. Additionally, DMF did affect the infiltration of CD4+ and CD8+ T-lymphocytes at the fDTH-EAE lesion.

Accuracy of Vitalograph lung monitor as a screening test for COPD in primary care.

Microspirometry may be useful as the second stage of a screening pathway among patients reporting respiratory symptoms. We assessed sensitivity and specificity of the Vitalograph® lung monitor compared with post-bronchodilator confirmatory spirometry (ndd Easy on-PC) among primary care chronic obstructive pulmonary disease (COPD) patients within the Birmingham COPD cohort. We report a case-control analysis within 71 general practices in the UK. Eligible patients were aged ≥40 years who were either on a clinical COPD register or reported chronic respiratory symptoms on a questionnaire. Participants performed pre- and post-bronchodilator microspirometry, prior to confirmatory spirometry. Out of the 544 participants, COPD was confirmed in 337 according to post-bronchodilator confirmatory spirometry. Pre-bronchodilator, using the LLN as a cut-point, the lung monitor had a sensitivity of 50.5% (95% CI 45.0%, 55.9%) and a specificity of 99.0% (95% CI 96.6%, 99.9%) in our sample. Using a fixed ratio of FEV1/FEV6 < 0.7 to define obstruction in the lung monitor, sensitivity increased (58.8%; 95% CI 53.0, 63.8) while specificity was virtually identical (98.6%; 95% CI 95.8, 99.7). Within our sample, the optimal cut-point for the lung monitor was FEV1/FEV6 < 0.78, with sensitivity of 82.8% (95% CI 78.3%, 86.7%) and specificity of 85.0% (95% CI 79.4%, 89.6%). Test performance of the lung monitor was unaffected by bronchodilation. The lung monitor could be used in primary care without a bronchodilator using a simple ratio of FEV1/FEV6 as part of a screening pathway for COPD among patients reporting respiratory symptoms.

Cessation of anti-VLA-4 therapy in a focal rat model of multiple sclerosis causes an increase in neuroinflammation.

BACKGROUND: Positron emission tomography (PET) can be used for in vivo evaluation of the pathology associated with multiple sclerosis. We investigated the use of longitudinal PET imaging and the 18-kDa translocator protein (TSPO) binding radioligand [18F]GE-180 to detect changes in a chronic multiple sclerosis-like focal delayed-type hypersensitivity experimental autoimmune encephalomyelitis (fDTH-EAE) rat model during and after anti-VLA-4 monoclonal antibody (mAb) treatment. Thirty days after lesion activation, fDTH-EAE rats were treated with the anti-VLA-4 mAb (n = 4) or a control mAb (n = 4; 5 mg/kg, every third day, subcutaneously) for 31 days. Animals were imaged with [18F]GE-180 on days 30, 44, 65, 86 and 142. Another group of animals (n = 4) was used for visualisation the microglia with Iba-1 at day 44 after a 2-week treatment period. RESULTS: After a 2-week treatment period on day 44, there was a declining trend (p = 0.067) in [18F]GE-180-binding in the anti-VLA-4 mAb-treated animals versus controls. However, cessation of treatment for 4 days after a 31-day treatment period increased [18F]GE-180 binding in animals treated with anti-VLA-4 mAb compared to the control group (p = 0.0003). There was no difference between the groups in TSPO binding by day 142. CONCLUSIONS: These results demonstrated that cessation of anti-VLA-4 mAb treatment for 4 days caused a transient rebound increase in neuroinflammation. This highlights the usefulness of serial TSPO imaging in the fDTH-EAE model to better understand the rebound phenomenon.

Under-utilization of the OTA Fracture Classification in the orthopaedic trauma literature.

BACKGROUND: The OTA Fracture Classification is designed to provide a common language and facilitate effective communication among orthopaedic surgeons. We attempted to measure the degree to which this classification is currently being utilized in orthopaedic trauma literature. METHODS: We reviewed all of the articles in the JOT in 2011. We determined which of these articles could have appropriately utilized the 2007 OTA Classification. We calculated the percentage that mentioned and correctly cited this classification system as a reference. RESULTS: There were 145 articles in 2011. One hundred of these articles were appropriate for classifying a fracture. 38% of these articles utilized the OTA classification in the text. Only 42% of articles mentioning the OTA Classification cited a reference. 38% of these citations used the old (1996) OTA Classification reference, and only 8% overall correctly cited the 2007 OTA Classification reference. 51% of articles mentioned some other classification system; 21 in addition to OTA and 30 instead of the OTA classification. CONCLUSIONS: The OTA Fracture Classification is being used more commonly (38%) but is not routinely used or correctly cited (8%) in articles currently being published in the Journal of Orthopaedic Trauma, despite the fact that it is "required" according to the instructions to authors. We conclude that future authors should utilize and correctly reference the 2007 OTA Classification so that the benefits of a common language can be realized. Routine and consistent utilization of the classification may ultimately lead to more consistency and improved interpretability of treatment outcomes in published orthopaedic trauma research. LEVEL OF EVIDENCE: Level-III case-control study, decision analysis.

Phase I study of capecitabine combined with radioembolization using yttrium-90 resin microspheres (SIR-Spheres) in patients with advanced cancer.

BACKGROUND: This was a prospective single-centre, phase I study to document the maximum tolerated dose (MTD), dose-limiting toxicity (DLT), and the recommended phase II dose for future study of capecitabine in combination with radioembolization. METHODS: Patients with advanced unresectable liver-dominant cancer were enrolled in a 3+3 design with escalating doses of capecitabine (375-1000 mg/m(2) b.i.d.) for 14 days every 21 days. Radioembolization with (90)Y-resin microspheres was administered using a sequential lobar approach with two cycles of capecitabine. RESULTS: Twenty-four patients (17 colorectal) were enrolled. The MTD was not reached. Haematologic events were generally mild. Common grade 1/2 non-haematologic toxicities included transient transaminitis/alkaline phosphatase elevation (9 (37.5%) patients), nausea (9 (37.5%)), abdominal pain (7 (29.0%)), fatigue (7 (29.0%)), and hand-foot syndrome or rash/desquamation (7 (29.0%)). One patient experienced a partial gastric antral perforation with a capecitabine dose of 750 mg/m(2). The best response was partial response in four (16.7%) patients, stable disease in 17 (70.8%) and progression in three (12.5%). Median time to progression and overall survival of the metastatic colorectal cancer cohort was 6.4 and 8.1 months, respectively. CONCLUSIONS: This combined modality treatment was generally well tolerated with encouraging clinical activity. Capecitabine 1000 mg/m(2) b.i.d. is recommended for phase II study with sequential lobar radioembolization.

Lentivirus-mediated α-melanocyte-stimulating hormone overexpression in the hypothalamus decreases diet induced obesity in mice.

Melanocyte stimulating hormone (MSH) derived from the pro-hormone pro-opiomelanocortin (POMC) has potent effects on metabolism and feeding that lead to reduced body weight in the long-term. To determine the individual roles of POMC derived peptides and their sites of action, we created a method for the delivery of single MSH peptides using lentiviral vectors and studied the long-term anti-obesity effects of hypothalamic α-MSH overexpression in mice. An α-MSH lentivirus (LVi-α-MSH-EGFP) vector carrying the N'-terminal part of POMC and the α-MSH sequence was generated and shown to produce bioactive peptide in an in vitro melanin synthesis assay. Stereotaxis was used to deliver the LVi-α-MSH-EGFP or control LVi-EGFP vector to the arcuate nucleus (ARC) of the hypothalamus of male C57Bl/6N mice fed on a high-fat diet. The effects of 6-week-treatment on body weight, food intake, glucose tolerance and organ weights were determined. Additionally, a 14-day pairfeeding study was conducted to assess whether the weight decreasing effect of the LVi-α-MSH-EGFP treatment is dependent on decreased food intake. The 6-week LVi-α-MSH-EGFP treatment reduced weight gain (8.4 ± 0.4 g versus 12.3 ± 0.6 g; P < 0.05), which was statistically significant starting from 1 week after the injections. The weight of mesenteric fat was decreased and glucose tolerance was improved compared to LVi-EGFP treated mice. Food intake was decreased during the first week in the LVi-α-MSH-EGFP treated mice but subsequently increased to the level of LVi-EGFP treated mice. The LVi-EGFP injected control mice gained more weight even when pairfed to the level of food intake by LVi-α-MSH-EGFP treated mice. We demonstrate that gene transfer of α-MSH, a single peptide product of POMC, into the ARC of the hypothalamus, reduces obesity and improves glucose tolerance, and that factors other than decreased food intake also influence the weight decreasing effects of α-MSH overexpression in the ARC. Furthermore, viral MSH vectors delivered stereotaxically provide a novel tool for further exploration of chronic site-specific effects of POMC peptides.

Does the method of administration influence the UK GMC patient questionnaire ratings?

AIM: To examine whether different methods of administration of a patient questionnaire (PQ) assessing a doctor's professional performance can influence the quality of data collected. BACKGROUND: Patient surveys are important information sources regarding a doctor's professional performance. Previous research across a range of patient outcomes suggests that the method of administration can influence response rates and ratings, although no data that explore how this might influence patients' assessments of a doctor's professional performance are available. METHODS: A volunteer sample of 13 UK doctors from primary care settings undertook a cross-sectional patient survey. Seven doctors distributed patient surveys using exit and touch-tone telephone administration, and six doctors used exit and postal administration. A consecutive sample of up to 40 patients per doctor completed each method of administration; postal and touch-tone surveys were administered retrospectively, whereas the exit surveys were administered prospectively. The GMC (General Medical Council) PQ included nine performance evaluation questions. We examined the response rates, item completion rates and response profiles of exit survey responses with those obtained from either postal or touch-tone telephone methods. RESULTS: The administration methods influence the quality and comparability of data obtained. The exit survey response rate was higher than touch-tone (82.1% versus 37.5%; P < 0.0001) or postal survey (no reminder) (76.7% versus 60.8%; P < 0.0001) administration, but comparable to the postal survey after one reminder (78.3% versus 75.0%; P = 0.39). Item completion rates were comparable for exit and touch-tone surveys (highest rates of missing data 4.1% and 4.6%, respectively), but exit surveys resulted in more missing values than postal surveys (10.3 to 11.7% versus 1.1 to 3.9%). Response profiles varied. Both touch-tone and postal surveys yielded significantly more critical ratings than the exit survey (three of nine items). CONCLUSION: Mixing administration methods requires caution when the data are used to create benchmarks against which a doctor's performance is assessed.

Assessing the professional performance of UK doctors: an evaluation of the utility of the General Medical Council patient and colleague questionnaires.

OBJECTIVE: To investigate the utility of the GMC patient and colleague questionnaires in assessing the professional performance of a large sample of UK doctors. DESIGN: Cross-sectional questionnaire surveys. SETTING: Range of UK clinical practice settings. PARTICIPANTS: 541 doctors gave preliminary agreement to take part in the study. Responses were received from 13 754 patients attending one of 380 participant doctors, and from 4269 colleagues of 309 participant doctors. MAIN OUTCOME MEASURES: Questionnaire performance and standardised scores for each doctor derived from patient and colleague responses. RESULTS: Participant doctors were similar to non-participants in respect of age and gender. The patient and colleague questionnaires were acceptable to participants as evidenced by low levels of missing data. One patient questionnaire item seemed to cause confusion for respondents and requires rewording. Both patient and colleague responses were highly skewed towards favourable impressions of doctor performance, with high internal consistency. To achieve acceptable levels of reliability, a minimum of 8 colleague questionnaires and 22 patient questionnaires are required. G coefficients for both questionnaires were comparable with internationally recognised survey instruments of broadly similar intent. Patient and colleague assessments provided complementary perspectives of doctors' performance. Older doctors had lower patient-derived and colleague-derived scores than younger doctors. Doctors from a mental health trust and doctors providing care in a variety of non-NHS settings had lower patient scores compared with doctors providing care in acute or primary care trust settings. CONCLUSIONS: The GMC patient and colleague questionnaires offer a reliable basis for the assessment of professionalism among UK doctors. If used in the revalidation of doctors' registration, they would be capable of discriminating a range of professional performance among doctors, and potentially identifying a minority whose practice should to subjected to further scrutiny.

Capturing users' experience of UK out-of-hours primary medical care: piloting and psychometric properties of the Out-of-hours Patient Questionnaire.

BACKGROUND AND OBJECTIVE: Provision of out-of-hours care in the UK National Health Service (NHS) has changed in recent years with new models of provision and the introduction of national quality requirements. Existing survey instruments tend to focus on users' satisfaction with service provision; most were developed without undertaking supporting qualitative fieldwork. In this study, a survey instrument was developed taking account of these changes in service provision and undertaking supporting qualitative fieldwork. This paper reports on the development and psychometric properties of the new survey instrument, the Out-of-hours Patient Questionnaire (OPQ), which aims to capture information on the entirety of users' experiences of out-of-hours care, from the decision to make contact through to completion of their care management. METHODS: An iterative approach was undertaken to develop the new instrument which was then tested in users of out-of-hours services in three geographically distributed UK settings. For the purposes of this study, "service users" were defined as "individuals about whom contact was made with an out-of-hours primary care medical service", whether that contact was made by the user themselves, or via a third party. Analysis was undertaken of the acceptability, reliability and validity of the survey instrument. RESULTS: The OPQ tested is a 56-item questionnaire, which was distributed to 1250 service users. Respondents were similar in respect of gender, but were older and more affluent (using a proxy measure) than non-respondents. Item completion rates were acceptable. Respondents sometimes completed sections of the questionnaire which did not equate to their principal mode of management as recorded in the record of the contact. Preliminary evidence suggests the OPQ is a valid and reliable instrument which contains within it two discrete scales--a consultation satisfaction scale (nine items) and an "entry-access" scale (four items). Further work is required to determine the generalisability of findings obtained following use of the OPQ, especially to non-white user populations. CONCLUSION: The OPQ is an acceptable instrument for capturing information on users' experiences of out-of-hours care. Preliminary evidence suggests it is both valid and reliable in use. Further work will report on its utility in informing out-of-hours service planning and configuration and standard-setting in relation to UK national quality requirements.

Exploring users' experiences of accessing out-of-hours primary medical care services.

BACKGROUND: Since 2000, out-of-hours primary medical care services in the UK have undergone major changes in the organisation and delivery of services in response to recommendations by the Carson Review and more recently, through the new General Medical Services Contract (GMS2). People calling their general practice in the evening or at weekends are redirected to the out-of-hours service which may offer telephone advice, a home visit or a visit to a treatment centre. Little is known about users' experiences under the new arrangements. AIM: To explore users' experiences of out-of-hours primary medical care. DESIGN OF STUDY: A qualitative study employing focus groups and telephone interviews. SETTING: Three out-of-hours primary medical care service providers in England. METHODS: Focus groups and telephone interviews were conducted with 27 recent users of out-of-hours services. RESULTS: Key areas of concern included the urgency with which cases are handled, and delays when waiting for a call back or home visit. Users felt that providers were reluctant to do home visits. The service was regarded as under-resourced and frequently misused. Many expressed anxiety about calling, feeling unsure about how appropriate their call was and many were uncertain about how the service operated. CONCLUSIONS: Service users need clear information on how current out-of-hours services operate and how it should be used. Problems with triaging need to be addressed, users should be kept informed of any delays, and care needs to be taken to ensure that the new arrangements do not alienate older people or individuals with complex health needs.

Molecular epidemiology of tuberculosis in London 1995-7 showing low rate of active transmission.

BACKGROUND: Tuberculosis notification rates for London have risen dramatically in recent years. Molecular typing of Mycobacterium tuberculosis has contributed to our understanding of the epidemiology of tuberculosis throughout the world. This study aimed to assess the degree of recent transmission of M tuberculosis in London and subpopulations of the community with high rates of recent transmission. METHODS: M tuberculosis isolates from all persons from Greater London diagnosed with culture positive tuberculosis between 1 July 1995 and 31 December 1997 were genetically fingerprinted using IS6110 restriction fragment length polymorphism (RFLP) typing. A structured proforma was used during record review of cases of culture confirmed tuberculosis. Cluster analysis was performed and risk factors for clustering were examined in a univariate analysis followed by a logistic regression analysis with membership of a cluster as the outcome variable. RESULTS: RFLP patterns were obtained for 2042 isolates with more than four copies of IS6110; 463 (22.7%) belonged to 169 molecular clusters, which ranged in size from two (65% of clusters) to 12 persons. The estimated rate of recent transmission was 14.4%. Young age (0-19 years) (odds ratio (OR) 2.65, 95% confidence interval (CI) 1.59 to 4.44), birth in the UK (OR 1.55, 95% CI 1.04 to 2.03), black Caribbean ethnic group (OR 2.19, 95% CI 1.15 to 4.16), alcohol dependence (OR 2.33, 95% CI 1.46 to 3.72), and streptomycin resistance (OR 1.82, 95% CI 1.15 to 2.88) were independently associated with an increased risk of clustering. CONCLUSIONS: Tuberculosis in London is largely caused by reactivation or importation of infection by recent immigrants. Newly acquired infection is also common among people with recognised risk factors. Preventative interventions and early diagnosis of immigrants from areas with a high incidence of tuberculosis, together with thorough contact tracing and monitoring of treatment outcome among all cases of tuberculosis (especially in groups at higher risk of recent infection), remains most important.

Comparison of variable number tandem repeat and IS6110-restriction fragment length polymorphism analyses for discrimination of high- and low-copy-number IS6110 Mycobacterium tuberculosis isolates.

The present study was designed to evaluate the use of variable number tandem repeat (VNTR) and IS6110-restriction fragment length polymorphism (RFLP) analyses in combination as a two-step strategy for discrimination (as measured by the Hunter-Gaston Discrimination Index [HGDI]) of both high- and low-copy-number IS6110 Mycobacterium tuberculosis isolates compared to IS6110-RFLP alone with an unselected collection of isolates. Individually, IS6110-RFLP fingerprinting produced six clusters that accounted for 69% of the low-copy-number IS6110 isolates (five clusters) and 5% of the high-copy-number IS6110 isolates (one cluster). A total of 39% of all the isolates were clustered (HGDI = 0.97). VNTR analysis generated a total of 35 different VNTR allele profile sets from 93 isolates (HGDI = 0.938). Combining IS6110-RFLP analysis with VNTR analysis reduced the overall percentage of clustered isolates to 29% (HGDI = 0.988) and discriminated a further 27% of low-copy-number isolates that would have been clustered by IS6110-RFLP alone. The use of VNTR analysis as an initial typing strategy facilitates further analysis by IS6110-RFLP, and more importantly, VNTR analysis subdivides some IS6110-RFLP-defined clusters containing low- and single-copy IS6110 isolates.

Statistical model for assessing the proportion of subjects with subjective sensitisations in adverse reactions to foods.

The outcome from a Double-Blind Placebo-Controlled Food Challenge is often of a subjective nature and cannot be measured directly. Reactions to placebo challenges are frequently observed, implying that some of the responses in the study are in fact 'false responses'. In order to adjust for these false responses, previous studies have used various methods, including removing subjects from the analysis who reacted to the placebo. Simply ignoring the false responses can lead to misleading estimates for the true proportion of sensitised individuals. This paper outlines two models which can account for these false responses. In the single challenge study, a simple model is developed which enables the estimation of the rate of false responses in the study, as well as the true proportion of sensitised subjects. This model is very easy to apply in practice. For a repeated challenge study, a more complicated model is developed which again enables the estimation of the rate of false responses and the true proportion of sensitised subjects.

False molecular clusters due to nonrandom association of IS6110 with Mycobacterium tuberculosis.

We sought to determine whether nonrandom association of IS6110 with Mycobacterium tuberculosis could result in false-positive clustering in unselected collections of isolates. We typed 196 strains of M. tuberculosis from an unselected community-based study in northern Tanzania by IS6110 and polymorphic GC-rich repetitive-sequence (PGRS) methodologies. The strains were analyzed by Gelcompar computer software. Analysis of 13 out of 25 groups showed that isolates with identical IS6110 and PGRS patterns were likely to be the same strain. Some IS6110 groups containing strains with identical PGRS patterns had similar IS6110 patterns that differed only by movement of the element. Isolates assigned to a single group (i.e., group 11) on the basis of sharing an identical IS6110 fingerprint pattern did not share identical PGRS fingerprint patterns. Six out of the nine bands in these isolates were in hot-spot locations, as previously defined. This indicates that nonrandom association may result in false-positive clustering in unselected community-based studies. Only strains with identical PGRS and IS6110 patterns are likely to be recently transmitted.

A comparison of statistical approaches to the derivation of EC3 values from local lymph node assay dose responses.

Effective risk assessment and management of allergic contact dermatitis require three key factors: adequate hazard identification, measurement of the relative potency of identified hazards and an understanding of the nature, extent and duration of exposure. Suitable methods for hazard identification, such as the murine local lymph node assay (LLNA) and the guinea-pig maximization test, are well established and conditions of human exposure normally can be well anticipated. Thus, the need is for a robust and quantitative method for the estimation of relative skin sensitizing potency. One possible approach is via the analysis of LLNA dose-response data. In the LLNA, contact allergens are defined currently as those chemicals that cause a threefold or greater increase in lymph node cell proliferative activity compared with concurrent vehicle-treated controls. It is possible to estimate the concentration of a sensitizer required to generate a threefold stimulation of proliferation in draining lymph nodes; such a concentration is known as the EC3 value. Using a variety of statistical approaches to derive EC3 values from LLNA dose-response data for 10 chemicals, it has been demonstrated that simple linear interpolation between the values either side of the threefold stimulation index provides a robust assessment of the EC3 value without the need for recourse to more sophisticated statistical techniques. Provided that the appropriate concentrations of test chemical have been selected, EC3 values obtained in this way are reproducible both within and between laboratories and form the basis for examination of the utility of this approach for the estimation of relative skin sensitizing potency.

Threshold for classification as a skin sensitizer in the local lymph node assay: a statistical evaluation.

For more than 15 years, the murine local lymph node assay (LLNA) has undergone development, evaluation and validation as an alternative approach to the predictive identification of skin sensitizing chemicals. The criteria by which sensitizing chemicals are distinguished from those without significant skin sensitising hazard were developed empirically and were based on experience rather than a mathematical formula or statistical method. The current practice is to classify, as skin sensitizers, those chemicals which at one or more test concentrations stimulate a threefold or greater increase in the proliferative activity in draining lymph node cells. Despite the apparent confirmation of the utility of this approach from the extensive data available, there has not previously been any attempt to substantiate the accuracy of this criterion. In this present investigations, data from 134 chemicals tested in the LLNA and in the guinea pig and/or for which there exists clear evidence relating to human skin sensitization potential, have been subjected to a rigorous statistical evaluation using Receiver Operating Characteristic (ROC) curves. Whether the analysis is based on a comparison with guinea pig or human data, the results indicate that the empirically derived threefold threshold is an acceptable practical value for hazard identification.