Risk factors for complications after emergency surgery for paediatric appendicitis: a national prospective observational cohort study.

Appendicectomy is a common procedure in children with a low risk of mortality, however, complication rates and risk factors are largely unknown. This study aimed to characterise the incidence and epidemiology of postoperative complications in children undergoing appendicectomy in the UK. This multicentre prospective observational cohort study, which included children aged 1-16 y who underwent surgery for suspected appendicitis, was conducted between November 2019 and January 2022. The primary outcome was 30-day postoperative morbidity. Data collected included: patient characteristics; comorbidities; and physiological status. Multivariable regression analysis was used to identify independent risk factors for poor outcomes. Data from 2799 children recruited from 80 hospitals were analysed, of which 185 (7%) developed postoperative complications. Children from black and 'other' minority ethnic groups were at significantly higher risk of poor outcomes: OR (95%CI) 4.13 (1.87-9.08), p < 0.001 and 2.08 (1.12-3.87), p = 0.021, respectively. This finding was independent of socio-economic status and type of appendicitis found on histology. Other risk factors for complications included: ASA physical status ≥ 3 (OR (95%CI) 4.05 (1.70-9.67), p = 0.002); raised C-reactive protein (OR 95%CI 1.01 (1.00-1.01), p < 0.001); pyrexia (OR (95%CI) 1.77(1.20-2.63), p = 0.004); and peri-operative oxygen supplementation (OR (95%CI) 4.20 (1.44-12.24), p = 0.009). In the UK NHS, which is a universally accessible healthcare system, ethnicity, but not socio-economic status, was associated with an increased risk of postoperative complications in children having surgery for acute appendicitis. Further evaluations and interventions are required to address this health inequality in keeping with NHS and international priorities.

Is cardiorespiratory fitness associated with cognitive outcomes in mid-adulthood? Findings from the 1958 British birth cohort.

Identifying causal factors to intervene on to delay age-related declines in cognitive function is urgently needed. We examined associations between non-exercise testing cardiorespiratory fitness (NETCRF; estimated using sex, age, body mass index, resting heart rate, and physical activity) at 45 years and cognitive function outcomes (immediate and delayed verbal memory; verbal fluency; visual processing speed) at 50 years in 8130 participants from the 1958 British birth cohort. In unadjusted models, higher NETCRF was associated with better cognitive function across all outcomes. When adjusted for confounding factors, associations disappeared. In this cohort, associations between 45 years NETCRF and 50 years cognitive function likely result from confounding factors.

Associations between diabetes status and grip strength trajectory sub-groups in adulthood: findings from over 16 years of follow-up in the MRC National Survey of Health and Development.

BACKGROUND: Cross-sectional studies suggest a relationship between diabetes status and weaker grip strength (GS) in adulthood and limited evidence from longitudinal studies has focussed on the association with average change in GS. We aimed to investigate whether diabetes status was related to membership of distinct GS trajectories in mid-to-late adulthood in 2,263 participants in the Medical Research Council National Survey of Health and Development. METHODS: Grip strength (kg) was measured at 53, 60-64 and 69 years. Pre-/diabetes was defined at 53 years based on HbA1c > 5.6% and/or doctor-diagnosis of diabetes. Sex-specific latent class trajectory models were developed and multinomial logistic regression was used to investigate the association between pre-/diabetes status and membership into GS trajectory classes. RESULTS: For both males and females, a 3-class solution ('High', 'Intermediate', 'Low') provided the best representation of the GS data and the most plausible solution. There was no evidence that pre-/diabetes status was associated with class membership in either sex: e.g., adjusted odds ratios of being in the 'Low' class (vs. 'High') for males with pre-/diabetes (vs. no-diabetes) was 1.07 (95% CI:0.45,2.55). CONCLUSION: Using a flexible data-driven approach to identify GS trajectories between 53 and 69 years, we observed three distinct GS trajectories, all declining, in both sexes. There was no association between pre-/diabetes status at 53 years and membership into these GS trajectories. Understanding the diabetes status-GS trajectories association is vital to ascertain the consequences that projected increases in pre-/diabetes prevalence's are likely to have.

Anaesthesia in a parturient with systemic mastocytosis.

Mastocytosis is characterized by clonal expansion of mast cells, with abnormal accumulation in different organs. Perioperatively, numerous stimuli may lead to the release of vasoactive substances by mast cells. Parturients with systemic mastocytosis pose a challenge to the anesthesiologist: on one hand, the pain and stress of labor may lead to greater mast cell activation and, on the other, the administration of drugs that may possibly trigger the release of mast cell mediators. The authors describe a case of a 34-year-old pregnant woman with systemic mastocytosis who requests labor analgesia. An epidural analgesia was performed after induction of labor, after considering anesthetic particularities. The epidural procedure, labor and delivery were uneventful. A review of systemic mastocytosis is provided and its anesthetic considerations are discussed.

Obesity in early adulthood and physical functioning in mid-life: Investigating the mediating role of c-reactive protein.

INTRODUCTION: Obesity in adulthood is associated with reduced physical functioning (PF) at older ages. However, mechanisms underpinning this association are not well understood. We investigated whether and the extent to which C-reactive protein (CRP) mediates the association between early-adult obesity and mid-life PF. METHODS: We used data from 8495 participants in the 1958 British birth cohort study. Body mass index (BMI), CRP and PF were measured at 33, 45 and 50y, respectively. Poor PF was defined as the lowest (sex-specific) 10% on the Short-form 36 Physical Functioning subscale. We accounted for prospectively measured confounders in early-life (e.g., social class at birth) and in mid-adulthood (e.g., 42y comorbidities). We decomposed the total effect of early-adult obesity on mid-life PF into direct and indirect (via CRP) effects, by employing a mediation analysis based on parametric g-computation. RESULTS: The estimated total effect of obesity at 33y on poor PF at 50y, expressed as an odds ratio (OR), was 2.41 (95% CI: 1.89, 3.08). The direct effect of obesity on poor PF (i.e., not operating via CRP), was 1.97 (95% CI: 1.51, 2.56), with an indirect effect of 1.23 (95% CI: 1.10, 1.37). As such, the proportion of the total effect which was mediated by the effect of obesity on CRP at 45y, was 23.27% (95% CI: 8.64%, 37.90%). CONCLUSION: Obesity in early-adulthood was associated with over twice the odds of poor PF in mid-life, with approximately 23% of the obesity effect operating via a downstream effect on CRP. As current younger generations are likely to spend greater proportions of their life course in older age and with obesity, both of which are associated with poor PF, there is an urgent need to identify mechanisms, and thus potential modifiable intermediaries, linking obesity to poor PF.

Family health and conditional cash transfer in Brazil and its effect on tuberculosis mortality.

BACKGROUND: Social protection can reduce poverty and act on the determinants of tuberculosis (TB). OBJECTIVE: To evaluate the impact of the Family Health Strategy (FHS) and the Bolsa Família Programme on TB-related mortality in Brazil. METHODS: This was an ecological study in which the units of analysis were Brazilian municipalities between 2001 and 2012. The principal independent variables were the levels of coverage of the primary health care system and the conditional cash transfer programme. The dependent variable was TB mortality rate (obtained from national databases). Descriptive analysis and negative binomial regression based on panel data using fixed-effects models were performed. Crude and adjusted estimates were calculated for continuous and categorical variables. RESULTS: A high FHS coverage was significantly associated with a reduction in the TB mortality rate (RR 0.80, 95%CI 0.72-0.89). An increase in the coverage of the Brazilian cash transfer programme was significantly associated with a reduction in the TB mortality rate (RR 0.87, 95%CI 0.81-0.96). CONCLUSION: FHS and the Bolsa Família conditional cash transfer programme had a positive impact on the TB mortality rate in Brazil. Public policies should include economic support combined with health promotion.

Tretinoin (0.05% cream vs. 5% peel) for photoaging and field cancerization of the forearms: randomized, evaluator-blinded, clinical trial.

BACKGROUND: Topical tretinoin cream is the gold standard treatment for skin ageing, particularly photoaging. The purpose of tretinoin peel was to obtain similar results, but in a shorter time, however, there have been few controlled trials on its effectiveness. OBJECTIVE: To compare efficacy and safety of tretinoin 0.05% cream and 5% as a peeling agent on photoaging and field cancerization of the forearms. METHODS: Clinical trial with therapeutic intervention, prospective, randomized (computer-generated randomization list), parallel, comparative (intrasubject) and evaluator-blinded (except for histology and immunohistochemistry), including 24 women (48 forearms) aged over 60 years who have not undergone hormone replacement and categorized as Fitzpatrick skin phototype II or III. The forearms of the participants were randomized for treatment with 0.05% tretinoin cream three nights a week, or 5% tretinoin peel every 2 weeks. The opinion of the participant, severity of photoaging, corneometry, profilometry, high-frequency ultrasound, histology (haematoxylin-eosin and Verhoeff stainings) and immunohistochemistry (p53, bcl-2, Ki67 and collagen I) were assessed. RESULTS: One participant dropped out. The mean photoaging score reduced 20% and the mean actinic keratosis (AK) count reduced 60% with no difference between treatments. Three efficacy parameters showed opposite effects between the tretinoin treatments (P < 0.05%): (i) thickness of the corneal layer decreased with 0.05% tretinoin and increased by 5%; (ii) dermis echogenicity increased by 0.05% and decreased by 5% and (iii) Ki67 expression increased by 0.05% and decreased by 5%. There was good tolerability for both regimens. CONCLUSION: Tretinoin as a cream 0.05% or peeling (5%) is safe and effective for the treatment of moderate photoaging and forearm field cancerization. The cream was superior in improving ultrasonographic parameters of ageing. Peeling was shown a superior performance in the stabilization of field cancerization.

Effect of Brazil's conditional cash transfer programme on tuberculosis incidence.

OBJECTIVE: To evaluate the impact of the Brazilian cash transfer programme (Bolsa Família Programme, BFP) on tuberculosis (TB) incidence in Brazil from 2004 to 2012. DESIGN: We studied tuberculosis surveillance data using a combination of an ecological multiple-group and time-trend design covering 2458 Brazilian municipalities. The main independent variable was BFP coverage and the outcome was the TB incidence rate. All study variables were obtained from national databases. We used fixed-effects negative binomial models for panel data adjusted for selected covariates and a variable representing time. RESULTS: After controlling for covariates, TB incidence rates were significantly reduced in municipalities with high BFP coverage compared with those with low and intermediate coverage (in a model with a time variable incidence rate ratio = 0.96, 95%CI 0.93-0.99). CONCLUSION: This was the first evidence of a statistically significant association between the increase in cash transfer programme coverage and a reduction in TB incidence rate. Our findings provide support for social protection interventions for tackling TB worldwide.

Shaping Ability of ProTaper Next, WaveOne, and Reciproc in Simulated Root Canals.

INTRODUCTION: The study aimed to compare the shaping and preservation of the original curvature of simulated curved root canals using the following instruments: Reciproc (Rcp), WaveOne (Wo), and the ProTaper Next system (Ptn). MATERIALS AND METHODS: A total of 45 resin blocks with simulated curved root canals were divided into three groups (n = 15), prepared using the Rcp (R25), Wo (25/0.8), and Ptn (X2) instruments. Standardized photographs were taken before and after canal instrumentation. After the superimposition of the images, the amount of resin removed from the curvature's inner and outer walls was measured at six apical levels, at intervals of 1 mm. The canals' angles of curvature before and after instrumentation were subtracted. RESULTS: There were no significant differences between the instruments in terms of the total amount of resin removed of the inner or outer walls of the apical curvature (p > 0.05). The Rcp instruments provided the best resin removed ratios between the walls. The means of the change in angle were as follows: Wo = 2.15°, Ptn = 0.92°, and Rcp = 0.21°. WaveOne caused significantly higher deviations than Rcp. CONCLUSION: All of the instruments demonstrated a tendency to straighten the simulated root canal. Instruments that use rotary movement achieved an effect similar to that of the reciprocating instruments in relation to change in angle. CLINICAL SIGNIFICANCE: Deviations from the original shape of the root canal could have a negative impact on the quality of a filling and consequently on the success of the endodontic treatment.

Urbanization effects on the composition and structure of macrophytes communities in a lotic ecosystem of Pernambuco State, Brazil / Efeitos da urbanização na composição e estrutura de comunidades de macrófitas aquáticas em um ecossistema lótico do Estado de Pernambuco, Brasil

Abstract Population growth in urban areas changes freshwater ecosystems, and this can have consequences for macrophyte communities as can be seen in the municipalities that border the Capibaribe River, Pernambuco, Brazil. This study reports the effects of urbanization on the composition and structure of macrophyte communities in areas along that river. The following urbanized and non-urbanized sampling sites were chosen: Sites 1 and 2 (municipality of Santa Cruz do Capibaribe), Sites 3 and 4 (municipality of Toritama), and Sites 5 and 6 (metropolitan region of Recife). These sites were visited every two months from January to July 2013 to observe seasonal variation (wet and dry seasons). Thirty-one species were identified. Generally, the non-urbanized sites had a higher number of species. Multivariate analyses indicated significant overall differences between urbanized and non-urbanized areas (R = 0.044; p < 0.001) and between seasons (R = 0.018; p < 0.019). Owing to the large variation in physical, chemical, and biological characteristics between urbanized and non-urbanized areas, we found that urbanization significantly influenced the floristic composition and structure of macrophyte communities.

Resumo O crescimento populacional em áreas urbanas causa alterações em ecossistemas aquáticos continentais com consequência sobre as comunidades de macrófitas. Este fato vem ocorrendo nos municípios que margeiam o rio Capibaribe, Pernambuco, Brasil. Este trabalho analisa os efeitos da urbanização sobre a composição e estrutura das macrófitas em trechos do referido Rio. Levando em consideração áreas urbanizadas e não urbanizadas, foram escolhidos os seguintes Pontos de Coleta: Pontos 1 e 2 no Município de Santa Cruz do Capibaribe, Pontos 3 e 4 no Município de Toritama, Pontos 5 e 6 na Região Metropolitana do Recife. Estes pontos foram visitados bimestralmente (janeiro – julho/2013), para a observação da variação sazonal (estações seca e chuvosa). Foram identificadas 31 espécies. Geralmente, os pontos das áreas não urbanizadas apresentaram um número maior de espécies. As análises multivariadas indicaram diferenças globais significativas entre áreas urbanizadas e não urbanizadas (R = 0,044, p < 0,001) e também entre as estações (R = 0,018; p < 0,019). Devido à grande variação física, química e biológica entre as áreas urbanizadas e não urbanizadas, observou-se que o fator urbanização influenciou significativamente na composição florística e na estrutura das comunidades de macrófitas.

Urbanization effects on the composition and structure of macrophytes communities in a lotic ecosystem of Pernambuco State, Brazil.

Population growth in urban areas changes freshwater ecosystems, and this can have consequences for macrophyte communities as can be seen in the municipalities that border the Capibaribe River, Pernambuco, Brazil. This study reports the effects of urbanization on the composition and structure of macrophyte communities in areas along that river. The following urbanized and non-urbanized sampling sites were chosen: Sites 1 and 2 (municipality of Santa Cruz do Capibaribe), Sites 3 and 4 (municipality of Toritama), and Sites 5 and 6 (metropolitan region of Recife). These sites were visited every two months from January to July 2013 to observe seasonal variation (wet and dry seasons). Thirty-one species were identified. Generally, the non-urbanized sites had a higher number of species. Multivariate analyses indicated significant overall differences between urbanized and non-urbanized areas (R = 0.044; p < 0.001) and between seasons (R = 0.018; p < 0.019). Owing to the large variation in physical, chemical, and biological characteristics between urbanized and non-urbanized areas, we found that urbanization significantly influenced the floristic composition and structure of macrophyte communities.

Parental obesity and risk factors for cardiovascular disease among their offspring in mid-life: findings from the 1958 British Birth Cohort Study.

BACKGROUND: Few studies have investigated whether parental adiposity is associated with offspring cardiovascular health or the underlying pathways. Studying these associations may help to illuminate the paradox of increasing prevalence of obesity and declining trends in cardiovascular disease (CVD) mortality, which may be partially explained by beneficial adaptations to an obesogenic environment among people exposed to such environments from younger ages. OBJECTIVE: To investigate associations between parental body mass index (BMI) and risk factors for CVD among their offspring in mid-life and to test whether associations of offspring BMI with CVD risk factors were modified by parental BMI. METHODS: Data from parents and offspring in the 1958 British birth cohort were used (N=9328). Parental BMI was assessed when offspring were aged 11 years; offspring BMI, waist circumference and CVD risk factors (lipid levels, blood pressure, glycosylated haemoglobin (HbA1c) and inflammatory and haemostatic markers) were measured at 44-45 years. RESULTS: Higher parental BMI was associated with less favourable levels of offspring risk factors for CVD. Most associations were maintained after adjustment for offspring lifestyle and socioeconomic factors but were largely abolished or reversed after adjustment for offspring adiposity. For some CVD risk factors, there was evidence of effect modification; the association between higher BMI and an adverse lipid profile among offspring was weaker if maternal BMI had been higher. Conversely, offspring BMI was more strongly associated with HbA1c if parental BMI had been higher. CONCLUSIONS: Intergenerational influences may be important in conferring the effect of high BMI on CVD risk among offspring.

Classification of color images of dermatological ulcers.

We present color image processing methods for the analysis of images of dermatological lesions. The focus of the present work is on the application of feature extraction and selection methods for classification and analysis of the tissue composition of skin lesions or ulcers, in terms of granulation (red), fibrin (yellow), necrotic (black), callous (white), and mixed tissue composition. The images were analyzed and classified by an expert dermatologist into the classes mentioned above. Indexing of the images was performed based on statistical texture features derived from cooccurrence matrices of the RGB (Red, Green, and Blue), HSI (Hue, Saturation, and Intensity), L*a*b*, and L*u*v* color components. Feature selection methods were applied using the Wrapper algorithm with different classifiers. The performance of classification was measured in terms of the percentage of correctly classified images and the area under the receiver operating characteristic curve, with values of up to 73.8% and 0.82, respectively.

Masticatory performance and taste perception in patients submitted to cancer treatment.

The aim of this study was to analyse mastication and the sense of taste in 39 patients submitted to cancer treatment in different areas of the body and to compare these variables with those of 44 control individuals within the same age range. The following aspects were assessed: dental status (DMFT); stimulated and non-stimulated salivary flow; sense of taste (salty, sweet, bitter and sour); and masticatory performance (MP), through the calculation of X(50). Logistic regression models were established to test the association between the independent variables and cancer treatment. Cancer patients had lesser stimulated salivary flow, a smaller number of teeth and occlusal units, worse MP, higher salty, sweet and sour taste scores and a lower bitter taste score (P < 0·05). A significant positive correlation was found between MP and the DMFT index in both groups (P < 0·05), meaning that a lower DMFT index value denoted a smaller X(50) value (better masticatory performance). The logistic regression model revealed that patients who had undergone cancer treatment had a greater probability of exhibiting a smaller number of teeth, higher salty and smaller bitter taste scores (P < 0·05). It was concluded that patients who were submitted to cancer treatment presented oral physiology alterations when compared with control subjects at the same age range.

Importância do controle de qualidade para a redução das amostras insatisfatórias cérvico-vaginais / The importance of quality control to reduce unsatisfactory cervicl smears

O objetivo deste estudo foi analisar as não-conformidades analíticas dos exames citopatológicos realizados no Setor de Citologia Oncótica, da Divisão de Patologia do Instituto Adolfo Lutz (SCO-IAL), e discutir ações corretivas para minimizar essas ocorrências. O SCO-IAL recebeu 44.197 amostras citopatológicas cérvico-vaginais enviadas pelas Unidades de Saúde (US), de setembro de 2005 a fevereiro de 2007, que foram coradas pelo método de Papanicolaou e classificadas segundo a Nomenclatura Brasileira recomendada pelo Ministério da Saúde. Do total, 1.155 (2,61%) foram classificadas como insatisfatórias, sendo: 351 por artefatos de dessecamento; 198 pela presença de piócitos; 98 por material insuficiente; 47 pela presença de sangue e 12 por superposição celular. Em 449 casos, houve associação de duas ou mais causas; sendo o dessecamento presente em 351 casos. Das 198 amostras insatisfatórias pela presença de piócitos, 37 apresentaram agentes infecciosos. Observou-se também nesse mesmo período que dos 1.558(3.52%) casos de atipias de significado indeterminado, 371 foram limitados em seu diagnóstico. Os resultados obtidos demonstram que programas de treinamento nas US são de melhor estratégia para melhoria na qualidade das amostras. O controle de qualidade interno e externo, desde a colheita até a emissão dos laudos, é fundamental para o sucesso dos programas de rastreamento citológico.

Self-sampling for human papillomavirus (HPV) testing as cervical cancer screening option. Experience from the LAMS study.

PURPOSE: To compare Hybrid Capture II (HC2) in detecting high-risk (HR) HPV in patient-collected vaginal samples with those obtained using gynaecologist collected samples. METHODS: Patients were submitted to Pap smears, visual inspection with acetic acid (VIA) and HC2 for hr-HPV. RESULTS: A total of 1,081 HC2 tests for HR-HPV were performed: 770 (71.2%) samples were collected by a physician and 311 (28.8%) were self-collected by the patients. In detecting any cervical lesion, the sensitivity of HC2 collected by a physician was higher (92.86%) than that (37.5%) in the self-sampling group. Negative predictive value (NPV) was high for both, 99.69% and 93.75%, respectively. Using the CIN2 cutoff, performance of HC2 was significantly improved: 92.9% and 62.5%, respectively. HC2 specificity for any cervical lesion and for CIN2 or higher were close to 90% in both groups. CONCLUSIONS: Self-sampled HPV testing is a powerful option to increase the detection of cervical lesions in women segregated from prevention programs.

A randomized comparative crossover study to assess the affect on circuit life of varying pre-dilution volume associated with CVVH and CVVHDF.

OBJECTIVE: To determine if circuit life is influenced by a higher pre-dilution volume used in CVVH when compared with a lower pre-dilution volume approach in CVVHDF. DESIGN: A comparative crossover study. Cases were randomized to receive either CVVH or CVVHDF followed by the alternative treatment. SUBJECTS: All patients >or= 18 yrs of age who required CRRT while in ICU were eligible to participate, but excluded if coagulopathic, thrombocytopenic or unable to receive heparin. Based on an intention-to-treat, 45 patients were randomized to receive either CVVH or CVVHDF followed by the alternative treatment. SETTING: A 24-bed, tertiary, medical and surgical adult intensive care unit (ICU). INTERVENTION: Blood flow rate, vascular access device and insertion site, hemofilter, anticoagulation and machine hardware were standardized. An ultrafiltrate dose of 35 ml/ kg/h delivered pre-filter was used for CVVH. A fixed pre-dilution volume of 600 mls/h with a dialysate dose of 1 L was used for CVVHDF. RESULTS: Thirty-one patients received CVVH or CVVHDF out of 45 participants followed by the alternative technique. There was a significant increase in circuit life in favor of CVVHDF (median=16 h 5 min, range=40 h 23 min) compared with CVVH (median=6 h 35 min, range=30 h 45 min). A Mann-Whitney U test was performed to compare circuit life between the two different CRRT modes (Z=-3.478, p<0.001). Measurements of circuit life on the 93 circuits which survived to clotting (50 CVVH and 43 CVVHDF) were log transformed prior to under taking a standard multiple regression analysis. None of the independent variables - activated prothrombin time (aPTT), platelet count, heparin dose, patient hematocrit or urea - had a coefficient partial correlation >0.09 (coefficient of the determination=0.117) or a linear relationship which could be associated with circuit life (p=0.228). CONCLUSION: Pre-diluted CVVHDF appeared to have a longer circuit life when compared to high volume pre-diluted CVVH. The choice of CRRT mode may be an important independent determinant of circuit life.

Neonatal BCG protection against tuberculosis lasts for 20 years in Brazil.

Bacille Calmette-Guérin (BCG) efficacy against pulmonary disease is highly variable; until very recently there was no evidence of protection after 10 years. In the control arm of a trial of efficacy of revaccination of schoolchildren in Brazil we found substantial protection (39%; 95%CI 9-58) of neonatal BCG against all forms of tuberculosis (TB) 15-20 years after vaccination, much longer than previously believed. This confirms recent findings from an earlier trial, and must be considered in the design of trials of new TB vaccines and in policy decisions based on assumed lack of neonatal BCG protection with time.

A comparison of dual skin test with mycobacterial antigens and tuberculin skin test alone in estimating prevalence of Mycobacterium tuberculosis infection from population surveys.

SETTING: City of Manaus, Amazonas, Brazil. OBJECTIVE: To compare estimates of Mycobacterium tuberculosis infection prevalence obtained using traditional tuberculin skin test (TST) criteria and dual skin test (DST) data. METHODS: A total of 1070 schoolchildren received DST with tuberculin and four environmental mycobacteria sensitins. Responses were classified as sensitin-dominant, tuberculin-dominant or non-dominant. Positive predictive values (PPV) were defined using 'narrow' and 'wide' standards based on DST responses. These predictive values were derived for each category of tuberculin indurations, and were used to calculate the prevalence estimates. RESULTS: Using DST data, the estimates of M. tuberculosis prevalence for scar-negative children were 7.4% (M. avium) and 7.8% (M. scrofulaceum) using the 'narrow' standard, and 16.9% (M. avium) and 15.2% (M. scrofulaceum) using the 'wide' standard. The percentage with TST > or =10 mm was 11.5%. Scar-positive children had higher estimates using both the 10 mm cut-off and DST data. CONCLUSION: In settings with a relatively low prevalence of M. tuberculosis infection and high cross-reactivity with environmental mycobacteria, DST can help to assess the validity of traditional thresholds for estimating the prevalence of M. tuberculosis infection. DST data with environmental antigens and tuberculin do not distinguish BCG-induced cross-reactivity.