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PubMed1996

The influence of carbon particles on the concentration of acid phosphatase and lysozyme enzymes within alveolar macrophages during the killing and degradation of Mycobacterium bovis.

SETTING: Diagnostic bronchoscopy performed on untreated African patients with tuberculosis revealed alveolar macrophages filled with carbon particles. It was postulated that this was the result of excessive inhalation of smoke from domestic fires and the consequent phagocytosis by alveolar macrophages. OBJECTIVE: To determine whether carbon particles influence acid phosphatase and lysozyme enzyme concentrations during the killing and degradation of Mycobacterium bovis by alveolar macrophages. DESIGN: Alveolar macrophages were recovered by bronchoalveolar lavage from adult rabbits and cultured. Experimental cultures were exposed to M. bovis and carbon particles, and controls only to M. bovis. Cultures were grown for 42 h for killing and degradation of organisms. Cells were microscopically enumerated for carbon particle content and enzyme stain intensity. The level of significance was determined by means of a statistical test for sample proportions and by using Student's t-test. RESULTS: The majority of alveolar macrophages in the experiments contained large amounts of carbon particles. The average percentage of alveolar macrophages that stained positive for acid phosphatase and lysozyme enzymes is significantly lower in the experiments than in the controls (P < 0.01 and P < 0.001 respectively). CONCLUSION: It is concluded that large amounts of carbon particles significantly decrease these enzyme concentrations intracellularly.

Acid Phosphatase↗

PubMed2006

A chain-binomial model for intra-household spread of Mycobacterium tuberculosis in a low socio-economic setting in Pakistan.

A simulation study using Greenwood's chain-binomial model was carried out to elucidate the spread and control of Mycobacterium tuberculosis among the household contacts of infectious pulmonary tuberculosis (TB) patients. Based on the observed data, the maximum-likelihood estimates (+/-S.E.) of chain-binomial probabilities of intra-household M. tuberculosis transmission from an index case in 3-person and 4-person households were 0.313+/-0.008 and 0.325+/-0.009 respectively. The chi2 goodness-of-fit test of observed and simulated mean expected frequencies of cases revealed good fit for 3-person (P=0.979) and 4-person (P=0.546) households. With the assumption of varying risk of M. tuberculosis transmission across the households under beta-distribution, goodness-of-fit tests of observed and mean simulated expected frequencies revealed the inadequacy of Greenwood's chain-binomial model both for 3-person (P=0.0185) and 4-person (P<0.001) households. Simulated M. tuberculosis control strategy comprising efficient diagnosis, segregation and prompt antibiotic therapy of index pulmonary TB patients showed a substantial reduction of new cases among the household contacts in both household sizes. In conclusion, segregation coupled with prompt antibiotic therapy of the index case, chemoprophylaxis of M. tuberculosis-exposed household contacts, and the assessment of household environmental risks to devise and implement an educational programme may help reduce the TB burden in this and similar settings.

Family Characteristics↗

PubMed2005

Establishment of a reference formulation for bioequivalence assessment of rifampicin-containing FDCs: an essential step towards improving tuberculosis treatment.

SETTING: Selection of a reference product for bioequivalence studies of rifampicin (RMP) in prequalifying fixed-dose combinations (FDC) for worldwide distribution through the WHO is critical. OBJECTIVE: To investigate the feasibility of establishing FDC formulations as reference products for bioequivalence studies of RMP in prequalification programmes. DESIGN: A biostudy was conducted as an open, two-period randomised cross-over trial. Two three-drug FDCs containing RMP, isoniazid and ethambutol hydrochloride were administered to a group of 22 volunteers with a wash-out period of 1 week. Plasma samples were collected and analysed for the concentration of RMP and desacetyl-RMP, a major active metabolite of RMP, up to 24 h. Pharmacokinetic parameters of RMP were calculated: Cmax, AUC0-24, Tmax, kel and absorption efficiencies. RESULTS: No significant difference was observed between the administered formulations with respect to the major pharmacokinetic parameters Cmax, Tmax and AUC0-24 when evaluated by parametric (two-way ANOVA) and non-parametric (Hauschke's analysis) statistical analysis. The concentration of RMP falls within the reported acceptable therapeutic range. CONCLUSION: FDCs can be developed as a reference product for bioequivalence studies.

Antibiotics, Antitubercular↗

PubMed1996

Transmission of tuberculosis to close contacts of patients with multidrug-resistant tuberculosis.

Multidrug-resistant tuberculosis (MDRTB) has emerged as a major public health problem worldwide. To determine the incidence and risk factors associated with tuberculosis among contacts of MDRTB index cases, we studied human immunodeficiency virus-seronegative close contacts of 64 culture-confirmed MDRTB patients in Rio de Janeiro, Brazil. Between March 1988 and July 1992, tuberculosis developed in 17 (7.8%) of 218 previously healthy close contacts of 64 MDRTB index cases (1.6 cases per 1,000-person-months of contact). Among strains of Mycobacterium tuberculosis isolated from 13 contacts of 12 index cases, six (46%) had susceptibility patterns identical to those of their index cases, four (31%) had different patterns of resistance, and three (23%) were susceptible to all drugs. Tuberculosis developed more frequently in male contacts (p < 0.05), persons > or = 15 yr of age (p < 0.05), nonwhites (p < 0.001), and persons not previously vaccinated with bacillus Calmette-Guerin (BCG) (p < 0.05). The association of BCG vaccination with decreased risk of disease was significant even when this variable was controlled (by Cox's regression analysis) for age, sex, race, purified protein derivative (PPD) status, and isoniazid prophylaxis. BCG vaccination appears to offer protection against tuberculosis during prolonged exposures to persons with MDRTB, which identifies a novel and specific indication of BCG use.

Adolescent↗

PubMed1993

Antigenic stimulation and multiple myeloma. A prospective study.

BACKGROUND: A causal relationship between antigenic conditions and multiple myeloma was suggested by case reports. Although controlled studies identified associations with individual conditions, they failed to give overall support to the hypothesis. Using a prospective cohort representative of the U.S. population, the authors hypothesized that immune-stimulating conditions are a risk factor for multiple myeloma. METHODS: The First National Health and Nutrition Examination Survey cohort of 14,407 persons were interviewed from 1971 to 1975 by the National Center for Health Statistics. Vital status with cause of death and hospitalizations were ascertained from 1982 to 1985 and in 1986. From the initial questionnaire, four risk factors were constructed: allergies (asthma, hives, hay fever, food allergies, and other allergies); autoimmune conditions (arthritis, thyroid disease and/or medication, rheumatic fever, diabetes, pernicious anemia); chronic bacterial conditions (chronic bronchitis or emphysema, chronic cough, tuberculosis, ulcers); and inflammatory conditions (gout, gallstones, recurrent or chronic enteritis, pleurisy). RESULTS: Eighteen multiple myeloma (MM) cases were documented. The rate ratio (RR) of MM increased as the number of reported inflammatory conditions increased (one condition, RR = 2.0, 95% confidence interval [CI] = 1.2-3.3; 2 or more conditions, RR = 4.3, 95% CI = 1.5-12.4). The RR of myeloma also increased (P = 0.0002) with time since start of inflammatory conditions (RR = 1.6 for every 10 years of exposure). When cases were restricted to those with more than five years of follow-up, myeloma risk increased with the number of inflammatory conditions (two conditions, RR = 4.6, 95% CI = 1.5-13.8). CONCLUSIONS: Although the number of cases is small and exposure may be misclassified, the prospective nature of the study design strengthens the results of the study.

Adult↗

PubMed1996

Increased limb lengths in patients with shortened spines due to tuberculosis in early childhood.

STUDY DESIGN: The spine and limb lengths of 26 patients who had a severe spinal deformity due to tuberculosis in childhood were measured and compared with similar data from 79 normal adult volunteers. OBJECTIVES: The aim of the study was to assess whether there are any compensatory growth mechanisms present in patients who had stunted spinal growth in childhood. SUMMARY OF BACKGROUND DATA: Previous studies have documented increased leg lengths in patients with adolescent idiopathic scoliosis who have had spinal fusions done. The aim of this study was to ascertain if this response was unique to scoliosis or was a more general response to the interruption of normal spine growth. METHODS: The standing height, spine height, leg length, and upper limb length were measured in 26 adults with stunted spinal growth due to tuberculosis of the spine contracted in early childhood, and compared with similar measurements in 79 normal volunteers. RESULTS: The patients with spinal deformity due to tuberculosis had significantly shorter mean standing and spine heights compared to the volunteers. However, the mean leg length of these patients was 19.4 mm longer than the volunteers and their mean upper limb length was 18.9 mm longer than the volunteers. These differences were statistically significant. CONCLUSION: Patients whose spinal growth was stunted due to disease in childhood have longer legs and upper limbs than healthy people. A compensatory stimulatory growth mechanism may be responsible for this. This has implications for the whole gamut of childhood spinal disorders that result in stunted spinal growth.

Adaptation, Physiological↗

PubMedDate not supplied

The effect of vitamin D as supplementary treatment in patients with moderately advanced pulmonary tuberculous lesion.

AIM: to compare the vitamin D group of pulmonary tuberculosis patients with a placebo group in terms of clinical improvement, nutritional status, sputum conversion, and radiological improvement. METHODS: sixty seven tuberculosis patient visiting the Pulmonary Clinic, of Cipto Mangunkusumo Hospital, Jakarta, from January 1st to August 31st, 2001 were included in this study. The subjects were randomised to receive vitamin D (0.25 mg/day) or placebo in a double blind method, during the 6th initial week of Tb treatment. The rate of sputum conversion, complete blood counts, blood chemistry as well as radiologic examination were evaluated. RESULTS: there were more male patients than females (39:28), 78.7% were in the productive age group, 71.6% had low nutritional status, 62.4% with low education level, and 67.2% with low income. One hundred percent of the vitamin D group and only 76.7% of the placebo group had sputum conversion. This difference is statistically significant (p=0.002). CONCLUSION: the sputum conversion had no correlation with the hemoglobin level, blood clotting time, calcium level, lymphocyte count, age, sex, and nutritional status. There were more subjects with radiological improvement in the vitamin D group.

Adolescent↗

PubMed1998

Does the efficacy of BCG decline with time since vaccination?

OBJECTIVE: To investigate whether the protective efficacy of bacille Calmette-Guérin (BCG) against tuberculosis decreases with time since vaccination. DESIGN: A quantitative review of all 10 randomized trials of BCG against tuberculosis in purified protein derivative (PPD)-negative individuals, that presented data for discrete periods. For each trial, we derived log rate ratios for the annual change in the efficacy of BCG. We also compared efficacy in the first two years, and the first 10 years, to that in the rest of the trial. RESULTS: There was considerable heterogeneity between trials in the annual change in the efficacy of BCG. In seven efficacy decreased overtime, while in three it increased. Average annual change in efficacy was not related to overall efficacy. Efficacy also varied between trials in the first two years after vaccination, at more than two years after vaccination and in the first ten years after vaccination. However the variation in efficacy between trials more than 10 years after vaccination was not statistically significant (P = 0.26). We therefore calculated that the average efficacy more than 10 years after vaccination was 14% (95% confidence interval -9% to 32%). CONCLUSION: BCG protection can wane with time since vaccination. There is no good evidence that BCG provides protection more than 10 years after vaccination.

BCG Vaccine↗

PubMed2005

Effectiveness of Bacillus Calmette Guerin (BCG) vaccination in the prevention of leprosy: a population-based case-control study in Yavatmal District, India.

OBJECTIVE: To estimate the effectiveness of Bacillus Calmette Guerin (BCG) vaccination in the prevention of leprosy. Study design. Population-based case-control study. METHODS: The study was carried out in Yavatmal District, Maharashtra, India. It included 364 cases of leprosy (diagnosed by the World Health Organization's criteria), born since 1962, that were detected during a leprosy survey conducted by the Government of Maharashtra in 2,175,514 people. Each case was pair-matched with one neighbourhood control for age, sex and socio-economic status. Exclusion criteria for controls included past or current history of tuberculosis or leprosy. BCG vaccination status was assessed by examination for the presence of a BCG scar, immunization records if available and information from subjects/parents of children. Subjects who were uncertain about BCG vaccination were not included. RESULTS: A significant protective association between BCG and leprosy was observed [odds ratio=0.46, 95% confidence intervals (CI) 0.34-0.61]. Overall vaccine effectiveness (VE) was 54% (95% CI 39-66). BCG effectiveness against multibacillary, paucibacillary and single skin lesion leprosy was 68% (95% CI 26-86), 57% (95% CI 29-74) and 48% (95% CI 22-65), respectively. Analysis of linear trend revealed a significant linear association between the protective effect of BCG and the type of leprosy. The BCG vaccine was more effective in those aged < or =20 years compared with those aged >20 years (VE 61%, 95% CI), among females compared with males (VE 60%, 95% CI), in lower socio-economic strata compared with upper and middle strata (VE 57%, 95% CI), and in subjects who had a BCG scar size < or =5 mm compared with those with a BCG scar size >5 mm (VE 61%, 95% CI). However, these differences were not statistically significant, as reflected by the overlapping 95% CIs. The overall prevented fraction was 35% (95% CI 22-46). CONCLUSION: The current study identified a beneficial role of BCG vaccination in the prevention of leprosy in the study population.

Adult↗

PubMed2006

[Meta-analysis on NRAMP1 gene polymorphisms and tuberculosis susceptibility in East-Asia population].

OBJECTIVE: To provide a quantitative summary in estimating the association between polymorphisms of 3 loci in NRAMP1 gene and susceptibility to tuberculosis in East-Asia population by means of meta-analysis. METHODS: We searched databases (MEDLINE, OVID and CBM disc) from January 1995 to May 2005 using "NRAMP1" or "SLC11A1", in combination with "tuberculosis", also performed a manual search of citations from relevant original studies and literature. For each study involved, information was collected concerning the characteristics of the subjects, such as mean age of cases and the size of study. These characteristics were used to evaluate the sources of variation. Summary ORs and corresponding 95% CI were estimated by fixed effects (Mantel-Haenszel) or random effects (DerSimonian and Laird) model. To check for publication bias,a funnel plot, using Egger's linear regression method, was constructed. Cumulative meta-analysis was performed to evaluate whether the summary OR for studies with the polymorphisms of the 3 loci in the NRAMP1 gene was changing along with the accumulation of more data. Chi-square goodness of fit was used to test deviation from Hardy-Weinberg equilibrium. RESULTS: Eight publications, with the number of cases and controls of 1067 and 1084 respectively, were identified and all genotype frequencies were consistent with Hardy-Weinberg equilibrium. The summary ORs for studies with polymorphisms of 3' UTR, D543N and INT4 loci of the NRAMPI gene among the East-Asia population were 1.68(95% CI: 1.31-2.16, P< 0.001), 1.78(95% CI: 1.38-2.30, P< 0.001), 1.56 (95% CI: 0.72- 3.35, P = 0.26), respectively when compared with their corresponding common homozygotes. Publication bias was not found in the studies with the three loci, except for INT4 locus, by Egger linear regression method. The cumulative summary effects ORs were 1.85 (P = 0.02) in 2000, 1.35 (P = 0.12) in 2002,1.64 (P= 0.001) in 2003, and 1.68 (P<0.001) in 2004 for 3'UTR locus, 1.88 (P = 0.001) in 2000,1.65(P = 0.001) in 2002,1.70(P<0.001) in 2003,1.76(P<0.001) in 2004, and 1.78(P<0.001) in 2005 for D543N locus, and 0.88(P = 0:70) in 2002, 2.50(P = 0.41) in 2003, 1.52(P = 0.42) in 2004 and 1.56(P = 0.26) in 2005 for INT4 loucs. CONCLUSION: Polymorphisms at 3' UTR and D543N loci had statistically significant association between the NRAMP1 variants and susceptibility to tuberculosis in the East-Asia descendants, and variant in the INT4 locus failed to show statistically significant association in the East-Asia population.

Asian People↗

PubMed2004

Differential induction of apoptosis and necrosis in monocytes from patients with tuberculosis and healthy control subjects.

BACKGROUND: Mycobacterium tuberculosis and purified protein derivative (PPD) induce apoptosis in murine macrophages and apoptosis and necrosis in human monocytes and alveolar epithelial cells. Macrophages from bronchoalveolar lavages and granulomas from patients with tuberculosis (TB) present both types of cell death; however, the significance of the type of cell death in TB remains uncertain. METHODS: Monocytes from PPD-positive control subjects and from patients with TB were exposed to PPD or M. tuberculosis. Apoptosis, necrosis, and the percentage of tumor necrosis factor (TNF)-alpha -positive and interleukin (IL)-10-positive cells were determined cytofluorometrically. Levels of lactate dehydrogenase, TNF-alpha, and IL-10 were measured in culture supernatants. The role of TNF-alpha and IL-10 was tested by blockade experiments. RESULTS: PPD and M. tuberculosis induced apoptosis in monocytes from PPD-positive control subjects, whereas cells from patients with TB presented apoptosis and necrosis. Cells from PPD-positive control subjects produced mainly TNF-alpha, whereas cells from patients with TB produced mainly IL-10. Blockade experiments suggest that TNF-alpha and IL-10 regulate the type of cell death occurring in response to M. tuberculosis. CONCLUSIONS: Results suggest that apoptosis of monocytes exposed to mycobacteria may partly explain the protective immune response found in PPD-positive control subjects, whereas necrosis may be determinant of the bacterial dissemination and tissue damage that occur in patients with active TB.

Adult↗

PubMed1988

Pathogenesis of Mycobacterium bovis infection in American bison.

Eighteen 12-month-old bison were randomly placed in each of 3 groups (6 animals/group): group-1 bison were exposed to live Mycobacterium bovis, group-2 bison were inoculated with killed M bovis in oil, and group-3 bison were noninfected controls. Six, 6-month-old, tuberculin test-negative calves were placed (pen contact) with group-1 bison 30 days after exposure to M bovis. Tuberculin skin test responses (caudal fold and/or comparative cervical) were detected in all bison in groups 1 and 2 at 2, 4, 6, 10, and 12 months. Tuberculin skin test responses were observed in 2 of 6 calves at 9 and 11 months after pen contact with M bovis-exposed bison (group 1). Statistically significant lymphocyte blastogenic responses to M bovis purified protein derivative were detected in group-1 bison exposed to live M bovis at 2 months after exposure (P less than 0.025). Significant ELISA reactions were detected in sera of bison at 2 months after exposure to killed M bovis in oil (P less than 0.005) and in bison 2 months after exposure to live M bovis (P less than 0.01). Significant tuberculin skin responses, ELISA reactions, or lymphocyte blastogenic responses to M bovis purified protein derivative were not observed in the 6 control bison. Grossly visible tuberculous lesions were observed in lymph nodes and/or lung collected at necropsy in 4 of 6 bison at 12 months after exposure to live M bovis. Microscopic granulomas compatible with tuberculosis were detected in 5 of 6 bison; M bovis was isolated from tissues of each of the 6 bison.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2004

Diagnostic accuracy of chest X-rays acquired using a digital camera for low-cost teleradiology.

Store-and-forward telemedicine, using e-mail to send clinical data and digital images, offers a low-cost alternative for physicians in developing countries to obtain second opinions from specialists. To explore the potential usefulness of this technique, 91 chest X-ray images were photographed using a digital camera and a view box. Four independent readers (three radiologists and one pulmonologist) read two types of digital (JPEG and JPEG2000) and original film images and indicated their confidence in the presence of eight features known to be radiological indicators of tuberculosis (TB). The results were compared to a "gold standard" established by two different radiologists, and assessed using receiver operating characteristic (ROC) curve analysis. There was no statistical difference in the overall performance between the readings from the original films and both types of digital images. The size of JPEG2000 images was approximately 120KB, making this technique feasible for slow internet connections. Our preliminary results show the potential usefulness of this technique particularly for tuberculosis and lung disease, but further studies are required to refine its potential.

Data Compression↗

PubMed2001

Tuberculosis and tuberculin quality: best intentions, misleading results.

OBJECTIVE: To compare the performance of three purified protein derivative (PPD) formulations: Tubersol (Connaught); RT23, Statens Serum Institut (SSI); and RT23, Mexico, tested in Mexican populations at low and high risk for tuberculosis (TB). DESIGN: A double-blinded clinical trial. SETTING: A university hospital in Mexico City. PARTICIPANTS: The low-risk population was first or second-year medical students with no patient contact; the high-risk population was healthcare workers at a university hospital. METHODS: Each of the study subjects received the three different PPD preparations. Risk factors for TB, including age, gender, occupation, bacille Calmette-Guérin (BCG) status, and TB exposure, were recorded. A 0.1-mL aliquot of each preparation was injected in the left and right forearms of volunteers using the Mantoux technique. Blind readings were done 48 to 72 hours later. Sensitivity and specificity were calculated at 10 mm of induration using Tubersol as the reference standard. The SSI tested the potency of the different PPD preparations in previously sensitized guinea pigs. RESULTS: The low-risk population had a prevalence of positive PPD of 26%. In the low-risk population, RT23 prepared in Mexico, compared to the 5 TU of Tubersol, had a sensitivity of 51%, a specificity of 100%, a positive predictive value of 100%, and a negative predictive value of 86%. The RT23 prepared at the SSI had a sensitivity of 69%, a specificity of 99%, a positive predictive value of 95%, and a negative predictive value of 90%. In the high-risk population, the prevalence of positive PPD was 57%. The RT23 prepared in Mexico had a sensitivity of 33%, a specificity of 100%, and a positive predictive value of 53%; the RT23 prepared at the SSI had a sensitivity of 91%, a specificity of 98%, a positive predictive value of 98%, and a negative predictive value of 89%. RT23 used in Mexico had a potency of only 23% of that of the control. There was no statistical association among those with a positive PPD, irrespective of previous BCG vaccination (relative risk, 0.97; 95% confidence interval, 0.76-1.3;P=.78). CONCLUSIONS: Healthcare workers had twice the prevalence of positive PPD compared to medical students. RT23 prepared in Mexico had a low sensitivity in both populations compared to 5 TU of Tubersol and RT23 prepared at the SSI. Previous BCG vaccination did not correlate with a positive PPD. Low potency of the RT23 preparation in Mexico was confirmed in guinea pigs. Best intentions in a TB program are not enough if they are not followed by high-quality control.

Adult↗

PubMedDate not supplied

[First results of anterior versus posterior instrumentation-fusion in the treatment of spondylodiscitis].

AIM: The present study on spondylodiscitis patients was carried out to compare prospectively and randomized the results of clinical and radiological outcomes of anterior versus posterior instrumentation after debridement and grafting. We aimed to make a recommendation concerning the optimum treatment of spondylodiscitis. METHOD: A total of 22 patients with spondylodiscitis were enrolled in the randomized trial to undergo an operation with anterior or posterior instrumentation after debridement and fusion with autologous bone transplant. 12 patients (group 1) were assigned to posterior Universal Spine System stabilization. 10 patients (group 2) were treated with anterior VentroFix instrumentation. In a prospective clinical investigation we have examined both operative therapies with regard to clinical and radiological outcome. The follow-up was one year. RESULTS: In patients with ventral Spondylodesis (group 2), prior recreation of patients was achieved in clinical examination and blood tests. Radiological results are even equivalent in both groups. Therefore we recommend ventral instrumentation as the superior surgical procedure. But the individual local situation has to enable ventral stabilization. CONCLUSION: We found advantages with anterior instrumentation in comparison to posterior stabilization in patients with spondylodiscitis. Advantages of ventral stabilization cause early mobilization postoperatively without any increase in complication rates. Except for operation time and intraoperative blood loss, no statistical difference were was seen. Important is the individual indication for each method depending on anatomical and clinical signs. Ventral instrumentation should be restricted to cases with sufficient bone stock.

Adult↗

PubMed1992

Efficacy of BCG vaccine against leprosy and tuberculosis in northern Malawi.

Protection afforded by BCG (bacillus Calmette-Guérin) vaccines against tuberculosis and leprosy varies widely between different populations. In the only controlled trial which assessed protective efficacy of BCG (Danish and Pasteur strains) against both diseases, there was slightly more protection against leprosy than against tuberculosis. We have studied the protective efficacy of BCG (Glaxo, freeze dried) vaccine against these two diseases in Karonga District, northern Malawi. BCG vaccination was introduced into this population in 1974. Prior information about BCG scar status was available for 83,455 individuals followed up between 1979 and 1989. 414 new cases of leprosy and 180 new cases of tuberculosis were found in this population over that period. Protection was estimated at 50% or greater against leprosy, and there was no evidence for lower protection against multibacillary (84%; 95% confidence interval 26% to 97%) than against paucibacillary (51%; 30% to 66%) disease. There was no statistically significant protection by BCG against tuberculosis in this population. These findings add to the evidence that BCG vaccines afford greater protection against leprosy than against tuberculosis.

Adolescent↗

PubMed2001

Cohort mortality study of North American industrial sand workers. II. Case-referent analysis of lung cancer and silicosis deaths.

BACKGROUND: A cohort mortality study of 2670 men in nine North American industrial sand plants resulted in 83 deaths from lung cancer 20 or more years after hire (standardized mortality ratio 139) and 37 deaths from silicosis (including seven from silico-tuberculosis). The lung cancer excess was unrelated to duration of employment and not found in all plants. OBJECTIVES: The primary aim was to determine whether lung cancer risk among these employees was related to quantitative estimates of crystalline silica exposure, after allowance for cigarette smoking. A secondary aim was to do the same for silicosis mortality, partly as a means of validating the estimated levels of exposure. METHODS: A nested case-referent study was undertaken with cases matched with up to two controls on plant, age and date of first employment from men who survived the case. Exposures were estimated by linking work histories to a job-exposure matrix, undertaken separately. Cigarette smoking information was obtained from medical records and other sources, blind as to case-control status. Matched statistical analyses were conducted using conditional logistic regression. FINDINGS: Odds ratios for silicosis mortality were significantly related to cumulative silica exposures and tended to a relationship with category of average crystalline silica concentration, but inconsistently with length of employment. After accounting for a strong effect of cigarette smoking, odds ratios for lung cancer were related to cumulative crystalline silica exposure and to average silica concentration, but not to length of employment. CONCLUSION: These findings support a causal relationship between lung cancer and quartz exposure after allowance for cigarette smoking, in the absence of cristobalite or other known occupational carcinogens.

Aged↗

PubMed2002

Size isn't everything.

Clinical trials now often involve thousands of patients, and statisticians emphasize the importance of trial size in ensuring that 'correct' answers are obtained. However, when a good treatment appears for a disease that was hitherto untreatable - for example, oranges for scurvy or streptomycin for tuberculosis - only a small trial is needed. Large trials are only needed to demonstrate small effects. The meta-analysis of small trials is often misleading, and may hide undesirable effects of individual drugs. The concept of equivalence between treatments is important, and while a statistically adequate equivalence trial may have to be very large, many clinicians will question the need for extreme statistical propriety. Clinical trials often do not reflect 'real world' practice, and the clinical relevance of a trial is more important than its size.

Digoxin↗