Feasibility and reliability of health-related quality of life measurements among tuberculosis patients

The dramatic global impact of tuberculosis on mortality has been well documented, but its impact on morbidity has not been well described. The emphasis on treatment of latent tuberculosis (TB) infection highlights the tradeoff between short-term decrements in health status from 'preventive' therapy, and long-term gains related to fewer cases of active TB. However, these changes in health status have not been characterized. As a first step, we examined the feasibility and reliability of administering two health status questionnaires, in a multicultural TB clinic setting. The Medical Outcomes Study SF-36 and the EuroQOL EQ-5D were self-administered during 3 weekly interviews. One hundred and eighty-six potentially eligible patients were identified, of whom 112 could be evaluated; 106 (57%) were confirmed eligible. Sixty-seven (63%) agreed to participate; 24 (36%) were women. Fifty-three participants (79%) were foreign-born, with median residence in Canada of 3.5 years. Fifty (75%) of the participants completed all study measurements: 25 were treated for latent TB, 17 for active TB, and eight had previous active TB. Cronbach's alpha coefficients ranged from 0.73 to 0.94 for the SF-36 domain scores. Intraclass correlation coefficients were 0.66 for the SF-36 physical component summary, 0.79 for the mental component summary, and 0.73 for the EQ-5D. These instruments appeared reliable in a highly selected group of TB patients.

Yield of casual contact investigation by the hour

OBJECTIVE

Among casual contacts of tuberculosis (TB) patients, to assess how duration of contact, prior mycobacterial exposure, and performance of one or two tuberculin skin tests (TST), affect the likelihood that a positive TST represents conversion.

METHODS

Published estimates of mycobacterial prevalence and BCG coverage, and their effect on single or repeated TSTs, were used to calculate baseline prevalence of TST reactions in four populations commonly encountered in North American contact investigations. Using published estimates of hourly risk of TB infection, the probability that a positive TST represented conversion was calculated.

RESULTS

Among casual contacts with 20 hours of exposure, the likelihood that a single positive TST performed after 8 weeks represented conversion was 77% in persons from populations with low prior mycobacterial exposure, but only 6-8% in foreign-born populations. If tuberculin testing was performed immediately and then again 8 weeks post-exposure, 14-38% of all positive tests would be due to boosting, related to prior exposure to mycobacteria or BCG. If one TST, performed 8 weeks after exposure, was positive in casual contacts from populations with high prevalence of prior mycobacterial exposures, the likelihood of true conversion was less than 40%, even after 200 hours of exposure.

CONCLUSIONS

A single TST performed 8 weeks after the end of exposure among casual contacts will detect all true conversions, and minimize misdiagnosis due to boosting. The decision to perform TST on casual contacts should consider the likelihood of prior mycobacterial exposure in the population, as well as the duration of exposure.

Factors associated with humoral response to ESAT-6, 38 kDa and 14 kDa in patients with a spectrum of tuberculosis

SETTING

Tertiary care chest hospital in Montreal, Canada, where the average annual incidence of TB is 10/100,000 population.

OBJECTIVES

To evaluate the clinical correlates of humoral response to three Mycobacterium tuberculosis antigens.

METHODS

Humoral response to three M. tuberculosis antigens, 38 kDa, 14 kDa and ESAT-6, was measured with ELISA in patients with a spectrum of TB-related conditions. The association of positive tests for each antigen, defined with receiver operator characteristics (ROC) analysis, and patient characteristics was assessed in multivariate regression.

RESULTS

A total of 383 patients underwent serologic testing. In multivariate analysis, humoral response to 38 kDa was associated with active disease, response to 14 kDa was associated with inactive TB and female sex, and response to ESAT-6 with inactive TB, female sex, prior contact with TB, and recent arrival in Canada from high prevalence countries.

CONCLUSIONS

Response to the 38 kDa antigen was associated with current active disease, and was very different from response to the 14 kDa and ESAT-6 antigens. These latter two antigens were associated with risk factors for future active, but not current disease, suggesting that they might be useful to identify persons with higher risk of reactivation of latent TB.

Surgical impact of adhesions following surgery in the upper abdomen

Background

The Surgical and Clinical Adhesions Research (SCAR) study set out to determine the long-term morbidity associated with postoperative adhesions following open abdominal and pelvic surgery, including the burden associated with adhesions after surgery in the upper abdomen.

Methods

Scotland's National Health Service hospital admissions are recorded by the Scottish Medical Record Linkage system. This system allows detailed analysis of hospital activity throughout Scotland including follow-through of individual patients, with sophisticated accuracy checks to ensure the quality and totality of the data set. Within the SCAR study, the total number of individuals who underwent an open abdominal or pelvic procedure in 1986 was defined, a subset of whom underwent surgery in the anatomical area of the upper abdomen (fore gut and related organs). Disease (International Classification of Diseases version 9) and procedure (Office of Population Censuses and Surveys 3/4) codes for adhesion-related problems or reoperations that might be complicated by the presence of adhesions were identified. For the purposes of the study only readmissions for directly related adhesion complications during the following 10 years were considered (e.g. small bowel obstruction and adhesiolysis). The study was steered by a multidisciplinary panel of surgeons, gynaecologists and health economists.

Results

In 1986 in Scotland, a total cohort of 8714 patients had open surgery in the upper abdomen which was considered likely to cause adhesions. This compared to 12 585 undergoing open surgery in the lower abdomen (mid hindgut) and 8489 in the female reproductive tract. The majority of patients in this cohort underwent open surgery on the gallbladder (44·4 per cent) or stomach (20·6 per cent). During the 10-year study 3293 individuals (37·8 per cent) required one or more readmissions for surgical or medical treatment for conditions either related to adhesions or involving a reoperation which could be complicated by adhesions. In total, 7048 surgical or medical readmissions were identified, with a mean of 2·1 readmissions per patient. At least 321 (4·6 per cent) of these readmissions were a direct result of abdominal or pelvic adhesions, constituting a large clinical burden. Analysis of readmissions over time showed that this burden continued steadily over the 10-year study period. As well as this workload burden, there was a risk for the patient associated with open surgery on the foregut with a mean of 3·7 readmissions for direct adhesion complications for every 100 initial procedures. This rate varied according to the site of initial surgery: 3·0 per 100 procedures for open surgery of the gallbladder, 3·5 per 100 for the stomach and 7·3 per 100 for open surgery on the pancreas.

Conclusion

The SCAR study provides the first epidemiological assessment of postoperative adhesions. Using an extremely conservative view, the medical and surgical impact following open surgery in the upper abdomen is considerable with 4·6 per cent of readmissions over a 10-year period directly attributable to adhesions. The full impact of adhesions, including their effect on subsequent surgery, is likely to be considerably greater and extensive research is being progressed with the SCAR data set to investigate further the burden and associated costs, and optimum strategies to reduce the problem.

Demonstrating the clinical and cost effectiveness of adhesion reduction strategies

OBJECTIVE: To examine the feasibility of conducting Randomized Controlled Trials (RCT) in lower abdominal surgery to demonstrate a reduction in adhesion-related admissions following use of an adhesion reduction product, and to model the cost effectiveness of such products. METHODS: The number of patients in each limb of a RCT comparing an adhesion reduction product to a control has been estimated based on 25% and 50% reductions in adhesion-related readmissions one year after surgery, for P = 0.05 at a power of 80% and P=0.01 at a power of 90%. A cost effectiveness model based on the Surgical and Clinical Adhesions Research Group (SCAR) database has been developed which calculates the percentage reduction in readmissions required of an adhesion reduction product to return the cost of investment. It also estimates the cumulative costs of adhesion-related readmissions for lower abdominal surgery and the cost savings associated with an adhesion reduction policy using a low or high cost product. RESULTS: 7.2% of patients undergoing lower abdominal surgery will readmit due to adhesions in the first year after surgery. To demonstrate a 25% reduction in readmissions one year after surgery, it is calculated that a RCT would require between 5686 (P = 0.05, power=80%) and 7766 (P = 0.01, power = 90%) lower abdominal surgery patients followed-up for one year. A cost effectiveness analysis demonstrates that routine use of adhesion reduction products costing pound 50 per patient will payback the cost of such investment if they reduce adhesion-related readmissions by 16% after 3 years. A product costing pound 200 will need to offer a 64.1% reduction in readmissions after 3 years. For the estimated 158 000 lower abdominal surgery operations conducted in the UK each year, the cumulative costs of adhesion-related readmissions over 10 years are estimated at pound 569 Million. CONCLUSION: Demonstrating the clinical effectiveness of adhesion reduction products in the RCT setting is unlikely to be feasible due to the large number of patients required. Products costing pound 200 or more are unlikely to payback their direct costs.

Chest radiograph abnormalities associated with tuberculosis: reproducibility and yield of active cases

SETTING

Tertiary care referral centre specialising in respiratory diseases.

OBJECTIVES

Chest radiography is a major screening and diagnostic tool for tuberculosis (TB). We evaluated the reproducibility of a radiographic classification system for screening for active TB of immigration applicants to Canada. We also evaluated the validity of this classification system for detection of prevalent active TB among the screened applicants, as well as tuberculin-positive close contacts and symptomatic patients.

METHODS

Reproducibility was assessed by re-reading a randomly selected 10% sample of screening chest films. Validity was estimated from the final clinical and microbiologic diagnosis of patients undergoing detailed clinical evaluation.

RESULTS

Inter-reader agreement using five broad categories was moderate (kappas of 0.44-0.56), while intra-reader agreement was substantial (kappas of 0.59-0.72). After adjustment for age and patient group, the adjusted odds of active tuberculosis, relative to normal or minor findings or granulomas, for fibronodular changes was 10.2 (95% confidence interval [CI] 3.2-33), for mass or pleural effusion it was 11.6 (95%CI 3.6-37), and for parenchymal infiltrate it was 46.1 (95%CI 18-117). Among tuberculin-positive close contacts, the probability of active tuberculosis was more than 50% if the radiographs showed any mass, pleural disease, or parenchymal infiltrates.

CONCLUSION

A simple classification of TB-related chest radiographic abnormalities into five broad categories had moderate to substantial reproducibility of readings, with reasonable validity.

Yield of smear, culture and amplification tests from repeated sputum induction for the diagnosis of pulmonary tuberculosis

OBJECTIVES

To assess the yield of repeated sputum induction for the diagnosis of active tuberculosis in patients who do not produce spontaneous sputum, or with smear-negative spontaneous samples.

METHODS

Induced sputum was examined with fluorescent microscopy, two amplification methods (PCR Amplicor MTB, and MTD2), and cultured for mycobacteria using liquid (Bactec 12B) and Lowenstein-Jensen media. Bronchoscopy and collection of other specimens were performed at the discretion of the treating physician.

RESULTS

A total of 1115 sputum inductions performed in 500 patients without adverse events yielded an adequate specimen in 1113 (99.8%), and microbiological confirmation in 43 of 44 (98%) culture-positive active TB cases. Yield increased with repeated sputum induction. The cumulative yield for acid-fast bacilli smear and mycobacterial culture was 64% and 70% respectively for one, 81% and 91% for two, 91% and 99% for three, and 98% and 100% for four induced samples. Yield of PCR also increased with the greater number of induced samples tested.

CONCLUSIONS

Repeated sputum induction could considerably improve diagnostic accuracy for pulmonary TB.

Postoperative adhesions: ten-year follow-up of 12,584 patients undergoing lower abdominal surgery

PURPOSE

Postoperative adhesions are a significant problem after colorectal surgery. However, the basic epidemiology and clinical burden are unknown. The Surgical and Clinical Adhesions Research Study has investigated the scale of the problem in a population of 5 million.

METHODS

Validated data from the Scottish National Health Service Medical Record Linkage Database were used to define a cohort of 12,584 patients undergoing open lower abdominal surgery in 1986. Readmissions for potential adhesion-related disease in the subsequent ten years were analyzed. The methodology was conservative in interpreting adhesion-related disease.

RESULTS

In the study cohort 32.6 percent of patients were readmitted a mean of 2.2 times in the subsequent ten years for a potential adhesion-related problem. Although 25.4 percent of readmissions were in the first postoperative year, they continued steadily throughout the study period. After open lower abdominal surgery 7.3 percent (643) of readmissions (8,861) were directly related to adhesions. This varied according to operation site: colon (7.1 percent), rectum (8.8 percent), and small intestine (7.6 percent). The readmission rate was assessed to provide an indicator of relative risk of adhesion-related problems after initial surgery. The overall average rate of readmissions was 70.4 per 100 initial operations, with 5.1 directly related to adhesions. This rose to 116.4 and 116.5, respectively, after colonic or rectal surgery-with 8.2 and 10.3 directly related to adhesions.

CONCLUSIONS

There is a high relative risk of adhesion-related problems after open lower abdominal surgery and a correspondingly high workload associated with these readmissions. This is influenced by the initial site of surgery, colon and rectum having both the greatest impact on workload and highest relative risk of directly adhesion-related problems. The study provides sound justification for improved adhesion prevention strategies.

Small bowel obstruction due to postoperative adhesions: treatment patterns and associated costs in 110 hospital admissions

The workload and costs of the emergency admissions and treatment of adhesive small bowel obstruction (ASBO) are unclear. This review details and costs the admission workload of ASBO. All admissions over a 2-year period for ASBO at two district general hospitals were identified through ICD10 diagnostic codes. Diagnostic investigations, treatment patterns, ward stay and outcome information for admissions were detailed from clinical records to develop mean cost estimates and assess the associated workload. Of the 298 admissions identified, 188 were not due to ASBO and were excluded from analysis. Of the 110 admissions detailed, 41 (37%) were treated surgically and 69 (63%) conservatively. Most admissions occurred through general practitioner referral (86.4%) to accident and emergency (90.0%). Mean (SD) length of stay was 16.3 days (11.0 days) for surgical treatment and 7.0 days (4.6 days) for conservative treatment. In-patient mortality was 9.8% for the surgical group and 7.2% for the conservative group. Costs were based on the mean values from both centres for surgical and conservative admissions and detailed according to the cost of referral and follow-up (100.98 Pounds surgical versus 102.61 Pounds conservative), hospital ward and ICU stay (3,327.48 Pounds versus 1,267.92 Pounds), theatre time (832.32 Pounds surgical only), investigations (282.73 Pounds versus 207.33 Pounds) and drug costs (133.90 Pounds versus 28.29 Pounds). Total treatment cost per admission for ASBO was 4,677.41 Pounds for surgically treated admissions and 1,606.15 Pounds for conservatively treated admissions. The impact of admissions for ASBO is considerable in terms of both costs and workload. Bed stay for these admissions represents the equivalent of almost one surgical bed per year and at least 2 days theatre time, impacting on surgical capacity and waiting lists. Adhesion prevention strategies may reduce the workload associated with ASBO. The review provides useful information for planning resource allocation.

Comparison of cost-effectiveness of tuberculosis screening of close contacts and foreign-born populations

Although tuberculosis (TB) screening of immigrants has been conducted for over 50 yr in many industrialized countries, its cost- effectiveness has never been evaluated. We prospectively compared the yield and cost-effectiveness of two immigrant TB screening programs, using close-contact investigation and passive case detection. Study subjects included all immigration applicants undergoing radiographic screening, already arrived immigrants requiring surveillance for inactive TB, and close contacts of active cases resident in Montreal, Quebec, Canada, who were referred from June 1996 to June 1997 to the Montreal Chest Institute (MCI), a referral center specializing in respiratory diseases. For all subjects seen, demographic data, investigations, diagnoses, and therapy were abstracted from administrative data bases and medical charts. Estimated costs of detecting and treating each prevalent active case and preventing future active cases, based on federal and provincial health reimbursement schedules, were compared with the costs for passively diagnosed cases of active TB. Over a period of 1 yr, the three programs detected 27 cases of prevalent active TB and prevented 14 future cases. As compared with passive case detection, close-contact investigation resulted in net savings of $815 for each prevalent active case detected and treated and of $2,186 for each future active case prevented. The incremental cost to treat each case of prevalent active TB was $39,409 for applicant screening and $24,225 for surveillance, and the cost of preventing each case was $33,275 for applicants and $65,126 for surveillance. Close-contact investigation was highly cost effective and resulted in net savings. Immigrant applicant screening and surveillance programs had a significant impact but were much less cost effective, in large part because of substantial operational problems.

Hospital ventilation and risk for tuberculous infection in canadian health care workers. Canadian Collaborative Group in Nosocomial Transmission of TB

BACKGROUND

The risk for and determinants of transmission of tuberculosis in hospitals caring for moderate numbers of patients with tuberculosis remain uncertain.

OBJECTIVE

To study the association of tuberculin conversion among health care workers with ventilation of patient care areas.

DESIGN

Cross-sectional observational survey.

SETTING

17 acute-care community or university hospitals.

PARTICIPANTS

All personnel who worked at least 2 days per week in the respiratory and physiotherapy departments or in selected nursing units.

MEASUREMENTS

Participating workers underwent tuberculin skin testing and completed self-administered questionnaires. Previous tuberculin tests and bacille Calmette-Guérin vaccinations were verified. Records of patients with tuberculosis who were hospitalized in the 3 years preceding the study were reviewed. Air exchanges per hour in patient care areas were measured by using a tracer gas technique. Multivariate proportional hazards regression was used to estimate the effect of occupational factors on documented tuberculin conversion, after adjustment for nonoccupational factors, among participants with at least one previous negative result on tuberculin skin testing.

RESULTS

Tuberculin conversion was associated with ventilation of general or nonisolation patient rooms of less than 2 air exchanges per hour (adjusted hazard ratio, 3.4 [95% CI, 2.1 to 5.8]); with work in moderate- to high-risk hospitals (adjusted hazard ratio, 2.2 [CI, 1.3 to 3.5]); and with work in the nursing (adjusted hazard ratio, 4.3 [CI, 2.7 to 6.9]), respiratory therapy (adjusted hazard ratio, 6.1 [CI, 3.1 to 12.0]), and physiotherapy (adjusted hazard ratio, 3.3 [CI, 1.5 to 7.2]) departments or housekeeping (adjusted hazard ratio, 4.2 [CI, 2.3 to 7.6]). Conversion was not associated with inadequate ventilation of respiratory isolation rooms (adjusted hazard ratio, 1.0 [CI, 0.8 to 1.3]).

CONCLUSION

Tuberculin conversion among health care workers was strongly associated with inadequate ventilation in general patient rooms and with type and duration of work, but not with ventilation of respiratory isolation rooms.

Does size matter? Utility of size of tuberculin reactions for the diagnosis of mycobacterial disease

It is a common belief that larger tuberculin reactions are more serious, and more likely to indicate patients with active tuberculosis (TB) or at high risk of disease in the future. Among 182 close contacts, and 502 patients suspected of possible active TB, 529 underwent tuberculin skin testing (TST) and 605 had a chest radiograph. Final diagnoses, based on all available clinical, microbiological, histological, and radiographic information, were active TB, 68; inactive TB, 274; nontuberculous mycobacterial disease, 14; conditions associated with anergy, 36; no detectable abnormality (except a positive TST) or condition unrelated to TB, 213; and negative TST, no further evaluation, 79. Among these patients, TST of 5 mm or larger was significantly more likely to indicate active or inactive TB (p < 0.001). However, among patients with TST of 5 mm or greater, the size and frequency distribution of tuberculin reactions were not different between subjects with different diagnoses, nor between subjects with different types or extent of radiographic findings. As well, TST reactions were no different in 121 subjects with or 176 subjects without a history of BCG vaccination. In close contacts or patients suspected of active TB, reactions less than 5 mm indicated lower likelihood of active or inactive disease, but above that threshold, size of tuberculin reaction did not matter.

Accuracy and utility of commercially available amplification and serologic tests for the diagnosis of minimal pulmonary tuberculosis

Diagnosis of patients with minimal active tuberculosis (TB) is difficult, as there is no single test with high sensitivity and specificity. The yield and clinical utility of a combination of diagnostic tests were prospectively studied among 500 consecutive patients referred for sputum induction for diagnosis of possible active TB. Patients underwent sputum induction, chest X-ray, tuberculin testing, and had blood drawn for serologic testing (Detect-TB test; Biochem ImmunoSystems). Sputum was examined with fluorescent microscopy and PCR (Amplicor MTB-Roche) and cultured for mycobacteria using liquid (BACTEC) and solid media. For the diagnosis of the 60 cases of active TB, sensitivity and specificity, respectively, of the following diagnostic tests were mycobacterial culture, 73% and 100%; PCR, 42% and 100%; chest X-ray, 67-77% and 66-76%; tuberculin testing, 94% and 20%; and serology, 33% and 87%. After consideration of PCR and radiographic and clinical characteristics, a positive serologic test was independantly associated with diagnosis of active disease (adjusted odds of disease if positive, 2.6; 95% confidence limits, 1.1,6.1). No currently available test has sensitivity and specificity high enough for the accurate diagnosis of minimal pulmonary TB. Utilization of a combination of tests, together with consideration of key clinical characteristics, could improve diagnostic accuracy.

What does tuberculin reactivity after bacille Calmette-Guérin vaccination tell us?

The effect of bacille Calmette-Guérin (BCG) vaccination on tuberculin reactivity is briefly reviewed. BCG vaccination will almost invariably result in tuberculin conversion with a positive tuberculin skin test developing 4-8 weeks after vaccination. However, these tuberculin reactions will wane-rapidly in all individuals who receive the vaccine in the neonatal period and more slowly in those who are vaccinated at an older age such as during the primary-school years. Of BCG vaccine recipients whose initial tuberculin skin test is negative, 10%-25% will have a positive tuberculin skin test if they are retested within 1-4 weeks-the so-called "booster phenomenon. " There is no relationship between tuberculin reactivity after BCG vaccination and the protective efficacy of the vaccine against development of active tuberculosis. Therefore, the ideal BCG vaccine would produce a scar at the site of injection to identify individuals who have been vaccinated but would have no effect on tuberculin reactivity.

Agreement in measuring socio-economic status: area-based versus individual measures

Area-based socio-economic status (SES) measures are frequently used in epidemiology. Such an approach assumes socio-economic homogeneity within an area. To quantify the agreement between area-based SES measures and SES assessed at the individual level, we conducted a cross-sectional study of 943 children who resided in 155 small enumeration areas and 117 census tracts from 18 schools in Montreal, Quebec. We used street address information together with 1986 census data and parental occupation to establish area-based and individual level SES indicators, respectively. As compared with the SES score determined at the level of the individual, 13 different area-based SES indices classified the children within the same quintile 28.7% (+/- 2.8%) of the time. The discrepancy was within one quintile in 35.3% (+/- 2.3%) of cases, two quintiles in 20.6% (+/- 3.6%), three quintiles in 11.3% (+/- 4.2%) and four quintiles in 4.1% (+/- 0.2%). In conclusion, we observed a substantial discrepancy between area- based SES measures and SES assessed at the individual level. Caution should therefore be used in designing or interpreting the results of studies in which area-based SES measures are used to test hypotheses or control for confounding.

Minimally invasive surgery for posterior gastric stromal tumors

BACKGROUND

Because involvement is extremely rare, surgery for gastric stromal tumors consists of local excision with clear resection margins. The aim of this study was to report the results of a consecutive series of nine patients with posterior gastric stromal tumors that were excised using a minimally invasive method.

METHODS

Patients received a general anesthetic before placement of three laparoscopic ports- a 10-mm (umbilical) port for the telescope and two working ports, a 12-mm port (left upper quadrant) and a 10-mm port (right upper quadrant). Grasping forceps were placed through an anteriorly placed gastrotomy to deliver the tumor through the gastrotomy into the abdominal cavity, thus allowing an endoscopic linear cutter to excise the tumor with a cuff of normal gastric tissue.

RESULTS

Nine consecutive patients with a median age of 73 years (range, 47-83) were treated. In seven patients, laparoscopic removal of the tumor was achieved. Two patients required conversion to an open operation because the tumor could not be delivered into the abdominal cavity. The median length of postoperative stay for the seven patients in whom the procedure was completed laparoscopically was 3 days (range, 2-6).

CONCLUSIONS

Posterior gastric stromal tumors can be removed safely using this minimally invasive method. Delivery of the tumor through the gastrotomy is essential for success.

Tuberculosis screening of immigrants to low-prevalence countries. A cost-effectiveness analysis

All adult immigrant applicants to Canada undergo chest radiographic screening for tuberculosis (TB). Tuberculin skin testing could reduce the number of chest X-rays, and identify more candidates for prophylaxis. We modeled the cost-effectiveness of chest radiography and tuberculin skin testing for TB prevention over a 20-yr time frame, among three simulated cohorts of 20-yr-old immigrants. Compared with no screening, radiographic screening prevented 4.3% of expected active TB cases in the highest risk cohort (50% TB-infected, 10% human immunodeficiency virus [HIV] seroprevalence), and 8.0% in the lowest risk cohort (5% TB-infected, 1% HIV seroprevalence). Tuberculin skin testing further reduced the expected incidence 8.0% and 4.0%, respectively. Compared with no screening, radiographic screening cost $3,943 Canadian per active TB case prevented in the highest risk cohort, and $236,496 per case prevented in the lowest risk group. Compared with radiographic screening, mass tuberculin skin testing cost $32,601 per additional case prevented in the highest risk group, and $68,799 per additional case prevented in the lowest risk group. Chest radiographic screening of young immigrants from countries with a high prevalence of TB is a relatively inexpensive means of TB prevention. Tuberculin skin testing is considerably less cost-effective. For immigrants from low-prevalence countries, both interventions are extremely costly with negligible impact. The cost-effectiveness of either strategy would be greatly enhanced by increased adherence to chemoprophylaxis recommendations. Radiographic screening of groups with a high prevalence of tuberculous infection will then likely save money.

Increased expression of IL-12 receptor mRNA in active pulmonary tuberculosis and sarcoidosis

Cytokines have been implicated in the pathophysiology and development of pulmonary diseases such as tuberculosis and sarcoidosis. In particular, the numbers of cells expressing Th1-type cytokines such as IFN-gamma and IL-12 are increased within the lungs of patients with these granulomatous diseases. As a factor promoting the commitment of naive lymphocytes to a Th1-type profile of cytokine expression, IL-12 may be pivotal in the cascade of proinflammatory events within the airways. In this study, we examined the expression of the IL-12 receptor (IL-12R) mRNA in bronchoalveolar lavage (BAL) fluid from patients with active pulmonary tuberculosis (n = 6) and active pulmonary sarcoidosis (n = 6), and from allergic asthmatics (n = 6) and normal control subjects (n = 6). Bronchoscopy with BAL was undertaken, and cell cytospins were examined using the technique of in situ hybridization. There was a significant increase in the numbers of cells expressing mRNA for both beta(1) and beta(2) subunits of the IL-12R in active pulmonary sarcoidosis (p < 0.02, p < 0.01, respectively) and active pulmonary tuberculosis (p < 0.01, p < 0.005, respectively) compared with normal control subjects. In contrast, the allergic asthmatic patients exhibited a significant decrease in the number of IL-12R mRNA-positive cells (both beta(1) and beta(2) subunits (p < 0.01, p < 0.005, respectively), compared with the normal control subjects. These patients did, however, exhibit a significant increase in IL-4R mRNA, which was not evident in those with either tuberculosis or sarcoidosis when compared with normal subjects (p < 0.05). Colocalization studies demonstrated that CD8+ve cells are a principal site for the expression of IL-12R in tuberculosis. In sarcoidosis, IL-12R was expressed both on CD4+ve and CD8+ve cells. The increased expression of receptors for IL-12 in granulomatous diseases such as pulmonary tuberculosis and sarcoidosis provides evidence supporting the commitment of lymphocytes to a Th1-type cytokine profile in vivo.