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

TB in a low-incidence country: differences between new immigrants, foreign-born residents and native residents

BACKGROUND

New immigrants and foreign-born residents add to the burden of pulmonary tuberculosis (TB) in low-incidence countries. The highest TB rates have been found among recent immigrants. Active screening programs are likely to change the clinical presentation of TB, but the extent of the difference between immigrant and resident populations has not been studied prospectively.

METHODS

Adult new immigrants were screened upon entry to 1 of 5 immigration centers in Switzerland. Immigrants with abnormal chest radiographs were enrolled and compared in a cohort study to consecutive admitted foreign-born residents from moderate-to-high incidence countries and native residents presenting with suspected TB.

RESULTS

Of 42,601 new immigrants screened, 112 had chest radiographs suspicious for TB. They were compared with foreign-born residents (n=118) and native residents (n=155) with suspected TB (n=385 patients included). Active TB was confirmed in 40.5% of all patients (immigrants 38.4%, foreign-born residents 50%, native residents 34.8%). Clinical signs and symptoms of TB and laboratory markers of inflammation were significantly less common in immigrants than in the other groups with normal results in >70%. The proportion of positive results on rapid testing to detect M. tuberculosis (MTB) in 3 respiratory specimens was significantly lower in immigrants (34.9% for acid-fast staining; 55.8% for polymerase chain reaction) compared with foreign-born residents (76.2% and 89.1%, respectively) and native residents (83.3% and 90.9%, respectively). Isoniazid resistance and multi-drug resistance were more prevalent in immigrants.

CONCLUSION

New immigrants with TB detected in a screening program are often asymptomatic and have a low yield of rapid diagnostic tests but are at higher risk for resistant MTB strains. Postmigration follow-up of pulmonary infiltrates is essential in order to control TB among immigrants, even in the absence of clinical and laboratory signs of infection.

Cost-effectiveness of tuberculosis evaluation and treatment of newly-arrived immigrants

BACKGROUND

Immigrants to the U.S. are required to undergo overseas screening for tuberculosis (TB), but the value of evaluation and treatment following entry to the U.S. is not well understood. We determined the cost-effectiveness of domestic follow-up of immigrants identified as tuberculosis suspects through overseas screening.

METHODS

Using a stochastic simulation for tuberculosis reactivation, transmission, and follow-up for a hypothetical cohort of 1000 individuals, we calculated the incremental cost-effectiveness of follow-up and evaluation interventions. We utilized published literature, California Reports of Verified Cases of Tuberculosis (RVCTs), demographic estimates from the California Department of Finance, Medicare reimbursement, and Medi-Cal reimbursement rates. Our target population was legal immigrants to the United States, our time horizon is twenty years, and our perspective was that of all domestic health-care payers. We examined the intervention to offer latent tuberculosis therapy to infected individuals, to increase the yield of domestic evaluation, and to increase the starting and completion rates of LTBI therapy with INH (isoniazid). Our outcome measures were the number of cases averted, the number of deaths averted, the incremental dollar cost (year 2004), and the number of quality-adjusted life-years saved.

RESULTS

Domestic follow-up of B-notification patients, including LTBI treatment for latently infected individuals, is highly cost-effective, and at times, cost-saving. B-notification follow-up in California would reduce the number of new tuberculosis cases by about 6-26 per year (out of a total of approximately 3000). Sensitivity analysis revealed that domestic follow-up remains cost-effective when the hepatitis rates due to INH therapy are over fifteen times our best estimates, when at least 0.4 percent of patients have active disease and when hospitalization of cases detected through domestic follow-up is no less likely than hospitalization of passively detected cases.

CONCLUSION

While the current immigration screening program is unlikely to result in a large change in case rates, domestic follow-up of B-notification patients, including LTBI treatment, is highly cost-effective. If as many as three percent of screened individuals have active TB, and early detection reduces the rate of hospitalization, net savings may be expected.

Current issues in global tuberculosis control

Despite attempts to standardize tuberculosis (TB) control strategies, there remains wide variation in the selection and implementation of control strategies within and among nations. Some of this variation is appropriate; based on wide variations in the available resources, the prevalence of TB infection, the incidence of TB disease, the relative contribution of reactivation versus recent transmission to incident cases, and the rate of HIV co-infection. This review will discuss three controversial questions relevant to global TB control: (1) What is the role of the treatment of latent TB infection in global TB control? (2) What are successful strategies to control immigrant TB in low incidence countries? (3) What are successful strategies to control TB in persons with HIV infection?

Socio-cultural factors influencing prevention and treatment of tuberculosis in immigrant and Aboriginal communities in Canada

This multi-method study used a participatory action research approach to examine the complex net of socio-cultural factors that influenced behaviour related to tuberculosis (TB) prevention and treatment in the 10 highest risk cultural groups consisting of immigrant and Aboriginal populations in the province of Alberta, Canada. Trained community research associates collected qualitative interview data and helped with interpretation and evaluation. A community advisory committee established foundation principles and monitored the ethical and cultural appropriateness of the research process. A key finding is that although patients with active disease learn about TB from health professionals, people in high-risk populations need to learn more about TB transmission and prevention prior to contact. This is particularly important given that lack of knowledge of TB was strongly associated with negative attitudes towards TB and a worse experience of the disease. The study results underline the need for accessible and culturally appropriate health education about TB in the high risk groups. This can be accomplished in collaboration with lay people, particularly those who have recovered from active TB, their family members and health workers from the community.

Domestic returns from investment in the control of tuberculosis in other countries

BACKGROUND

We hypothesized that investments to improve the control of tuberculosis in selected high-incidence countries would prove to be cost saving for the United States by reducing the incidence of the disease among migrants.

METHODS

Using decision analysis, we estimated tuberculosis-related morbidity, mortality, and costs among legal immigrants and refugees, undocumented migrants, and temporary visitors from Mexico after their entry into the United States. We assessed the current strategy of radiographic screening of legal immigrants plus current tuberculosis-control programs alone and with the addition of either U.S.-funded expansion of the strategy of directly observed treatment, short course (DOTS), in Mexico or tuberculin skin testing to screen legal immigrants from Mexico. We also examined tuberculosis-related outcomes among migrants from Haiti and the Dominican Republic using the same three strategies.

RESULTS

As compared with the current strategy, expanding the DOTS program in Mexico at a cost to the United States of 34.9 million dollars would result in 2591 fewer cases of tuberculosis in the United States, with 349 fewer deaths from the disease and net discounted savings of 108 million dollars over a 20-year period. Adding tuberculin skin testing to radiographic screening of legal immigrants from Mexico would result in 401 fewer cases of tuberculosis in the United States but would cost an additional 329 million dollars. Expansion of the DOTS program would remain cost saving even if the initial investment were doubled, if the United States paid for all antituberculosis drugs in Mexico, or if the decline in the incidence of tuberculosis in Mexico was less than projected. A 9.4 million dollars investment to expand the DOTS program in Haiti and the Dominican Republic would result in net U.S. savings of 20 million dollars over a 20-year period.

CONCLUSIONS

U.S.-funded efforts to expand the DOTS program in Mexico, Haiti, and the Dominican Republic could reduce tuberculosis-related morbidity and mortality among migrants to the United States, producing net cost savings for the United States.

Screening of Immigrants and Refugees for Pulmonary Tuberculosis in San Diego County, California

STUDY OBJECTIVES

To evaluate the outcomes of a tuberculosis (TB) screening program for recent immigrants to San Diego County, CA, and to compare the demographic and clinical characteristics of pulmonary TB cases occurring in recently arrived foreign-born persons detected through this screening with those of similar cases found through routine surveillance.

DESIGN

Retrospective review of computer databases and medical records.

SETTING

Local public health department.

PATIENTS

Recent immigrants and refugees classified as TB suspects in their country of departure and foreign-born patients with active TB detected through routine surveillance.

RESULTS

Five hundred seventy-one of 658 immigrants and refugees (87%) of completed screening. Thirty-nine subjects (7%) were found to have active TB, and 433 subjects (76%) were found to have latent TB. A diagnosis of active TB was associated with age of 25 to 44 years (odds ratio, 3.6; 95% confidence interval, 1.1 to 11.6) and A (odds ratio, 25.7; 95% confidence interval, 1.3 to 512.2) or B1 classifications (odds ratio, 4.3; 95% confidence interval, 1.5 to 12.5). Cases detected through screening comprised 12% of all reported foreign-born persons with active TB. Compared to other recently arrived foreign-born persons with active TB, those detected through immigrant screening were more likely to be Asian and born in the Philippines and less likely to have advanced disease.

CONCLUSIONS

Most immigrants and refugees classified as TB suspects by foreign screening completed the US screening process, which had a high yield for detecting active and latent TB. Only a minority of foreign-born persons (12%) with active TB were discovered through this program, however, and additional measures are needed to facilitate early case finding in other foreign-born populations.

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.

Utility of the Lateral Chest Radiograph in the Evaluation of Patients With a Positive Tuberculin Skin Test Result *

STUDY OBJECTIVES

In the United States, chest radiographs are performed on patients with positive tuberculin skin test (TST) results. It is not known whether, in addition to a single posteroanterior radiograph, a lateral chest radiograph is clinically indicated or cost-effective. We sought to determine the utility of the lateral chest radiograph in evaluating TST-positive adults.

DESIGN

Cross-sectional study.

SETTING

Tertiary-care hospital.

PATIENTS

Adults with positive TST results.

MEASUREMENTS

Findings on posteroanterior radiographs alone were compared to posteroanterior and lateral chest radiographs.

RESULTS

In 2 of 535 cases (0.4%), lateral chest radiographs revealed a calcified granuloma not visible on posteroanterior radiographs. This finding did not alter patient management. In all other cases, lateral radiographs only confirmed findings seen on posteroanterior chest radiographs.

CONCLUSION

Treatment altering findings were always visible on posteroanterior radiographs alone. These results suggest that lateral chest radiographs are not useful in evaluating adults with positive TST results.

Tuberculosis among Tibetan refugee claimants in Toronto: 1998 to 2000

BACKGROUND AND OBJECTIVES

Between 1998 and 2000, approximately 525 Tibetan people previously living in the United States claimed refugee status in Canada, many of whom were referred to our centers for completion of tuberculosis (TB) screening. We reviewed TB-related outcomes in this cohort, to compare our experience with previously published work, and to assess follow-up after a stay in a low-incidence region.

METHODS

We performed a retrospective study of all patients of Tibetan origin assessed at our centers (St. Michael's Hospital and West Park Healthcare Centre, both in Toronto) for completion of TB screening, referred because of abnormal chest radiographic findings or positive tuberculin skin test (TST) result. We compared rates of active and drug-resistant TB in our cohort with local and national rates, as well as those previously published in similar groups.

RESULTS

One hundred eighty-nine individuals were referred to us for assessment, and 181 records were available for review. The mean duration of stay in Canada prior to presentation was 2.6 months, after having spent a mean of 11 months in the United States. Thirty-two percent of patients gave a history of previous TB, and 97% were TST positive. Culture-positive TB was diagnosed in 24 patients (13%, 4,571 per 100,000), 12 patients had at least one drug resistance (50% of cases), and 4 patients were resistant to at least isoniazid and rifampin (multidrug resistant, 17% of cases).

INTERPRETATION

People from highly TB endemic areas retain a very high risk of active TB and drug resistance, despite an intervening period in a low-prevalence country. It is important to maintain a high degree of suspicion for TB in all people from high-incidence areas. Treatment of all cases of latent TB infection or ongoing medical surveillance is likely justified in this population.

Conventional and molecular epidemiology of tuberculosis in Manitoba

BACKGROUND

To describe the demographic and geographic distribution of tuberculosis (TB) in Manitoba, thus determining risk factors associated with clustering and higher incidence rates in distinct subpopulations.

METHODS

Data from the Manitoba TB Registry was compiled to generate a database on 855 patients with tuberculosis and their contacts from 1992-1999. Recovered isolates of M. tuberculosis were typed by IS6110 restriction fragment length polymorphisms. Bivariate and multivariate logistic regression models were used to identify risk factors involved in clustering.

RESULTS

A trend to clustering was observed among the Canadian-born treaty Aboriginal subgroup in contrast to the foreign-born. The dominant type, designated fingerprint type 1, accounts for 25.8% of total cases and 75.3% of treaty Aboriginal cases. Among type 1 patients residing in urban areas, 98.9% lived in Winnipeg. In rural areas, 92.8% lived on Aboriginal reserves. Statistical models revealed that significant risk factors for acquiring clustered tuberculosis are gender, age, ethnic origin and residence. Those at increased risk are: males (p < 0.05); those under age 65 (p < 0.01 for each age subgroup); treaty Aboriginals (p < 0.001), and those living on reserve land (p < 0.001).

CONCLUSION

Molecular typing of isolates in conjunction with contact tracing data supports the notion of the largest ongoing transmission of a single strain of TB within the treaty-status population of Canada recorded to date. This data demonstrates the necessity of continued surveillance of countries with low prevalence of the disease in order to determine and target high-risk populations for concentrated prevention and control measures.

Costs and effectiveness--the impact of economic studies on TB control

This paper assesses the impact of economic studies on TB control during the period 1982-2002, with a focus on cost and cost-effectiveness studies. It begins by identifying broad categories of economic study relevant to TB control, and how economic studies can, theoretically, have an impact on TB control. The impact that economic studies of TB control have had in practice is then analysed through a systematic review of the literature on cost and cost-effectiveness studies related to TB control, and three case studies (one cost study and two cost-effectiveness studies). The results show that in the past 20 years, 66 cost-effectiveness studies and 31 cost studies have been done on a variety of important TB control topics, with a marked increase occurring after 1994. In terms of numbers, these studies have had most potential for impact in industrialized countries, and within industrialized countries are most likely to have had an impact on policy and practice related to screening and preventive therapy. In developing countries with a high burden of tuberculosis, far fewer studies have been undertaken. Here, the main impact of economic studies has been influencing policy and practice on the use of short-course chemotherapy, justifying the implementation of community-based care in Africa, and helping to mobilize funding for TB control based on the argument that short-course treatment for TB is one of the most cost-effective health interventions available. For the future, cost and cost-effectiveness studies will continue to be relevant, as will other types of economic study.

Global drug-resistance patterns and the management of latent tuberculosis infection in immigrants to the United States

BACKGROUND

In the United States, an increasingly disproportionate burden of tuberculosis among the foreign-born population has led to calls for improvements in the detection and treatment of latent infection in new immigrants. Current treatment guidelines do not take into account global differences in drug-resistance patterns or their implications for the treatment of immigrants. The use of multinational surveillance systems to guide the management of latent infection according to region-specific drug-resistance profiles could improve the efficiency of efforts to reduce the burden of tuberculosis in immigrants to the United States.

METHODS

We constructed a decision-analysis model by using a hypothetical cohort of all documented immigrants entering the United States from developing nations. Region-specific drug-resistance profiles were derived from data on 30,388 cases of infection. The model examined the effectiveness and cost effectiveness of four strategies: no intervention or tuberculin skin testing followed by treatment with isoniazid, treatment with rifampin, or treatment with rifampin plus pyrazinamide for those with a positive test result.

RESULTS

A strategy of detecting and treating latent tuberculosis infection was cost-saving among immigrants from Mexico, Haiti, sub-Saharan Africa, South Asia, and developing nations in East Asia and the Pacific. This strategy was highly cost effective among immigrants from other developing nations. Rifampin plus pyrazinamide was the preferred strategy for treating latent infection in immigrants from Vietnam, Haiti, and the Philippines.

CONCLUSIONS

For new immigrants to the United States from developing nations, a strategy of detecting and treating latent tuberculosis infection would lead to substantial health and economic benefits. Because of the high prevalence of resistance to isoniazid, treatment with a rifampin-containing regimen should be strongly considered for immigrants from Vietnam, Haiti, and the Philippines.

Mandatory screening and treatment of immigrants for latent tuberculosis in the USA: just restraint?

A report by the Institute of Medicine, Ending Neglect, and sponsored by the US Centers for Disease Control and Prevention, makes recommendations for achieving elimination of tuberculosis in the USA. Among them is the recommendation that a mandatory screening programme be introduced for latent tuberculosis infection in immigrants from high prevalence countries, and that the provision of a permanent residence card (green card) be linked to the completion of an approved course of preventive treatment. We examine the evidence put forward to support this proposal and assess whether such a mandatory programme for preventive treatment of individuals, who do not pose an immediate risk but could pose a risk in the future, meets internationally recognised standards for coercive public-health measures. We conclude from our analysis that there is reason to question (i) the risk analysis, (ii) the estimates of effectiveness of such a policy, (iii) the cost calculations, and (iv) the operational consequences put forward in the report. Moreover, we show that international standards for mandatory screening and treatment are not met.

The impact of non-compliance on the cost-effectiveness of pharmaceuticals: a review of the literature

Non-compliance with drug therapies not only limits their effectiveness, but in some instances, is associated with grave clinical sequelae and substantial economic burden. It is important, therefore, to consider non-compliance in economic evaluations. A review of pharmacoeconomic evaluations, which have applied sensitivity analysis to non-compliance rates, was undertaken to evaluate the impact of non-compliance on the cost-effectiveness of different drug therapies. Although 22 evaluations satisfied the inclusion criteria, additional information was obtained from the authors of most studies, as the published details were inadequate. The majority of evaluations assumed altered effectiveness owing to reduced compliance in the absence of supportive clinical evidence. Because of the disparity in the nature of the outcomes, the measures of non-compliance and the time horizon of the studies evaluated, it was not possible to compare the magnitude of the impact of non-compliance among different drug-disease combinations. However, it was evident that non-compliance always results in a reduction in efficacy, but its impact on costs varied substantially. The importance of incorporating measures of compliance is highlighted, as failing to account for 'real world' compliance rates in pharmacoeconomic evaluations may lead to selection of sub-optimal treatment strategies.

Miniature chest radiograph screening for tuberculosis in jails: a cost-effectiveness analysis

Jails are an important reservoir of tuberculosis infection in the United States. Screening for active disease in these high-risk settings is difficult. We used decision analysis to assess the cost effectiveness of routine miniature chest radiography for screening for tuberculosis on admission to jail. Infection rates, probabilities, and costs associated with detecting and treating tuberculosis were derived from published studies. We calculated an average total cost of $6.60 per inmate for routine radiograph screening on admission to jail. The cost of screening for active tuberculosis with miniature chest radiography was estimated to be $9,600 per case identified, compared with $32,100 per case with tuberculin skin testing and $54,100 per case with symptom screening. Chest radiography would also identify substantially more cases than other methods of screening. Screening for tuberculosis with miniature chest radiography is cost effective even under a wide range of assumptions regarding risk factors and prevalence of disease. Miniature chest radiography should be strongly considered as an important tool in the fight to eliminate tuberculosis from the high-risk populations that may be reached through screening in jails.