Tuberculin skin testing of physicians at a midwestern teaching hospital: a 6-year prospective study

Occupational respiratory infections

PURPOSE OF REVIEW

In the last decade, descriptions of outbreaks of extensively drug-resistant strains of tuberculosis (TB) have increased concern about the nosocomial transmission of TB - a potentially life-threatening occupational respiratory infection. In addition, outbreaks of avian influenza caused by an H5N1 virus, severe acute respiratory syndrome caused by a coronavirus A and the recent pandemic caused by an H1N1 influenza virus have heightened concern about occupational infectious illnesses among workers in healthcare and agriculture.

RECENT FINDINGS

The last decade has witnessed extensive research into the modes, patterns, determinants and extent of transmission of these illnesses. The most important findings regarding risk, determinants and preventive measures of these occupational infections and recent guidelines are reviewed in this article.

SUMMARY

Administrative, personal and engineering measures to control respiratory infection are effective and should be implemented in healthcare facilities. The use of N95 personal respirators by healthcare workers who are caring for pulmonary TB and viral respiratory infections patients is strongly recommended. Vaccination against influenza (including H1N1) is effective and strongly recommended for healthcare workers. Ultraviolet germicidal irradiation is underused at present, despite good evidence of safety and efficacy in elimination of airborne respiratory infectious agents including TB.

Job-related risk of latent tuberculosis infection in a homogeneous population of hospital workers in a low incidence area

BACKGROUND

Few comprehensive tuberculin surveys were carried out in a homogeneous population of health care workers (HCWs) in a low incidence area to assess the risk of tuberculosis (TB) infection by different occupational groups and units.

METHODS

Community and occupational factors and tuberculin skin test (TST) reactivity were determined in 1,755 HCWs.

RESULTS

The overall prevalence of tuberculin reactivity was 6%. Predicting factors for TST reactivity were age >47 years (OR = 2.88), history of household TB contact (OR = 2.41), years of work as HCW (OR = 2.57), physician (OR = 1.88), and working in microbiology (OR = 4.94), dialysis/nephrology (OR = 2.00), gynecology/obstetrics (OR = 2.01). In a multiple regression model working in microbiology [OR = 4.16 (1.27-13.6)], dialysis/nephrology [OR = 2.52 (1.36-4.65)], gynecology/obstetrics [OR = 2.46 (1.24-4.86)] and age >47 years [OR = 1.98 (1.14-3.46)] were significant predictors for infection.

CONCLUSIONS

A higher risk of latent infection can be demonstrated in well-defined groups of HCWs.

Les nouveaux tests immunologiques dans le diagnostic de la tuberculose (TB or not TB)

INTRODUCTION

Targeted testing and treatment of individuals with latent tuberculosis infection (LTBI), at high risk of progression to active tuberculosis (ATB), are key elements in the battle against tuberculosis, both in France and in many parts of the world. Though the finding of tubercle bacilli is the essential examination for the diagnosis of ATB, there is no indisputable test for LTBI.

BACKGROUND

The help currently given to the diagnosis of LTBI by the degree of positivity of the tuberculin skin test (TST) is limited, both operationally and logistically, in populations vaccinated with BCG or sensitised by atypical mycobacteria, and by its low sensitivity in those immuno-suppressed persons who are at greatest risk of progression. Moreover the TST has other operational limitations linked to return visits, repeat testing causing a boosting effect and subjective interpretation. A new approach follows the availability of two biological tests for the diagnosis of LTBI (QuantiFERON-TB and T-SPOT-TB) that measure the in-vitro production of interferon gamma (IFN-gamma) by the blood mononuclear cells in response to M. tuberculosis specific antigens (ESAT-6 and CFP10). This revue analyses the published studies, undertaken with varying numbers of patients, that evaluate the diagnostic accuracy of these two tests in comparison with TST. However, validation is handicapped by the lack of a "gold standard" for the diagnosis of LTBI. These studies demonstrate similar levels of specificity for the two biological tests. They are statistically higher than those for TST, particularly in populations vaccinated by BCG. On the other hand, their sensitivity was at least equivalent to that of TST and, in certain studies, superior with T-SPOT-TB. Finally, several studies in contacts have been undertaken with the aim of measuring the concordance between these biological tests and TST. The essential finding is of a very good correlation between positivity of the biological tests and the degree of exposure of the contacts. These tests have additional operational advantages over TST: completed in one visit, results available in 24 hours, absence of inter and intra observer divergence, detection of potential immuno-depression and avoidance of boosting by repeat testing.

VIEWPOINT

Currently, however, these biological tests present several operational limits: lower sensitivity in severe disease, incomplete data in immuno-suppressed subjects and in children, lack of predictive value for future development of ATB, lack of distinction between LTBI and ATB. Numerous clinical studies are under way, in France and elsewhere, in order to reduce these limitations and to allow the appropriate incorporation of these tests into protocols for the diagnosis of tuberculosis.

CONCLUSIONS

These two biological tests should, in the near future, replace or complement TST in the diagnosis of recent LTBI, leading to their optimal incorporation into the decision making processes of the national plans for the control of tuberculosis.

Review of epidemiological studies on the occupational risk of tuberculosis in low-incidence areas

This review summarizes the epidemiological evidence for occupationally acquired tuberculosis and considers the implications for the prevention of tuberculosis. The relevant epidemiological studies were identified on the basis of the Medline data bank, starting with the year 1966. The evaluation of occupational groups with an elevated tuberculosis risk is exclusively based on epidemiologic studies of good or acceptable quality, applying clearly defined criteria of methodological quality. In summary, the available epidemiological evidence suggests that the risk of tuberculosis is elevated in the following occupational groups: hospital employees in wards with tuberculosis patients; nurses in hospitals; nurses attending HIV-positive or drug-addicted patients; pathology and laboratory workers; respiratory therapists and physiotherapists; physicians in internal medicine, anaesthesia, surgery and psychiatry; non-medical hospital personnel in housekeeping and transport work; funeral home employees, and prison employees. However, the epidemiological evidence is limited for all these occupations, with the exception of the nurses, because of the lack of methodologically adequate studies that have got the statistical power to differentiate between specific work tasks. There is a need for large population-based studies with precise definition of exposure, which should include molecular epidemiologic methods in the investigation of occupational risk factors of tuberculosis.

Screening and treatment of latent tuberculosis among healthcare workers at low, moderate, and high risk for tuberculosis exposure: a cost-effectiveness analysis

OBJECTIVE

To evaluate cost-effective screening and treatment strategies for healthcare workers (HCWs) at risk for tuberculosis exposure.

DESIGN

A Markov model was developed to track three hypothetical cohorts of HCWs at low, moderate, and high risk for tuberculosis exposure. For those found to be tuberculin reactors at entry, the choice was for isoniazid treatment or no treatment. For those without tuberculin reactivity, the choice of screening intervals was 6 months, 1 year, 2 years, or 5 years. Outcomes measured were tuberculosis cases, death, life expectancy, and cost. Assumptions were derived from published data and analyses.

RESULTS

Treatment of initial reactors with isoniazid in all three risk groups was associated with a net savings of $14,800 to $15,700 for each tuberculosis case prevented. For those without evidence of infection at entry, the most cost-effective screening interval was 1 year for high-risk groups, 2 years for moderate-risk groups, and 5 years for low-risk groups, with a net savings $0.20 to $26 per HCW per year. Screening at a more frequent interval was still cost-effective.

CONCLUSIONS

For HCWs found to be tuberculin reactors, treatment of their latent infection is to their benefit and is associated with a net cost-savings. Regular tuberculin screening of HCWs can be cost-effective or result in a net cost-savings. Each institution could use its own skin test surveillance data to create an optimum screening program for its employees. However, for most HCWs, a 1-year screening interval would be a cost-effective and safe choice.

Risk of tuberculous infection among healthcare workers in a tertiary-care hospital in Ankara, Turkey

OBJECTIVE

To determine risk factors for tuberculin skin test (TST) positivity among healthcare workers (HCWs).

DESIGN

Two-step TST was performed in 2002.

SETTING

Tertiary-care hospital in Ankara, Turkey.

PARTICIPANTS

A sample of 491 hospital HCWs were included. Information related to demographics, profession, work duration, department, and individual and family history of tuberculosis (TB) was obtained by a structured questionnaire.

RESULTS

Four hundred eight (83%) had two-step TST positivity. On multivariate analysis, male physicians (relative risk [RR], 1.5; 95% confidence interval [CI95], 1.23-1.69; P = .001), nurses (RR, 1.5; CI95, 1.29-1.66; P = .005), radiology technicians (RR, 1.7; CI95, 1.35-1.73; P = .002), laboratory technicians (RR, 1.6; CI95, 1.3-1.74; P = .007), and male housekeepers (RR, 1.6; (HCWs). CI95, 1.38-1.7; P < .001) had a higher risk than did female physicians. Among laboratory technicians, radiology technicians had the highest TST positivity (85%). HCWs working for less than 1 year (RR, 0.8; CI95, 0.72-0.98; P = .027) had a lower risk of infection. The HCWs having bacille Calmette-Guerin vaccination (RR, 1.12; CI95, 1.08-1.45) had higher TST positivity.

CONCLUSION

Male physicians, nurses, and laboratory technicians had increased risk of Mycobacterium tuberculosis infection in this setting, but community exposure likely accounted for most infections.