Miguel G. Madariaga, MD, Assistant Professor of Medicine, Section of Infectious Diseases, University of Nebraska Medical Center, Omaha, NE, USA.
Philip W. Smith, MD, Professor of Medicine and Division Chief, Section of Infectious Diseases, University of Nebraska Medical Center, Omaha, NE, USA.

Tuberculosis is a re-emerging public health threat. This article discusses the particular characteristics of tuberculosis among older adults and the use of the tuberculin skin test as a tool for diagnosis of tuberculosis infection with emphasis in long-term care facility residents. An overview of new diagnostic tests based on gamma interferon release is also included.
Key words: tuberculosis, tuberculin skin test, long-term care facilities, purified protein derivative.

Richard Long, MD, Professor, Department of Medicine, University of Alberta, Edmonton, AB; Chairman, Tuberculosis Committee, Canadian Thoracic Society.

The incidence of tuberculosis increases with age in Canadians. The prevalence of latent tuberculosis infection (LTBI) may also increase with age in Canadians, though information on the age distribution of LTBI is less precise. Chronic inflammatory conditions that currently constitute the major indications for new biologic therapies (tumour necrosis factor inhibitors), such as Crohn's disease and rheumatoid arthritis, often have an older age onset. Biologic therapies have the potential to cause LTBI to progress to active tuberculosis disease. Their use in older Canadians or other populations that may have a higher than average prevalence of LTBI poses a challenge to tuberculosis control.
Key words: tuberculosis, tumour necrosis factor inhibitors, age, rheumatoid arthritis, Crohn's disease.

Common Presentations, Diagnostic Strategies, and Principles of Treatment

Michael A. Gardam MSc, MD, CM, FRCPC
Medical Director,
Tuberculosis Clinic,
Associate Hospital Epidemiologist,
University Health Network,Toronto.

The elderly are one of four sub populations in Canada, which also include the foreign born, homeless persons, and Native Canadians, that are at high risk for developing active tuberculosis. There are several reasons why tuberculosis is common among the elderly: Firstly, today's elderly have a high possibility of being infected with M. tuberculosis. They are survivors of the earlier part of the twentieth century in which an estimated three-quarters or more of the population were infected with tuberculosis by the time they were 30 years of age. Secondly, the elderly often suffer from other conditions which predispose them to reactivation of tuberculosis, such as diabetes mellitus, chronic renal failure, malnutrition, and diseases requiring prolonged corticosteroid therapy. Finally, residents of nursing homes and long-term care facilities may become infected or reinfected through contact with other residents with active disease.

Symptoms
While the clinical symptoms of tuberculosis may be vague and non-specific in any age group, this is particularly true in elderly persons. Fever, malaise, weakness, and failure to thrive are the most consistent symptoms.

Kimby N. Barton, MSc
Assistant Editor,
Geriatrics & Aging

I have to admit that I was feeling more nervous than I had expected as I placed the mask over my face. Until this point the reality of my being about to enter a unit with patients who have active tuberculosis (TB), and are capable of infecting me with the disease, had not really sunk in. Suddenly, it seemed vitally important for the mask to form a proper seal around my nose and under my chin to ensure that no bacteria could enter any gap left between the mask and my face. Tuberculosis is an infectious disease caused by the bacterium Mycobacterium tuberculosis. Infection may result from the inhalation of minute droplets of infected sputum; hence the need for a sealed mask to protect me from accidentally inhaling any bacteria. Having secured the mask, I was ready to enter the inpatient tuberculosis clinic at West Park Hospital.

Tuberculosis is a devastating disease. It is suspected that TB has plagued humankind for more than 2000 years, and in fact, several reports describe Egyptian mummies, almost 4000 years in age, showing signs of tubercular decay in their skeletons! It is estimated that almost one third of the global population is infected and that there are 7 to 8 million new cases per year. In Canada, approximately 2000 new cases of TB occur each year, almost one-quarter of these in Toronto. In almost 90% of these cases the patients are recent immigrants from areas where TB is still a common problem.

Michael A. Gardam MSc, MD, CM, FRCPC
Medical Director, Tuberculosis Clinic
Associate Hospital Epidemiologist
University Health Network

What is a Skin Test and How is it Administered?
Tuberculin skin testing is the most established method of diagnosing tuberculosis infection, that is both active disease and asymptomatic latent infection. Different skin testing techniques have been developed over the past 70 years. The Mantoux test, however, is the standard procedure in North America. The Mantoux test involves the intradermal injection of 0.1 ml of purified protein derivative (PPD--a precipitate prepared from filtered heat-sterilized cultures of Mycobacterium tuberculosis). The only absolute contraindication to administering the test is a history of anaphylaxis induced by any of the components. Those with a history of BCG vaccination may be skin tested.

The test is usually administered in an area that is free of blood vessels, hair or edema, on the flexor surface of the forearm, but it may also be administered on the upper chest or back. The needle should be inserted just under the skin with the bevel facing up until the bevel is fully inserted. A bleb should be raised when the PPD is injected. If this is not accomplished, or the PPD leaks out onto the skin, the test should be readministered in a different site. The test must be read at 48 to 72 hours by a trained healthcare professional.