Appendix 2: Tuberculosis in Canada 2012 – Definitions and terms used in TB surveillance in Canada

Appendix 2: Definitions and terms used in TB surveillance in Canada^{Footnote 8}

TB case definition in the CTBRS

(in effect since 2005):

1. Cases with Mycobacterium tuberculosis complex (i.e. M. tuberculosis,M.canetti, M. bovis [excluding BCG strain], M. africanum, M.caprae. M.microti or M. pinnipedii) demonstrated on culture.

   OR

   In the absence of bacteriological proof, cases clinically compatible with active tuberculosis that have, for example:

   • chest x-ray changes compatible with active tuberculosis, including idiopathic pleurisy with effusion
   • active non-respiratory tuberculosis (meningeal, bone, kidney, peripheral lymph nodes, etc.)
   • pathologic or post-mortem evidence of active tuberculosis
   • favourable response to therapeutic trial of anti-tuberculosis drugs

   Note: Molecular biological techniques are research tools and are not included in the definition.

2. Cases of tuberculosis diagnosed in Canada include all cases: Canadian-born, immigrants, refugees, refugee claimants, convention refugees, students, visitors, migrant workers, and illegal aliens.
3. As of 2008, the CTBRS classifies all cases as new or re-treatment cases; see Canadian Tuberculosis Standards, 7th ed., Appendix C for complete definitions: New case No documented evidence or adequate history of previously active TB. Re-treatment case Documented evidence or adequate history of previously active TB that was declared cured or treatment completed by current standards; At least six months have passed since the last day of previous treatment; and Diagnosed with a subsequent episode of TB that meets the case definition for active TB. OR Documented evidence or adequate history of previously active TB that cannot be declared cured or treatment completed by current standards; Inactive for six months or longer after the last day of previous treatment; and Diagnosed with a subsequent episode of TB that meets the active TB case definition.

Diagnostic classification

The diagnostic classification of TB in Canada is based upon the International Classification of Diseases, 9th and 10th Editions.^{Footnote 7},^{Footnote 8} For each case of TB, up to five individual diagnoses can be captured for reporting purposes. The main diagnostic sites are divided into the following two broad categories: respiratory and non-respiratory. Respiratory is further subdivided into primary, pulmonary, and other respiratory:

• Primary includes primary respiratory tuberculosis and tuberculous pleurisy in primary progressive tuberculosis (ICD-9 codes 010.0-010.9; ICD-10 codes A15.7 and A16.7).
• Pulmonary includes tuberculosis of the lungs and conducting airways: tuberculous fibrosis of the lung, tuberculous bronchiectasis, tuberculous pneumonia, tuberculous pneumothorax, isolated tracheal or bronchial tuberculosis, and tuberculous laryngitis (ICD-9 codes 011-011.9, 012.2, 012.3; ICD-10 codes A15.0-A15.3, A15.5, A15.9, A16.0-A16.2, A16.4, A16.9).
• Other respiratory includes tuberculous pleurisy (non-primary); tuberculosis of: intrathoracic lymph nodes, mediastinum, nasopharynx, nose (septum), and sinus (any nasal) (ICD-9 codes: 012.0, 012.1 and 012.8; ICD-10 codes: A15.4, A15.6, A15.8, A16.3, A16.5, A16.8).
• Non-respiratory tuberculosis includes miliary, CNS, lymph, and other sites.

The table below summarizes the codes used by the two ICD systems for each diagnostic category.

For cases with multiple diagnostic sites, the placement of the case into a disease group is determined using the hierarchy below:

1. primary TB
2. pulmonary
3. other respiratory TB
4. miliary/disseminated
5. meninges/central nervous system
6. peripheral lymph nodes
7. other sites (includes TB of intestines, peritoneum, and mesenteric glands, bones and joints, genitourinary system, skin, eye, ear, thyroid, adrenal, and spleen)

For example, a case may have been diagnosed with TB of the peripheral lymph nodes (scrofula, scrofulous abscess, tuberculous adenitis) (ICD-9 17.2) and tuberculosis of lung, infiltrative (ICD-9 11.0). Because pulmonary TB is above peripheral lymph TB in the hierarchy, this case is classified as pulmonary TB.

Further reading

More information on definitions and medical terminology for bacteriological aspects, diagnosis, dissemination, treatment, prevention, screening, and control of tuberculosis is available in the Canadian Tuberculosis Standards, Seventh edition.^{Footnote 6}