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Current RMA Instruments:
|Reasonable Hypothesis SOP||81 of 2015|
|Balance of Probabilities SOP||82 of 2015|
Changes from previous instruments:SOP Bulletin 184
- ICD-9-CM Codes: 010 – 017.5, 017.7 – 017.9, 018
- ICD-10-AM Codes: A15, A16, A17, A18, A19
Tuberculosis is a bacterial infection with one of the Mycobacterium tuberculosis group of organisms.
The infection can be in any location in the body and can be active or quiescent. If it is quiescent it is called ‘latent’ and is asymptomatic with no material impairment. A latent infection can subsequently be reactivated if the person becomes immunosuppressed. Typically in our veteran community most cases of tuberculosis will occur in the lungs and will usually be latent.
Tuberculosis is a notifiable disease. The Australian Immunisation Handbook in its 10th edition (2014)[i] states “approximately 1200 cases of TB are notified to Australian health authorities each year”, “the annual notification rate for TB has been relatively stable at approximately 5 to 6 cases per 100 000 population since 1985” and “most TB cases in Australia (over 85%) occur in persons born overseas, particularly those born in Asia, southern and eastern European countries, Pacific island nations, and north and sub-Saharan Africa”. Tuberculosis is carried in a human reservoir and it is present in Australia.
Confirming the diagnosis:
To confirm the diagnosis: for active pulmonary infection there needs to be a positive sputum culture, together with chest imaging. Latent infection is established by a positive interferon gamma release assay (blood test) specific for tuberculosis. A positive Mantoux skin test may not be sufficient since it could be a false positive due to past immunisation depending on the level, or a positive reading from other Mycobacterium such as M. avium, M. intracellulare, M. kansasii, M. marinum or M. ulcerans which are specifically excluded from this SOP.
The relevant medical specialist is an infectious disease physician or respiratory physician.
Additional diagnoses covered by these SOPs
- Latent tuberculosis (TB)
- Primary TB
- Reactivated TB
- Infection with Mycobacterium (M.) tuberculosis, M. africanum, M. canettii, M. bovis, M. caprae, M. microti, M. orygis, or M. pinnipedi.
Conditions not covered by these SOPs
- Infections by atypical mycobacterium such as M. avium, M. intracellulare, M. kansasii, M. marinum or M. ulcerans#
# non-SOP condition
This SOP is complicated since it includes both symptomatic (active) and asymptomatic (latent) tuberculosis infection.
For ‘active’ tuberculosis, the clinical onset will be when the symptoms or signs, subsequently attributed by a medical practitioner to active TB following confirmation of the disease by testing, first began.
For the ‘latent’ tuberculosis, the condition is asymptomatic and hence does not really have a clinical onset apart from the date of first confirmed positive test. If there is a typical lung focus of past infection, then the latent tuberculosis clinical onset could be taken back to the date of the first positive chest imaging.
The natural history of tuberculosis is complicated and depends upon the individual host response. As such it is recommended that an opinion from an infectious disease physician be sought, to provide an opinion on whether a clinical worsening is out of keeping with the natural history of the underlying pathology.
Riley (2015)[ii] states that “Among the approximately 5 to 10 percent of infected individuals who develop active disease, approximately half will do so within the first two to three years following infection” and “Among individuals with latent infection and no underlying medical problems, reactivation disease occurs in approximately 5 to 10 percent of cases during their lifetime” and “immunosuppression is clearly associated with reactivation TB…”.
Tuberculosis should be actively treated if the infection is active. The appropriate medical treatment for latent tuberculosis is variable. One approach is to eradicate the tuberculosis by using antimicrobial chemotherapy. The other approach is to not utilise any medication, but to monitor the veteran regularly. Both treatments are considered reasonable, given that the medications used are not without side effects. As such the choice of approach is often given to the patient to decide.
Comments on SOP factors
- Incidence of tuberculosis in cases per 100,000 of population per year. The World Health Organisation (WHO) has an online database which can be searched for the current incidence in the specific country. http://www.who.int/tb/country/data/profiles/en
- Pasteurisation is the ‘partial sterilisation’ by heating. It was named for Louis Pasteur.
- BCG is an abbreviation for Bacillus Calmette Guerin. This is a live but attenuated form of the tuberculosis which is used to immunise people prophylactically against future tuberculosis. It is also used as a treatment for bladder cancer when instilled directly into the bladder. Unfortunately in some circumstances, the BCG can unintentionally cause active tuberculosis.
[i] 2014, The Australian Immunisation Handbook, http://www.immunise.health.gov.au/internet/immunis...
[ii] Riley, L. 2015, ‘Natural history, microbiology, and pathogenesis of tuberculosis’, UpToDate, March 10, http://www.uptodate.com/contents/natural-history-m...