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NANASI 6: September 2002

NANASI 6: September 2002

In this issue of NANASI:

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  • Opportunistic infections: Tuberculosis
  • Question and Answer: How reliable are HIV  tests?
  • Where to refer your patients: In Central and Eastern Provinces
  • Spotlight on Chogoria: "Seizing the day" during circumcision season
  • "Sheet D" For Counselors: David and Damaris - A discordant couple

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OPPORTUNISTIC INFECTIONS: TUBERCULOSIS

Tuberculosis is the most important opportunistic infection in AIDS patients in Africa.  According to Dr. Chakaya, noted Kenyan tuberculosis consultant, about 40% of AIDS patients have active tuberculosis. About 40% of patients with active tuberculosis have AIDS. For this reason, some authorities recommend that all tuberculosis patients be routinely tested for HIV infection.

Of course, patients who clearly have active tuberculosis (by X-ray or sputum examination) should be given a full course of anti-tuberculosis treatment whether they are infected with HIV or not.

The problem arises in diagnosing active tuberculosis in AIDS patients who do NOT have the usual manifestations of tuberculosis. HIV infection can alter the response of the body to Mycobacterium tuberculosis. In fact, an AIDS patient's active tuberculosis condition can be totally overlooked on clinical examination. A Mantoux test can be "negative" in a patient with AIDS or with overwhelming tuberculosis infection.

If an AIDS patient does not respond to standard treatment for diarrhea, pneumonia, etc., a trial of anti-tuberculosis therapy may be warranted. Indeed, patents who do not respond to anti-retroviral therapy (ART) also might be given a therapeutic trial of anti-tuberculosis drugs, using the national treatment guidelines.

Much discussion has arisen as to how long anti-tuberculosis drugs should continue in an AIDS patient. Some suggest that the maintenance phase of treatment (INH and EMB) should be continued beyond the first six months for an additional six months as "secondary preventive therapy".

Should HIV-positive patients, without evidence of active tuberculosis, but with a positive Mantoux test receive "primary preventive therapy", ie., nine months of treatment with only  INH.?  The World Health Organization endorses this regimen, however the Kenyan heath authorities do not authorize its use in Kenyan patients.  Such INH monotherapy could foster increased resistance to this important drug.  In Kenya Mycobacterium tuberculosis resistance to INH already is 9-10 %.

    - From the AIDS Team of Nazareth Hospital


Q AND A: HOW RELIABLE ARE HIV TESTS?
    
Question: A laboratory technician from Nyeri asks: How reliable are the current HIV tests that we use in our hospital? Should we always do a confirmatory test?

Answer: Virtually all HIV tests approved for use in  Kenyan hospitals (Determine, Unigold, Unicomb, ELISA, Unimed). are tests for the presence of antibodies  to HIV.  These tests, if carefully protected and properly performed, are quite sensitive and specific (>97%). Three testing situations are mentioned:

(1) Testing blood for transfusion:
All the tests mentioned above are acceptable for testing blood for transfusion. If the test result is sero-positive, the blood must be thrown away immediately.

If the test result is sero-negative the blood generally is safe for transfusion, and a confirmatory test, is not obligatory. Transfusions always are dangerous, and one should never transfuse a patient unless it is absolutely necessary to save the patient's life. Blood donors should be interviewed and if they practice risky behaviors, their blood donation should be refused. For scheduled surgical operations which will require transfusions, one should encourage an autologous transfusion of the patient's own blood.
 

(2) Testing blood in symptomatic patients:
If a patient already has the signs and symptoms of HIV infection (weight loss, diarrhea, TB, oral thrush, etc.), and the test result is sero-positive, then this test result can be regarded as a "true positive" and no confirmatory test is warranted.

If  the test result is sero-negative, then HIV infection is not the cause of the patient's  illness.
 

(3) Testing blood in asymptomatic patients:
If the person has no signs or symptoms of HIV infection, but a test result is sero-positive,  this result occasionally may be a "false positive". In this case, a confirmatory test is recommended, and it should be a different test from the initial testing test.

If the test result is sero-negative for the asymptomatic person, he/she can be considered as non-infected, and no further testing is necessary. However, if one has reason to suspect that the patient recently has been infected, and might be in the "window period", a confirmatory test may be done 2-3 months later.

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Note on "the window period":
Antibodies do not become detectable in the blood until about six weeks after a person is infected with HIV. For this reason, there always is a very slight possibility that a person who has a sero-negative test result actually may have been infected by a recent exposure to the HIV,  but this is unusual. A second, or confirmatory antibody test would give no confirmation of the first sero-negative test result, unless the second test is done more than six weeks after the first test. (Confirmation is possible sooner, but it requires an HIV-PCR test, which is expensive and not available in most Kenyan hospitals.)


 

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