64 HIV Associated TB

Ankur 18/10/18

300,000 deaths yearly by HIV/TB coinfection

Globally that’s 1/5 of all TB deaths and 1/3 of all HIV+ deaths Responsible for 1/4 HIV admissions in SSA. TB found in 40% of HIV+ Postmor

TB Symptoms counts as any one of the four WHO TB Screening Questions. (Cough, Fever, Weight Loss, Night Sweats)

64.1 Why is it hard to diagnose HIV and TB

Symptoms are all dependent on a host immune response to TB, which you might not have with HIV. Same with CXR and Sputum Dx

You don’t really form granuloma with HIV +ve patients.

Patients are often “non-specifically septic” with TB and advanced HIV. It makes it difficult to distinguish from other opportunistic infections.

“Diagnostic Yield” - Likelihood that the diagnostic test will provide the information required. Will take into account sensitivity, but also the chance of your test actually being able to be performed properly (like actually getting the sputum)

64.2 Different Tests

Smear Microscopy - Poor/Mod sensitivity in in HIV. Needs 10,000 CFU/ml

Liquid Culture - SLOW - can take up to 6 weeks. EXPENSIVE. Needs 10-50 CFU/ml. It’s sensitive though

Gene Xpert - Needs 130 CFU/ml. Moderately expensive (~$20 per test). It’s sensitive and specific. Also less useful in HIV. Can use any fluid pretty much. Good for identifying MDR

Urine LAM Assay - Only moderate sensitivity, in HIV patients its a bad test (10-15% sensitivity). Really only good for patients who are seriously unwell with severe TB. It’s cheap though. It’s a good “rule-in” test, it’s a bad “rule-out” test.

MODS - Microscopic Overservation Drug Susceptibility Assay. It’s cheap ish, it’s good for TB drug resistance. Lower cost and quicker than liquid culture. Takes 7 days. Only really used in Peru

CXR - Moderate expensive. Not great sensitivity in HIV. Needs infrastructrue. Good for other diagnoses.

WHO 4 Symptom Screen - Good sensitivity. Poor specificity. Close to free.

Trial of Antibiotics - Not a great approach

64.3 Diagnostic Algorithm For HIV Positive Patients

GET ALGORITHM OFF SLIDES AND ADD TO FLASHCARDS