Episode Details

Episode 87: Latent TB Infection.  

By Mariana Gomez, MD (Romulo Gallegos University School of Medicine, Carillion Clinic Infectious Disease), and Hector Arreaza, MD (Romulo Gallegos University School of Medicine, Rio Bravo Family Medicine Residency Program). 

Dr. Gomez explains how to screen for and treat Latent TB infection. 

Today is March 18, 2022.

Dr. Mariana Gomez graduated from medical school at the Romulo Gallegos University in Venezuela. She completed her residency in Internal Medicine in St Barnabas Hospital, which is affiliated with the Albert Einstein School of Medicine, Bronx, New York. She then completed a fellowship in Infectious Diseases at Carilion Clinic, which is affiliated with Virginia Tech School of Medicine. She currently works in Virginia, United States. 

This is Rio Bravo qWeek, your weekly dose of knowledge brought to you by the Rio Bravo Family Medicine Residency Program from Bakersfield, California. Our program is affiliated with UCLA, and it’s sponsored by Clinica Sierra Vista, Let Us Be Your Healthcare Home. 

Some questions discussed during this episode:

Who should be screened for latent TB infection? 

A CDC questionnaire can determine the risk for latent TB infection. Some patients who may be screened are those who resided for 1 month in a country with high TB prevalence, those who are currently immunosuppressed or planning immunosuppression in the near future (50 mg of prednisone or equivalent a day for 1 month), and those who had close contact with patients with TB infection (Latent Tuberculosis Infection: A Guide for Primary Health Care Providers (cdc.gov)). 

The USPSTF recommends screening for latent tuberculosis infection (LTBI) in populations at increased risk.

Screening Tests: Currently, there are two types of screening tests for LTBI in the United States: the tuberculin skin test (TST, also known as PPD) and the Interferon Gamma Release Assay (IGRA, brand names QuantiFERON®-TB and T-SPOT®.TB). 

The TST requires intradermal placement of purified protein derivative and interpretation of response 48 to 72 hours later. The induration is measured in millimeters. The induration is the palpable, raised, hardened area or swelling, not the erythema.

IGRA requires a single venous blood sample, and the result is obtained in 1-2 days. Two types of IGRAs are currently approved by the US Food and Drug Administration: T-SPOT.TB (Oxford Immunotec Global) and QuantiFERON-TB Gold In-Tube (Qiagen). 

The CDC recommends screening with either test (TST or IGRA) but not both. 

IGRAs is preferred for patients who received a BCG vaccine (bacille Calmette–Guérin) or if they are unlikely to return for TST interpretation.

Why should we screen for LTBI?

How can we decide between Questionnaire only vs PPD vs QuantiFERON Gold?

What is the next step in assessing asymptomatic individuals with positive PPD?

A useful resource is the online TST/IGRA Interpreter (tstin3d.com). 

You can calculate the risk of latent TB infection and the risk of INH-induced hepatitis.

How can we decide to treat LTBI?

What are the recommended regimens? 

CDC recommends three preferred regimens. These are chosen for effectiveness, safety, and high treatment completion rates. These regimens are rifamycin-based. They are:

INH+rifapentine for 3 months: once-weekly isoniazid plus rifapentine for adults and children older than age 2, regardless of HIV status.

Rifampin for 4 months: daily rifampin.

INH+rifampin for 3 months: daily isoniazid plus rifampin.

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Now we conclude our episode number