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PPDs Vs. Quantiferons

Which exam is right for you?

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Physical Exam

When deciding which TB test is right fit many answers can crop up around cost, efficiency and availability. There’s also a lot of medical lingo and acronyms which we’ve created a glossary sheet for here for reference. Below we’ll outlind the pros and cons of two most commonly used tuberculosis tests: Purified Protein Derivative Test (PPDs) and QuantiFERONS. For a better understanding of the evolution of TB testing check out our infographic that lays it all out.

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  • What is a PPD?
  • What are the pros and cons PPDs?
  • What is a QuantiFERON?
  • What are the pros and cons of QuantiFERONS?
  • What is a PPD?


    A PPD test consists of the patient receiving a Mantoux implant under the top layer of skin on their forearm. The PPD implant contains Tuberculosis antigens called purified protein derivatives (PPD) – if the patient has been exposed to the tuberculosis bacteria, a firm red bump will develop at the point of the injection within two days.

    The induration (area where patient is injected) must be read 24-48 hours after the procedure to validate the exam. This means, that patients must make two office visits when doing a PPD test. Based on the size of the induration, either non-present or 5-15mm, the clinician will make a prognosis.

    PPDs therefore have a reputation of not being incredibly reliable as results are rely heavily on the clinician doing the reading.

    What are the pros and cons of PPDs?


    A PPD implant is typically the most affordable test used but given that it requires a second office visit for the implant to be read it isn’t always the most cost-effective in the end. False positives are one of the drawbacks of PPDs as they can happen regularly and ultimately, cost you or your agency an extra week in waiting for exams.

    What is a QuantiFERON?


    A QuantiFERON (QFT) is a blood assay used to test for tuberculosis. Patients must get their blood drawn for a QuantiFERON exam with the perk of receiving exam results in 48-72 hours.

    What are the pros and cons of QuantiFERON test?


    The tests is approved by the FDA and “contains a cocktail of three mycobacterial proteins which stimulate the patient’s T-cells in vitro to release interferon-gamma, which is then meaured using ELISA technology”.

    That’s fancy medical lingo to say, the QuantiFERON is known to be incredibly reliable and prevents false positive readings as is common with PPDs.

    Though a more expensive up front, the QuantiFERON on average saves 4 days of time which ultimately could cost patients a lost job or agencies a lost case.