TB or not TB? Testing Clinician Knowledge Regarding PPD and IGRAs with an Educational Intervention

Joey Parker, DO and Michael Myint, MD Virginia Mason Medical Center, Seattle, Washington

Abstract - revised Introduction: A patient safety alert (PSA) was initiated at our institution after a hospitalized patient with risk factors, radiographic and systemic findings suspicious for active tuberculosis disease was taken off airborne precautions after having a negative Interferon Gamma Release Assay (IGRA). This patient’s third sputum smear and culture for acid fast bacilli were positive and confirmed Mycobacterium tuberculosis resulting in several employees being exposed to TB without adequate precautions. Methods: A study was initiated based on concern for knowledge deficits in clinicians interpreting the purified protein derivative (PPD) and IGRA tests for both active and latent tuberculosis diagnosis. A short 9-question, multiple choice survey was distributed to residents, hospitalists, and sub-specialists related to the PPD and IGRA tests with an emphasis on whether these tests can distinguish active from latent tuberculosis. Data was gathered and pooled, and a 1-page educational tool was made and distributed which highlighted core principles regarding the use and limitations of both the PPD and IGRAs. A 15-minute presentation with similar information was also filmed and made available as online learning. Results: Findings included significant knowledge deficits in interpretation of PPDs and IGRAs across training levels and specialties. 33.1% of our 124 respondents felt that IGRA tests can distinguish active from latent tuberculosis. The pre-test revealed that 56.6% of respondents did not feel comfortable interpreting PPD and IGRAs, which improved to 25% in the post test. Conclusion: Understanding of PPD and IGRAs is challenging for many providers, and a targeted risk assessment and directed education can improve knowledge and use of these tests, and perhaps prevent unnecessary exposure to potentially deadly pathogens.

A 60 year-old immune-competent male who was admitted to VMMC with a history and chest X‐ray consistent with acute on chronic pneumonia with suspicion for pulmonary tuberculosis. The patient was born and spent his childhood in Vietnam. An IGRA test, drawn as an outpatient, was reported negative and the patient was taken out of his initial airborne precautions. It was recognized a day later that the IGRA result was misapplied and the patient was placed back on airborne precautions, while sequential sputum was taken for acid fast bacilli (AFB) smear and culture. Subsequently, one of three sputum samples tested was AFB smear positive and all three sputum cultures grew Mycobacterium tuberculosis, confirming pulmonary tuberculosis. Several employees at our institution were exposed to pulmonary TB due to this misinterpretation of the IGRA test. A patient safety alert was filed leading to formation of a group to address educational gaps in TB precautions that we describe here. It was clear from this case as well as our experience that knowledge gaps existed in both the utility and interpretation of the Interferon Gamma Release Assays.

To assess areas of knowledge deficit, a brief, 9-question true/false and multiple-choice survey was sent out to residents, hospitalists, and sub-specialists by an online survey. Data was gathered, pooled, and compared across different specialties. Following this, a brief, 1-page educational tool was made and distributed which highlighted key principles surrounding interpretation of PPDs and IGRAs. A 15 minute presentation complete with power point was also made and made available online for access and quick learning. Finally, a short 7-question post-test was distributed three months afterwards and results compared.

PPDs and IGRAs are essential tools in helping to identify those with tuberculosis infection, though neither differentiates between latent infection and active disease. The importance of interpreting these tests is increased due to increased use of immune suppressing agents, especially TNF blocking agents. Our survey confirmed that clinicians have difficulty interpreting these tests. We identified multiple areas of knowledge gaps regarding the PPDs and IGRAs that we directly addressed with multi-media education options. Further, this education tool improved the comfort level of clinicians interpretation of these tests and decreased misinterpretation even in the group that had pre-test comfort. Anecdotally, clinicians are asking questions earlier and ordering tests more appropriately. We see the most improvement in clinicians not ordering IGRAs to “rule out” a positive PPD. Lastly, this methodology was validated to address knowledge deficits in an efficient and targeted manner. Concise and goal orientated education focused on identified and specific knowledge deficits is a critical part of improving clinical quality and safety. This method can quickly educate clinicians on rapidly changing and potentially high risk clinical issues.

Survey and Results

Case Presentation – Patient Safety Alert

Results Interpretation

Discussion

Results of selected questions Pre-survey Post-survey

Figure 1 – Demographics. The survey was sent to approximately 250 clinicians with 124 responses

Figure 3 – Understanding of IGRA tests in distinguishing active and latent TB

Figure 4 – Utility of PPD or IGRA to confirm or refute a positive test

Figure 5 – Comfort of clinician in interpreting PPD and IGRA’s Figure 2 – Survey and educational intervention tool

We had approximately a 50% response rate to our survey. The 124 clinicians who responded were a diverse group including both primary care and subspecialty representation, as well as internal medicine house-staff. Interestingly, those respondents who initially stated they felt comfortable with interpreting IGRAs and PPDs were more likely to misinterpret the utility of an IGRA to confirm or refute a positive PPD (without BCG). Otherwise, specialty or year of training did not have a significant impact on the respondents’ answers. Similar knowledge gaps were revealed in all groups.

Selected results are shown on figures 3-5 showing our intervention impacted clinician interpretation of these tests. The percent of respondents feeling uncomfortable interpreting IGRAs or PPDs decreased from 56.6% to 25%. In the post-test group who felt comfortable interpreting PPD and IGRAs, there was no longer misinterpretation of PPDs or IGRAs ability to confirm or refute each other.

Mailtop G2-ID 909 University Street,

Seattle, WA 98101 joey.parker@vmmc.org or michael.myint@vmmc.org

p(206)340-0846 f(206)223-6814

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