Awareness : Did You Know? 2017

Did You Know? Weekly Educational Series #15

For the Week of May 22, 2017-Laboratory

New CDC recommendations are to test first with the interferon-γ release assay (IGRA) when the physician determines it’s appropriate to test for latent TB infection.  Historically, the tuberculin skin test (TST) has been performed for testing TB.  When the patient meets the following criteria, you should test with the IGRA:

  • 5 years of age or older
  • Likely to be infected with Mycobacterium tuberculosis (Mtb)
  • Low or intermediate risk of progression of the disease
  • History of Bacillus Calmette Guerin (BCG) vaccination
  • Will probably not return for a TST reading

The guidelines also indicate “initial testing”, when indicated, using TST if the prior conditions aren’t met, or if the IGRA test is not readily available or too costly.

The TST could show false positives for BCG-vaccinated individuals.  This is why IGRA blood test is useful for patients who have had prior BCG vaccination, because the test measures immune response to two TB-specific proteins — ESAT-6 and CFP-10 — that were never included in the BCG vaccine. Also, these proteins are absent from most non-tuberculous mycobacteria, therefore avoiding false-positive results for exposure to other mycobacteria.

Bill CPT code 86580 (Skin test; tuberculosis, intradermal) for a TST. Other references to the TST may be a Mantoux test or a PPD (purified protein derivative) test. Diagnosis: Do not code an active TB case based on the results of TST or IGRA testing.  You bill the findings using a ICD-10 code such as R76.1- (Nonspecific reaction to test for tuberculosis…).

When a TST or IGRA test indicates infection with Mtb, that doesn’t mean the patient has an active TB infection. Practitioners should follow a positive test result with evaluation of symptoms and with a chest x-ray and/or sputum collection for testing for an active infection.

The new guidelines recommend performing acid-fast bacilli (AFB) stain microscopy on sputum for all patients with suspected pulmonary TB. The lab would perform and code this test as 87206 (Smear, primary source with interpretation; fluorescent and/or acid fast stain for bacteria, fungi, parasites, viruses or cell types).

The gold standard for active TB infection diagnosis is a positive culture that isolates the Mtb organism from a respiratory or other specimen. Bill a TB culture by using CPT code 87116 (Culture, tubercle or other acid-fast bacilli [e.g., TB, AFB, mycobacteria] any source, with isolation and presumptive identification of isolates)

The new CDC guidelines recommend performing nucleic acid amplification tests (NAATs) rather than a TB culture, because it identifies Mtb quicker in respiratory specimens. The CPT code for these tests is 87556 (Infectious agent detection by nucleic acid [DNA or RNA]; mycobacteria tuberculosis, amplified probe technique). For similar tests using direct probe or quantification, code 87555 or 87557 in the same family of codes.

If the lab performs the concentration step, bill 87015 (Concentration [any type], for infectious agents). Diagnosis Coding for Respiratory Tuberculosis:  Use A15.0 – A15.9 (Respiratory tuberculosis…)Use the most specific code, such as A15.0 (Tuberculosis of lung) or A15.6 (Tuberculous pleurisy).