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BANA test

The popular BANA test uses smears of tongue coatings or subgingival plaque to detect three species of anaerobic bacteria, often associated with periodontal conditions and oral malodor: Porphyromonas gingivalis, Treponema denticola, and Bacteroides forsythus.

BANA, short for N-benzoyl-DL-arginine-B-napthylamide, is a synthetic peptide that can be hydrolyzed only by these particular species. In the test, a chromogenic diazo reagent that reacts with one of the hydrolytic products of the peptide breakdown produces a blue color, and the intensity of this color determines whether it is a “positive” or “weak” reaction.

The test was developed by Walter J. Loesche et al., at The University of Michigan School of Dentistry.

The commercial chairside BANA test setup consists of the BANA test strips and an incubator. As of June, 2019, the incubator costs $480.00, and a pack of 20 test strips is priced at $120.00.

No doubt, the ability to quickly and inexpensively test for pathogenic oral bacteria is a significant breakthrough in periodontics, along with the recognition that “periodontal diseases are the result of an immunological response to specific bacterial challenges,” as one supplier\’s website puts it. This mirrors the revelation some years ago that most peptic ulcers were the result of a Helicobacter pylori infection—not spicy food, acid or stress—and could be best treated with antibiotics.

While it is true that any blue color indicates the presence of BANA-positive organisms on the test, the manufacturer does recommend that clinical judgment be used when interpreting test results, owing to variations in color intensity and how the color may be distributed across the strip. The manufacturer of the BANA test apparatus also states:

Evaluate weak reactions in the context of the patient’s history of periodontal disease and current clinical status as well as to the level of malodor that the clinician can detect.

Generally, a weak-positive result indicates the presence of low levels of bacteria capable of producing foul-smelling compounds. If the BANA test is only weak-positive, the clinician may choose to reinforce oral hygiene procedures.

Thus, this test that is touted by some as a inexpensive alternative to the Halimeter® is asking the user to detect, using some other means, the level of oral malodor!

A few points can be made here

1.     Colorimetric testing, in general, is best suited to “go/no-go” determinations. Problems in interpretation will occur when results fall into the broad middle ground.

2.     We readily agree that a strong positive result is indicative of bacterial infection. Yet, how useful is a “go/no-go” measurement of bacterial infection in monitoring the progress of treatment of oral malodor?

3.     A simple “go/no-go” colorimetric test is no substitute for an analytical, numerical measurement of the concentration of volatile sulfur compounds—the very chemicals that cause bad breath. One cannot compare instrumental measurements in parts-per-billion to a visual color indication. If you want to measure oral malodor, then measure oral malodor, rather than extrapolate and approximate it via bacterial counts.

4.     Inexpensive colorimetric methods—the best are called “detector tubes”—have been available in the world of gas detection for many years, but have serious limitations. Those interested in analytical gas detection seek out companies like Interscan [shameless plug].

5.     We must also mention that there are cases of oral malodor not of oral etiology, and the BANA test will be of little benefit in these scenarios. With the Halimeter®, the practitioner can measure volatile sulfur compounds in mouth, nose, and lung air, to isolate the source of the problem.

So… Is the BANA test a substitute for the Halimeter®? As the old Hertz commercials used to say, “Not exactly!”