Characterization of a clinical olfactory test with an artificial nose

Abstract

Clinical olfactory tests are used to address hyposmia/anosmia levels in patients with different types of olfactory impairments. Typically, a given test is employed clinically and then replaced by a new one after a certain period of use which can range from days to several months. There is a need to assess control quality of these tests and also for a procedure to quantify their degradation over time. In this paper we propose a protocol to employ low-cost artificial noses for the quantitative characterization of olfactory tests used in clinical studies. In particular, we discuss a preliminary study on the Connecticut Chemosensorial Clinical Research Center Test kit which shows that some odorants, as sensed by an artificial nose, seem to degrade while others are potentiated as the test ages. We also discuss the need to establish a map of correspondence between human and machine olfaction when artificial noses are used to characterize or compare human smell performance in research and clinical studies.

Keywords: anosmia; artificial noses; electronic noses; map of human and machine olfaction; olfaction; olfactory dysfunction; quality control of clinical olfactory tests.

Figure 1

The Connecticut Chemosensorial Clinical Research Center Test used in this study. The brown bottles contain the butanol threshold test, while the white plastic jars contain the identification test.

Figure 2

Analysis platform used in this study with the TGS2600-B00 (Figaro Engineering Inc.) chemoresistive sensor.

Figure 3

Response of the artificial nose to three dilutions of the CCCRC kit for two different sets: a kit that has been used for over one year (dilutions labeled as 2O, 3O, and 4O) and a new one (dilutions labeled as 2N, 3N, and 4N). For each dilution we show the mean of five measurements (middle trace) together with the standard deviation (upper and lower traces). Note that the artificial nose signal for dilution 3O is nearly as close to 3N as to 4N. A quality control criteria based in the relative distance between the peaks of the signals would result in discarding the old test kit.

Figure 4

Response of the artificial nose to two samples (peanut butter—left panel and coffee—right panel) of the identification part of the CCCRC kit. For each sample we show the mean of five measurements (middle trace) together with the standard deviation (upper and lower traces). Note that, as sensed by the artificial nose, the old peanut butter (OP) and coffee jars (OC) have higher odor intensity than the ones that contain a new test (NP and NC, respectively).