An evaluation of the use of saccharin clearance time as a measure of nasal function
Havas, Thomas
Saccharin Clearance Time (SCT) has been used for many years as a test of mucociliary function in the nasal cavity. We attempted to replicate the previous findings of studies that used Saccharin Clearance Time as a measurement of nasal function, and to validate the assumptions that underlie the use of the test in previous studies. An analysis of our data, combined with other literature, suggests that Saccharin Clearance Time is a reliable, robust test, but that it is uncertain what type of function it is measuring in the nasal cavity. As such, we believe that caution should be exercised in using this test in future research without further thorough validation of the test.
The Saccharin Clearance Time test (also known as Saccharin Transport Time or Mucociliary Clearance Time) has been used extensively in studies as an indicator of the clearance function of the human nasal cavity. It has been used to determine the effectiveness of nasal irrigations (Talbot et al 1998), and to determine the effect of altitude (Barry et al 1997), radiation (Stringer et al 1995), various ciliotoxic substances (Rijntijes 1995, Chetan 1993), and bums (Rose et al 1996) on the nasal mucosa, among other examples.
However, it is rarely discussed as to what physiological processes are actually involved, or which affect the measurement of Saccharin Clearance Time. Many studies have assumed that Saccharin Clearance Time is a direct indicator of nasal mucociliary function, without little supporting evidence. Other studies have suggested that Saccharin Clearance Time may have multi-factorial physiological bases (Deitmer and Miller 1992), but have failed to determine the factors involved. Indeed, it has not yet been proven that Saccharin Clearance Time bears any relation to any useful, functional physiological process.
The present study aims to determine what assumptions can be made about the Saccharin Clearance Time test, and to use this information in order to appraise the previous literature where Saccharin Clearance Time is used as a primary measure for research.
Patients and Methods
50 patients (26 males and 24 females) presenting to the author’s practice who agreed to participate were recruited for this study. Subjects were asked to breathe through their nose onto a condensation plate in order to determine congested and uncongested nasal passages.
Subjects were given a stopwatch. In random fashion, one nasal passage (congested/decongested side) was selected, and a standardised measure of saccharin solution was placed, using a microcurette, at the front of the subject’s inferior turbinate. At this time, the stopwatch was started. Subjects were requested to stop the stopwatch when they first detected a sweet taste. The time was then recorded and reset, and subjects were given a drink of water, requested to blow their nose, and to wait 10 minutes until the other side was tested in the same fashion.
The majority of subjects were then retested in both passages, in the same fashion as described above.
Results
Data Definition
Of the 50 subjects enlisted for this study, 16 (32%) were smokers and 34 (68%) were non-smokers. 7 subjects (14%) were concurrently diagnosed with rhinosinusitus, and a further 4 (8%) had previously had a history of rhinosinusitus that had been treated by a surgical procedure. 39 (78%) had not had any current or past history of rhinosinusitus. Subjects ranged in age from 8 to 87, with a mean (standard deviation) of 43.2 (19.78). The distribution was not significantly different from the normal distribution, with kurtosis of 0.125 and skewness of -0.349.
Intertest Reliability
It was found that all trials of Saccharin Clearance Time strongly and positively correlated with all other trials. Details are presented in Table 1. This would suggest that, for each subject, this test could be replicated faithfully.
Practice Effects
Suggestions that there may have been practice effects as a result of repeated trials by the same subject were not supported by the data. It was suspected that subjects would become more familiar with the test process and recognise the taste in subsequent trials. However, analysis by dependent samples t-test found that there were no significant differences between first and second trials in both the decongested (t = 1.011, p = NS) and congested (t = 1.286, p = NS) nasal pathways. This suggests that subjects do not become “primed” to the test with repeated testing.
Saccharin Clearance Time by Congestion of Nasal Passage
Analysis revealed no significant differences in Saccharin Clearance Time (SCT) between the congested and decongested nasal passages of subjects in both their first attempts (t = 0.893, P = NS) or second attempts (t = 1.519, p = NS),
Saccharin Clearance Time by Rhinosinusitus Status
It was found that patients with a history of rhinosinusitus had slower SCTs than those without any history of rhinosinusitus on all trials. The results are presented in Table 2.
Saccharin Clearance Time by Age
Our study showed that age bore no significant relation to Saccharin Clearance Time, as presented in Table 3. This suggests that the age of the subject has no effect on individual Saccharin Clearance Times.
Saccharin Clearance Time by Smoking Status
No significant differences were found between smokers and non-smokers on Saccharin Clearance Time scores. The results are presented in Table 4.
Discussion
The present study aimed to determine whether the assumptions that underlie the assertions made in previous studies are indeed correct. The assumption underlying Saccharin Clearance Time testing is that the test can be used to detect underlying changes in the health of the nasal mucosa (particularly the nasal cilia), and is a sensitive and reliable test in doing so. The present study suggests that those assumptions may need to be questioned.
The study found that Saccharin Clearance Time tests were, in themselves, reliable tests that could be replicated strongly. However, we also found that due to the wide “within group” variation in individual Saccharin Clearance Times, it was not possible to set normative data points for the diagnosis of normal or abnormal nasal mucosa. There was no relation between Saccharin Clearance Time and age of subject, which is consistent with previous literature on nasal inflammation and age (Jorissen et al 1998).
In attempting to benchmark the effects of rhinosinusitus, smoking and age on Saccharin Clearance Time, some interesting findings arose. The study demonstrated that there was a marked prolongation of Saccharin Clearance Time in subjects with a history of rhinosinusitus. However, it has been documented (e.g. photometric and scanning electron microscopy methods) that elements of cigarette smoke have detrimental effects on the nasal mucosa, in particular the nasal cilia (Agius et al 1995), yet our study did not show any consequent lengthening of Saccharin Clearance Time in smokers. This would suggest that Saccharin Clearance Time as a test may not be a direct measurement of the cilial function, as is the assumption implicit in many studies using this measurement.
What, then, does the Saccharin Clearance Time test measure? There are a number of factors that may affect Saccharin Clearance Time (Deitmer and Miller 1992):
* Gravity, and other non nasal factors (e.g. forces exerted by swallowing)
* Presence of nasal obstruction * The nasal cilia
* The viscosity of the sol and gel layers in which the cilia exist
Studies using Saccharin Clearance Time as a measurement have not been able to establish which of these, or other, effects impact on the results. It is often assumed that fully functioning cilia are the main factor in producing normal Saccharin Clearance Times. Yet our data suggest that those persons who have been previously shown to have less than optimally functioning cilia (smokers) do not display significantly depressed Saccharin Clearance Times. On the other hand, patients with Rhinosinusitus showed significantly depressed Saccharin Clearance Times.
Summary
In order for meaningful research to continue using Saccharin Clearance Time as a measure, the test must be reassessed in order to determine how it can be correctly applied to studies of nasal function. Questions still remain as to the physiological processes which actually underlie Saccharin Clearance Time measurements. Further research should be directed towards this goal.
References
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BARRY P.W., MASON N.P., O’CALLAGHAN C. (1997) Nasal mucociliary transport is impaired at altitude. Eur. Respir. J. 10, 35-37. BRAAT J.P., AINGE G., BOWLES LAX., RICHARDS D.H., VAN RIESSEN D., VISSER W.J., RUNTUES E. (1995) The lack of effect of benzalkonium chloride on the cilia of the nasal mucosa in patients with perennial allergic rhinitis: a combined functional, light, scanning and transmission electron microscopy study. Clin. Exper. Allergy 25, 957-965.
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JORISSEN M., WILLEMS T., VAN DER SCHUEREN B. (1998) Nasal ciliary beat frequency is age independent. Laryngoscope 108, 1042-1047.
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STRINGER S.P., STILES W., SLATTERY W.H., KRUMERMAN J., PARSONS LT., MENDENHALL W.M., CASSISI N.J. (1995) Nasal mucociliary clearance after radiation therapy. Laryngoscope 105, 380-382.
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In those cases in which the naso-pharynx is in an unhealthy state we must begin by treating this condition. If the nostrils are obstructed, and the mucous membrane swollen, the injection of an
alkaline, or slightly astringent, solution through the inferior meatus will prove serviceable. The surgeon may, according to circumstances, use a lotion containing common salt, bicarbonate of soda, borax (zeta to a pint), or tannin (grs. i-iii. ad zetai). A still more effective method of making applications to the nares consists in the use of the anterior nasal spray. An alkaline solution for cleansing purposes, followed immediately by an astringent, will in many cases be found a most efficient means of treating nasal inflammation. Thick mucus and crusts are thus washed away, leaving a clean surface, upon which the astringent takes effect. If the latter be applied to a surface coated with mucus, it in most cases forms an impervious layer of coagulated albumen-a result not to be desired.
If a rhinoscopic examination reveals the presence of inspissated mucus on the roof of the pharynx or turbinated bones, it may also be desirable to employ the posterior nasal spray, using here also an alkaline followed by an astringent application.
P. McBRIDE 1884 Edinburgh
THOMAS HAVAS
Sydney Children’s Hospital New South Wales
Thomas E. Havas F.R.C.S. (Ed.), F.R.A.C.S., F.A.C.S. Otolaryngology, Head and Neck Surgery Sydney Children’s Hospital High Street, Randwick NSW 2031 Australia
Correspondence: Dr Thomas E. Havas Suite 506, 253 Oxford Street, Bondi Junction NSW 2022 Ph: (02) 9389 5404
Copyright Australian Society of Otolaryngology Head & Neck Surgery Ltd. Jul 1999
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