Nasal Clearance and Mucus Weights

In the 4 Pittsburgh studies, two quantitative measures of clinical upper respiratory illness were collected:  nasal mucociliary clearance function and nasal mucus production.  These data were used to determine whether participants who had become infected with the challenge virus met criteria for clinical illness, as per the objective definition (Cohen et al., 1997; see also Assessment of Infection and Colds).  The BCS also included a measure of mucus production.  However, because the measure was not collected at baseline, mucus production was not used as a criterion for determining the presence of clinical illness in this study.

Nasal Mucociliary Clearance Function (PCS1, PCS2, PMBC, PCS3)

Purpose

To evaluate objective signs of illness associated with viral infection

Description

Nasal mucociliary clearance function refers to the effectiveness of nasal cilia in clearing mucus from the nasal passage toward the nasopharynx.  Under conditions when mucus is being over-produced (e.g., when one has a cold), ineffective clearance results in an accumulation of mucus within the nasal passages.  Thus, mucociliary clearance function can be used as an indirect measure of nasal congestion.  In the 3 Pittsburgh Cold Studies and PMBC, nasal clearance function was assessed as the time required for a dye that was administered into the anterior nose to reach the uppermost part of the pharynx.  A substantial lag (i.e., several minutes) between administration of the dye and detection in the back of the throat is an indication of poor mucociliary function.

Variables/Scoring

• Baseline-adjusted daily nasal mucociliary clearance time scores were calculated by subtracting the baseline nasal clearance time value from each daily post-exposure value.  Negative adjusted scores were reassigned a value of 0. 

• The average adjusted nasal clearance time score was calculated by averaging across the respective adjusted daily scores over all post-challenge quarantine days. An average adjusted nasal clearance time of 490 seconds (7 minutes) or longer was one of the criteria comprising the objective definition of a clinical cold (see Assessment of Infection and Colds).

• In some publications (e.g., Cohen et al., 2003), nasal clearance is presented as the total adjusted time across days rather than the average across days.  In these studies, a total time of 35 minutes was used as the nasal clearance criterion.

Nasal Mucus Weight (BCS, PCS1, PCS2, PMBC, PCS3)

Purpose

To evaluate objective signs of illness associated with viral infection

Description

Daily nasal mucus production was assessed by having participants expel all nasal secretions into pre-weighed paper tissues and then collect the used tissues in plastic bags.  Briefly, on each day in quarantine participants were provided with a pre-weighed sandwich-type plastic bag with zip lock seal (earlier studies used plastic ties) and a recorded number of tissues.  Additional tissues were available upon request.  At the end of the day, study staff collected the sealed bags containing participants’ used tissues as well as any unused tissues that participants had remaining.  Tissue collections were weighed, and the weight of produced mucus was determined by subtracting the weights of the plastic bag (empty) and tissues (unused) from the total weight of the collection.

Variables/Scoring (PCS1, PCS2, PMBC, PCS3)

• Adjusted daily mucus production scores were calculated by subtracting the baseline mucus weight value from each daily post-exposure value.  Negative adjusted scores were reassigned a value of 0. 
• The total adjusted mucus weight score was calculated by summing the respective adjusted daily scores over all post-challenge quarantine days. A total adjusted mucus weight of 10 grams or more was one of the criteria comprising the objective definition of a clinical cold (see Assessment of Infection and Colds).

References

Cohen, S., Doyle, W. J., Turner, R. B., Alper, C. M., & Skoner, D. P.  (2003). Emotional style and susceptibility to the common cold. Psychosomatic Medicine, 65, 652-657.

Doyle, W. J., McBride, T. P., Skoner, D. P., Maddern, B. R., Gwaltney, J. M., Jr., & Uhrin, M. (1988). A double-blind, placebo-controlled clinical trial of the effect of chlorpheniramine on the response of the nasal airway, middle ear and eustachian tube to provocative rhinovirus challenge. The Pediatric Infectious Disease Journal, 7, 229-238.