A double-blinded randomised controlled trial of the effects of sodium citrate on olfactory thresholds

• Register: ISRCTN
• Last refreshed on: 4 March 2013
• Main ID: ISRCTN50895907
• Date of registration: 28/09/2007
• Primary sponsor: University Hospitals of Leicester NHS Trust (UK)
• Public title: A double-blinded randomised controlled trial of the effects of sodium citrate on olfactory thresholds N/A
• Date of first enrolment: Aug 11 2008
• Target sample size: 100
• Recruitment status: Completed/Not recruiting
• URL: http://isrctn.org/ISRCTN50895907
• Study type: Interventional
• Study design: Randomised controlled trial

Countries of recruitment

United Kingdom

Contacts

• Name: Carl Philpott

Key inclusion & exclusion criteria

Inclusion criteria: All patients with an objective reduction in their ability to smell.
Exclusion criteria: Current inclusion criteria as of 19/02/2013:
1. Patients who are proven to have a normal sense of smell
2. Patients with nasal polyps or other sinonasal disease

Previous inclusion criteria until 19/02/2013:
1. Patients who are proven to have a normal sense of smell
2. Patients with nasal polyps

Age minimum:
Age maximum:
Gender:

Health Condition(s) or Problem(s) studied

Ear, Nose and Throat: Smell ability

Intervention(s)

Current interventions as of 19/02/2013:
The study will be undertaken at the ENT department of the Leicester Royal Infirmary and in a research laboratory at the University of Leicester and also in the ENT department at the James Paget University Hospital. Fifty subjects will be recruited. Subjects will be invited to undergo a series of smell tests using graded concentrations of 4 odours in 120ml bottles (1). This test has been described and validated by our previous work (2). The test will be fully explained to the subject beforehand by the researcher who will test the patient. The subject will be started with the smallest concentration of each odour and will ascend through the bottles until they detect 2 in a row, at which point the weaker concentration of the odour will be taken as their threshold. They will have a threshold levels determined for the odours phenethyl alcohol (roses), 1-butanol (pear-like), acetic acid (vinegar) and eucalyptol (menthol).

Then, the subject will then have either 1cm3 sodium citrate 9% or sterile water (half per nostril) sprayed into the nose. Patients will be randomly allocated to one of the two groups using a coded bottle system controlled by the pharmacies at both sites. Both patient and tester will be blinded to the solution used as these will be made in the pharmacy and coded for anonymity - the code will be broken at the end of the trial. Subjects will then be retested with the bottles and threshold levels will be observed for the four odours at 15 minute intervals over 2 hours. The purpose of the repeated tests is to determine the length of the effect (if present) of the citrate on the olfactory ability of the patients (NB: sodium citrate is a licensed product for use in body cavities (e.g. stomach, bladder) and can be found in the British National Formulary - the concentrations proposed do not exceed those used elsewhere).

Previous interventions until 19/02/2013:
The study will be undertaken at the ENT department of the Leicester Royal Infirmary and in a research laboratory at the University of Leicester and also in the ENT department at the West Suffolk Hospital. One hundred subjects will be recruited. Subjects will be invited to undergo a series of smell tests using graded concentrations of 4 odours in 120ml bottles (1). This test has been described and validated by our previous work (2). The test will be fully explained to the subject beforehand by the researcher who will test the patient. The subject will be started with the smallest concentration of each odour and will ascend through the bottles until they detect 2 in a row, at which point the weaker concentration of the odour will be taken as their threshold. They will have a threshold levels determined for the odours phenethyl alcohol (roses), mercaptan (gas), acetic acid (vinegar) and eucalyptol (menthol).

Then, the subject will undergo a sodium citrate nasal douche at a specific concentration or will douche with sterile water. There will be three concentrations used (3%, 6% and 9%) and a control solution (sterile water). Patients will be randomly allocated to one of the four groups using a coded bottle system. Both patient and tester will be blinded to the solution used as these will be made in the pharmacy and coded for anonymity - the code will be broken at the end of the trial. Subjects will then be retested with the bottles and threshold levels will be observed for the four odours at 15 minute intervals over 2 hours. The purpose of the repeated tests is to determine the length of the effect (if present) of the citrate on the olfactory ability of the patients (NB: sodium citrate is a licensed product for use in body cavities (e.g. stomach, bladder) and can be found in the British National Formulary - the concentrations proposed do not exceed those used elsewhere).

Primary Outcome(s)

Current primary outcome measures as of 19/02/2013:
An improvement in their olfactory thresholds.

Previous primary outcome measures until 19/02/2013:
An improvement in their sense of smell and their general well-being.

Secondary Outcome(s)

Secondary outcome measures added as of 19/02/2013:
A subjective improvement in their sense of smell and their general well-being

Secondary ID(s)

N0274185293

Source(s) of Monetary Support

James Paget University Hospital R&D Department (UK), NHS R&D Support Funding

Secondary Sponsor(s)

N/A