Total SNOT Score and Average SNOT Score
Author: Jay Piccirillo, MD
The SNOT instruments can be scored as the sum of the individual item scores (range 0 to 5).
Alternatively, and in circumstances where the investigator is concerned about missing values for one or more items, the SNOT score can be calculated as the mean score for each item, in which case the total SNOT score, regardless of which instrument, will be between 0 and 5.
Total SNOT Score
The Total SNOT Score is calculated as the sum of the score for all items, even if the participant fails to answer all items.
The possible range of Total SNOT scores is between 0 and 80 for the SNOT-16, 0 to 100 for the SNOT-20, and 0 to 110 for the SNOT-22.
Higher scores indicate greater rhinosinusitis-related health burden.
SNOT Absolute Change Score
The SNOT Absolute Change Score is the difference between pre-treatment and post-treatment Total SNOT Score.
The SNOT Relative Change Score
The SNOT Relative Change Score is the difference between pre-treatment and post-treatment Total SNOT Score divided by the pre-treatment Total SNOT Score.
Important items
The SNOT instrument allows patients to identify the items (maximum of 5 items) that are most important to them and which they hope will improve the most with therapy. A separate SNOT Score can be calculated as the sum of the items identified as important.
Clinically meaningful difference
Impact of treatment is assessed with the SNOT-22 Absolute Change Score. An absolute difference of 8.9 or greater between two compared SNOT-22 instrument scores is considered clinically meaningful.1
An absolute value for a clinically meaningful change in SNOT-20 and SNOT-16 has not been defined (see below for clinically meaningful change in average SNOT-20 and SNOT-16 scores).
Percentage of patients who achieve a clinically meaningful difference
We encourage investigators to report the percentage of patients who achieve a clinically meaningful change (i.e., as a proportion), rather than the absolute difference (i.e., as a continuous value).2
Average SNOT Score
The Average SNOT Score is calculated as the sum of each individual item value divided by the number of all items that are answered. Therefore, if the participant fails to answer an item, do not include this item in the average score.
The possible range of Average SNOT scores is 0 to 5, with higher scores indicating greater rhinosinusitis-related health burden.
SNOT Relative Change Score
The SNOT Relative Change Score is the difference between pre-treatment and post-treatment Average SNOT Score divided by the pre-treatment Average SNOT Score.
Important items
The SNOT instrument allows patients to identify the items (maximum of 5 items) that are most important to them and which they hope will improve the most with therapy. A separate average SNOT score can be calculated as the mean for the items identified as important.
Clinically meaningful difference
Impact of treatment is assessed with the SNOT-22 Absolute Change Score. A difference of 0.8 or greater in the mean value between two compared SNOT-20 scores is considered clinically meaningful.3 A difference of 0.5 or greater in the average SNOT 16 score is considered clinically meaningful.4
References
- Hopkins C, Gillett S, Slack R, Lund VJ, Browne JP. Psychometric validity of the 22-item Sinonasal Outcome Test. Clinical Otolaryngology. 2009; 34(5): 447-454.
- Guyatt GH, Osoba D, Wu AW, Wyrwich KW, Norman GR. Methods to explain the clinical significance of health status measures. Mayo Clinic Proceedings. 2002; 77(4): 371-383.
- Piccirillo JF, Merritt MGJ, Richards ML. Psychometric and clinimetric validity of the 20-Item Sino-Nasal Outcome Test (SNOT-20). Otolaryngology — Head & Neck Surgery. 2002; 126(1): 41-47.
- Garbutt J, Spitznagel E, Piccirillo J. Use of the modified SNOT-16 in primary care patients with clinically diagnosed acute rhinosinusitis. Archives of Otolaryngology — Head & Neck Surgery. 2011; 137(8): 792-797.