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Validation of Minimal Clinically Important Difference (MCID) for University of Pennsylvania Smell Identification Test
Ashna Mahadev1, Dorina Kallogjeri1, Jay F Piccirillo1
1Department of Otolaryngology - Head and Neck Surgery, Washington University School of Medicine, St. Louis, MO, USA.
Background:
The University of Pennsylvania Smell Identification Test is widely used to measure change in olfactory function, but a minimal clinically important difference (MCID) has not been well-established. A study published in 1997 regarding patients with head trauma reported an MCID of 4 but did not detail the methods used in the calculation.
Objective:
To validate the MCID for UPSIT in patients with postviral, sinusitis, and procedure-associated olfactory loss.
Methods:
This was a secondary analysis of prospectively collected data from 5 clinical research studies related to olfactory function. Three studies included subjects with COVID-19-related olfactory dysfunction, one with chronic sinusitis subjects, and one with subjects undergoing transsphenoidal surgery. All subjects had completed a baseline and follow-up UPSIT, baseline and follow-up Clinical Global Impression-Severity (CGI-Severity), and a follow-up CGI-Improvement. Both distribution- and anchor-based methods were used to determine the MCID of UPSIT. Distribution-based method calculated MCID using half standard deviation of baseline UPSIT and delta UPSIT scores. Clinical-anchor method determined MCID by comparing delta UPSIT scores between consecutive CGI-I clinical categories ranging from very much better to very much worse.
Results:
The study population comprised 295 subjects. Subjects had a mean (SD) baseline UPSIT score of 27 (7.5), and follow-up score of 28 (7.9), and a mean UPSIT change of 0.6 (5.8). Half the baseline UPSIT SD was 3.75 and half the delta UPSIT SD was 2.9. With the anchor-based approach, an MCID of 4 was defined as clinically meaningful by exploring the relationship between delta UPSIT and CGI-Improvement. Using a more conservative approach based on the MCID values identified from both methods, we determined that a change of 4 or greater is the appropriate MCID for UPSIT.
Conclusion:
Investigators in the future should use 4 as MCID for UPSIT and report the percentage of study subjects who achieve a clinically meaningful difference.
Level Of Evidence:
III.
Insights
The minimal clinically important difference (MCID) for the University of Pennsylvania Smell Identification Test (UPSIT) was validated as 4 points. This finding is crucial for accurately measuring olfactory function changes in clinical practice.
Area of Science:
- Olfactory Neuroscience
- Clinical Measurement Science
Background:
- The University of Pennsylvania Smell Identification Test (UPSIT) is a standard tool for assessing olfactory function.
- Establishing a minimal clinically important difference (MCID) for UPSIT is essential for interpreting results but has been lacking.
- Previous research on head trauma patients suggested an MCID of 4, without detailed methodology.
Purpose of the Study:
- To validate the MCID for the UPSIT in patients experiencing olfactory loss due to postviral conditions, sinusitis, or surgical procedures.
- To provide a reliable threshold for determining meaningful improvement in olfactory function.
Main Methods:
- Secondary analysis of prospectively collected data from five olfactory function studies.
- Inclusion of subjects with olfactory dysfunction from COVID-19, chronic sinusitis, and transsphenoidal surgery.
- Utilized both distribution-based (half standard deviation) and anchor-based (Clinical Global Impression-Improvement) methods to determine MCID.
Main Results:
- The study included 295 subjects with a mean baseline UPSIT score of 27 (SD 7.5).
- Distribution-based methods yielded MCID values of 3.75 (half baseline SD) and 2.9 (half delta SD).
- The anchor-based method, correlating UPSIT change with clinical improvement, identified an MCID of 4. A conservative approach combining both methods confirmed an MCID of 4 or greater.
Conclusions:
- An MCID of 4 should be adopted for the UPSIT in future research and clinical practice.
- Clinicians and researchers should report the proportion of patients achieving this clinically meaningful difference.
- This validated MCID enhances the clinical utility of the UPSIT for various olfactory disorders.
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