Functional status is a recognized predictor of many surgical outcomes. While patients can be risk stratified by formal measurements of functional status during preoperative work-up, this is expensive and time consuming. Developing and validating alternative tools for evaluating functional status, such as estimating mobility using the Mobility Assessment Tool short form (MAT-sf) [1], may be useful in optimizing preoperative care [2,3].
We analyzed the relationship between self-assessed mobility via the MAT-sf and an objective mobility measurement, the Timed Up and Go (TUG) test [4]. These data were then compared to clinician-assessed functional status preoperatively determined by nurse practitioners (NP rating). We hypothesized that scores on the MAT-sf will be significantly associated with both assessments, and patients would over-estimate their mobility.
The study was approved by Vanderbilt University Medical Center’s Human Research Protections Program (IRB #: 170117). Written, informed consent was obtained from all participants. After consenting, a nurse practitioner assessed patient functional status in the preoperative clinic (NP rating). Next, patients independently completed the 10 question MAT-sf on a tablet computer to measure the subject’s perceived mobility. Then patients performed the TUG test, which records the required time for patients to ambulate 10 ft starting from a seated position, turn around, return to their chair, and reseat themselves.
Spearman’s correlation coefficient, with 95% confidence interval, was reported to assess the association between each method. The secondary result of interest was to compare the relative magnitudes of each assessment. Finally, to gauge the MAT-sf’s effectiveness as a triaging tool, we evaluated its ability to detect a normal level of patient functional mobility [5]. We defined normal mobility, or a “positive” test, as a score of Good, Very Good, or Excellent; below normal mobility, or a “negative” result, was defined as Fair or Poor scores. With this analysis, we sought to answer four questions: (1) What was the probability the MAT-sf produces a positive score, given the patient had a normal TUG times? (2) What was the probability the MAT-sf produces a negative score, given below normal TUG times? (3) What was the probability of obtaining normal TUG times given that the MAT-sf score was positive? (4) What was the probability of obtaining below normal TUG times given that the MAT-sf score is negative? These questions correspond to the sensitivity, specificity, positive predictive power, and negative predictive power of the MAT-sf, respectively.
A total of 102 patients completed this study. The Spearman’s rank correlation between the MAT-sf and TUG was statistically significant of magnitude −0.57 with 95% CI: (−0.70, −0.41). The MAT-sf and NP rating had Spearman’s rank correlation coefficient of −0.30 with 95% CI (−0.47, −0.09). There was no significant association between TUG times and NP rating. The comparison results revealed that 74 (72.6%) people assessed their mobility higher on the MAT-sf than the TUG, 83 (81.4%) patients attained a higher MAT-sf score than NP rating, and 86 (84.3%) patients had an equal or better TUG time than their corresponding NP rating (Table 1). MAT-sf greatly surpassed NP rating in sensitivity (97.7%), positive predictive power (51.2%), and negative predictive power (95.0%), but not specificity (32.2%).
Table 1.
Association results.
| Frequency (n) | Agreement (%) | Spearman’s correlation (95% CI) | |
|---|---|---|---|
| Nurse practitioner (NP) rating vs Timed Up and Go (TUG) test | ρ = 0.154 (−0.04, 0.33) | ||
| NP rating higher | 16 | 15.69% | |
| Same rating | 36 | 35.29% | |
| TUG rating higher | 50 | 49.02% | |
| NP rating vs Mobility Assessment Tool short form (MAT-sf) | ρ = −0.303 (−0.50, −0.09) | ||
| NP rating higher | 7 | 6.86% | |
| Same rating | 12 | 11.76% | |
| MAT-sf rating higher | 83 | 81.37% | |
| MAT-sf vs TUG test | ρ = −0.573 (−0.70, −0.41) | ||
| MAT-sf rating higher | 74 | 72.55% | |
| Same rating | 20 | 19.61% | |
| TUG rating higher | 8 | 7.84% |
The results of our analysis confirmed our hypotheses. They suggest that the MAT-sf could be used lieu of a physical measurement of mobility (i.e. TUG). We observed that patients tend to overestimate functional status while clinicians underestimate it. The high sensitivity of the MAT-sf revealed that low scores efficiently confirmed low functional status. In conclusion, the MAT-sf may be an effective surgical triage tool to be performed by patients at home which could determine who needs additional preoperative screening (Table 1).
Acknowledgments
Funding
REF-NIH-NCATS 1KL2TR002245; other authors, institutional or departmental funding.
Footnotes
Declaration of competing interest
N/A.
References
- [1].Rejeski WJ, Ip EH, Marsh AP, Barnard RT. Development and validation of a video-animated tool for assessing mobility. Journals Gerontol - Ser A Biol Sci Med Sci 2010. 10.1093/gerona/glq055. [DOI] [PMC free article] [PubMed]
- [2].Kim S, Marsh AP, Rustowicz L, Roach C, Leng XI, Kritchevsky SB, et al. Self-reported mobility in older patients predicts early postoperative outcomes after elective non-cardiac surgery. Anesthesiology 2016. 10.1097/ALN.0000000000001011. [DOI] [PMC free article] [PubMed]
- [3].Cella D, Riley W, Stone A, Rothrock N, Reeve B, Yount S, et al. The patient-reported outcomes measurement information system (PROMIS) developed and tested its first wave of adult self-reported health outcome item banks: 2005–2008. J Clin Epidemiol 2010. 10.1016/j.jclinepi.2010.04.011. [DOI] [PMC free article] [PubMed]
- [4].Richardson S The timed “up & go”: a test of basic functional mobility for frail elderly persons. J Am Geriatr Soc 1991. 10.1111/j.1532-5415.1991.tb01616.x. [DOI] [PubMed]
- [5].Skaik YE-W. Understanding and using sensitivity, specificity and predictive values. Indian J Ophthalmol 2009. doi: 10.4103/0301-4738.41424. [DOI] [PMC free article] [PubMed]