Patients often underestimate functional capacity

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LAS VEGAS – Patient reported functional capacity does not accurately reflect exercise determined capacity, data presented during a poster presentation at the American Academy of Physician Assistants' 39th Annual Meeting indicates.

Functional capacity (FC) can accurately predict the operative risk in patients about to undergo noncardiac surgery and is a strong indicator of prognosis in patients with CAD and CHF. Prior to a procedure, FC is often assessed indirectly by inquiring about each patient's ability to perform various activities. The patient's risk is then determined using a number of clinical scales.

Although the reliability of self-reported functional capacity (SRFC) remains unclear in community-based clinical practices, more reliable measures of FC such as exercise capacity remain costly and require too much time. Abraham S. Salacata, MD, a researcher at Endeavor Medical Research in Alpena, Mich., and colleagues attempted to measure how accurate SRFC is in a community practice setting.

The research team interviewed patients who were referred to their laboratory for exercise stress testing about their ability to perform certain physical activities enumerated in the modified Duke Activity Status Index (DASI). Patients' SRFC was then rated according to the scale: one or poor (capable of ≤ 4 METS), two or moderate (2, 4-7 METS), three or good (7-10 METS), or four or excellent (>10 METS).

The patients then underwent maximal exercise testing using Bruce protocol, and exercise determined functional capacity (EFC) was then determined using commercially available stress software. Researchers then compared the SRFC and EFC of patients with a high reported SRFC using the Wilcoxon Matched-Pairs Signed-Ranks test.

A total of 87 patients were identified with high SRFC with an average age of 64.8 ± 11.5 years. Eighty-two percent had a history of hypertension, 38% had coronary artery disease, and 28% had diabetes.

The researchers found that there was a significant discrepency between the patients' self-reported functional capacity and their actual EFC, with the majority of participants overestimating their EFC by up to two functional classes.

“The results suggest that in a community setting, patient reported functional capacity does not accurately reflect their exercise determined functional capacity,” the researchers wrote. “Formal evaluation by stress testing should thus be performed if clinicians have any doubt as to the patient's reported functional capacity.”

Salacata A, Keavey S, Moser S, et al. "Self-reported exercise capacity: when in doubt, test." Presented at: American Academy of Physician Assistants' 39th Annual PA Conference. 2011: Las Vegas, Nevada. 

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