The 5-Factor Modified Frailty Index in the Geriatric Surgical Population

The modified frailty index (mFI-11) is a National Surgical Quality Improvement Program (NSQIP)-based 11-factor index that has been proven to adequately reflect frailty and predict mortality and morbidity. In the past years, certain NSQIP variables have been removed from the database; as of 2015, only 5 out of the original 11 factors remain. While the predictive power and usefulness of this 5-factor index (mFI-5) has been proven in previous work, it has yet to be studied in the geriatrics population. The goal of our study was to compare the mFI-5 to the mFI-11 in terms of value and predictive ability for mortality, postoperative infection, and unplanned 30-day readmission for patients aged 65 years and older.

Spearman's Rho was calculated to compare the value, and unadjusted and adjusted logistic regressions were created for three outcomes in nine surgical subspecialties. Correlation coefficients were above .86 across all surgical specialties except for cardiac surgery. Adjusted and unadjusted models showed similar C-statistics for mFI-5 and 11.

Overall predictive values of geriatric mFI-5 and mFI-11 were lower than those for the general population but still had effective predictive value for mortality and post-operative complications (C-Stat ≥ .7) and weak predictive value for 30-day readmission.

The mFI-5 is an equally effective predictor as the mFI-11 in all subspecialties and an effective predictor of mortality and postoperative complication in the geriatric population. This index has credibility for future use to study frailty within NSQIP, within other databases, and for clinical assessment and use.