Interpreting validity indexes for diagnostic tests: An illustration using the Berg Balance Test

Physical therapists routinely make diagnostic and prognostic decisions in t he course of patient care. The purpose of this clinical perspective is to i llustrate what sue believe is the optimal method for interpreting the resul ts of studies that describe the diagnostic or prognostic accuracy of examin ation procedures. To illustrate our points, we chose the Berg Balance Test as an exemplar measure. We combined the data from 2 previously published re search reports designed to determine the validity of the Berg Balance Test for predicting risk of falls among elderly people. We calculated the most c ommon validity indexes, including sensitivity, specificity, predictive valu es, and likelihood ratios for the combined data. Clinical scenarios were us ed to demonstrate how we believe these validity indexes should be used to g uide clinical decisions. We believe therapists should use validity indexes to decrease the uncertainty associated with diagnostic and prognostic decis ions. More studies of the accuracy of diagnostic and prognostic tests used by physical therapists are urgently needed. (Riddle DL, Stratford PW.. Inte rpreting validity indexes for diagnostic tests: an illustration using the B erg Balance Test.