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Alexanderson H, Broman L, Tollback A, Josefson A, Lundberg IE, Stenstrom CH. Functional Index-2: validity and reliability of a disease-specific measure of impairment in patients with polymyositis and dermatomyositis. Arthritis Rheum 2006;55:114 –22

This study summarizes the main outcome measures in adult and juvenile dermatomyositis, polymyositis, and inclusion body myositis.

This review aims to discuss the evolution of IIM classification criteria.

The FI-2 is a disease-specific observational tool for adult patients with polymyositis (PM)/dermatomyositis (DM) to measure muscle endurance. The FI-2 is a more developed version of the original Functional Index (FI), which was presented in 1996 as the first disease-specific muscle impairment measure for patients with PM/DM.

It measures the number of repetitions performed in 7 muscle groups: shoulder flexion, shoulder abduction, neck flexion, hip flexion, and knee extension (step test; performed at a pace of 40 beats per minute, which is monitored by a digital metronome), and heel lifts and toe lifts (performed at a pace of 80 beats per minute). Each muscle group is scored as the number of correctly performed repetitions, with no total score, presenting a profile of muscle impairment for the upper and lower extremities and the neck.

Each muscle group is scored by the number of repetitions performed, and the score range from 0 – 60 for the shoulder flexion, shoulder abduction, neck flexion, hip flexion, and step test tasks, or from 0–120 for the heel and toe lifts. 

The number of correctly performed repetitions is recorded, together with the perceived muscle exertion for each task.