Fatigue Severity Scale [FSS-16]

Scale Analysis

The Fatigue Severity Scale (FSS-16) is a self-administered questionnaire designed to assess the severity of fatigue in various situations over a specific period. Originally developed by Krupp and colleagues, the scale aims to quantify how fatigue impacts individuals’ daily lives.

Purpose

The primary purpose of the FSS is to differentiate fatigue from clinical depression, as both conditions can share overlapping symptoms.

Scoring

Each item on the scale is rated from 1 to 7, where 1 indicates strong disagreement and 7 indicates strong agreement. The final score is calculated as the average of the 9 items. This unidimensional scale consists of 9 questions that address the most fundamental symptoms of fatigue and its impact on daily functioning.

Statistical Analysis

The FSS yields a composite score derived from the statistical processing of the responses, calculated as the mean value of the 9 items. Respondents rate their agreement using a Likert-type scale, where 1 = strongly disagree, 7 = strongly agree, and 4 represents a neutral midpoint. The neutral point (4) is the upper limit for indicating the absence of clinically significant fatigue.

Validity and Reliability

The FSS is the most widely used fatigue assessment tool. Its reliability and validity have been confirmed in numerous studies across English-speaking and non-English-speaking populations with various systemic and neurological conditions.