The assessment of fibromyalgia (FM) is challenging because there are no biomarkers for this condition. Clinicians must rely upon patient-reported symptoms in order to understand the complexities of this condition. While in 1990 the American College of Rheumatology developed research classification criteria involving tender point counts, it has only been within the past year that the American College of Rheumatology (ACR) proposed clinical diagnostic criteria1. Historically, many symptoms have been thought to be associated with FM. In order to narrow the field to those symptoms with the greatest clinical relevance, a working group within OMERACT (Outcome Measures in Rheumatology) conducted several Delphi exercises within both patients and clinicians to obtain consensus regarding which domains should be assessed in clinical trials for FM 2,3. The instruments to be reviewed in this paper reflect the clinically relevant domains defined by this OMERACT working group.
A wide variety of instruments have been used to index the OMERACT domains for FM. Many of the instruments were developed for use generically or have been borrowed from other clinical populations. In recent phase 2 & 3 clinical trials of medications for FM, wide variation was observed in the selection of domain indices (see Table 1). While many of these measures are reviewed elsewhere in this special issue, we have selected a representative measure from each of the following domains of relevance: pain (Brief Pain Inventory), fatigue (Multi-dimensional Fatigue Inventory), sleep disturbance (MOS Sleep Scale), and cognitive dysfunction (Multiple Ability Self-Report Questionnaire. Mood and Functional status are also important domains for FM; however the instruments most commonly used to assess these domains are reviewed elsewhere in this special issue and will not be repeated here (e.g. mood (Hospital Anxiety and Depression Scale), and functional status (SF-36). Recent work in the development of responder indices suggest that either these specific instruments or other measurement tools from within the same domain can be used to differentiate responders from non-responders in clinical treatment trials for FM 4. The precision by which these domains will be able to be assessed in the future is likely to be enhanced as newer measurements that are being developed using either classical test construction methods or methods such as item response theory and computer adaptive testing as is being done in the NIH-sponsored Patient Reported Outcomes Measurement System (PROMIS) 5.