Distinguishing Fibromyalgia From Rheumatoid Arthritis and Systemic Lupus in Clinical Questionnaires

An Analysis of the Revised Fibromyalgia Impact Questionnaire (FIQR) and its Variant, the Symptom Impact Questionnaire (SIQR), Along With Pain Locations

Ronald Friend; Robert M Bennett

Disclosures

Arthritis Res Ther. 2011;13(2) 

In This Article

Abstract and Introduction

Abstract

Introduction: The purpose of this study was to explore a data set of patients with fibromyalgia (FM), rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) who completed the Revised Fibromyalgia Impact Questionnaire (FIQR) and its variant, the Symptom Impact Questionnaire (SIQR), for discriminating features that could be used to differentiate FM from RA and SLE in clinical surveys.
Methods: The frequency and means of comparing FM, RA and SLE patients on all pain sites and SIQR variables were calculated. Multiple regression analysis was then conducted to identify the significant pain sites and SIQR predictors of group membership. Thereafter stepwise multiple regression analysis was performed to identify the order of variables in predicting their maximal statistical contribution to group membership. Partial correlations assessed their unique contribution, and, last, two-group discriminant analysis provided a classification table.
Results: The data set contained information on the SIQR and also pain locations in 202 FM, 31 RA and 20 SLE patients. As the SIQR and pain locations did not differ much between the RA and SLE patients, they were grouped together (RA/SLE) to provide a more robust analysis. The combination of eight SIQR items and seven pain sites correctly classified 99% of FM and 90% of RA/SLE patients in a two-group discriminant analysis. The largest reported SIQR differences (FM minus RA/SLE) were seen for the parameters "tenderness to touch," "difficulty cleaning floors" and "discomfort on sitting for 45 minutes." Combining the SIQR and pain locations in a stepwise multiple regression analysis revealed that the seven most important predictors of group membership were mid-lower back pain (29%; 79% vs. 16%), tenderness to touch (11.5%; 6.86 vs. 3.02), neck pain (6.8%; 91% vs. 39%), hand pain (5%; 64% vs. 77%), arm pain (3%; 69% vs. 18%), outer lower back pain (1.7%; 80% vs. 22%) and sitting for 45 minutes (1.4%; 5.56 vs. 1.49).
Conclusions: A combination of two SIQR questions ("tenderness to touch" and "difficulty sitting for 45 minutes") plus pain in the lower back, neck, hands and arms may be useful in the construction of clinical questionnaires designed for patients with musculoskeletal pain. This combination provided the correct diagnosis in 97% of patients, with only 7 of 253 patients misclassified.

Introduction

Rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and fibromyalgia (FM) are usually easily discriminated on clinical examination, but have several overlapping features that make their differentiation more problematic in epidemiological surveys. For instance, pain, fatigue and morning stiffness are commonly reported in all three disorders. The current study was stimulated by the increasing interest in developing questionnaires that can accurately predict the occurrence of FM in both epidemiological and clinical settings.[1–5] During the evaluation of an updated version of the Fibromyalgia Impact Questionnaire (FIQR), we compared its properties in patients with FM with those in patients with RA, SLE and major depressive disorder (MDD).[6] Although the primary intent of this analysis was to validate the FIQR as a useful instrument in assessing the overall impact and severity of FM, it was incidentally noted that it had some diagnostic utility in differentiating FM from SLE and RA.[6] A slightly modified version of the FIQR, the Symptom Impact Questionnaire (SIQR), was used for the SLE and RA groups. The SIQR is identical to the FIQR, but does not contain any reference to FM.[6] For instance, the total SIQR score discriminated FM from these three disorders, with FM having a total FIQR score of 56.6, whereas RA had a score of 27.9, SLE had a score of 29.5 and MDD had a score of 17.3. We also reported on pain in 24 locations in the FIQR study to confirm that FM patients who had not been seen recently still had widespread pain. While this pain location questionnaire was not used in FIQR scoring, the number of pain locations was, as expected, much higher in FM patients: 16 pain sites for patients with FM compared to 6 sites in patients with RA, 7 sites in patients with SLE, 4 sites in patients with MDD and 1.6 sites in healthy controls. The objective of the current study was to identify individual SIQR symptoms and pain locations that best discriminated FM patients from RA/SLE patients in this data set. Doing so provides some pointers as to which pain sites and common symptoms may best discriminate FM from RA/SLE in patient questionnaires.

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