An attempt was made to see if rheumatoid arthritis (RA) patients can use visual analogue scales (VAS) to distinguish and grade the severity of pain at night, during rest, and on joint movement and to determine if discriminate measurement of these three pain components enhances the value of VAS estimation.
Two hundred and fifty two consecutive RA patients were evaluated by a single observer using 10 cm VAS for pain at night, at rest during the day, and on movement. Values were correlated against age, disease duration, joint tenderness, swollen joint count, erythrocyte sedimentation rate (ESR), C reactive protein (CRP), and Larsen x ray scores.
Night pain was recorded by 71 (28%) and this component of pain was lower than VAS scores for daytime rest and movement. However, those with nocturnal pain had significantly more joint tenderness (p < 0.0001), swollen joints (p < 0.0001), and higher ESR and CRP. Age, disease duration, and radiographic scores were similar in those with and without night pain. Correlations of joint tenderness were apparent for all three pain scores but only nocturnal pain correlated with swollen joints (p < 0.001) and CRP (p < 0.005). Age, disease duration, and radiographic severity correlated with daytime rest or movement scores but not nocturnal pain.
Patients were able to distinguish and estimate the severity of pain at rest, on movement, and at night. The occurrence of night pain characterised those with more active disease and night pain VAS measurement correlated best with measures of joint inflammation whereas daytime pain scores, both at rest and on movement, seemed influenced by the degree of permanent joint damage. Thus, discrete measurement of rest, movement, and nocturnal pain may provide useful information about RA disease status.