Factors that affect the number of tender points in fibromyalgia and chronic widespread pain patients who did not meet the ACR 1990 criteria for fibromyalgia: are tender points a reflection of neuropathic pain?

OBJECTIVE: This study aims to compare fibromyalgia (FM) and chronic widespread pain (CWP) patients who do not fulfill the criteria for tender points (TP).
METHODS: We included 150 patients diagnosed with FM according to ACR 1990 criteria and 42 patients with CWP who did not fulfill TP criteria for FM into the study. The clinical features of the patients were recorded, and the TP count was determined. By means of a visual analog scale (VAS), all patients were questioned about the severity of pain and FM-related symptoms. In addition, the patients were administered the Duke Anxiety Depression (Duke-AD) scale and somatization symptom questionnaire. Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) pain scale was used to determine the neuropathic pain score.
RESULTS: According to VAS, the severity of pain, sleep disturbance, the number of somatization symptoms, LANSS, and Duke-AD scores were significantly higher in FM patients than in patients with CWP (all P values <0.05). The number of TP correlated with severity of pain (r = 0.32, P < 0.001), the number of somatization symptoms (r = 0.26, P = 0.01), sleep disturbance (r = 0.18, P = 0.01), and LANSS score (r = 0.4, P < 0.001). Multiple logistic regression analysis revealed that independent factors that affected the presence of > or =11 TP were the severity of pain on VAS (OR: 1.03, 95% CI: 1.01-1.06, P = 0.045) and LANSS score (OR: 1.36, 95% CI: 1.12-1.62, P = 0.001).
CONCLUSIONS: CWP patients have symptoms similar to FM patients, though less severe. The most important factor that affects the criteria for fulfilling the number TP in CWP patients is the neuropathic pain score, which suggests that FM is primarily a neuropathic pain syndrome.