Interrelationships of Biochemical Parameters in Classification of Fibromyalgia Syndrome and Healthy Normal Controls

Abstract

Objective. To determine if a combination of biochemical variables [e.g., plasma amino acids and catecholamines] would better classify patients with fibromyalgia syndrome [FMS] and pain-free normal controls than a single variable alone. Methods. Plasma amino acids and catecholamines as well as urinary catecholamines were analyzed in 29 patients with FMS and 30 painfree normal controls who were clinically and psychologically evaluated. Discriminant analysis was used to select a number of biochemical variables which in combination would best classify the study subjects. Results. A combination of 7 variables [plasma histidine, methionine, tryptophan, norepinephrine, isoleucine and leucine, and urinary dopamine] provided the optimum sensitivity of 86%. Pain, fatigue, poor sleep and number of tender points, but not anxiety, depression or mental stress, significantly [P < 0.001] correlated with the discriminant scores. Conclusion. A combination of biochemical variables better classifies patients with FMS and normal painfree controls than a single variable alone. The interrelationships of these variables may be important in the biophysical mechanisms of FMS. Further studies are indicated.