Clinical Laboratory Test Findings in Patients With Chronic Fatigue Syndrome

Background: Results of readily available clinical laboratory tests in patients with chronic fatigue syndrome were compared with results in healthy control subjects. Methods: Cases consisted of all 579 patients who met either the Centers for Disease Control and Prevention, Atlanta, Ga, British, or Australian case definition for chronic fatigue syndrome. They were from chronic fatigue clinics in Boston, Mass, and Seattle, Wash. Control subjects consisted of 147 blood donors who denied chronic fatigue. Outcome measures were the results of 18 clinical laboratory tests. Results: Age- and sex-adjusted odds ratios of abnormal results, comparing cases with control subjects, were as follows: circulating immune complexes, 26.5 (95% confidence interval [CI], 3.4-206); atypical lymphocytosis, 11.4 (95% CI, 1.4-94); elevated immunoglobulin G, 8.5 (95% CI, 2.0-37); elevated alkaline phosphatase, 4.2 (95% CI, 1.6-11); elevated total cholesterol, 2.1 (95% CI, 1.2-3.4); and elevated lactic dehydrogenase, 0.30 (95% CI, 0.16-0.56). Also, antinuclear antibodies were detected in 15% of cases vs 0% in the control subjects. The results of these tests were generally comparable for the cases from Seattle and Boston. Although these tests served to discriminate the population of patients from healthy control subjects, at the individual level they were not as useful. Conclusions: Patients with chronic fatigue syndrome who were located in two geographically distant areas had abnormalities in the results of several readily available clinical laboratory tests compared with healthy control subjects. The immunologic abnormalities are in accord with a growing body of evidence suggesting chronic, low-level activation of the immune system in chronic fatigue syndrome. While each of these laboratory findings supports the diagnosis of chronic fatigue syndrome, each lacks sufficient sensitivity to be a diagnostic test. Furthermore, the specificity of these findings relative to other organic and psychiatric conditions that can produce fatigue remains to be established.