Preliminary Determination of the Association between Symptom Expression and Urinary Metabolites in Subjects with Chronic Fatigue Syndrome

Chronic fatigue syndrome (CFS) patients have a urinary metabolite labeled CFSUM1 with increased incidence (P< 0.004) and relative abundance (P< 0.00003). The relative abundances of urinary CFSUM1 and β-alanine were associated with alterations in metabolite excretion and symptom incidence. In 20 CFS patients and 45 non-CFS subjects, symptom/metabolite associations were investigated by assessing symptom sensitivity and specificity, and symptom indices of total symptom incidence, CFS core symptoms, cognitive, neurological, musculoskeletal, gastrointestinal, infection-related and genitourinary symptom indices, as well as a visual analogue pain scale of average pain intensity. Thirty-three symptoms had significant (P< 0.005) sensitivity and specificity in the CFS patients compared to that in the non-CFS controls. Severe fatigue was the only symptom with 100% sensitivity and specificity and CFSUM1 excretion was the primary metabolite for expression of this symptom. All nine symptom indices had elevated responses in the CFS patients (allP< 0.0000001). Multiple regression analyses indicated that all the symptom indices had significant correlations (R2) with changes in the urinary excretion of metabolites (P< 0.0001). CFSUM1 and β-alanine were the first and second metabolites correlated with the CFS core symptom index and CFSUM1 was primarily associated with infection-related and musculoskeletal indices whereas β-alanine was primarily associated with gastrointestinal and genitourinary indices. The strong associations of CFSUM1 and β-alanine with CFS symptom expression provide a molecular basis for developing an objective test for CFS.