Validation of a fatigue impact score in primary biliary cirrhosis: towards a standard for clinical and trial use.

OBJECTIVE

Fatigue is the commonest symptom of the chronic liver disease primary biliary cirrhosis (PBC). PBC is increasingly being diagnosed earlier in its natural history at a stage when concerns about progression to liver failure may be less prominent than current symptoms. The importance of symptomatic treatment is therefore increasingly being recognised. Research into the aetiology and treatment of fatigue in PBC has been hampered by the lack of relevant, reproducible measures of fatigue severity. The aim of this study was to validate the Fisk Fatigue Severity Score (FFSS), a measure of the impact of fatigue on daily living, for use in PBC and to use the FFSS to study the severity and correlates of fatigue in this condition.

METHODS

Fifty-eight patients with PBC and 31 matched control patients attending hospital for nonhepatic disease were studied. The reproducibility of FFSS was assessed over periods from 1 hour to 1 month. Fatigue, as measured by FFSS, was compared in PBC patients and controls. The severity of fatigue in the patients with PBC was correlated with other symptoms and with established biochemical and histological markers of severity.

RESULTS

The FFSS questionnaire was acceptable to patients and had reasonable intra-observer variation (coefficient of reproducibility 13% of mean value at 1 hour). The FFSS was more reproducible than a visual analogue scale. FFSSs varied over 4 weeks by up to 36%. Median FFSS's were 2.3 times higher in PBC patients than controls (p<0.005). There were no associations between FFSS and patient age, disease duration, or histological or biochemical markers of severity.

CONCLUSIONS

The FFSS is a highly acceptable, internally consistent and reproducible measure of fatigue severity in PBC. We advocate its use in clinical assessment of patients, in studies of the aetiology of fatigue in PBC and, most importantly, in therapeutic trials of symptomatic treatment.