Assessment of fatigue using the Identity-Consequence Fatigue Scale in patients with lung cancer

OBJECTIVE: To evaluate the properties of the Identity-Consequence Fatigue Scale (ICFS) in patients with lung cancer (LC), assessing the intensity of fatigue and associated factors. METHODS: This was a cross-sectional study involving LC patients, treated at a teaching hospital in Brazil, who completed the ICFS. Patients with chronic heart disease (CHD) and healthy controls, matched for age and gender, also completed the scale. Initially, a Brazilian Portuguese-language version of the ICFS was administered to 50 LC patients by two independent interviewers; to test for reproducibility, it was readministered to those same patients. At baseline, the LC patients were submitted to spirometry and the six-minute walk test, as well as completing the Epworth Sleepiness Scale (ESS), Hospital Anxiety and Depression Scale (HADS), Medical Outcomes Study 36-item Short-Form Health Survey (SF-36), and Fatigue Severity Scale (FSS). Inflammatory status was assessed by blood C-reactive protein (CRP) levels. To validate the ICFS, we assessed the correlations of its scores with those variables. RESULTS: The sample comprised 50 patients in each group (LC, CHD, and control). In the LC group, the intraclass correlation coefficients for intra-rater and inter-rater reliability regarding ICFS summary variables ranged from 0.94 to 0.76 and from 0.94 to 0.79, respectively. The ICFS presented excellent internal consistency, and Bland-Altman plots showed good test-retest reliability. The ICFS correlated significantly with FSS, HADS, and SF-36 scores, as well as with CRP levels. Mean ICFS scores in the LC group differed significantly from those in the CHD and control groups. CONCLUSIONS: The ICFS is a valid, reliable instrument for evaluating LC patients, in whom depression, quality of life, and CRP levels seem to be significantly associated with fatigue.