Reliability and validity of the german version of the sickness impact profile in patients with chronic obstructive pulmonary disease

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Abstract
Reliability and validity of the German version of the Sickness Impact Profile (SIP) were investigated in a simple of 58 O2 department paitents with chronic obstructive pulmonary disease (COPD). Internal consistency (Cronbach Alpha) was. 93 for the entire instrument, while it was .85 for me SIP psycho-social scale and .89 for the SIP physical scale. The Cronbach Alphas ranged from .55 to .86 for the subscales of the German SIP version. The subscale “Eating” was discarded because of low internal consistency (.40) and split-half reliability (.24). Indices of respiratory function (FEV1, FVC, PaO2, SaO2), functional impairment and dyspnea (BOI) were substantially associated with the total SIP, Psychosocial and Physical score, ranging from r = -.33 tp r = -.48. A stepwise discriminant analysis between the 14 Patients, who died during the course of the study and the survivors revealed one single discriminant function with an Eigenvalue of .5859 (canonical correlation r = .61; Chi2= 21.21; df=3; p < 0.001). The FVC (Wilk's Lambda.76), the severity of dyspnea (BDI) (Wilk's Lambda.71), the SIP total score (Wilk;s Lambda of .65) and the FEV1 (Wilk's Lambda .63) were identified as discriminating variables, allowing the correct classification of 85% of the survivors and 91% of the fatalities.