Table 1. Concept and terminology of disease-related QoL and diseased QoL used in outcome assessment of complex interventions for breast cancer.

Disease-related QoL

Health, disease and QoL are key concepts in medicine (Wulff, 2002), but their definitions should be derived from empirically testable and clinically relevant attributes (Lorenz et al, 1999; Lorenz and Koller, 2002; Wulff, 2002; Velikova et al, 2004). Health is neither absence of disease nor an aggregate amount of disease states. Disease as the vehicle of clinical experience (Wulff, 2002) has its own, characteristic (molecular, clinical, physical and psychosocial) specificity (Lorenz et al, 1999; Bowling, 2001). QoL as part of the outcome construct is again specifically related to this disease concept. For example, in sepsis, emotional distress (depression, sickness behaviour) is associated with cytokine expression in specific brain areas (Bauhofer et al, 2004). Clinically measured QoL is related to the total concept of disease. Hence, QoL  – is assessed in a specifically diagnosed disease, including the critical model of Wulff (Lorenz et al, 1999; Wulff, 2002)  – entails self-perception and self-report in three domains: somatic, psychological and social  – includes health- and therapy-related expectations and coping  – is influenced by basic psychosocial variables such as negative affect  – is part of a three-component outcome model (Lorenz et al, 1999; Koller and Lorenz, 2002; Lorenz and Koller, 2002) For each attribute in this definition, at least one empirical (prospective) trial is available and usable

Diseased QoL

As part of the disease concept, QoL is not just a measurement, but has a medical/clinical value. ‘Diseased’ characterises QoL as negative medical value, ‘healed’ QoL is the corresponding positive result of therapeutic improvement. The cutoff point between disease and health for any dimension in the QoL profile is <50 points in scales of 0–100 (worst–optimal QoL)  – It is not yet defined by a gold standard, but by face validity using 4-point Likert scales (Koller and Lorenz, 2002)  – by psychological theories on adaptation level and social comparison (Koller and Lorenz, 2002),  – by asking patients at which value in a range of 0–100 they would approach their doctor (iatrotropy; Koller and Lorenz, 2002) and  – by a change in global QoL as a general dimension if QoL in a specific dimension (in 1/10 in the QoL profile) declined below a value of 50 as the lowest in the range of the normal German population (Klinkhammer-Schalke et al, 2008b)

Abbreviation: QoL=quality of life.

Methodology: Definitions in medicine according to Popper et al (1998): combine attributes, but only from empirical studies. Presentation of attributes: use meta-levels according to Reichenbach (1947, 1951).