Some statistical considerations in the development of new quality of life (QoL) scales in schizophrenia

Assessing the effect of novel pharmaceutical treatments on the quality of life (QoL) of a patient, or group of patients, has been approached in numerous ways over the last 20 years. Techniques as diverse as single questions to multidimensional scales requiring trained assessors to devote several hours to each assessment; from generic questions about how life might have changed to specific issues such as the ability to use a toothbrush. In the pharmaceutical industry, the emphasis is on the registration of a product with national licensing bodies. Each body has tended to see the issue from a different perspective, which has driven study designs to be different in different countries; even different over time within one country. This paper emphasises the basic statistical steps necessary to ensure that a measure of QoL is appropriately recorded, while retaining sufficient flexibility to support the registration in several countries. Aspects about possible study design are included to assist with developing some simple concepts about analysing and then interpreting the results. It is not the intention of the paper to provide the answer, merely to provide the tools to develop the answer robustly. Put briefly, with the right approach generic solutions are feasible and these solutions will have greater utility. The challenge is to recognise exactly what QoL is, and not to deviate from it.