SUPPLEMENTARY INFORMATION
Supplementary information is linked to the online version of the paper at www.nature.com/nrrheum
doi:10.1038/
Measuring the cost of SLE
Studies to evaluate the burden of an illness should aim to itemize, value and sum the costs of a specific problem, and thus estimate the values of a wide range of morbidity effects.1 The monetary value is known as the “opportunity cost”, the value of the forgone opportunity to use in a different way those resources that are used or lost due to illness. In addition, most chronic illnesses affect patients’ quality of life (QoL), self-esteem, family and marital relationships and psychosocial health. These intangible costs are difficult to evaluate and most studies have focussed mainly on the discrepancy of QoL.
Direct costs
Direct costs refer to expenditures for diagnosis, treatment, continuing care and rehabilitation. They can be further divided into direct health-care and non-health-care expenditures. Direct health-care costs include in-patient, out-patient and emergency care; services of primary physicians, specialists and other health professionals; drugs and drug sundries; and rehabilitation counseling and appliances. Other healthcare costs to society are those for research, administrative functions and prevention, which are difficult to measure and often not evaluated. Direct non-healthcare costs include the costs of transportation to health providers and certain household expenditures, as well as a variety of expenses that are incurred in caring for a sick member of the family. These include care provided by family and friends; extra domestic help for household chores; items for rehabilitation and comfort; alterations of property and other special housing facilities.1
Indirect costs
Indirect costs result from a loss of productivity due to illness. Output loss includes both diminished labour market and non-market or household activity. Illness reduces the productivity of persons at work and causes absenteeism. Additional costs include unwanted job changes and loss of opportunities for promotion and education. The time a patient and/or their family members spend visiting health professionals also contributes to indirect costs.2 For SLE, a disease that predominantly affects young women, a significant portion of output loss will result from a reduction in non-labour market activities, such as housekeeping and childcare.
Intangible costs
The assessment of HRQoL in SLE has traditionally been under-appreciated and poorly understood. Wide variations in estimates of the impact of the psychosocial aspects of SLE result from methodologic weaknesses such as the lack of an accepted definition and the failure to use standardized measures. Numerous QoL questionnaires, varying considerably in length and in the domains assessed, have been developed and tested in SLE. The short form-36 questionnaire3 appears to be the best available generic instrument for the assessment of HRQoL in SLE, though it is likely to be complemented by several newly developed disease-specific HRQoL instruments.4–6
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