TNF and rheumatoid arthritis: A Canadian observational study of 1086 RA patients (799 treated with anti-TNF agents) found that the annual mean (direct and indirect) costs of the disease were directly proportional to disability as measured by means of the HAQ: the costs were three times higher for patients with severe disability (HAQ > 2) than for patients without disability (HAQ < 0.5), with working disability being the major indirect cost [34].