The most widely validated functional disability measure in rheumatology. Assesses difficulty with daily activities across eight domains, from dressing to walking to grip strength. Used in virtually every major RA clinical trial as a primary or secondary functional outcome.
The HAQ-DI measures functional disability across eight domains of daily living: dressing and grooming, arising, eating, walking, hygiene, reach, grip, and activities. Each domain contains two or three specific questions rated 0 (no difficulty), 1 (some difficulty), 2 (much difficulty), or 3 (unable to do). The domain score is the maximum (hardest) question in that domain. The overall HAQ-DI is the average of the eight domain scores, ranging from 0 to 3.
An important scoring adjustment: if the patient uses aids or devices (e.g. a raised toilet seat, cane, or jar opener), or requires help from another person for any activity in a domain, the minimum domain score for that domain is raised to 2, even if the unaided answers were lower.
| HAQ-DI Score | Disability Level | Functional Meaning |
|---|---|---|
| 0 to 0.5 | None / Minimal | Little to no functional limitation. Consistent with remission or very low disease activity. |
| 0.5 to 1.0 | Mild | Some difficulty with activities. Warrants monitoring but may not require therapy change. |
| 1.0 to 2.0 | Moderate | Meaningful functional impairment affecting daily life. Associated with work disability risk. |
| 2.0 to 3.0 | Severe | Significant disability. High risk of work loss and need for assistance with daily activities. |
A change of 0.22 or more in HAQ-DI is generally considered the minimal clinically important difference (MCID) in RA. Values above 1.0 are associated with markedly increased mortality in long-term studies.
The HAQ was originally developed by Fries, Spitz, and colleagues at Stanford and published in Arthritis and Rheumatism in 1980. The Disability Index subscale (HAQ-DI) became the standard functional outcome measure in rheumatology and has been used in virtually every pivotal RA clinical trial over the past 40 years. It has been translated and validated in over 60 languages.
The minimal clinically important difference (MCID) of 0.22 was established through multiple validation studies comparing HAQ-DI changes to patient global impression of change. The mortality association was established in long-term registry data, most notably by Pincus et al., who demonstrated that HAQ-DI was a stronger independent predictor of mortality than traditional cardiovascular risk factors in established RA.