Does recall of preinjury disability change over time?

BACKGROUND: Pre-injury disability must be determined when assessing whether treatment programs return people to pre-injury status, however there is little empirical evidence to support recommendations that this be done as soon as possible after injury to prevent recall bias.
OBJECTIVES: To determine disagreement between recall of pre-injury disability at different time points post-injury and bias towards under- or overestimating pre-injury disability.
METHODS: Self-reported pre-injury global disability was assessed within days, 6 months and 12 months post-injury in patients admitted to two level 1 adult trauma centres. Kappa statistics and multiple logistic regression models identified predictors of disagreement between time-points.
RESULTS: Pre-injury disability was measured at all time-points in 801 patients. Pre-injury disability at baseline was rated as none, mild, moderate, marked and severe in 80%, 12%, 5.1%, 1.9% and 1.0% respectively. Absolute agreement between baseline and 6 and 12 months respectively, was 79% and 80%. Corresponding kappa values (95% confidence intervals) were 0.33 (0.26-0.40) and 0.32 (0-25-0.38). Patients over 65 years or not completing high school were more likely to report less pre-injury disability at 6 and 12 months than at baseline with adjusted odds ratios (95% confidence intervals) for these groups being 8.24 (4.32-15.72) and 1.93 (1.03-3.64) respectively.
CONCLUSIONS: There was little evidence of recall bias in an adult trauma population if self-reported global pre-injury disability was assessed 6 months post-injury. The recall of pre-injury disability up to 6 months post-injury can be used to determine return to pre-injury status, if assessment is not feasible shortly after injury.