PROGNOSTIC FACTORS FOR NON-RECOVERY
The capacity to predict outcome following whiplash injury is important for several reasons. Predictive factors may be modifiable or non-modifiable, and treatments directed at the former factors may improve outcomes for those identified as at risk of poor recovery. This, in turn, may assist in the curtailment of both personal and financial costs associated with the condition. The identification of those who show good potential for recovery is also important so that both injured people and clinicians can have greater confidence in a good outcome. An understanding of prognostic indicators for both outcomes will allow the appropriate allocation of resources by policy-makers.
Fifteen years ago, the Quebec Task Force identified predictive studies as an area requiring urgent investigation in whiplash research. Since that time the number of cohort studies has substantially increased and now several systematic reviews of prognosis are available. However, these have not been undertaken without difficulty owing to shortcomings in some of the primary cohort studies, including inconsistencies between studies in time from injury until baseline data collection, time to follow-up and use of various and sometimes un-validated outcome measures. There is also variation between the systematic reviews, with some performing meta-analysis, others indicating that due to heterogeneity data pooling could not be undertaken, and others comprising task force findings that were not peer reviewed. Nevertheless, the findings of the various reviews have generally been in agreement that the factors of higher initial predictors of poor functional recovery.
It is not the aim of this chapter to conduct another systematic review of currently available cohort studies. Rather, it is to present an overview of systematic potential findings, discuss emerging factors that show potential for prognostic capacity of both recovery and non-recovery, and outline the clinical implications for the recognition of prognostic indicators.
PRESENTING SIGNS AND SYMPTOMS
Clearly, the most consistent predictor of poor functional recovery is the intensity of neck pain at the initial or baseline assessment point. Walton et al. synthesized the data from eight cohorts and established a cut-off point of 55 out of 100 or 5 out of 10 on a visual analogue pain scale. These authors report that a pain intensity of greater than 55 out of 100 demonstrated a nearly six-fold (OR, 5.77; 95% CI: 2.89-11.52) increase in the risk of persistent pain or disability at follow-up. This factor was slightly more robust at predicting an outcome of disability when compared to pain outcomes. Initially, moderate-to-high levels of pain-related disability have also shown predictive capacity.
Some reviews pointed to other symptoms, such as the presence of headache, or neurological symptoms, such as arm pain or paresthesia, as also showing predictive capacity. The Quebec Task Force classification (see Chapter 1 for description), a predominantly symptom-based system, was evaluated in two reviews, with the authors concluding that increasing grades of whiplash associated disorders (WAD) predicted increasingly higher pain intensities and disability two years later. Walton et al. reported that the size of effect was significant when WAD grades II and III were compared against grades I and 0, and this effect was consistent at various follow-up times points.
Other symptoms, such as dizziness, reported sleep disturbances and cognitive difficulties, have not emerged from the systematic reviews as showing any predictive capacity.