A further limitation of this study is that it only dealt with a regional aspect of the impact of the French law. Other studies reviewed were not based on the total population at risk. The only accepted study that provides information about the effect of headrests is that by Nygren et al. Although the true population at risk cannot be deduced, there is evidence that the risk of WAD varies with the make of vehicle and whether there is a headrest or not. The role of the type of headrest in this study is inconclusive.
Several studies suggest the type of collision is a risk factor for soft-tissue neck injuries.
For instance, whiplash injuries may be more likely to occur in rear-end collisions. Although this seems obvious and compatible with biomechanical models of neck injuries, there are no studies based on an acceptable denominator, thus precluding estimation of relative risks. As part of its effort to summarize the Consensus of the Task Force, the Methods and Reporting Secretariat met to construct a grid on Diagnostic Methods. We also contemplated changing the Grid to show the diagnostic tests in the rows and attributes such as predictive value, sensitivity, specificity and acceptability in the columns. These are the attributes that are essential to a scientific and clinically relevant approach to the evaluation of diagnostic tests.