Pooled metaanalysis of radiographic progression: comparison of Sharp and Larsen methods.

Metaanalysis refers to the statistical analysis of results from individual studies for the purpose of integrating the findings. However, numerous biases can threaten the internal validity of metaanalyses. This paper specifically addresses the issue of study heterogeneity in metaanalyses of radiographic progression. It considers the validity of pooling studies that have used either the Sharp score (or its variants) or the Larsen score (or its variants) by examining whether the 2 scoring methods are sufficiently concordant for pooling in terms of content of items, scaling and measurement properties. Despite differences between the Sharp and Larsen methods, they essentially measure the construct of radiographic damage, and as long as the spectrum of radiographic damage in the pooled series is similar, then the scoring methods are robust to pooling. However, where the spectrum of damage is not similar, for example, studies of radiographic progression of early disease compared with late disease, pooling should be exercised with caution.