Pitfalls in subgroup analysis based on growth mixture models: a commentary on Van Leeuwen et al. (2012).

OBJECTIVES: This article is a brief commentary in response to "van Leeuwen et al. (Qual Life Res 21:1499-1508, 2012)" METHODS AND RESULTS: The commentary argues that in the context of mixture modeling, assigning individuals to specific subgroups for conducting a secondary set of analyses ignores the original uncertainty in group membership, thereby biasing any subsequent results and inference. CONCLUSIONS: Alternative approaches to subgroup analysis that attempt to preserve uncertainty in group membership are discussed and illustrated.