Table 2.

Study Results Compared with Results from Previous Studies.

Parameter	Caswell [28]	Gotzsche et al. [33]	Horton [32]	Rosell Pradas & Lacasaña Navarro [29]	Tierney et al. [8]	Present Study
Letters not associated with a previous article	35%			72%	40/55%	59%
Reader Responses receiving Author Replies		45%	40%			38%
Mean number of authors				3.0	2.6	4.5
Mean number of references				5.7	3.6	7.0
Letters including graphics				24%	38%	39%